Journals Highlights

On the Cover
Laser-induced periodic surface structures (LIPSS) provide a direct laser writing method for fabricating nano-gratings on sample surfaces. These periodic nano-structures efficiently modify the properties of materials and have many applications in surface coloring, large-area grating, birefringence optical elements, data storage, and surface wettability.
Photonics Research
  • Jun. 01, 2021
  • Vol.9, Issue 6 (2021)
On the Cover
Optical pulses are essential ingredients in the deployment of imaging systems, precision manufacturing and high-speed communications. The ability to manipulate their properties, including their spectral bandwidth is therefore an important function.
Photonics Research
  • Apr. 27, 2021
  • Vol.9, Issue 4 (2021)
On the Cover
Photonics integration is a burgeoning field from both academic and industrial points of view because of its great potentials in aggregating photonic technology with high-performance integrated circuits that may revolutionarily change the architecture of computing. However, many photonics integration platforms suffer from huge challenges in robustness, which make device fabrication, assembling and packaging not compatible with massive production and large-scale integration. To this end, topological concepts are applied and successfully clarified many extraordinary phenomena and further promoted the performance of many devices, as a result, spawn a new branch of modern optics – topological photonics.
Photonics Research
  • Apr. 13, 2021
  • Vol.8, Issue 11 (2020)
On the Cover
Optical imaging typically relies on a camera with millions of photodetectors. By contrast, imaging can also take place with a single detector. This is particularly advantageous for imaging at non-visible spectrum where the conventional pixelated cameras lose the sensitivity or become very costly for a good performance.
Photonics Research
  • Mar. 31, 2021
  • Vol.9, Issue 3 (2021)
On the Cover
With advanced nanotechnology, the emerging structural color filter which works based on the light-matter interaction is able to overcome the drawbacks of the traditional dye-based color filters including environmental hazards and performance degradation. Therefore, it has been regarded as an essential optical component and widely applied in daily life.
Photonics Research
  • Mar. 23, 2021
  • Vol.9, Issue 1 (2021)
On the Cover
Electromagnetic waves with higher spectral purity, frequency stability, and accuracy are consistently pursued in communication, radar systems and global position systems for the goal of large communication capacity and high positioning accuracy. Microwave frequency synthesizers are frequently employed for their generation at any desired frequencies in the microwave region with the same excellent frequency stability and accuracy as those of microwave oscillators or clocks, supporting the variety of applications listed above.
Photonics Research
  • Mar. 22, 2021
  • Vol.9, Issue 2 (2021)
On the Cover
High-accuracy long distance ranging plays a significant role in frontier sciences and advanced industrial processing, such as satellite formation flying, spacecraft landing, synthetic aperture radar (SAR), large-scale profile meter, which heavily relies on the precision of a real-time position detection system. During the past decades, laser-based light detection and ranging (LIDAR) takes a major interest in the scientific community for the high angle, distance and velocity resolution, high anti-interference capability.
Photonics Research
  • Jan. 14, 2021
  • Vol.8, Issue 12 (2020)
On the Cover
The pursuit of optical-electrics with small size, integration and fast operation requires the efficient control of photon coupling and propagation at nanoscale. The coupling of luminescent medium to optical cavity promotes the directional transmission and reduce the loss of light. Moreover, the confined light can interact with medium.
Photonics Research
  • Dec. 02, 2020
  • Vol.8, Issue 11 (2020)
On the Cover
Active sources such as lasers and amplifiers are essential components for photonic integrated circuits (PICs) serving a myriad of applications. Silicon nitride (Si3N4) photonics, due to its low propagation loss (~0.1 dB/cm), wide transparency window (~400 nm to 2.35 µm) and good CMOS compatibility, is found to have increasing number of applications in the fields such as microwave photonics, nonlinear photonics, bio-sensing, and in technology towards autonomous driving like lidar and gyroscopes. In most applications, integration of active components onto the passive Si3N4 platform is required. The integration of III-V semiconductor optical amplifiers (SOAs) and Si3N4 by butt-coupling has led to external cavity lasers of exceptional performance. However, sophisticated assembly and packaging steps with high precision alignment are required, which significantly limits cost-effective scaling of manufacturing.
Photonics Research
  • Nov. 04, 2020
  • Vol.8, Issue 10 (2020)
On the Cover
Active imaging over long ranges is of considerable interest in a wide range of applications including remote sensing and target recognition. Single-photon light detection and ranging (LiDAR) presents single-photon sensitivity and picosecond time resolution, which is desirable for long-range imaging. Important progress has been made in the field, and 3D imaging at up to10-km range has been reported. However, further expanding the imaging range presents enormous challenges, because only weak echo photons return and are mixed with strong noise.
Photonics Research
  • Nov. 04, 2020
  • Vol.8, Issue 9 (2020)
On the Cover
Smith-Purcell radiation (SPR) is the electromagnetic wave generated by free electrons passing above a diffraction grating, which has played an important role in free electron light sources and particle accelerators. Since SPR is derived from the scattering of the evanescent wave around the free electrons by grating, the characteristics of SPR, including radiation wavelength, intensity, and polarization, could be controlled by manipulating the free electrons and the structure interacting with electrons. In recent years, orbital angular momentum (OAM) has been known as a new degree of freedom of light, which shows promising application in increasing the bandwidth of optical communication, manipulating micro-particles, fabrication of nano-structures, and so on.
Photonics Research
  • Sep. 10, 2020
  • Vol.8, Issue 8 (2020)
On the Cover
Airy optical beams have come out to stir up enormous research interests due to their extraordinary characteristics of self-accelerating, self-healing, and being nearly diffraction free. There are various schemes to generate Airy beams, for instance, using spatial light modulators (SLMs). However, they significantly condense the quality of the generated Airy beams due to the poor phase discretization, as Airy beams possessing specific characteristics need phase profiles with large phase slope. Although lately several plasmonic or dielectric metasurface-based generators provide phase profiles with subwavelength pixelization offering a compact and cost-effective platform, the method based on synchronous manipulation of the amplitude and phase limits the generation efficiency of Airy beams. Besides, most of currently demonstrated metasurface-based Airy beam generators are polarization-sensitive.
Photonics Research
  • Aug. 07, 2020
  • Vol.8, Issue 7 (2020)
On the Cover
Optical vortex is a special light field with a helical phase front. Due to the helical phase distribution, there is a phase singularity at the center of the vortex field, which causes a point of zero intensity. These unique optical properties make optical vortex show strong application value in many frontier fields including super-resolution imaging, optical manipulation and quantum information technology.
Photonics Research
  • Jul. 09, 2020
  • Vol.8, Issue 6 (2020)
On the Cover
As a basic optical element, micro-resonator has been playing an important role in the field of silicon photonics. Ultra-high-Q and compact micro-resonators are recognized as the key for many functional devices for optical filtering, lasering, optical modulation/switching and all-optical photonics. Unfortunately, it is still challenging to realize compact silicon micro-resonators with Q>106 because silicon photonic waveguides fabricated with standard CMOS processes usually have a propagation loss of >1 dB/cm.
Photonics Research
  • Jun. 09, 2020
  • Vol.8, Issue 5 (2020)
On the Cover
Inverse design is an attractive and emerging approach to achieve ultra-compact, high-performance, and even new-function integrated silicon photonic devices. Inverse-designed integrated photonic devices can usually have two types of subwavelength structures, "analog" and "digital". For the analog subwavelength photonic device, the cell structure (called "pixel") has a fine size, and the device etched pattern usually has a complex boundary of "arbitrary" bending; its high degree of freedom in inverse design may theoretically achieve high-quality design goals, but the performance of the device is usually greatly affected by fabrication errors. For the digital subwavelength photonic device, the pixel size is generally about an order of magnitude larger, and the device etched pattern has relatively regular rectangular or circular boundaries; the inverse design of digital devices can use simple optimization algorithms to obtain excellent performance and large fabrication tolerance.
Photonics Research
  • May. 15, 2020
  • Vol.8, Issue 4 (2020)
On the Cover
In physics and other science disciplines, it has long been a fundamental issue to make a bridge connecting effectively and efficiently an object in the microscopic world and the observer in the macroscopic world. This is by no means an easy task and it needs great cautions, skills and wisdoms to accomplish.
Photonics Research
  • Apr. 16, 2020
  • Vol.8, Issue 3 (2020)
On the Cover
A photonic spin Hall (PSH) device sorts photons with different spin states and is a fundamental component of photonic information technologies. However, the PSH effect is rather weak for measurements using bulky and expensive equipment. The metasurface is a promising way to dramatically shrink an optical element to a size suitable for photonic spin devices. Using V-shaped nano-antennas, a metasurface device with a strong PSH effect is demonstrated with normal incidence. The emergence of a variety of Pancharatnam–Berry phase components has led to development of various photonic spin devices. However, most of these metasurface devices suffer from the low efficiency issues. On-chip photonic spin devices are also designed based on spin-orbital coupling by using micro-disks and nano-antennas, but the intrinsic resonance in this design limits the device’s bandwidth and prevents the wide use.
Photonics Research
  • Mar. 24, 2020
  • Vol.8, Issue 2 (2020)
On the Cover
Owing to their ultracompact physical sizes, highly localized coherent output, and efficient waveguiding, one dimensional (1D) components, such as nanowires (NWs), nanotubes, and microwires (MWs), have been considered as one of the most promising building blocks for fully integrated nano/microscale photonic and optoelectronic devices. ZnO has been recognized as a competent candidate for photoelectronic devices because of their excellent inherent electronic and optoelectronic properties. In the study of the research group from Nanjing University of Aeronautics and Astronautics (NUAA), individual ZnO MWs with controlled Ga-doping concentration (ZnO:Ga MWs) were successfully prepared in the synthesis process via chemical vapor deposition (CVD) by means of adjusting the Ga2O3 weight ratios in the precursor reaction mixtures, as well as corresponding the sizes of MWs.
Photonics Research
  • Mar. 17, 2020
  • Vol.8, Issue 1 (2020)
On the Cover
Terahertz (THz) imaging, benefiting from THz radiation’s capabilities of non-ionizing and penetration of non-conducting materials, serves as a cutting-edge non-destructive evaluation technology. One of the major challenges in photonics is complex amplitude wavefront sensing, the amplitude image indicates the absorption properties, while the phase image reveals the refractive and thickness information, thus simultaneously determining that the amplitude and phase distributions of the wavefront are highly desirable for applications ranging from bioimaging to material characterization. Due to the long wavelength of the THz wave, the imaging resolution is also one of the key considerations for THz applications.
Photonics Research
  • Feb. 12, 2020
  • Vol.7, Issue 12 (2019)
On the Cover
Inspired by the discovery of graphene, researchers have developed a family of two-dimensional (2D) layered materials and investigated their unique optoelectronic properties. Molybdenum disulfide (MoS2), as a kind of typical 2D material, has been intensively investigated due to potential applications in novel electrical and optoelectronic devices. However, in spite of great efforts dedicated to 2D MoS2 study from both experiment and theory, the main challenge remained to be addressed is to achieve 2D MoS2 with high quality and large area, which is the key point for realization of its commercial application.
Photonics Research
  • Oct. 30, 2019
  • Vol.7, Issue 10 (2019)
On the Cover
To confirm the feasibility of the new thin film LN approach, Dr. Lutong Cai and Prof. Gianluca Piazza from the Department of Electrical and Computer Engineering at Carnegie Mellon University carried out the first proof-of-concept work of implementing AO modulation devices in LNOI. This work is published in Photonics Research, Volume 7, No. 9, 2019 (L. Cai, et al., Acousto-optical modulation of thin film lithium niobate waveguide devices).
Photonics Research
  • Oct. 11, 2019
  • Vol.7, Issue 9 (2019)
On the Cover
The sophisticated technology that powers face recognition in many modern smartphones someday could receive a high-tech upgrade that sounds-and looks-surprisingly low-tech.This window to the future is none other than a piece of glass-and University of Wisconsin-Madison engineers have devised a method to create pieces of smart glass that can recognize images without requiring any sensors or circuits or power sources.
Photonics Research
  • Aug. 14, 2019
  • Vol.7, Issue 8 (2019)
On the Cover
1 Gbps free-space deep ultraviolet communications based on micro-LEDsDeep Ultraviolet (UV) light with wavelengths below 300 nm is widely used for many different kinds of applications as these short wavelengths can trigger chemical reactions and excite fluorescence in materials. This makes deep UV extremely useful for label tracking, optical sensors, disinfection and decontamination of surfaces and water, curing materials and forensic or drug detection. These applications have driven the development of compact and efficient AlGaN-based deep UV light emitting diodes (LEDs). Another intriguing application is deep UV free-space optical communications, the potential of which has been known for some time, as the properties of light at these short wavelengths can enable unique embodiments of this technology. For example, as most of solar deep UV radiation is absorbed by the ozone layer in Earths stratosphere, deep UV provides the opportunity to establish high-security free-space optical communication links between satellites in the upper atmosphere where the atmosphere "shields" the communication links from attempts at eavesdropping. Furthermore, since deep UV is strongly scattered in air, a low background noise non-line-of-sight (NLOS) optical communication link with low pointing, acquisition and tracking requirements can be constructed using deep UV light sources on the ground. As a result, it is possible to build a multi-access NLOS optical communication link by using deep UV transmitters. While deep UV communication links have been reported, their performance has been severely limited by the low efficiency and/or modulation bandwidth of the light sources, being either flash tubes, lamps or conventional deep UV LEDs. Therefore, developing deep UV light sources with high modulation bandwidth is of paramount importance.In recent years, micro-LEDs (μLEDs) have been developed as novel transmitters for visible light based free-space optical communications. These μLEDs, which have lateral dimensions of less than 100 μm, have extremely high modulation bandwidths (in excess of 800 MHz has been reported) which is enabled by their small feature size, which in turn supports very high wireless data transmission rates. It is well known that the modulation bandwidth of LEDs is determined by two factors, namely the resistance-capacitance (RC) time constant and the differential carrier lifetime. For conventional LEDs, the modulation bandwidth is mainly dominated by a large RC time constant due to the large area of the LEDs. As a result, the modulation bandwidth of conventional LEDs is relatively low, typically on the order of 10 MHz. However, in contrast, the modulation bandwidth of μLEDs is mainly dominated by their differential carrier lifetime, thanks to their small area. This carrier lifetime is the average time for electrical charge carriers take to recombine inside the µLEDs active region and emit light. The shorter the lifetime, the more rapidly the µLEDs optical output can respond to a fast electrical signal and therefore the higher the devices modulation bandwidth. The small feature size of μLEDs allows them to be driven at very high current densities which, since the carrier lifetime generally decreases at higher current densities, means that the modulation bandwidth of μLEDs can be an order of magnitude higher than that of conventional LEDs. These novel characteristics make μLEDs strong transmitter candidates for high-speed free-space optical communications. For example, a data transmission rate over 10 Gbps at a free-space transmission distance of 5 m was recently demonstrated using a series-biased μLED as a transmitter in a visible light free-space optical communication system. It is expected that the µLED device format can also be used to achieve high modulation bandwidths at deep UV wavelengths.The researchers from the Institute of Photonics, University of Strathclyde and Li-Fi R&D Centre, University of Edinburgh have investigated the modulation characteristics of μLEDs emitting in the UV-C region (200-280 nm) and their applications as light sources in deep UV free-space optical communications. The research results are published in Photonics Research, Volume 7, No. 7, 2019 (X. He, et al., 1 Gbps free-space deep-ultraviolet communications based on III-nitride micro-LEDs emitting at 262 nm).The deep UV μLEDs fabricated in this work present a great improvement in the modulation bandwidth, which is around 3 times higher than the previously reported modulation bandwidths of other UV-C LEDs. Moreover, at low current densities, the measured modulation bandwidth of the deep UV μLEDs is much higher than that of visible μLEDs, which illustrates the huge potential of the deep UV μLEDs for high-speed free-space optical communications. By applying these deep UV μLEDs into a free-space optical communication link, the data transmission rate is significantly increased, which is more than 15 times higher than the previously reported deep UV optical wireless links. Moreover, the measured modulation bandwidths of the deep UV μLEDs and system data transmission rates are limited by the cut-off frequency of the avalanche photodiode (APD) detector used for the measurement. The researchers consider that an even higher modulation bandwidth of the deep UV μLEDs and, in turn, an even higher deep UV data transmission rate will be achieved if a higher modulation bandwidth APD detector can be applied.This work presented the excellent modulation performance of the deep UV μLEDs. Moreover, the application of these μLEDs in deep UV high-speed free-space optical communications has also been demonstrated. Future work will focus on the further optimizations of the deep UV μLEDs and optical set up in order to fully explore and realize the potential of these deep UV μLED transmitters. Recently, by adjusting the optical set up and using a high modulation bandwidth APD detector, a deep UV data transmission rate over 3 Gbps is achieved at a free-space transmission distance of 1 m. Furthermore, a NLOS communication link based on the deep UV μLEDs will be constructed in the future.Cross-sectional schematic diagram of a single deep-ultraviolet μLED
Photonics Research
  • Aug. 13, 2019
  • Vol.7, Issue 7 (2019)
On the Cover
The device introduced by Dr. Henri Partanen from a research group from the University of Eastern Finland in Photonics Research, Volume 7, Issue 6, 2019 (H. Partanen, et al., Spectral measurement of coherence Stokes parameters of random broadband light beams) is a general-purpose device to measure the spectral two-point Stokes parameters of arbitrary broadband light beams. To demonstrate the system a well-defined test source with complicated electromagnetic coherence properties is constructed. This is achieved by modulating a uniformly linearly polarized, spatially partially coherent light from a superluminescent diode with a quartz wedge depolarizer leading to a beam with spatially and spectrally varying electromagnetic coherence structure. In order to verify the beam characteristics experimentally we measure the spectral electromagnetic two-point Stokes-parameter distributions, which is achieved in terms of standard, commonly available devices: a double-pinhole interferometer (digital micromirror device), suitable polarization elements (circular polarizers), and a spectrometer (grating). The setup is flexible as the individual components can be chosen for specific situations, e.g., the interferometer can be replaced with a more light-efficient wavefront folding interferometer. As a secondary result, the coherence and polarization variations as a function of wavelength were found to take place at a subnanometer scale.
Photonics Research
  • Jul. 08, 2019
  • Vol.7, Issue 6 (2019)
On the Cover
Metasurfaces have enabled rapid development of ultrathin optical devices that can modify the light wavefront by altering its phase and amplitude. Since metasurfaces open a new route to redirect a reflected wave around the object, numerous structures have been put forward to reduce the reflection and scattering of objects, resulting in desired camouflage or invisibility. However, most current phase-gradient metasurfaces are designed in only a single spectrum with narrow bandwidth. Though some dual-band and wideband approaches are achieved by the vertical stacking of metasurfaces, the volume and fabrication difficulty are inevitably increased. In addition, these low-reflection metasurfaces generally cannot achieve thermal invisibility at the same time due to their high infrared absorption/emission arising from the complex metal–dielectric composites.In order to provide a solution to this challenge, a team of researchers from the State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences presents a kind of ultrathin silicon-based metasurfaces to simultaneously implement low infrared specular reflection and emission in dual-band and ultra-broadband ranges, respectively. Related research results are published in Photonics Research, Vol. 7, Issue 5, 2019 (Xin Xie, et al.. Dual-band and ultra-broadband photonic spin-orbit interaction for electromagnetic shaping based on single-layer silicon metasurfaces).Both the metasurfaces comprise a monolayer of amorphous silicon gratings with the same geometry but diverse spatial orientations tiled on a metal mirror, which can generate high-efficiency dual-band and ultra-wideband photonic spin-orbit interaction and geometric phase. The first one is designed to suppress the specular reflectances in dual-band of 1.05-1.08 μm and 5-12 μm below 10%. The second one is for an ultra-broadband of 4.6-14 μm. At the same time, the presented structures exhibit low thermal emission due to the low absorption loss of silicon in the infrared spectrum, which can be regarded as an achievement of laser-infrared compatible camouflage.Dr. Xin Xie from the research team believes that this work provides a new idea for multispectral and multifunctional electromagnetic wave modulation. Further work will focus on how to extend this strategy to tunable metasurfaces to achieve dynamic electromagnetic camouflage.Single-layer silicon metasurfaces that can achieve high-efficiency dual-spectrum or ultra-broadband photonic spin-orbit interaction and geometric phase modulation.
Photonics Research
  • May. 23, 2019
  • Vol.7, Issue 5 (2019)
On the Cover
Micro light-emitting diodes (μLEDs) are promising candidates for the next generation display technology. However, the efficiency of μLEDs decreases as the size shrinks. Additionally, in order to realize monolithic full-color micro-display, the cost of the RGB mass transfer is enormous, and the color conversion efficiency of the quantum dot (QD) color conversion technology still needs to be improved.In order to enable μLEDs to be mass-produced as soon as possible. A research group, led by Prof. Hao-Chung Kuo from Institute of Electro-Optical Engineering in Taiwan Chiao Tung University and Dr. Tingzhu Wu from Department of Electronic Science in Xiamen University, carried out the study of full-color monolithic hybrid quantum dot nanoring (NR) μLEDs with improved efficiency. The research results are published in Photonics Research, Volume 7, Issue 4, 2019 (S. Huang Chen, et al., Full-color monolithic hybrid quantum dot nanoring micro light-emitting diodes with improved efficiency using atomic layer deposition and nonradiative resonant energy transfer).This study reports a novel structure which is the hybrid quantum dot NR micro-LED (QD-NR-μLED). NR structures are fabricated on a green LED epitaxial wafer; the color of NR-μLEDs is tuned from green to blue through strain relaxation. Using the technology of atomic layer deposition (ALD), a 1-nm Al2O3 layer is deposited on the sidewall of blue NR-μLEDs, which improves the photoluminescence intensity of blue NR-μLEDs by 143.7%. Coupling with the exposed multiple quantum wells through nonradiative resonant energy transfer (NRET), red QDs are printed to blue NR-μLEDs for a full-color display. To further improve the color purity of the red light, a distributed Bragg reflector is developed to reuse the excitation light.In this work, the NR structure provides a structural basis for monolithic full-color micro-display. The ALD sidewall passivation technology improves the luminous efficiency of μLEDs. The NRET mechanism improves the color conversion efficiency of red quantum dots. Therefore, Prof. Kuo and Dr. Wu believes that this novel QD-NR-μLEDs can provide a new idea and a new method for the application of full color micro-displays.Further work will focus on the optimized thickness of ALD layer as well as how to combine QD-NR-μLEDs with a flexible substrate to achieve flexible transparent micro-displays.Three subpixels of a green μLED, a blue NR-μLED, and a red QD-NR-μLED, with the deposition of a transparent conducting oxide layer and the pn electrodes.
Photonics Research
  • Apr. 22, 2019
  • Vol.7, Issue 4 (2019)
On the Cover
Conventional photodiode detectors made of crystalline semiconductor materials may have special requirements on fabrication affecting device integration, and their response wavelengths are limited by bandgaps, thereby causing limitation on many applications. Comparatively, plasmonic hot electron photodetectors are advantageous in these aspects. The desired response waveband can be obtained by employing appropriate materials and the response spectrum can be adjusted with designed plasmonic characteristics. Therefore, such a type of photodetectors has a broad application prospect in the field of integrated photonics. However, plasmonic hot electron photodetectors require the fabrication of nanostructures, mostly relying on electron beam lithography at present. Not only the process cost is high, but also large-area fabrication is challenging.In order to provide a solution to this challenge, a nanocone array template is formed on a silica substrate by plasma etching using a monolayer polystyrene nanosphere mask. Metal-semiconductor-metal films are successively deposited on the template, forming an MSM structure for photodetector devices. This work is carried out by Prof. Ting Mei’s group from the Shaanxi Key Laboratory of Optical Information Technology, Northwestern Polytechnical University. The related results are published in Photonics Research, Vol. 7, No. 3, 2019 (Zhiqiang Yang, et al., Silica nanocone array as a template for fabricating a plasmon induced hot electron photodetector).The nanostructures enable surface plasmon excitation by the incident electromagnetic waves, and propagation of surface plasmon polaritons along the Au interface enhances optical absorption in the Au film. Hot electrons are generated due to plasmon decay, and those with energy larger than the Schottky barrier are emitted over the barrier into the TiO2 layer and eventually reach the Al electrode, accomplishing photoelectric conversion. Especially under an external bias, the response of the device increases, and its response peak gradually shifts red, indicating that the tunneling effect of hot electrons increases with increasing bias voltage. The researchers also use finite element simulation and related numerical theory to confirm the experimental results. In this work, costly electron beam lithography is avoided and the size of the device reaches centimeter level, which will be advantageous for the integration of hot electron photodetectors with a vast variety of optoelectronic and microelectronic devices.Prof. Mei believes that this work not only gives a new fabrication process for plasmonic hot electron devices compatible for low-cost large-scale monolithic integration, but also provides theoretical guidance on the excitation and transport processes of hot electrons.Further work will focus on studying nanostructures with stronger plasmon resonance on the basis of which to increase the optical absorption in metal and the efficiency of hot electron generation, and to improve the quantum efficiency of the device.Device architecture of a plasmonic hot electron photodetector based on a silica nanocone template. Hot electrons are excited due to plasmon decay in the Au film and then travel through the TiO2 layer and eventually reach the Al electrode, forming photocurrent.
Photonics Research
  • Mar. 12, 2019
  • Vol.7, Issue 3 (2019)
On the Cover
Silicon photonics has rapidly emerged as one of the most prominent technological platforms for the implementation of integrated optical devices. Its compatibility with standard complementary metal-oxide-semiconductor transistor (CMOS) fabrication processes, has enabled low-cost and high-volume manufacturing, making silicon photonics suitable for the implementation of high bit-rate transceivers for data-centre and direct-detection scheme applications. At the same time, silicon photonics technology has been in the forefront for the realization of a number of integrated components for various applications ranging from sensors to microfluidics.Historically, one of the biggest challenges in designing silicon photonic components, has been related to the realization of high-performance mode converters which can efficiently transfer the light from a standard optical fibre to the integrated circuits. Indeed, this task is particularly challenging due to the strong intrinsic birefringence of integrated silicon waveguides, and to the large size mismatch existing between the optical mode of silicon waveguides and that of single mode fibres (which is almost 800 times larger).To overcome this issue, the scientific community has proposed different solutions over the last 20 years, which can be schematically divided into two main categories: “end-fire” and “vertical” coupling techniques. In “end-fire” configurations the optical coupling takes place at the edge of the chip in a direction parallel to the chip surface thanks to spot size converters; conversely “vertical” coupling occurs when the incoming beam impinges on the silicon chip almost perpendicularly to its surface and takes advantage of diffractive grating couplers to re-direct the incoming radiations.Both coupling strategies have different strengths and weaknesses, in terms of performance and ease of fabrication, and can in turn be divided into many different sub-categories, according to the specific design approach employed, and to the chosen materials and fabrication technology.The group led by Dr. Cosimo Lacava from the Optoelectronics Research Centre, University of Southampton, provides a comprehensive scientific description and view of the various possible solutions that researchers have produced over the last years. They provide the reader with an exhaustive analysis of more than 70 structures reported in the literature, characterized by different level of design and fabrication complexity.In the review they first describe the physical phenomena underlying the optical coupling mechanism; then they analyze the different coupling solutions available, in terms of their performance (such as coupling efficiency, bandwidth, polarization sensitivity and alignment tolerances) and their compatibility with standard CMOS process flows and packaging techniques. For the benefit of the reader, they benchmark the various coupling solutions against each other in a table at the end, providing the reader with a useful reference, without the need to scan the entire review. This work is published in Photonics Research, Volume 7, Issue 2, 2019 (Riccardo Marchetti, et al., Coupling strategies for silicon photonics integrated chips).Dr. Cosimo Lacava comments on this work: “The ability to couple a light beam from a SM-fibre to a nanophotonic circuit has always represented a significant challenge for researches working in this field. Although the wording of the problem is simple (How we squeeze the light into a waveguide, which is 800 times smaller than an optical fibre without losing too much energy?), the physics involved is intriguing and technologically complex, and has inspired many scientists who have developed a number of elegant solutions over the years. If you are starting your career as silicon photonic engineer or simply you are looking at the various solutions available to couple the light to your designed integrated circuit, here we provide a comprehensive reference, containing the most common techniques and solutions to accomplish this basic task, vital for the realization of any modern integrated component.”They believe that future work in the field will be focused on the development of even more efficient coupling structures, where the effort to reduce the couplers insertion loss will have to cope with the necessity to attain full CMOS compatibility and reduction of assembly time and cost, in the perspective of mass-markets manufacturing.Schematic of a Silicon Photonics circuit. Arrays of angle-polished and planar polished fibres are respectively used to couple the grating- and edge-couplers integrated on the chip. An enlarged schematic of a grating is shown at the top.
Photonics Research
  • Mar. 12, 2019
  • Vol.7, Issue 2 (2019)
On the Cover
Nonlinear frequency conversion is a crucial technology for operating high power pulsed laser systems at the arbitrary wavelengths required by applications ranging from biological imaging to undersea communications, among many others. A stable and efficient solution based on guided waves, for instance using optical fibers, is in high demand; however, efforts to generate such a device have been limited by the need to conserve momentum, or phase match, in fibers.Multimode fibers provide the ability to examine nonlinear interactions between guided modes – with the idea multiple modes allow for multiple possible combinations to achieve phase matching. However, in practice, typical intermodal four-wave mixing interactions are only phase-matched over narrow wavelength ranges, leading to impractically narrowband nonlinear gain, inefficiencies in conversion, and limitations in the ability to spectrally and temporally tailor the converted light pulses.To solve this limitation, the research group from the Nanostructured Fibers and Nonlinear Optics laboratory of Boston University, led by Professor Siddharth Ramachandran, has demonstrated that tailoring of the relative intermodal group velocity, in addition to phase matching, is the key to unlocking extended nonlinear gain bandwidths. This new work highlights an intermodal four-wave mixing process where a pump pulse guided in a superposition of the LP0,4 and LP0,5 modes is converted to two group-velocity-matched pulses in the LP0,4 and LP0,5 modes at wavelengths shorter and longer than that of the pump, respectively. By matching the group velocities of these output pulses, the phase-matched bandwidth is increased by more than order of magnitude compared with typical intermodal processes, leading to broadband gain regions separated by nearly an octave (63 nm centered at 1553 nm, and 17 nm centered at 791 nm). By seeding this process, the authors demonstrate an efficient, quasi-CW, high power and wavelength tunable all-fiber analogue of the ubiquitous Ti:Sapphire laser. This work is published in Photonics Research, Volume 7, Issue 1, 2019 (Jeff Demas, et al., Intermodal group-velocity engineering for broadband nonlinear optics).In general, these results represent a new parameter space in which to design and implement intermodal parametric nonlinearities – analogous to group velocity dispersion engineering in photonic crystal fibers. Future work will explore using the design flexibility inherent to these multimode systems to target specific wavelength bands for applications underserved by conventional frequency conversion systems, as well as exploiting the bandwidth and group-velocity-matching in these systems to explore fiber-based four-wave mixing in the ultrafast pulse regime.Schematic of intermodal four-wave mixing: The intense pump pulse (green), guided in a superposition of the LP0,4 and LP0,5 modes (mode image inset), is converted to broadband anti-Stokes (blue) and Stokes (red) pulses along the length of the optical fiber.
Photonics Research
  • Mar. 12, 2019
  • Vol.7, Issue 1 (2019)
Editors' Picks
Two-photon excited fluorescence (TPEF) materials can be excited by a near-infrared laser and emit in the visible light band. In view of their high three-dimensional spatial selectivity and superior imaging penetration depth, TPEF materials and technology have charming application prospect in fields of life sciences and medicine.
Photonics Research
  • May. 31, 2021
  • Vol.9, Issue 5 (2021)
Editors' Picks
As an important supplement to wireless radio frequency communication in free space and acoustic wave communication in underwater environment, visible light communication (VLC) is considered to be a strong contender for the next generation mobile wireless "last mile" access technology, which has great potential to be widely used in 5G+ or 6G.
Photonics Research
  • May. 28, 2021
  • Vol.9, Issue 5 (2021)
Editors' Picks
Promoted by enthusiasm for future massive data processing by photons in parallel architectures, spatial light modulators (SLMs) were invented half a century ago. With the help of external control signals, such devices can manipulate light by modulating its amplitude, phase or polarization both spatially and temporally at will, which enables encoding information into an optical wavefront.
Photonics Research
  • May. 11, 2021
  • Vol.9, Issue 4 (2021)
Editors' Picks
Polarization state, as one of the important properties of light, is widely used in many fields, such as satellite remote sensing, astronomy, polarization imaging, chemical analysis, and biomedical diagnosis. The traditional polarization measurement methods need to rotate the optical components several times to obtain multiple images of different polarization components of the target, so it is impossible to get real-time polarization information of the dynamic target.
Photonics Research
  • May. 06, 2021
  • Vol.9, Issue 4 (2021)
Editors' Picks
Optical and electrical breakdown of materials, which describe material modification in the presence of extreme optical or electrical fields, have been studied since the 1950s. However, simultaneous application of optical and electrical fields, especially, to biologically relevant systems hasnt been explored before. Prof. Vladislav V. Yakovlev from Texas A&M University said by investigating the synergistic action of electrical and optical pulses, they were able to promote highly localized breakdown, while reducing the threshold for such breakdown.
Photonics Research
  • Apr. 07, 2021
  • Vol.9, Issue 3 (2021)
Editors' Picks
In the quantum optics research area, a central goal is to develop techniques for a complete control of light-matter interaction at the single-quantum level, which underlies the essential physics of many phenomena and applications. A new quantum revolution on optics and photonics is also accelerating the progress of quantum information processing (QIP), with the rapid innovation of the advanced photonic nanomaterials and processing technologies.
Photonics Research
  • Mar. 26, 2021
  • Vol.9, Issue 3 (2021)
Editors' Picks
Recent explosive expansion of web-based video platform services pushes the data traffic increase enormously, and has become a driving force in the development of the next-generation communication technologies. The number of communication channels in optical communication is upgraded by using the wavelength division multiplexing (WDM) technology. The bottleneck of communication capacity occurs at the fronthaul connecting radio-access networks of 5G communication.
Photonics Research
  • Mar. 17, 2021
  • Vol.9, Issue 2 (2021)
Editors' Picks
Dichroic laser mirrors are usually used as harmonic separators, beam combiners or splitters, and play an important role in many laser applications, including inertial confinement fusion laser, petawatt femtosecond laser, high power fiber lasers, compact Q-switched or mode-locked lasers, and other emerging lasers.
Photonics Research
  • Mar. 11, 2021
  • Vol.9, Issue 2 (2021)
Editors' Picks
Over the past decades, the advent and development of electronic integrated circuits and optical communication technology has brought the global human society into the "Information Explosion" era. Recently, owing to the soaring demand on information exchanging and processing speed and efficiency, photonic integrated circuit (PIC) has attracted tremendous interest for the potential to provide the better performances than its electronic counterpart.
Photonics Research
  • Mar. 09, 2021
  • Vol.8, Issue 12 (2020)
Editors' Picks
The interference phenomenon forms the most important evidence of the wave-like property of light. The phase of the wave is the key concept underlying the interpretation of constructive and destructive interferences of superposed light beams. On the other hand, it is known that even when light is considered as a particle or photon, a single photon can interfere with itself. Although light exhibits both wave- and particle-like properties, the linear superposition of the field amplitudes for light waves is the same as that of the probability amplitudes of a photon in the case of first-order interference.
Photonics Research
  • Feb. 23, 2021
  • Vol.9, Issue 1 (2021)
Editors' Picks
Optical modulators provide the information encoding engines for most long-haul terrestrial and undersea fiber-optic transmission systems. The Internet that connects the people and businesses around the world can be possible because of the widespread of reliable, low-loss and high-speed optical modulators. As the trend toward ever-increasing bandwidths in fiber-optic communications continues, the optical modulator will remain an indispensable component for transmitting information. Today, hundreds of millions of modulators have been deployed worldwide, and many of them are lithium niobate (LiNbO3) modulators.
Photonics Research
  • Jan. 08, 2021
  • Vol.8, Issue 12 (2020)
Editors' Picks
With the booming development of cloud services, artificial intelligence (AI) and 5G applications, the explosive growth of global traffic requires higher and higher bandwidth of data center interface. As the 400GbE standard has been approved as IEEE Std 802.3bs, more and more researches are focusing on next generation of 800 Gb transceiver technology and its standard.
Photonics Research
  • Dec. 18, 2020
  • Vol.8, Issue 11 (2020)
Editors' Picks
InGaN-based materials have broad application prospects in visible light range due to its tunable wide band-gap. Micro size light emitting diode (micro-LED) display is one of the most promising applications. Future smart phones, watches, virtual reality glasses, and other small screens will benefit from micro-LED technology.
Photonics Research
  • Nov. 26, 2020
  • Vol.8, Issue 11 (2020)
Editors' Picks
Solitons, non-spreading wave structures, are universal in a variety of research fields that ranging from fluid and condensed matter physics to chemistry and neurobiology. Optical solitons can be formed and propagated in laser cavities with remarkable stability thanks to a double balance between loss and gain and between dispersion and nonlinearity. Optical solitons show particle-like interactions and can form various bound states akin to chemical molecules, which are frequently referred as soliton molecules. Soliton molecules have attracted tremendous attention due to their potential to upgrade the transmission capability of optical communication and to demonstrate complex soliton interaction behaviors in dynamical nonlinear systems.
Photonics Research
  • Oct. 29, 2020
  • Vol.8, Issue 10 (2020)
Editors' Picks
In recent years, the 2 μm waveband has attracted increasing research for broad applications, including optical communication, optical sensing, and even the next generation of gravitational-wave observatories. Particularly, thanks to hollow-core fibers with low latency and low loss in an ultrawide bandwidth, and thulium (Tm) doped fiber amplifiers with a broad gain spectrum, 2 μm possesses the promising application of next-generation optical communication with ultralow latency and further higher capacity. Several 2 μm optical short-reach interconnections over hollow-core fibers have been carried out in our previous works, achieving a record single-lane speed of 100 Gbps. Meanwhile, the photonic integrated platform for 2 μm optical interconnection is also an essential field that needs to be exploited.
Photonics Research
  • Oct. 09, 2020
  • Vol.8, Issue 9 (2020)
Editors' Picks
Quantum optical coherence tomography (QOCT) was proposed some time ago as a highly promising alternative to its classical counterpart for obtaining morphological information of semi-transparent, e.g. biological, samples. In particular, since the time when QOCT was first proposed two key advantages were identified with respect to an equivalent classical system: even-order dispersion cancellation in the sample under study, as well as a factor-of-two improvement in axial resolution. However, the low-flux nature of photon pair sources and the resulting long times of data acquisition, have severely limited the practical applicability of QOCT. Our present work aims to overcome some of these limitations through the implementation of a Fourier domain version of the technique which eliminates the need for axial scanning.
Photonics Research
  • Sep. 10, 2020
  • Vol.8, Issue 6 (2020)
Editors' Picks
High-performance swept sources with high sweep rate, flat spectrum, wide sweep range and long coherence length will find applications in many photonic systems, especially in optical coherence tomography (OCT) and LiDAR. OCT technology was rapidly commercialized after its invention by D. Huang et al. in 1991. Swept source OCT is a promising candidate to satisfy the increasing demand for real-time high-speed imaging in the next generation OCT. In a swept source OCT system, a single-point high-speed photodetector is utilized to acquire the interference signal of the reflected light from the reference arm and the sample arm of the Michelson interferometer. The axial scan rate can be up to tens of millions of scans per second benefiting from the high-speed photodetector and the motionless configuration. When the bandwidth of the photodetector is sufficiently large, the performance of the swept source OCT depends predominantly on the performance of the swept source. MEMS-VCSEL, Fourier domain mode locked laser, and time-stretched swept laser have been proposed to be the swept sources of megahertz OCT. Among them, the swept source based on time-stretching is the only technology that has demonstrated sweep rates higher than 10 MHz. A highly coherent seed laser with a high repetition rate and a broad flat spectrum is the key to generate high performance time-stretched swept source. The spectrum of mode locked fiber laser output however is not sufficiently broad for time stretching. Supercontinuum can achieve a broad spectrum but suffers from the large shot-to-shot spectral fluctuation, which impedes its application in time-stretching. Finally, reconfiguration of time-stretched swept sources to operate at different sweep rates has not been demonstrated.
Photonics Research
  • Sep. 10, 2020
  • Vol.8, Issue 8 (2020)
Editors' Picks
Data communications in data centers and high-performance computing (HPC) have grown tremendously due to emerging applications in social media, video streaming, artificial intelligence (AI), and the internet of things (IoT). Hyperscale data centers and Exascale HPC require high-bandwidth and energy-efficient optical interconnects. In this context, silicon photonic interconnects are attractive, thanks to the high integration and low cost. To further increase the data rate, advanced modulation formats are preferred which can relax the bandwidth limitation of integrated circuitry or optical devices. However, the optical link may suffer degraded signal-to-noise ratio (SNR), which requires either a higher-power laser or a higher-sensitivity receiver to retain the bit error rate (BER). Using a receiver with better sensitivity can yield a lower total link power consumption compared to using a high-power laser and consequently improve the energy efficiency. Particularly, high-sensitivity detectors relax the link budget requirements for on-chip lasers with limited output power. An avalanche photodiode (APD) with internal gain is the ideal candidate to increase the receiver sensitivity. Since APDs introduce the excess noise while bringing the multiplication gain, a novel device structure with optimum layer thickness and doping profile is necessary for higher gain and lower noise. Typically, there are trade-offs among APD design metrics: breakdown voltage, quantum efficiency, multiplication gain, bandwidth, and excess noise. It is a big challenge to decouple these trade-offs and optimize the overall performance.
Photonics Research
  • Sep. 03, 2020
  • Vol.8, Issue 7 (2020)
Editors' Picks
Visible light communication (VLC) is a wireless method that enables high-speed transmission of data with visible light. This data is transmitted by modulating the intensity of light given off by a light source. The signal is received by a photodiode device that transforms the data into forms that are readable and readily-consumed by end users. It is widely expected that VLC systems and their extension to fully networked, bi-directional multiuser wireless systems referred to as LiFi will play a key part in 5G-and-beyond connectivity, especially for indoor environments.
Photonics Research
  • Sep. 03, 2020
  • Vol.8, Issue 7 (2020)
Editors' Picks
UVC-LEDs with light emission from 200-280 nm were mainly used to introduce germicidal radiation to microorganisms (bacteria, viruses, spores and other pathogens). It damages and changes the structure of DNA (deoxyribonucleic acid), so that the microorganisms die or loss the reproduction capability immediately, and achieve the purpose of sterilization and disinfection. UVC-LED has a great market potential with a wide range of applications in air sterilization, surface disinfection and water treatment, because of its stability and safety, environmental friendliness, long lifetime, low maintenance cost and zero chemical residue. However, the biggest challenge for the UVC-LED is its low external quantum efficiency and insufficient output optical power density under high current. In addition to the poor quality of the Al-rich UVC epitaxial material and the low injection efficiency of the carrier, the main reason for the low quantum efficiency is due to the low extraction efficiency of TM mode (E//C) photons. TM mode UVC photons are confined in the epitaxial layer and suffer from the total internal reflection and re-absorption. Previous methods known to improve the light extraction of visible LEDs have little effect on TM mode light in the UVC-LED.
Photonics Research
  • Jul. 30, 2020
  • Vol.8, Issue 6 (2020)
Editors' Picks
The amplitude, phase, and state of polarization (SOP) are fundamental parameters for describing light waves. The real-time measurement of the polarization and phase information of light is very important and desirable in optics. At present, however, most photodetectors are only sensitive to the light intensity, which makes traditional polarization and phase detection systems complex, bulky and difficult to integrate.
Photonics Research
  • May. 21, 2020
  • Vol.8, Issue 4 (2020)
Editors' Picks
An optical vortex refers to a beam whose wavefront shows a helical shape. Compared with the conventional Gaussian beam, since the optical vortex has doughnut intensity distribution and orbital angular momentum (OAM), it has acquired considerable interest in quantum information, optical trapping and manipulation, super-resolution microscopy and high-order harmonic generation (HHG). Spurred by these exciting technologies, widespread attention has been paid to the generation and manipulation of optical vortex. However, due to the low damage threshold and transmittance of optical components, it is difficult to directly generate high-energy mid-infrared (mid-IR) femtosecond optical vortex pulses using spiral phase plates (SPPs), spatial light modulators (SLMs), etc. Optical parametric chirped pulse amplification (OPCPA), combining optical parametric amplification (OPA) and chirped pulse amplification (CPA) technologies, displays unique advantages, such as high gain, high temporal contrast, less thermal effect and tunable wavelength, and it has been widely employed in recent high peak power laser systems. Therefore, OPCPA is able to be an effective technology to generate high energy femtosecond mid-IR optical vortices.
Photonics Research
  • Apr. 30, 2020
  • Vol.8, Issue 3 (2020)
Editors' Picks
Due to its excellent electro-optical and nonlinear optical properties, paired with a relative easiness of fabricating waveguides, the lithium niobate (LN) crystal has its place as an ideal platform for highly efficient and compact devices for quantum and/or classical optical applications. Up to now, most of commercially available integrated optics devices are based on LN waveguides fabricated either by Ti-indiffusion or by one of the conventional liquid-phase Proton Exchange techniques. These techniques allow fabricating waveguides with preserved electro-optical and nonlinear properties but, unfortunately, exhibiting low-index contrast typically in the range of 0.01 and 0.03. These low values limit the benefit linked to the confinement of the light in a waveguide. In this context, the challenge of modern photonics based on LN is to provide integrated configurations that ideally meet all these requirements: high-index contrast, low propagation losses, undegraded optical nonlinearity and electro-optical efficiency, stability, robustness, compactness, easiness of implementation, and low power consumption.
Photonics Research
  • Apr. 01, 2020
  • Vol.8, Issue 1 (2020)
News
Silicon photonics has been developing at an increasingly fast pace with many passive and active silicon photonic devices demonstrated with unprecedented performances. Large-scale silicon photonic circuits have been realized with high integration density for many applications ranging from telecom and Datacom to sensing, metrology, and quantum photonics. This special issue aims to provide a comprehensively overview of this exciting field, including recent progress, in-depth discussions of the state-of-the-art, and insights into forthcoming developments from worlds most prominent research groups driving silicon photonics technology into its next-generation phase.
Photonics Research
  • May. 25, 2021
  • Vol., Issue (2021)
News
Recent progress in photonics research has led to the discovery of novel optical materials, in which metallic halide perovskites plays a large role for semiconductor photonics. Owing to their stunning optical properties, perovskites have been widely considered as promising platforms for the manipulation of photons in free space/matter based on bulk and low-dimensional systems. Recently, a series of significant efforts and breakthroughs in perovskite photonics have been reported by institutions and companies around the world, opening a bright path to demonstrating next-generation excellent-performance, low-consumption optoelectronic devices.
Photonics Research
  • Feb. 24, 2020
  • Vol.8, Issue (2020)
News
This feature issue in Photonics Research will serve as a venue for the most recent publications in the areas of emerging topological photonics and beyond, reporting recent results and innovative approaches for integrating topological physics in photonics with nonlinear, synthetic, or quantum photonic systems.
Photonics Research
  • Feb. 24, 2020
  • Vol.8, Issue (2020)
Spotlight on Optics
Understanding matter—a collection of many interacting constituents, such as atoms and electrons, which is a major endeavor in physics. Discoveries of topological insulator and quantum Hall effect have boosted the exploration of novel topological phases of matters. It provides both fascinating physics and exciting opportunities for devices.
Photonics Research
  • Apr. 22, 2021
  • Vol.9, Issue 1 (2021)
Spotlight on Optics
Organic solar cells (OSCs) have many advantages such as low cost, light weight, and flexibility. They have broad prospects and have become one of the most important directions in photovoltaic technologies. Large-area fabrication of organic photovoltaic modules (OPMs) is the key technique to realizing the commercialization of organic photovoltaics. Therefore, it has great practical significance to develop the high-performance large-area OPMs.
Photonics Research
  • Apr. 14, 2021
  • Vol.9, Issue 3 (2021)
Spotlight on Optics
Optical fiber is the most broadly used optical waveguide for transmitting light because of its low loss transmission even over long distances and its flexibility, which has been used for illumination and collection of light in various applications including optical fiber biosensors and chemical sensors, fiber lasers, and in-fiber near-field imaging. With the increasing demand for nanoscale photonic devices and quantum communication, an efficient way is needed to focus the light transmitted by optical fiber (the photonic mode) down to nanoscale-confined light. Surface plasmon polariton (SPP) waveguides can control and confine light in the nanometer scale as the light is propagating along the metal-dielectric interface. However, the travel distance of SPP is in the micrometer scale due to the high optical loss. Thus, efficient coupling of low-loss photonic waveguide modes to the highly-confined SPP mode and vice versa is necessary for practical nanoscale fiber optics. The development of these optical fiber nanofocusing devices has been challenging as it requires the phase matching of photonic mode and plasmonic mode that exhibit different mode sizes (microscale vs nanoscale) and mode profiles (with the plasmonic mode being naturally radially polarized). Additionally, current attempts to integrate a nanometer-sized plasmonic nano-waveguide, e.g. a metal nanowire, onto a micrometer-sized fiber have required a challenging fabrication process with multiple procedures and precise alignments.
Photonics Research
  • Apr. 08, 2021
  • Vol.9, Issue 2 (2021)
Spotlight on Optics
Silicon based integrated optical circuit can confine the light field in sub-micron scale, and the fabrication process is compatible with mature microelectronic CMOS process. It can realize large-scale, high-density and low-cost on-chip photonic integration, which has become a hot direction of academic research and industrial applications.
Photonics Research
  • Feb. 02, 2021
  • Vol.8, Issue 12 (2020)
Spotlight on Optics
Optical frequency combs (OFCs) consisting of equally spaced discrete optical frequency components have emerged as promising tools for a wide range of applications including metrology, optical communications, optical clock distribution/recovery, radio-over-fibre signal generation and optical sampling. Among all approaches for OFCs generations, semiconductor mode-locked lasers (MLLs), motivated by its ability to generate stable and cost-effective high-repetition-rate optical pulses with extremely simple structures, are being heavily investigated as light sources in optical-communications systems. Moreover, an MLL typically provides 5-10 nm bandwidth, promising comb-based transmitters.
Photonics Research
  • Jan. 04, 2021
  • Vol.8, Issue 12 (2020)
Spotlight on Optics
Lead halide perovskites have drawn extensive attention over recent decades owing to their advantages of high absorption coefficient, large carrier diffusion lengths, and superior photoelectric properties, which make them as promising candidates for solar cells, light-emitting diodes, photodetectors and lasers. However, their toxicity and instability as big issues need to be solved for further commercialization. So far, many efforts have been made to explore low- or non-toxic elements to replace lead, including tin (Sn), bismuth (Bi), silver (Ag), indium (In), antimony (Sb), germanium (Ge), and copper (Cu). Among these rising lead-free perovskite materials, all inorganic copper-based perovskites benefit from low cost and earth-abundant. In the previous reports, a limited number of synthetic methods have been used to fabricate copper based inorganic perovskites, and there are some problems in these methods, such as energy consumption, time consuming and solvent consuming, which is not accord with the concept of environment-friendly development.
Photonics Research
  • Jul. 31, 2020
  • Vol.8, Issue 6 (2020)
Spotlight on Optics
The intelligence technology represented by artificial neural networks has brought tremendous changes in various fields. However, the design and training of different artificial neural networks for different target tasks usually involve complex parameter optimization processes. With the continuous growth of the current network scale as well as the confronted bottleneck of Moores Law, the time cost and energy consumption required for training and implementing artificial neural networks with the electronic computing are dramatically increasing that cannot support the continuous development of artificial intelligence. Optoelectronic computing possesses the advantages of high speed, high parallelism, and low power consumption. Therefore, developing the optical neural networks and its in situ optical training methods based on optoelectronic computing platforms are expected to achieve disruptive improvement in training time, computation speed, and energy efficiency of artificial intelligence systems.
Photonics Research
  • Jul. 15, 2020
  • Vol.8, Issue 6 (2020)
Spotlight on Optics
Silicon quantum photonic circuit is an important way to realize the integration of photonic quantum information functions. In telecom band, silicon waveguides have very high third-order optical nonlinear coefficient. They are promising candidates for realizing four-wave mixing (FWM) based quantum light sources operating at room temperature. On the other hand, a variety of silicon photonic devices with different functions provide rich means for on-chip manipulation of photonic quantum states.
Photonics Research
  • Apr. 26, 2020
  • Vol.8, Issue 3 (2020)
Spotlight on Optics
Optical neuromorphic computing offers an alternative approach to realize artificial neural computing. Compared to digital neural computing, it has several potential advantages such as ultra-fast speed and ultra-low energy consumption. In this paper, we introduce a platform to realize artificial neural computing based on metasurfaces (Zhicheng Wu, Ming Zhou, Erfan Khoram, Boyuan Liu, Zongfu Yu. Neuromorphic metasurface[J]. Photonics Research, 2020, 8(1): 01000046). Metasurfaces were developed to perform arbitrary wavefront engineering. Their optical functions are realized by the resonant scattering of nanoscale scatterers. And the scatterers are fabricated on a flat surface. Besides, the metasurface is also compatible with today’s nanofabrication and can be mass-produced at a low cost. Based on the property of metasurface, here, we use it to perform neural computing. In the following, we describe the design procedures and show it utility by the recognition of handwritten digits.
Photonics Research
  • Mar. 17, 2020
  • Vol.8, Issue 1 (2020)
Spotlight on Optics
When talking about photonic integrated circuits, one of the first questions we are asked about is their polarization sensitivity. The main reason is that it is extremely challenging to realize photonic devices that are polarization insensitive, especially when we use high-index-contrast platforms like silicon photonics. On the other hand, it is also true that making a device with an ultra-high polarization dependence can be equally difficult. Polarizers should be as transparent as possible to one polarization state while being as lossy as possible to the orthogonal state. However, it’s still a challenge to produce integrated polarizers with a small size, low loss, high polarization selectivity, and operating on a broad band.
Photonics Research
  • Feb. 13, 2020
  • Vol.7, Issue 12 (2019)
PR Highlights
The record power conversion efficiency of perovskite solar cells (PSCs) has impressively exceeded 25% in 10 years due to composition engineering, perovskite film growth control and perovskite/transport layer interface modification. However, the high efficiency PSCs are usually small-area (<0.1 cm2). For commercial application, the preparation of large-area devices is the necessary step for the development of PSCs.
Photonics Research
  • Jan. 05, 2021
  • Vol.8, Issue 7 (2020)
PR Highlights
As a candidate for the next generation display technology, micro-LED has the potential to replace LCD and OLED display technology. However, micro-LED still faces some difficulties that need to be overcome. First is the wavelength stability of micro-LED chips. The micro-LED device needs to dynamically adjust the operation current according to the intensity of ambient light, so the wavelength of the Micro-LED will shift significantly, resulting in serious color shift. Second is the fabrication of the quantum-dot color-conversion layer. the traditional spray process is still too slow to fabricate commercial quantum-dot color-conversion layers.
Photonics Research
  • Jun. 12, 2020
  • Vol.8, Issue 5 (2020)
PR Highlights
3D and flexible devices benefit from many advantages over their rigid counterparts, including amenability to large-area, low-cost fabrication via roll-to-roll processing, and the possibility of conformal integration on curvilinear surfaces or biological tissues. Following in the footsteps of the widely successful 3D electronics, 3D integrated photonics has recently attracted increasing attention in an effort to provide the same deployment flexibility to optical systems, with applications covering biotechnology, sensing, 3D manufacturing, optical interconnects, and others. 3D integrated photonics is thus poised to expand the reach of photonics by enabling both the extension of traditional applications to non-planar geometries and adding novel functionalities that cannot be attained with planar devices.
Photonics Research
  • Apr. 16, 2020
  • Vol.8, Issue 2 (2020)
PR Highlights
Metamaterials, composed of periodic arrangements of artificial sub-wavelength unit cells, have aroused great attention in the scientific community due to their novel optical properties. The well-known basic block is plasmonic split-ring resonators (SRRs). Based on the design of the geometric configuration, they exhibit excellent modulation performance for terahertz waves (THz). However, the fixed structures of SRRs make it difficult to actively modulate THz waves owing to unalterable resonant characteristics. Although the methods of applying external electric and optical fields to change the electromagnetic characteristics of SRRs, and thus achieving active modulation have been reported, the complicated heterostructure fabrication and optical measuring systems have also bring certain difficulties in experiments.
Photonics Research
  • Mar. 30, 2020
  • Vol.7, Issue 12 (2019)
PR Highlights
Analog-to-digital converters (ADCs) along with their counterparts the digital-to-analog converters (DACs) are an indispensable link between our analog physical world and the virtual digital world where data are stored and processed digitally. Besides, the transmission of such data is required to be at high-speed in the current high-capacity communication networks, which are likely to be optical. Driven by advanced applications such as optical communications, imaging and Lidar systems, better performance ADCs and DACs that are also scalable are constantly in demand. The existing ADCs deployed in our current applications are mostly implemented in the electronic domain as integrated circuits where vast amount of circuitry is needed to perform the complex operations that are necessary to quantize the continuous signal into a stream of high-fidelity discrete data. The amount of processing effort of these components often limits the performance of the electronic ADCs and the users are left with the choice of speed versus fidelity. In photonics applications, methods that can digitize the analog optical signal without the need for optical-electrical conversion are preferred because the operation can be done passively and they can improve the operation speed while lowering the power consumption at the same time. There has been an extended effort in the development of such photonic ADC solutions and many have been proposed and demonstrated in recent years. In general, nonlinear optical fiber and bulk optics-based systems have better performance metrics but they are bulky and are not scalable. Integrated photonic ADCs, which are scalable and mass manufacturable have become the research focus of current most advanced high-performance photonic ADCs field.
Photonics Research
  • Dec. 25, 2019
  • Vol.7, Issue 10 (2019)
Special Issue
Silicon photonics has been developing at an increasingly fast pace with many passive and active silicon photonic devices demonstrated with unprecedented performances. Large-scale silicon photonic circuits have been realized with high integration density for many applications ranging from telecom and Datacom to sensing, metrology, and quantum photonics. This special issue aims to provide a comprehensively overview of this exciting field, including recent progress, in-depth discussions of the state-of-the-art, and insights into forthcoming developments from worlds most prominent research groups driving silicon photonics technology into its next-generation phase.
Photonics Research
  • May. 25, 2021
  • Vol.9, Issue 10 (2021)
Special Issue
Topological photonics has been raising significant interest in the past years, due to the exciting fundamental advances it has unveiled in the way we can control light with engineered materials, and for the broad opportunities it has opened for applications. The intention of this feature issue is to provide a snapshot andoverview of the recent advances in this thriving field of research. On the Cover for this virtual special issueTopological photonics opens a new avenue to understand varieties of exotic and novel photonic phenomena, and it is expected to boost a series of key applications of photonics and optoelectronic in many aspects. See Xuefan Yin et al., page 11000B25.
Photonics Research
  • Feb. 24, 2020
  • Vol.8, Issue (2020)
Special Issue
Recent progress in photonics research has led to the discovery of novel optical materials, in which metallic halide perovskites plays a large role for semiconductor photonics. Owing to their stunning optical properties, perovskites have been widely considered as promising platforms for the manipulation of photons in free space/matter based on bulk and low-dimensional systems. Recently, a series of significant efforts and breakthroughs in perovskite photonics have been reported by institutions and companies around the world, opening a bright path to demonstrating next-generation excellent-performance, low-consumption optoelectronic devices. On the Cover for this virtual special issue Large area perovskite solar cells: the way for application. See Yang Zhao et al., page 070000A1.
Photonics Research
  • Feb. 24, 2020
  • Vol.8, Issue (2020)
Special Issue
Quantum photonics is an increasingly important emerging field because of the rising demand for experimental demonstration of quantum communication, quantum computing, and quantum simulation, and photonic chips possess prominent advantages as a potential analog for digital quantum computers and a versatile tool for probing fundamental quantum physics.Using the photonic structure to form a large state-space not only may be fundamentally interesting but also may provide a powerful platform for quantum simulation and quantum computing. This Feature Issue will explore the use of photonic platforms to investigate quantum advantage/supremacy in various quantum computing protocols, such as Boson sampling, quantum walk, fast hitting, and even universal quantum computing protocols.
Photonics Research
  • Mar. 13, 2019
  • Vol.7, Issue (2019)
Special Issue
UV light has been utilized by people in numerous critical applications for over 100 years. However, mainstream UV emitters and detectors are often bulky and inefficient. Recently, large investment and progress have been made by institutions and companies around the world to create and improve semiconductor materials, structures, and devices for more efficient generation and manipulation of UV light with a much smaller footprint and better reliability. This feature issue will cover modeling, experimentation, and applications related to UV photonics research and its applications.This feature issue in Photonics Research will serve as a venue for the most recent publications in the increasingly popular research area of semiconductor ultraviolet (UV) photonics, which has found broad applications in sterilization, communication, sensing, curing, medical treatment, and national security.
Photonics Research
  • Mar. 13, 2019
  • Vol.7, Issue (2019)
Special Issue
The emergence of graphene saturable absorbers towards the generation of ultra-short pulses in mode-locked lasers have significantly attracted world-wide attention in the related fields. Graphene-based saturable absorbers have been verified to possess unique properties, such as broad operation bandwidth, ultrafast response time, relatively high modulation depth and low saturation intensity. Inspired by the great success of graphene, graphene-like two-dimensional (2D) layered materials have also been demonstrated for ultrafast pulse generation with distinctive advantages of tunable bandgap, low optical losses, high optical nonlinearities. This feature issue is aimed at scientists, engineers and practitioners interested in understanding the novel nonlinear optical properties of 2D materials and exploring their potential applications in mode locked lasers.
Photonics Research
  • Mar. 13, 2019
  • Vol.6, Issue 10 (2018)
Special Issue
The idea of parity-time (PT) symmetry, first introduced in quantum mechanics, was recently realized in the context of photonics in the form of balanced gain-loss structures with special symmetries. In recent years, these systems have been shown to have many exotic features and behaviors with various potential applications, including unidirectional invisibility, coherent perfect absorption, negative refraction, novel laser designs, optical isolation, and unusual wave diffraction dynamics. One of the main characteristics of such non-Hermitian configurations is the existence of abrupt effective phase transitions that occur when the gain-loss amplitude exceeds a certain threshold value, providing even greater control over device design and functionality. More general gain-loss structures can exhibit an even richer variety of non-Hermitian optical properties, and the breadth of these properties has yet to be fully explored. This special issue is on a wide range of recent developments in the new area of parity-time (PT) symmetric and Non-Hermitian Optics, considering theoretical, experimental, and practical aspects of synthetic structures that contain gain and loss.
Photonics Research
  • Mar. 13, 2019
  • Vol.6, Issue 8 (2018)
Special Issue
Advances in integrated optoelectronics and nanophotonics have been very rich in recent years. These include the spectacular developments of nonlinear group four photonic platforms as well as the integration of components and functions based on III-V semiconductor materials. One of the strongest trends for the future is the development of all-optical signal processing functions within integrated, compact, low-loss devices, paving the way for new applications. This approach, relying on materials, components and the integration of optical functions, is based on a wide range of exciting physical phenomena, exploiting the nonlinear optical response of materials for the generation of frequency combs, the conversion of light wavelength, the generation of supercontinuum radiation, and many other phenomena exploiting the unprecedented power of light control by waves. This special issue has drawn a critical overview of the recent and significant burgeoning advances in the field, as well as to identify the next technological and scientific milestones to come for the development of integrated nonlinear photonics. Meanwhile, it aims to shed light on the interdisciplinary dimension of the work carried out in the field, based, for example, on the control of optical waves by acoustic waves, opening the way to the fields of nonlinear optomechanics and optoacoustics.
Photonics Research
  • Mar. 13, 2019
  • Vol.6, Issue 5 (2018)
Special Issue
Optical microcavities have attracted tremendous interests in both fundamental and applied research in the past few decades, thanks to their small footprint, easy integrability, and high quality factors. Using total internal reflection from a dielectric interface or photonic band gaps in a periodic structure, these devices do not rely on conventional metal-coated mirrors to confine light in small volumes, which have brought forth new developments in both classical and quantum optics.
Photonics Research
  • Mar. 13, 2019
  • Vol.5, Issue 6 (2017-2018)
Special Issue
Light-emitting diode (LED) technology has advanced considerably over the last few decades, yet many device physics mechanisms remain not well understood, and performances at certain wavelengths (especially deep ultraviolet, as well as the green wavelength regime) leave much room for improvement. This special issue of original research articles focus on all aspects of light-emitting diode (LED) technology.
Photonics Research
  • Mar. 13, 2019
  • Vol.5, Issue 2 (2017)
Special Issue
This special issue focuses on optical vortices and solicits original papers on all aspects of optical vortices.
Photonics Research
  • Mar. 13, 2019
  • Vol.4, Issue 5 (2016)
Special Issue
This special issue discusses advancements in terahertz technology relating to both instrumentation and material characterization. Terahertz systems have come a long way since the first demonstration of terahertz generation using photonics. New methods to utilize and manipulate terahertz light are evolving which in turn facilitate improved material characterization and opportunities for new applications.
Photonics Research
  • Mar. 13, 2019
  • Vol.4, Issue 3 (2016)
Special Issue
Integrated Photonics, which has achieved great success since Integrated Photonics was proposed by Dr. Miller in 1969. Currently various materials and technologies have been developed to realize photonic integrated circuits for many applications. The comprehensive reviews for the state-of-the-art for all aspects of integrated photonics will be very helpful for this field. It is even more important to have a deep discussion on the challenges and perspectives for integrated photonics, which will be definitely very beneficial for the young scientists and students.
Photonics Research
  • Mar. 13, 2019
  • Vol.3, Issue 5 (2015)
Special Issue
Photonics Based on Two Dimensional Materials
Photonics Research
  • Mar. 13, 2019
  • Vol.3, Issue 2 (2015)
Special Issue
This special issue on Microwave Photonics provides participants of the Asia Communications and Photonics Conference (ACP) 2013 with the opportunity to publish an account of their microwave photonics research as a peer-reviewed archival paper in the Journal. While meeting participants are particularly encouraged to submit their work, the special issue is open to all contributions in this particular area.
Photonics Research
  • Mar. 13, 2019
  • Vol.2, Issue 4 (2014)
Special Issue
The scope of this special issue on Group Four Photonics spans all aspects (both basic science and device applications) of photonics related research involving the use of group IV elements (carbon, silicon, germanium, tin, etc.). Example topics include novel passive silicon photonics, nonlinear silicon photonics, active silicon photonics, hybrid III-V on silicon lasers, germanium-based photodetectors, lasers or modulators, graphene photonics, diamond photonics and photonics using organic materials.
Photonics Research
  • Mar. 13, 2019
  • Vol.2, Issue 3 (2014)