The image on the cover for Advanced Photonics Volume 3, Issue 3, depicts tunneling ionization of an atom, as induced by a strong laser pulse. The complex hologram in the photoelectron momentum spectrum, which encodes rich structural and dynamic information of the atom, originates from the interference of the photoelectrons tunneling at different times during the laser pulse. By introducing a weak second harmonic field, the contributions of the photoelectrons tunneling at different times are identified, a significant step toward imaging the ultrafast dynamics in atoms and molecules with the photoelectron spectroscopy of tunneling ionization.The image is based on original research by Jia Tan et al. presented in their paper “Resolving and weighing the quantum orbits in strong-field tunneling ionization,” Adv. Photon.3(3), 035001 (2021).
Photonics Insights will be a high-quality，peer-reviewed, Diamond Open Access journal. It will feature review articles which present the current status of a given topic, with background, research progress, conclusions, and possible future developments.
The image on the cover of Photonics Research Volume 9, Issue 4, demonstrates temperature tunable spectral broadening using a nonlinear ultra-silicon-rich nitride device consisting of a 3-mm-long cladding-modulated Bragg grating and a 7-mm-long nonlinear channel waveguide. Provided by Y. Cao et al., researchers from Singapore University of Technology and Design, Ecole Polytechnique Fédérale de Lausanne, Institute of Microelectronics, A*STAR and The University of Sydney, the image is based on the research presented in their article "Thermo-optically tunable spectral broadening in a nonlinear ultra-silicon-rich nitride Bragg grating", Photonics Research 9(4) 04000596, doi 10.1364/PRJ.411073.
The image on the cover of Chinese Optics Letters Volume 19, Issue 4, indicates that a new type of optical bi-layer metasurface system is designed and studied, which is based on subwavelength metal slit arrays with phase-gradient modulation, referred to as metagratings (MGs). Provided by Q. Shi et al., researchers from Soochow University, Nanjing University of Aeronautics and Astronautics and North University of China, the image is based on the research presented in their article "Optical beam splitting and asymmetric transmission in bi-layer metagratings", Chinese Optics Letters 19(4) 042602, doi 10.3788/COL202119.042602.
The image on the cover of Photonics Research Volume 9, Issue 3, presents a new imaging modality, deep compressed imaging via optimized-pattern scanning, which can significantly increase the acquisition speed for a single-detector-based imaging system. Provided by K. Zhang, J. Hu and W. Yang, researchers from University of California, the image is based on the research presented in their article "Deep compressed imaging via optimized pattern scanning", Photonics Research 9(3) 03000B57, doi 10.1364/PRJ.410556.
In the study of exceptional point (EP)-based sensors, the concrete form of the output spectrum is often dismissed, and it is assumed that there is a corre
In the study of exceptional point (EP)-based sensors, the concrete form of the output spectrum is often dismissed, and it is assumed that there is a corresponding relation between the peaks/valleys in the transmission spectrum and the real parts of the eigenvalues of the system. We point out that this assumption does not always hold. An effect, which is mathematically similar to electromagnetically induced transparency (EIT), may result in a ‘pseudo spectrum splitting’ that does not correspond to the splitting between the eigenvalues. The effect shall be taken care of when designing an EP-based sensor since it may cause measurement error and misunderstanding such as recognization of the spectrum splitting as the eigenvalue splitting at the exceptional point. We also propose to intentionally utilize this ‘pseudo splitting’ to design a sensor, which does not work at an EP, that has an EP-like spectrum splitting.show less
With its unique and exclusive linear and nonlinear optical characteristics, epsilon-near-zero (ENZ) photonics has drawn a tremendous amount of attention i
With its unique and exclusive linear and nonlinear optical characteristics, epsilon-near-zero (ENZ) photonics has drawn a tremendous amount of attention in the recent decade in the fields of nanophotonics, nonlinear optics, plasmonics, light-matter interactions, material science, applied optical science, etc. The extraordinary optical properties, relatively high tuning flexibility, and CMOS compatibility of ENZ materials make them popular and competitive candidates for nanophotonic devices and on-chip integration in all-optical and electro-optical platforms. With exclusive features and high performance, ENZ photonics can play a big role in optical communications and optical data processing. In this review, we give a focused discussion on recent advances of the theoretical and experimental studies on ENZ photonics, especially in the regime of nonlinear ENZ nanophotonics and its applications. First, we overview the basics of the ENZ concepts, mechanisms, and nonlinear ENZ nanophotonics. Then the new advancements in theoretical and experimental optical physics are reviewed. For nanophotonic applications, the recent decades saw rapid developments in various kinds of different ENZ-based devices and systems, which are discussed and analyzed in detail. Finally, we give our perspectives on where future endeavors can be made.show less
Metasurfaces composed of meta-atoms provide promising platforms for manipulating amplitude, phase, and polarization of light. However, the traditional des
Metasurfaces composed of meta-atoms provide promising platforms for manipulating amplitude, phase, and polarization of light. However, the traditional design methods of metasurfaces are time consuming and laborious. Here, we propose a bidirectional cascaded deep neural network with a pretrained autoencoder for rapid design of dielectric metasurfaces in the range of 450 nm to 850 nm. The forward model realizes a prediction of amplitude and phase responses with a mean absolute error of 0.03. Meanwhile, the backward model can retrieve patterns of meta-atoms in an inverse-design manner. The availability of this model is demonstrated by database establishment, model evaluation, and generalization testing. Furthermore, we try to reveal the mechanism behind the model in a visualization way. The proposed approach is beneficial to reduce the cost of computation burden and improve nanophotonic design efficiency for solving electromagnetic on-demand design issues automatically.show less
In this work, we propose a novel approach to produce three-dimensional (3D) optical trapping with sub-wavelength size through an engineered microsphere, u
In this work, we propose a novel approach to produce three-dimensional (3D) optical trapping with sub-wavelength size through an engineered microsphere, under linear polarization states of an incident light. The engineered microsphere is designed to contain the segmented regions of diffractive patterns and made by focused ion beam fabrication. We simulate and experimentally characterize the focus performance of the engineered microsphere. The emitted light field from the exit surface of the engineered microsphere forms a pair of axially arranged focused beams, and they are connected with a continuous optical field embracing a 3D optical null at the center, forming the so-called optical bottle beam. Experimental results and numerical simulation are in good agreement. Such micro-optics can be used for precise and localized optical trapping.show less
In this paper, a high-power and high-efficient 4.3 µm mid-infrared (MIR) optical parametric oscillator (OPO) based on ZnGeP2 (ZGP) crystal is demonstrated. An acousto-optically (AO) Q-s
In this paper, a high-power and high-efficient 4.3 µm mid-infrared (MIR) optical parametric oscillator (OPO) based on ZnGeP2 (ZGP) crystal is demonstrated. An acousto-optically (AO) Q-switched Ho:YAG laser operating at 2.1 µm with a maximum average output power of 35 W and pulse width of 38 ns at a repetition rate of 15 kHz is established and employed as the pump source. A doubly-resonant OPO (DRO) is designed and realized with the total MIR output power of 13.27 W, including the signal and idler output power of 2.65 W@4.07 µm and 10.62 W @4.3 µm. The corresponding total optical-to-optical and slope efficiency are 37.9% and 67.1%, respectively. The shortest pulse width, the beam quality factor and the output power instability are measured to be 36 ns, Mx2=1.8, My2=2.0 and RMS<1.9%@8 hours, respectively. Our results pave a way for designing high-power and high-efficient 4-5 µm MIR laser sources.show less
A tunable multi-wavelength EDFL with precise wavelength interval control is reported theoretically and experimentally in this paper. It is made up of MZI filter and Sagnac filter, and s
A tunable multi-wavelength EDFL with precise wavelength interval control is reported theoretically and experimentally in this paper. It is made up of MZI filter and Sagnac filter, and supplemented by four-wave-mixing effect. Compared with other filters, the proposed MZI filter based on the fused taper technology can change the wavelength interval more flexibly. The experiment result shows that the wavelength tuning can be achieved and the tuning range can reach ~15nm. Moreover, the variation in the number of wavelengths are also realized. The maximum SMSR can reach 39dB. show less
A new unsaturated wind-chime model is proposed for calculating the formation time of the diffraction rings induced by spatial self-phase modulation (SSPM) in molybdenum disulfide suspen
A new unsaturated wind-chime model is proposed for calculating the formation time of the diffraction rings induced by spatial self-phase modulation (SSPM) in molybdenum disulfide suspension. To optimize the traditional wind-chime model, the concentration variable of 2D material was introduced. The results of the unsaturated wind-chime model match quite well with the SSPM experimental results of molybdenum disulfide. Based on this model, the shortest formation time of diffraction rings and their corresponding concentration and light intensity can be predicted using limited data. Theoretically, by increasing the viscosity coefficient of the solution, the response time of the diffraction ring, to reach the maximum value, can be significantly reduced. It has advanced significance in shortening the response time of photonic diodes. show less
In this paper, we use electromagnetic simulations to systematically investigate the influence of a thin dielectric layer on the local electric field and molecular spectroscopy in the pl
In this paper, we use electromagnetic simulations to systematically investigate the influence of a thin dielectric layer on the local electric field and molecular spectroscopy in the plasmonic junction. It is found that both the intensity and spatial confinement of the electric field and the molecular spectroscopy can be significantly enhanced by applying a dielectric layer with large dielectric constant. We also discuss the optimal dielectric layer thickness to obtain the largest quantum efficiency of a dipole emitter. These results may be instructive for further studies in molecular spectroscopy and optoelectronics in plasmonic junctions.show less