Journals Highlights

On the Cover
Conventional Fano-resonant metasurfaces can only reflect light with a specific frequency, a planar wavefront, and linear polarization; the newly proposed metasurfaces can be tailored to be reflective to light with an arbitrary wavefront shape and circular polarization (doi: 10.1117/1.AP.3.2.026002)
Advanced Photonics
  • Jun. 16, 2021
  • Vol.3, Issue 2 (2021)
On the Cover
Tiny molecular forces at the surface of water droplets can play a big role in laser output emissions. As the most fundamental matrix of life, water drives numerous essential biological activities, through interactions with biomolecules and organisms. Studying the mechanical effects of water-involved interactions contributes to the understanding of biochemical processes. According to Yu-Cheng Chen, professor of electronic engineering at Nanyang Technological University (NTU), "As water interacts with a surface, the hydrophobicity at the bio-interface mainly determines the mechanical equilibrium of the water. Molecular hydrophobicity at the interface can serve as the basis for monitoring subtle biomolecular interactions and dynamics."
Advanced Photonics
  • Mar. 18, 2021
  • Vol.3, Issue 1 (2021)
On the Cover
Optical barcodes enable detection and tracking via unique spectral fingerprints. Theyve been widely applied in areas ranging from multiplexed bioassays and cell tagging to anticounterfeiting and security. Yu-Cheng Chen of the Bio+Intelligent Photonics Laboratory at Nanyang Technological University notes that the concept of optical barcodes typically refers to a fixed spectral pattern corresponding to a single target.
Advanced Photonics
  • Jan. 22, 2021
  • Vol.2, Issue 6 (2020)
On the Cover
As a novel type of low-dimensional semiconductor perovskite nanocrystals (NCs) can possess a fluorescent quantum yield of about 100% with size- and composition-tunable emission covering the broad spectral range from the near-UV to the near-infrared.
Advanced Photonics
  • Jan. 22, 2021
  • Vol.2, Issue 5 (2020)
On the Cover
The optical vortex plays an increasingly important role in optical information processing. As an information carrier, it improves the capacity of channels and offers an independent aspect for analysis—different from polarization, intensity, phase, and path. A new degree of freedom for encoding and encrypting optical information may be provided via nonlinear optics, using vortex beams known as azimuthons, which carry an orbital angular momentum and can now be made to exhibit a mutual conversion pattern known as Rabi oscillation.
Advanced Photonics
  • Sep. 24, 2020
  • Vol.2, Issue 4 (2020)
On the Cover
Terahertz (THz) spectroscopy (frequency range 0.1–10 THz, wavelength range 30–3000 μm) can provide unique and crucial information in a spectral region less covered by the more mature optical and microwave technologies. However, despite of its developments since 1980s, a form of THz spectroscopy that can overcome the performance bottleneck with an affordable platform still remains elusive to unlock more real-world applications.
Advanced Photonics
  • Jul. 02, 2020
  • Vol.2, Issue 3 (2020)
On the Cover
In order to extract the quantitative three-dimensional (3-D) distribution of refractive index (RI) in live cells noninvasively, optical diffraction tomography (ODT) uses the non-ionizing light sources instead of x-rays to perform a computational holographic tomography. To resolve the cellular structures with sub-wavelength resolution, the cells are sampled using tomographic scanning with oblique illumination and as many as possible scattered photons are collected with high numerical aperture (NA) objective as shown in Figs. 1(a) and 1(b). Practically, the tomographic rotation of incident beam [Fig. 1(a)] or sample [Fig. 1(b)] is always confined by a limited NA of the objective or a working distance of the imaging optics. The scattering spectrum [Figs. 1(c) and 1(d)] at certain rotation direction is, therefore, bounded at high spatial frequencies. ODT reconstructs the 3-D distribution of RI by casting scattering spectrum caps from different rotation directions together, which leads to a range of missing data in a spatial frequency domain along the rotation axis of illumination or a sample: the so-called "missing cone." For this reason, the reconstructed 3-D images are distorted and dim, making the segmentation and quantitative analysis difficult. Solving the missing cone problem is a crucial step for widening ODT applications in cell biology research and 3-D imaging of other subwavelength structures.
Advanced Photonics
  • May. 29, 2020
  • Vol.2, Issue 2 (2020)
On the Cover
Recently, a research group led by Prof. Shian Zhang and Prof. Zhenrong Sun from State Key Laboratory of Precision Spectroscopy, East China Normal University, published an invited review entitled "single-shot compressed ultrafast photography: a review" in Advanced Photonics (Dalong Qi, Shian Zhang, Chengshuai Yang, Yilin He, Fengyan Cao, Jiali Yao, Pengpeng Ding, Liang Gao, Tianqing Jia, Jinyang Liang, Zhenrong Sun, Lihong V. Wang. Single-shot compressed ultrafast photography: a review[J]. Advanced Photonics, 2020, 2(1): 014003). In this mini-review, the authors gave a comprehensive introduction on compressed ultrafast photography (CUP), including the background, work principles, technical improvements, technical extensions, related applications, and future prospects.
Advanced Photonics
  • Apr. 22, 2020
  • Vol.2, Issue 1 (2020)
On the Cover
The cell is the structural and functional unit of life. Live cells are highly dynamic in all three dimensions. The visualization of cell dynamics in 3D, such as membrane fluctuations, mass transport, growth, and motility, has been a long-standing pursuit in optical microscopy. However, the cytoplasm and most organelles of biological cells have very weak absorption, so they produce very little contrast under normal illumination in a traditional brightfield microscope. To overcome this difficulty, conventional approaches have relied heavily on exogenous labeling techniques, such as fluorescence confocal microscopy, that require fluorescent dyes and proteins as biomarkers, and are thus ill-suited for samples that are non- fluorescent or cannot be easily fluorescently tagged. Besides, the photobleaching and phototoxicity of the fluorescent agents prevent live cells imaging over extended periods of time.
Advanced Photonics
  • Mar. 25, 2020
  • Vol.1, Issue 6 (2020)
On the Cover
Coherent Raman scattering (CRS) imaging is based on a multiphoton scattering process that employs two near-infrared laser pulses to excite Raman modes in the midinfrared spectral range. Owing to its chemical selectivity without labelling, it has found a wide scope of applications in biomedical microscopy, such as live cell, tissue, and DNA imaging, over the past years. Its most prominent representatives are coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS). In both cases, two beams, the so-called pump and Stokes beam, with an energy difference matching the Raman resonance, interact with each, giving rise to the generation of a new frequency (CARS) or to an energy exchange between the two beams (SRS).
Advanced Photonics
  • Nov. 27, 2019
  • Vol.1, Issue 5 (2019)
On the Cover
Distribution of non-classical correlations through optical fibers constitutes a keystone for future quantum networks. Indeed, purely quantum protocols based on entangled systems can disclose communication advantages with respect to what can be achieved with classical resources. A crucial challenging task in this context is then the capability to perform long distance transmission of photon states by preserving their quantum correlations. In the last few years, several demonstrations have been performed showing the transmission over long distances of polarization-entangled photons. Further improvements can be disclosed by handling and distributing high-dimensional systems, allowing to enlarge the information content as well as to improve the security in quantum cryptographic protocols.
Advanced Photonics
  • Oct. 30, 2019
  • Vol.1, Issue 4 (2019)
On the Cover
Optical metasurfaces made from all-dielectric building blocks have been established as a versatile way to implement various optical functionalities, including lenses, holograms, and vortex-beam generators. In a recent breakthrough, researchers demonstrated a metasurface enabling three-dimensional imaging with only a single camera.
Advanced Photonics
  • Oct. 18, 2019
  • Vol.1, Issue 3 (2019)
On the Cover
Optical phase measurement plays a significant role in computer-aided non-contact optical metrology in recent decades. It has been widely used in many scientific and engineering applications such as industrial detection, machine vision, biomedicine, nanostructure characterization and so on. Representative phase measurement techniques include optical interferometry, digital holography, electronic speckle interferometry, Moire profilometry, and fringe projection profilometry. One of their common features is that the captured periodic fringes are formed by means of interference or projection, so that the physical quantities to be measured (such as the surface shape, displacement, strain, roughness, defects, etc.) are directly or indirectly reflected in the phase information of the fringes (Figure 1). Therefore, these techniques need to analyze the fringe pattern for the phase extraction, and then convert the phase distribution into the physical quantity of interest. Basically, the measurement accuracy of these optical techniques depends directly on the phase demodulation accuracy of recorded fringe patterns. Therefore, the fringe pattern analysis is the most important yet the most difficult step in optical phase measurements.Figure 1. Applications of fringe analysis (images from the internet).In the early stage, the fringe pattern is usually recorded by a film and analyzed through visual inspection to identify the shapes, positions, peaks, valleys, and the fringe order in order to infer the phase distribution of the measured object. However, the accuracy and efficiency of this method arequite low, since only 1/10~1/20 wavelength (λ) precision can be achieved and only partial phase information of the whole measured object can be obtained. Since the 1960s, the rapid development of optoelectronics, computer, and laser technologies has established a solid technical foundation for the real-time optoelectronic measurement of phase distribution. The invention of the charge coupled device (CCD) makes the fringe recording process digitalized. The development and popularization of personal computers make the fringe analysis evolve from naked eye detection to automatic demodulation through computer programs. This greatly improves the accuracy, speed, and automation of the phase measurement approaches and brings about various novel fringe analysis techniques, thus promoting a leap in optical metrology. Even now, how to extract the phase information of fringe patterns with the highest accuracy, fastest speed, and full automation is still a research hotspot and focus in the field of optical metrology.In the past few decades, researchers and engineers have devoted themselves to developing various fringe analysis techniques, which can be roughly classified into two categories: (1) Time-domain phase-shifting methods [1]: extract the phase information using multiple phase-shifted fringe patterns; (2) Space-domain phase demodulation methods: estimate the phase distribution through a single high-frequency fringe pattern, such as Fourier transform method [2], windowed Fourier transform method [3], and wavelet transform method [4]. The phase-shifting methods can achieve high-resolution pixel-wise phase measurement, thus having higher accuracy than the space-domain phase demodulation methods. However, such approaches are vulnerable to disturbances such as object motion/environmental vibration, thus making them difficult to be applied to high-speed measurements. In contrast, spatial phase demodulation methods have higher robustness to vibration/motion, because they can demodulate the phase from a snapshot. But they are sensitive to the large depth changes, fringe discontinuities, and rich details of testing surfaces, preventing them from high-precision and high-resolution phase measurement of complex surfaces. In addition, spatial approaches usually have many parameters to adjust in order to achieve better results, making them difficult to be fully automatic in practical applications.When Alpha Go defeated the world champion Lee Sedol in 2016 [5], artificial intelligence (AI) technologies represented by deep learning, came into the publics view. The discussion on AI technology became more heated. It was believed that AI would probably bring about a technological revolution and profoundly change our lives in the next 10 years. As predicted at that time, AI has already made great breakthroughs in many fields such as computer vision, image and speech processing. Also, it is worth noting that the deep learning technique has gradually penetrated into and demonstrated great potential for optical imaging, computational imaging, holographic microscopy, and other fields. Recently, for the first time, researchers at Nanjing University of Science and Technology (NJUST) prove that the fringe analysis can be carried out with high-accuracy and high-efficiency through deep learning. The idea is to train deep neural networks to mimic the temporal phase-shifting algorithm for phase measurement but using only a single fringe pattern. As shown in Figure 2, two convolutional networks (CNN1 and CNN2) are developed and are used together to determine the phase distribution. With a fringe image as input (I), CNN1 can estimate a background image (A) that does not involve any stripes. Then, CNN2 exploits both the background image and the raw fringe image to calculate two parts: sinusoidal (M) and cosine (D) parts. These two parts are then fed into the arctangent function for the final phase calculation. In the training stage, the deep neural networks learn to extract phase-related information with large amounts of ground truth data obtained by standard 12-step phase-shifting algorithm. After appropriate training, they can output high-accuracy phase map using a single fringe image for objects that are not present in the training data.Figure 2. Flowchart of the fringe analysis using deep neural networks.In their experiments, researchers at NJUST measured the phase and the 3D shape of different samples. Experimental results show that compared with Fourier transform method and windowed Fourier transform method, the depth-learning-based fringe analysis can demodulate the phase distribution with significantly higher accuracy (with a reduction of more than 50% phase error). Besides, it preserves the details of object boundary and contour with higher fidelity, producing 3D reconstructions that almost reproduce the results of the 12-step phase-shifting method (Figure 3). Further, unlike the Fourier transform method and windowed Fourier transform method where the performance heavily relies on fine-tuning of several parameters, this approach is fully automatic and does not require a manual parameter search to optimize its performance once the neural network has been trained. With a single fringe pattern, an accurate phase map can be obtained within a second through the deep neural networks. Hence, this novel fringe analysis technique realizes the goal of high accuracy, high efficiency, and full automation for optical phase measurements simultaneously. Currently, the researchers are trying to apply this technique to high-speed and high-resolution 3D surface imaging of transient events. The fringe analysis using deep learning is expected to be widely used in various optical phase measurement applications in the future.Figure 3. Comparison of 3D reconstruction results of different approaches: (a) Fourier analysis, (b) windowed Fourier analysis, (c) deep-learning-based fringe analysis, (d) 12-step phase-shifting method. Read More Feng Shijie, Chen Qian, Gu Guohua, Tao Tianyang, Zhang Liang, Hu Yan, Yin Wei, Zuo Chao. Fringe pattern analysis using deep learning[J]. Advanced Photonics, 2019, 1(2):025001 Reference[1] C. Zuo et al., “Phase shifting algorithms for fringe projection profilometry: a review,” Opt. Lasers Eng. 109, 23–59 (2018).[2] X. Su and Q. Zhang, “Dynamic 3-D shape measurement method: a review,” Opt. Lasers Eng. 48(2), 191–204 (2010).[3] Q. Kemao, “Two-dimensional windowed Fourier transform for fringe pattern analysis: principles, applications and implementations,”Opt. Lasers Eng. 45(2), 304–317 (2007).[4] J. Zhong and J. Weng, “Spatial carrier-fringe pattern analysis by means of wavelet transform: wavelet transform profilometry,” Appl. Opt. 43(26), 4993–4998 (2004).[5] Borowiec S. “AlphaGo seals 4-1 victory over Go grandmaster Lee Sedol”. The Guardian, 15, (2016).
Advanced Photonics
  • Mar. 26, 2019
  • Vol.1, Issue 2 (2019)
AP Highlights
The demand for detecting infrared (IR) light, invisible to human eyes, is constantly growing, due to a wide variety of applications ranging from food quality control and remote sensing to night vision devices and lidar. Commercial IR cameras require the conversion of infrared light to electrons and the projection of the resultant image on a display. This display blocks the transmission of visible light, thereby disrupting normal vision. Moreover, such IR detectors require low temperature and even cryogenic cooling due to the low energies of the IR photons, making IR detectors bulky and heavy.
Advanced Photonics
  • Jun. 22, 2021
  • Vol.3, Issue 3 (2021)
AP Highlights
The fast-growing amount of data that are produced every year creates an urgent need for ultracapacity storage media. Light has many unique advantages including easy accessibility, no need of physical contact, high spatial and temporal resolution, and easy tuning of emission wavelength and intensity, showing great convenience in information storage in a noninvasive manner. Therefore, optical storage has become a significant data storage technology in the information age and has been widely applied in daily life, economy and military due to its large capacity, long lifetime, and low energy consumption. Photoresponsive materials can well realize information recording and readout because they can undergo a series of reversible changes in certain physical and chemical properties in response to light stimulus, which are specifically manifested as variations in optical properties (absorption and emission properties), conformation, electrochemical properties, conductivity, refractive index, etc. Among these variations, optical properties play a decisive role in information storage because the success of information (re)writing and erasing, encryption and decryption, and anti-counterfeiting is directly judged by the change in the color and/or luminescent color of photoresponsive materials. Organic photoresponsive materials are one of the most promising candidates for information storage owing to their light weight, low cost, high flexibility, good scalability, and compatibility with large-area solution-processing techniques including inkjet printing and screen printing. More importantly, their storage characteristics can be easily regulated through molecular design-cum-synthesis strategies. In light of the rapid development in this area, it is very necessary to systematically sum up and discuss the current research progress, and point out the future development of the entire research field of organic photoresponsive materials for information storage.
Advanced Photonics
  • Apr. 29, 2021
  • Vol.3, Issue 1 (2021)
AP Highlights
Chromatic aberration-free meta-devices is realized by satisfying the key criteria of desirable phase dispersion and high reflection amplitudes, which largely enhances the working bandwidth and greatly improves the efficiency.
Advanced Photonics
  • Apr. 26, 2021
  • Vol.3, Issue 1 (2021)
AP Highlights
Microscopy is an essential tool in multiple research fields and industries, such as biology, medicine, materials science, and quality control, to name a few. Although many microscopy techniques exist, each has pros and cons, mostly in terms of spatial resolution, speed (images per second), and applicability. For example, scanning electron microscopy can capture images with nanometric resolution, but it offers lower speed and is impractical for certain samples. Other simpler light-based microscopy techniques, such as fluorescence microscopy, are not suitable for visualizing living cells or other small structures because these are generally transparent and thin, which results in low light absorption.
Advanced Photonics
  • Dec. 23, 2020
  • Vol.2, Issue 6 (2020)
AP Highlights
The pursuit of ever-higher imaging resolution in microscopy is coupled with growing demands for compact portability and high throughput. While imaging performance has improved, conventional microscopes still suffer from the bulky, heavy elements and architectures associated with refractive optics. Metalenses offer a solution: theyre ultrathin, ultralight, and flat, and benefit from lots of recent research that has improved their efficiency, FOV, and polarization functionalities.
Advanced Photonics
  • Dec. 16, 2020
  • Vol.2, Issue 6 (2020)
AP Highlights
Terahertz (THz) waves, located between the millimeter and far-infrared frequency ranges, are an electromagnetic frequency band that is as-yet incompletely recognized and understood. Xiaojun Wu of Beihang University leads a group of researchers actively seeking ways to understand, generate, and control THz radiation. Wu notes that THz waves have great potential for expanding real applications—from imaging to information encryption—but the development of THz science and technology has been hindered by a lack of sufficiently efficient sources.
Advanced Photonics
  • Nov. 17, 2020
  • Vol.2, Issue 6 (2020)
AP Highlights
Optical barcodes enable detection and tracking via unique spectral fingerprints. Theyve been widely applied in areas ranging from multiplexed bioassays and cell tagging to anticounterfeiting and security. Yu-Cheng Chen of the Bio+Intelligent Photonics Laboratory at Nanyang Technological University notes that the concept of optical barcodes typically refers to a fixed spectral pattern corresponding to a single target.
Advanced Photonics
  • Nov. 17, 2020
  • Vol.2, Issue 6 (2020)
AP Highlights
Extreme events occur in many observable contexts. Nature is a prolific source: rogue water waves surging high above the swell, monsoon rains, wildfire, etc. From climate science to optics, physicists have classified the characteristics of extreme events, extending the notion to their respective domains of expertise. For instance, extreme events can take place in telecommunication data streams. In fiber-optic communications where a vast number of spatio-temporal fluctuations can occur in transoceanic systems, a sudden surge is an extreme event that must be suppressed, as it can potentially alter components associated with the physical layer or disrupt the transmission of private messages.
Advanced Photonics
  • Nov. 17, 2020
  • Vol.2, Issue 6 (2020)
AP Highlights
Wave scattering appears practically everywhere in everyday life—from conversations across rooms, to ocean waves breaking on a shore, from colorful sunsets, to radar waves reflecting from aircraft. Scattering phenomena also appear in realms as diverse as quantum mechanics and gravitation. According to Pavel Ginzburg, professor at Tel Aviv Universitys School of Electrical Engineering, these phenomena become especially interesting when the waves in question encounter a moving object.
Advanced Photonics
  • Nov. 16, 2020
  • Vol.2, Issue 5 (2020)
AP Highlights
Metamaterials—nanoengineered structures designed for precise control and manipulation of electromagnetic waves—have enabled such innovations as invisibility cloaks and super-resolution microscopes. Using transformation optics, these novel devices operate by manipulating light propagation in "optical spacetime," which may be different from the actual physical spacetime. According to Igor Smolyaninov of the University of Maryland, "One of the more unusual applications of metamaterials was a theoretical proposal to construct a physical system that would exhibit two-time physics behavior on small scales." That proposal was recently realized experimentally by demonstration of two-time (2T) behavior in ferro-fluid-based hyperbolic metamaterials by Smolyaninov and a team of researchers from Towson University, led by Vera Smolyaninova. The observed 2T behavior has potential for use in ultrafast all-optical hypercomputing.
Advanced Photonics
  • Nov. 16, 2020
  • Vol.2, Issue 5 (2020)
AP Highlights
In the last few decades, only temporal modes have been considered for mode-locked fiber lasers using single-mode fibers. Mode-locked single-mode fiber lasers offer advantages due to their high-gain doping, intrinsically single-spatial mode, and compact setups. However, in terms of power levels, mode-locked fiber lasers suffer from high nonlinearity, which is introduced by the small core size of the single-mode fibers. Researchers from École Polytechnique Fédérale de Lausanne, Switzerland (EPFL) recently developed a new approach for generating high-energy, ultrashort pulses with single-mode beam quality: nonlinear beam cleaning in a multimode laser cavity.
Advanced Photonics
  • Oct. 30, 2020
  • Vol.2, Issue 5 (2020)
AP Highlights
Tiny bubbles can solve large problems. Microbubbles—around 1-50 micrometers in diameter—have widespread applications. Theyre used for drug delivery, membrane cleaning, biofilm control, and water treatment. Theyve been applied as actuators in lab-on-a-chip devices for microfluidic mixing, ink-jet printing, and logic circuitry, and in photonics lithography and optical resonators. And theyve contributed remarkably to biomedical imaging and applications like DNA trapping and manipulation.
Advanced Photonics
  • Oct. 30, 2020
  • Vol.2, Issue 5 (2020)
AP Highlights
Four frame images of the ultrafast rotating optical field recorded in the single-shot mode at 15 Tfps. Zeng et al., doi 10.1117/1.AP.2.5.056002.High-speed cameras can take pictures in quick succession. This makes them useful for visualizing ultrafast dynamic phenomena, such as femtosecond laser ablation for precise machining and manufacturing processes, fast ignition for nuclear fusion energy systems, shock-wave interactions in living cells, and certain chemical reactions.Among the various parameters in photography, the sequential imaging of microscopic ultrafast dynamic processes requires high frame rates and high spatial and temporal resolutions. In current imaging systems, these characteristics are in a tradeoff with one another.However, scientists at Shenzhen University, China, have recently developed an all-optical ultrafast imaging system with high spatial and temporal resolutions, as well as a high frame rate. Because the method is all-optical, its free from the bottlenecks that arise from scanning with mechanical and electronic components.Their design bases on some non-collinear optical parametric amplifiers (OPAs). An amplifier is a nolinear optical crystal that, when simultaneously irradiated with a desired signal light beam and a higher-frequency pump light beam, amplifies the signal beam and produces another light beam known as an idler. Because the crystal used in this study is non-collinear, the idler is fired in a different direction from that of the signal beam. But how is such a device useful in a high-speed imaging system?The answer lies in cascading OPAs. The information of the target, contained in the signal beam, is mapped onto the idler beam by the OPA while the pump beam is active. Because the idler moves in a different direction, it can be captured using a conventional charge-coupled device (CCD) camera "set to the side" while the signal beam moves toward the next stage in the OPA cascade.Just like how water would descend in a waterfall, the signal beam reaches the subsequent OPA, and the pump beam generated from the same laser source activates it; except now, a delay line makes the pump beam arrive later, causing the CCD camera next to the OPA in the second stage to take a picture later. Through a cascade of four OPAs with four associated CCD cameras and four different delay lines for the pump laser, the scientists created a system that can take four pictures in extremely quick succession.(Top). Basic schematic of the proposed imaging system. The sampling pulse hits the target and goes through four optical image converters (OIC), which are the non-collinear optical parametric amplifiers (OPA). The idler signals (labelled as "Recorded") appear when the pump laser pulses (labelled as "Trigger") hits the OPAs. Introducing a delay between these trigger pulses allows for taking images in quick succession by capturing the idler signals using conventional CCD cameras. (Bottom) Four sequential images of a rotating optical field spinning at 10 trillion radians per second.The speed of capturing consecutive pictures is limited by how small the difference between two laser delay lines can be. In this regard, this system achieved an effective frame rate of 15 trillion frames per second - a record shutter speed for high-spatial-resolution cameras. Conversely, the temporal resolution depends on the duration of the laser pulses triggering the OPAs and generating the idler signals. In this case, the pulse width was 50 fs (fifty millionths of a nanosecond). Coupled with the incredibly fast frame rate, this method is able to observe ultrafast physical phenomena, such as an air plasma grating and a rotating optical field spinning at 10 trillion radians per second.According to Anatoly Zayats, Co-Editor-in-Chief of Advanced Photonics, "The team at Shenzhen University has demonstrated ultrafast photographic imaging with the record fastest shutter speed. This research opens up new opportunities for studies of ultrafast processes in various fields."This imaging method has scope for improvement but could easily become a new microscopy technique. Future research will unlock the potential of this approach to give us a clearer picture of ultrafast transient phenomena.Read the original open access research article: Xuanke Zeng et al., "High-spatial-resolution ultrafast framing imaging at 15 trillion frames per second by optical parametric amplification," Adv. Photon. 2(5), 056002 (2020), doi 10.1117/1.AP.2.5.056002.
Advanced Photonics
  • Oct. 27, 2020
  • Vol.2, Issue 5 (2020)
AP Highlights
Optical vortices with helical phase front and doughnut intensity distribution have garnered tremendous interest in recent times and have been applied in various fields such as quantum optics, microscopy and optical communication. Motivated by these applications, approaches to generating optical vortices have become a current subject of intense research. Basically, the methods for generating the optical vortices can be classified into passive and active categories, depending on whether the vortices are created directly at the source. The direct emission from a laser cavity, namely the active method, has raised greater interest due to its excellent features of compactness, high efficiency, and high purity. However, to exploit the extra degree of freedom provided by optical vortices for new intriguing applications, it is essential to further develop laser sources, which is capable to provide vortices over a wide spectral range.
Advanced Photonics
  • Aug. 19, 2020
  • Vol.2, Issue 4 (2020)
AP Highlights
Propagate light through any kind of medium – be it free space or biological tissue – and light will scatter. Robustness to scattering is a common requirement for communications and for imaging systems. Structured light, with its use of projected patterns, is resistant to scattering, and has therefore emerged as a versatile tool. In particular, modes of structured light carrying orbital angular momentum (OAM) have attracted significant attention for applications in biomedical imaging.
Advanced Photonics
  • Aug. 14, 2020
  • Vol.2, Issue 3 (2020)
AP Highlights
Frequency combs are becoming one of the great enabling technologies of the 21st century. High-precision atomic clocks, and high-precision spectroscopy are just two technologies that have benefited from the development of highly precise frequency combs. However, the original frequency comb sources required a room full of equipment. And it turns out that if you suggest that a room full of delicate equipment is perfect for a commercial application, the development engineer makes a beeline for the nearest exit.
Advanced Photonics
  • Aug. 13, 2020
  • Vol.2, Issue 4 (2020)
AP Highlights
Oscillators that are capable of producing radio frequency (RF) and microwave signals are widely used in our modern society, such as communication link, radar, medical treatment, remote sensing, radio astronomy, spectroscopy and RF energy. One of the key parameters of an RF/microwave oscillator is its phase noise performance, which reflects the stability of the output signal. Conventional electronic oscillators such as quartz oscillators are commonly used for the generation of low-phase-noise RF/microwave signals at low frequencies. However, the generation of low-phase-noise signals at high frequencies is challenging because the quality factor (Q-factor) of an electronic oscillator, which indicates how well energy is stored within the resonant cavity, is low due to the lack of high-Q energy storage elements at high frequencies.
Advanced Photonics
  • Aug. 05, 2020
  • Vol.2, Issue 4 (2020)
AP Highlights
Optical frequency combs are comprised of discrete and equidistant frequencies, just like a precise "light ruler" in frequency domain. They have been regarded as revolutionary light sources for various research fields including advanced frequency metrology, optical atom clock, precision spectroscopy, ultrahigh-speed communication, distance ranging, molecule detection, and exoplanet searching. Traditional frequency combs are usually built on complicated solid- or fiber-based mode-locked lasers; while highly-integrated systems with reduced size, weight, power and cost (even like a flash disk in our daily life), turns to be crucial to reach their full potentials in out-of-lab applications. Prof. Wenfu Zhangs research team from Xian Institute of Optics and Mechanics, Chinese Academy of Sciences, reviews recent progress of soliton comb generations in chip-scale microresonators that pave the way for miniaturized integration of frequency comb systems, which is newly published in Advanced Photonics, Vol. 2, Issue 3, 2020 (Weiqiang Wang, Leiran Wang, Wenfu Zhang. Advances in soliton microcomb generation[J]. Advanced Photonics, 2020, 2(3): 034001).
Advanced Photonics
  • Jul. 16, 2020
  • Vol.2, Issue 3 (2020)
AP Highlights
The development of metasurfaces has offered unprecedented capabilities for the advance of planar photonics. Among various metadevices, the metalens has attracted widespread attentions due to their practical applications in imaging and spectroscopy. Recently, they have been developed for multifunctional wavefront manipulations, replacing the traditional refractive lenses made of polished crystals or polymers and embracing the trend of miniaturization and integration of photonic systems. Nevertheless, their functions remain static once they are fabricated. Thereby, many researchers are focusing on realizing active metalenses via introducing functional materials. The majority of them possess either switchable bifocal properties or discrete focal lengths. Till now, dynamic function, especially the tunable chromatic aberration, still remains a formidable challenge.
Advanced Photonics
  • Jun. 17, 2020
  • Vol.2, Issue 3 (2020)
AP Highlights
Arrays of subwavelength nanoparticles, so-called metasurfaces, have been a subject of intense research recently, due to their extraordinary optical properties, which can find diverse applications, such as superlenses, tunable images, and holograms. Over the past decade, one of the widely studied response of metasurfaces is Fano resonances, which generally occur as a result of close interaction of a discrete (localized) state with a continuum of propagation modes. It has been shown that Fano resonances can increase the storage time of photons, within subwavelength resonators. Such a characteristic can facilitate various applications including enhanced mixing light colours, optical sensing, optoacoustic vibrations and narrowband filtering.
Advanced Photonics
  • Jun. 15, 2020
  • Vol.2, Issue 2 (2020)
AP Highlights
Spectroscopy has roots in early 19th century curiosity about interactions between matter and electromagnetic radiation. Thanks to advances in electronics and materials science, various spectroscopy techniques are now routinely used to study the composition of materials and the nature of their chemical bonds by analyzing how they absorb or reflect electromagnetic waves.
Advanced Photonics
  • Jun. 09, 2020
  • Vol.2, Issue 3 (2020)
AP Highlights
Recently, laser-induced ionization in matter, including gas, cluster, liquid, and solid have attracted considerable interest in generating coherent, intense, broadband terahertz (THz) waves through nonlinear processes of laser-matter interaction. When a laser pulse with an intensity above the ionization threshold is focused into the target, photoionization creates electrons and ions, which can be driven by the ponderomotive force or electric fields, generating transient currents. These particles radiate electromagnetic waves covering the spectrum from microwaves to X-rays. Concurrently, radiated waves can be used to characterize target material.
Advanced Photonics
  • May. 29, 2020
  • Vol.2, Issue 1 (2020)
AP Highlights
One of the challenges of optical microscopy is to continually increase the imaging power, or resolution. In the past three hundred odd years, scientists have been building ever-better microscopes. The limit, for a long time, was determined by only two factors: the contrast of the object being viewed, and the resolving power of the optics in the microscope. The last 50 years, in particular, have led to an explosion in techniques to improve both the contrast of object and the quality of the optics.
Advanced Photonics
  • May. 22, 2020
  • Vol.2, Issue 3 (2020)
AP Highlights
In biological microscopy and x-ray imaging, many transparent objects or structures are difficult to observe. Due to their low absorption of light, the usual intensity measurements dont work. Instead, the structural information is mainly conveyed by the different phase changes of light as it propagates through different parts of an object.
Advanced Photonics
  • May. 15, 2020
  • Vol.2, Issue 1 (2020)
AP Highlights
Under normal conditions, molecules in the gas phase rotate freely and their orientation in space is random. Molecules can be of two kinds – symmetric without a preferred direction; or they can have a preferred direction, namely there is a head and a tail which аrе distinguishable.
Advanced Photonics
  • Apr. 26, 2020
  • Vol.2, Issue 2 (2020)
AP Highlights
Surface plasmon polaritons (SPPs) in the optical range have enjoyed increasingly attentions in recent years, particularly after the exploration of extra-ordinary transmission. Propagating at metal-dielectric interfaces with confined field distribution and reduced wavelength, SPPs promise many compact and integrated cutting-edge applications ranging from sensing, imaging, and processing to plasmonic circuitries. However, their counterparts in the terahertz (THz) regime, namely, THz surface plasmonic waves (SPWs), received much less attentions, due to their poor field confinement resulted from the perfect-electric-conductor-like conductivity of metals in the terahertz regime. Owing to the unique spectral property of THz waves, THz science and technology is of great potential in many frontier applications, including spectroscopy, imaging, sensing, and communications. However, current THz devices and systems based on free-space THz waves are commonly large in volume. Meanwhile, large analyte volume is required to increase the interaction length with THz waves. One direct solution is to reduce the three-dimensional propagation of THz waves to two-dimensional, namely, utilizing THz SPWs. Therefore, studying THz SPWs and making them possess similar confining properties as optical SPPs is highly demanded for compact THz applications.
Advanced Photonics
  • Apr. 02, 2020
  • Vol.2, Issue 1 (2020)
AP Highlights
Photonic crystals are predicted to be one of the wonders of the 21st century. In the 20th century, new understanding of the electronic band structure-the physics that determines when a solid conducts or insulates-revolutionized the world. That same physics, when applied to photonic crystals, allows us to control light in a similar manner to how we control electrons. If photonic crystals live up to their promise, all-optical transistors that consume little power and enable even more powerful computers could become a reality.
Advanced Photonics
  • Mar. 23, 2020
  • Vol.1, Issue 6 (2019)
AP Highlights
Advanced Photonics Special Collection by Topic: Imaging and Sensing
Advanced Photonics
  • Mar. 13, 2020
  • Vol., Issue (2019-2020)
AP Highlights
In the past, generation of MHz mid-infrared femtosecond pulses relied on synchronously-pumped optical parametric oscillator (OPO), which needed a strong femtosecond pumping source and a rigid repetition-matching OPO cavity. Mode-locked fluoride fiber laser provides a direct and efficient way to produce mid-infrared femtosecond pulses, which facilitates a wide range of applications such as mid-infrared supercontinuum generation, material modification, medical imaging, and mid-infrared ultrafast spectroscopy. However, due to lack of dispersion-compensation technique in the mid-infrared, mode-locked fluoride fiber lasers are confined to soliton mode-locking regime, which fundamentally limits the scaling of pulse energy and peak power.Intracavity dispersion management is an effective way to overcome the limitation of pulse energy and peak power. In the past, dispersion-managed fiber lasers have been widely employed in the near-infrared and proved successful in controlling the pulse evolution forms such as stretched pulse, dissipative soliton, and similariton, significantly improving the performance of the femtosecond fiber laser. The sign and amount of group velocity dispersion (GVD) can be conveniently engineered by ion doping or by structures designing in the conventional silica fiber system. However, fluoride glass-based dispersion-compensation fiber is unavailable at present, which blocks the development of mid-infrared mode-locked fluoride fiber lasers.Schematic of the breathing-pulse mode-locked Er:ZBLAN fiber laser. Original article: Zhipeng Qin et al., "Mode-locked 2.8 μm fluoride fiber laser: from soliton to breathing pulse"Characteristics of the breathing-pulse mode-locked fluoride fiber laser. Evolution of (a) pulse energy, duration, (b) autocorrelation trace, and (c) mode-locking spectrum with the inserted Ge rod length. The net intracavity dispersions are -0.191, -0.158, -0.141, -0.090 ps2 for Ge rod lengths of 0, 2, 3, and 6 cm, respectively. Evolution of the (d) pulse energy and duration with the launched pump power in the soliton and breathing-pulse regimes. (e) Measured autocorrelation trace and (f) mode-locking spectrum for 9.3-nJ output pulses.;Researchers from Shanghai Jiao Tong University recently reported a versatile and practical dispersion-compensation approach for mode-locked fluoride fiber lasers using an infrared-bandgap semiconductor. Related research results were published in Advanced Photonics, Vol. 1, Issue 6, 2019 (Zhipeng Qin, Guoqiang Xie, Hongan Gu, Ting Hai, Peng Yuan, Jingui Ma, Liejia Qian. Mode-locked 2.8-μm fluoride fiber laser: from soliton to breathing pulse[J]. Advanced Photonics, 2019, 1(6): 065001).They found that semiconductor material possesses a huge GVD near the absorption edge resulting from the rapid change of refractive index. For example, germanium has a huge normal GVD at 2.8 μm which is 20 times larger than that of fluoride fiber. Thus, Ge rod with centimeters scale in length is sufficient to manage the intracavity dispersion of mode-locked fluoride fiber laser.Benefitting from the intracavity dispersion management, mid-infrared mode-locked fluoride fiber lasers are no longer confined to soliton mode-locking regime. A new form of dispersion-managed soliton, breathing pulse was demonstrated in a mode-locked fluoride fiber laser at 2.8 μm using nonlinear polarization rotation technique. A record peak power (43 KW) was produced from the dispersion-managed femtosecond fluoride fiber laser, which has reached the level of state-of-the-art mid-infrared femtosecond OPOs around 2.8 μm.This work provides a versatile and practical scheme of mid-infrared dispersion management and opens the door for realizing new operation regimes in mode-locked fluoride fiber lasers, creating a great potential for further scaling of pulse energy and peak power of mid-infrared femtosecond fluoride fiber lasers.
Advanced Photonics
  • Mar. 20, 2020
  • Vol.1, Issue 6 (2019)
AP Highlights
Real-time visualizations of cell morphology and tissue architecture in vivo are of great importance to both biomedical research and clinical practice. It often involves an imaging process after deep penetration into organs or tissues, which is a formidable task to conventional microscopy. While fiber-optic imaging systems (FOISs) have been applied in this area due to their miniature sizes and flexible image transfer capabilities, conventional FOISs are faced with several challenges, such as poor compatibility with broadband illumination, bulky distal optics, low imaging quality and speed, and extreme sensitivity to perturbations. Current limitations are mainly attributed to the physical properties of optical fibers and image processing techniques. Widely-used optical fibers, such as multicore optical fibers and multimode optical fibers, suffer from strong mode coupling and low mode densities. Any external mechanical or thermal perturbation can modify the mode coupling and degrade the imaging quality. Many existing image processing techniques require complicated, expensive, and noise-sensitive experimental configurations, which are typically incompatible with broadband illumination and result in slow imaging speed.
Advanced Photonics
  • Dec. 06, 2019
  • Vol.1, Issue 6 (2019)
AP Highlights
Ultra-high intense laser pulses have been applied in the field of laser-matter interaction, such as proton or electron acceleration in thin solid targets and electron generation in fast-ignition inertial confinement fusion. State-of-the-art high-power laser systems can produce intense pulses with peak powers of 10 PW. The 100-PW level laser system with focal intensities of 1021 – 1024 W/cm2 is expected in the near future. For the PW laser pulse, the temporal contrast is one of the most important parameters since the prepulse noise has disturbing influence to the laser-matter interaction. Thus, the temporal contrast measurement for the ultra-intense laser pulse is critical. Since the PW laser systems are operated at low repetition rate, the single-shot measurement is necessary.
Advanced Photonics
  • Dec. 25, 2019
  • Vol.1, Issue 5 (2019)
News
Chinese Laser Press (CLP) is pleased to announce that Advanced Photonics is indexed in Science Citation Index-Expanded (SCIE).
Advanced Photonics
  • Apr. 27, 2021
  • Vol., Issue (2021)
News
Co-Editors-in-ChiefXiaocong(Larry) Yuan (袁小聪),Shenzhen University, ChinaAnatoly Zayats,Kings College London, UKEditorial Board MembersKishan Dholakia,University of St Andrews, UKJennifer Dionne,Stanford University, USNicholas(Ned) J. Ekins-Daukes,University of New South Wales, AustraliaYeshaiahu (Shaya) Fainman,University of California at San Diego, USHarald Giessen,University of Stuttgart, GermanyChaoyang Lu (陆朝阳),University of Science and Technology of China, ChinaOlivier J. F. Martin,Ecole Polytech Federale de Lausanne, SwitzerlandTing Mei (梅霆),Northwestern Polytechnical University, ChinaMin Qiu (仇旻),Westlake University, ChinaMichael G. Somekh,Shenzhen University, ChinaPeng Xi (席鹏),Peking University, ChinaSiyuan Yu (余思远),University of Bristol, UK; Sun Yat-Sen University, ChinaShuang Zhang,University of Birmingham, UK
Advanced Photonics
  • Mar. 13, 2019
  • Vol., Issue (2019)
News
Copublished by SPIE and Chinese Laser Press, Advanced Photonics is a highly selective, open-access, international journal publishing innovative research in all areas of optics and photonics, including fundamental and applied research. The journal publishes top-quality original papers, letters, and review articles, reflecting significant advances and breakthroughs in theoretical and experimental research and novel applications with considerable potential.The journal seeks high-quality, high-impact articles across the entire spectrum of optics, photonics, and related fields with specific emphasis on the following acceptance criteria:*New concepts in terms of fundamental research with great impact and significance*State-of-the-art technologies in terms of novel methods for important applications*Reviews of recent major advances and discoveries and state-of-the-art benchmarking.The journal also publishes news and commentaries highlighting scientific and technological discoveries, breakthroughs, and achievements in optics, photonics, and related fields.Research areas covered include:*Photonic devices and systems for communications*Photonics for clean energy*Photonics in chemistry, biology, and medicine*Optical imaging, metrology, and sensors*Photonics for data storage, data manipulation, and displays*Materials, artificial materials, and nanostructures for photonics*Photonics in quantum technologies*Nonlinear and ultrafast optics*Optoelectronics and optical information processing*Optical manipulation techniques, optomechanics, and optofluidicsResearchers may submit manuscripts beginning in spring 2018. Detailed submission information and author guidelines will be forthcoming.The first bimonthly issue will be published in January 2019. Articles will be published online as they are reviewed, accepted, copyedited, and typeset, starting in late 2018.All articles will be open access (CC BY) with the article publication charge waived in the first year.
Advanced Photonics
  • Mar. 13, 2019
  • Vol., Issue (2019)
Editors' Picks
Digital holography is a widely-used imaging technique that can record the entire wavefront information, including amplitude and phase, of a 3D object. With an interferometer and an image sensor, a 2D hologram can be acquired and stored in a computer. Due to the noninvasive and label-free properties, it has been applied to biological imaging, air/water quality monitoring, and quantitative surface characterization measurement.After capturing a digital hologram, appropriate algorithms are utilised to reconstruct the object numerically. Although effective, conventional approaches require prior knowledge and cumbersome operations for an in-focus and successful reconstruction. In addition, for quantitative phase imaging, the inevitable phase aberration has to be compensated by physical or numerical means, and subsequently an unwrapping step is needed to recover the true object profile. The former either requires additional hardware or strong assumptions, whereas the phase unwrapping algorithms are often sensitive to noise and distortion. Furthermore, for a 3D object, an all-in-focus image and a depth map are particularly desired for many applications, but current approaches tend to be computationally demanding. Therefore, how to further improve these conventional reconstruction methods in an automatic fashion with high accuracy attracts researchers’ interest in the field of digital holography.Recently, researchers at the University of Hong Kong demonstrated an “all-in-one” method that can tackle these holographic reconstruction problems by simply training a deep neural network with appropriate data. By constructing and training an end-to-end learning framework, which is motivated by the residual learning scheme, cumbersome operations in conventional reconstruction approaches are thus avoided and system parameters become unnecessary.After appropriate training, the network can holographically reconstruct the amplitude, quantitative phase, extended focused image and depth map, respectively. Qualitative visualization and quantitative measurements confirm the superior performance of learning-based method over conventional ones. The intensive computational demand is also significantly alleviated with a totally automatic manner.Through this data-driven approach, we show that it is possible to reconstruct a noise-free image that does not require any prior knowledge and can handle diverse reconstruction modalities simultaneously. To push this work forward, the researchers plan to apply this technique to high-speed and high-resolution temporal holographic reconstruction of 3D scenarios. We believe that this method is universal to various digital holographic configurations and is potentially applicable to biological and industrial applications.Figure 1. (a) Schematic of the deep learning workflow and the structure of HRNet. It consists of three functional blocks: input, feature extraction and reconstruction. In the first block, the input is a hologram of either an amplitude object (top), a phase object (middle) or a two-sectional object (bottom). The third block is the reconstructed output image according to the specific input. The second block shows the structure of HRNet. (b) and (c) elaborate the detailed structures of the residual unit and the sub-pixel convolutional layer, respectively.Original article: End-to-end deep learning framework for digital holographic reconstruction
Advanced Photonics
  • May. 28, 2019
  • Vol.1, Issue 1 (2019)
Editors' Picks
Mode locking is a technique that locks a large number of longitudinal modes together to produce ultrafast pulses. Mode-locked lasers have enabled some of the most precise measurements, e.g., metrology with frequency combs. Passively mode-locked fiber lasers have widespread applications in the fields of fiber telecommunication, optical sensing, metrology, and microscopy, because of their compact and low-cost configuration as well as excellent features of high stability and low noise. Mode-locked fiber laser is also an ideal platform for researchers to explore new optical nonlinear phenomena.Starting dynamics of mode-locked lasers have been investigated experimentally and theoretically since 1990s, but the spectral dynamics during the build-up of pulse lasers has not been measured directly. The transient non-repetitive processes cannot be measured by conventional technologies due to the speed limitation of electronic devices. Real-time spectroscopy based on an emerging time-stretch dispersive Fourier transform (TS-DFT) technique can map the spectral information of optical waves into the time domain, thus opening several fascinating explorations of nonlinear dynamics in mode-locked lasers. The TS-DFT technique provides a powerful way for real-time, single-shot measurements of ultrafast phenomena. The pulse-resolved spectral evolution of a femtosecond pulse train in a mode-locked laser and the transient coherent multi-soliton states had been captured by using the TS-DFT technique.Recently, by means of the TS-DFT technique, Herink et al. observed the internal dynamics of soliton molecules (Science 356, 50, 2017) and resolved the build-up of solitons in mode-locked lasers (Nat. Photon. 10, 321, 2016). They demonstrated the process from transient to stable bound states. Ryczkowski et al. resolved real-time full-field characterization of transient dissipative soliton dynamics in mode-locked lasers (Nat. Photon. 12, 221, 2018). They characterized the spectral and temporal evolutions of ultrashort dissipative solitons as their dynamics pass through a transient unstable regime with complex break-up and collisions before stabilization. However, the entire build-up dynamics of solitons in mode-locked lasers have not been observed directly so far.The self-starting process of mode-locked lasers is quite sensitive to the environmental perturbation, which drives the transient behaviors of lasers to deviate from the real process of soliton formation. Here, the Q-switched lasing is completely suppressed by reducing the environmental perturbation, improving the stability of the laser, and optimizing the mode-locker. We therefore demonstrate the first observation of the entire build-up process of solitons in a mode-locked laser, revealing two possible ways to generate the solitons. One way includes the dynamics of raised relaxation oscillation, quasi mode-locking stage, spectral beating behavior, and finally the stable single-soliton mode-locking. The other way contains, however, an extra transient bound-state stage before the final single-pulse mode-locking operation. Figure 1 exhibits the conceptual representation of different stages during the entire build-up process of solitons in a mode-locked laser. The plots in the top and down rows demonstrate the entire build-up process of solitons in temporal and spectral domains, respectively.Figure 1. Conceptual representation of the entire build-up process of solitons in a mode-locked laser, successively undergoing the raised relaxation oscillation, quasi mode-locking stage, spectral beating dynamics, transient bound-state stage and stable mode-locking. Top and down rows: the entire build-up process of solitons in temporal and spectral domains, respectively.Moreover, we have proposed theoretical models to describe the raised relaxation oscillation and evolution dynamics in the birth of solitons, which can successfully predict the build-up time of solitons. Our findings provide new perspectives into the ultrafast transient dynamics and bring real-time insights into laser design and applications. The real-time spectroscopy technique is expected to provide new insight into a wider class of phenomena in complex nonlinear systems.Read More[1] Liu Xueming, Cui Yudong. Revealing the behavior of soliton buildup in a mode-locked laser[J]. Advanced Photonics, 2019, 1(1):016003
Advanced Photonics
  • Mar. 26, 2019
  • Vol.1, Issue 1 (2019)
Editors' Picks
Semiconductor lasers are among the smallest and most power-efficient lasers of any kind. They measure in size a fraction of the thickness of human hair. These lasers found applications in many areas of technologies and in our daily life, from driving the internet in optical communication system across the globe, powering our data centers and supercomputers, performing face recognition in smart phones, to sensing in autonomous driving and artificial/augmented intelligence or reality! As in other semiconductor-based technologies such as microelectronics, miniaturization in photonics and lasers has been a constant theme, with size reduction down to nanometers, or nanolasers being the important frontier of research over the last ten years. In this paper, the author reviews the progress, existing issues, and prospects of nanolasers, especially those using electrons in metals (or so-called plasmons) for the ultimate size reduction.The paper starts with the introduction of what the author considers the three major challenges for semiconductor photonics and lasers: 1) Device size and energy-efficiency challenge; 2) Wavelength or bandgap diversity challenge; and 3) Integration challenge. These questions and their related challenges are important for realizing future integrated nanophotonic circuits on a chip for various applications. The author argues that these challenges will remain unresolved in the near future and the efforts and results in resolving them will have profound impact to semiconductor photonics. In each of these challenges, breakthroughs are expected by going nano: using nanoscale physics of light-semiconductor interactions as principles of new device design, using nanoscale techniques for the growth of materials and fabrication of devices, and carrying out characterizations of materials and devices on nanoscale! In short, resolution of all three challenges can benefit tremendously from nanoscale science and technology of semiconductors.The overall theme of this paper is on nanoscale semiconductor lasers and how such nanolasers could help resolve the size and energy efficiency challenges. While nanolasers represent additional benefits for many applications, they are simply imperative to integrated optical communication inside future supercomputers and data centers. This is because all existing semiconductor lasers are too large and too energy-hungry to meets the need for such usage in the long run. The author then reviews briefly major types of semiconductor lasers including conventional edge emitting lasers, surface emitting lasers, microdisk lasers, photonic crystal lasers, nanowire lasers, nanolasers based on the new emerging 2D materials, and plasmonic or metallic cavity lasers. Using typical devices sizes and geometries for these lasers, the author compares their normalized volumes. While almost all the other types of lasers have exhausted their miniaturization potential, plasmonic nanolasers are the smallest and can be made even smaller.Next the author discusses plasmonic lasers in detail, including brief history and recent progress. The major advantages are discussed such as smallest sizes compared to any other types of lasers, highest possible modulation speed, and better thermal dissipation. As important advantages of plasmonic lasers, the author uses examples from their earlier study, showing one of the often-unexpected advantage of plasmonic laser: lower threshold than pure dielectric/semiconductor cavity laser due to an interesting trade-off between internal absorption and far-filed radiation loss.The article ends with comparative analysis of all major type of lasers and their respective potential or limitation in meeting the size and energy-efficiency challenge and some concluding remarks about the prospects of nanolasers.Read More[1] Ning Cun-Zheng. Semiconductor nanolasers and the size-energy-efficiency challenge: a review[J]. Advanced Photonics, 2019, 1(1):014002
Advanced Photonics
  • Mar. 25, 2019
  • Vol.1, Issue 1 (2019)