We conducted a systematic investigation of the light extraction efficiency (LEE) of GaN-based vertical micro-scale light-emitting diode (μ-LED) structures using three-dimensional finite-difference time-domain (FDTD) simulations. The LEE of μ-LED structures was found to have a strong dependence on structural parameters such as the shape of the chip cross section, chip dimension, and p-GaN thickness

Convolutional neural network (CNN) has great potentials in holographic reconstruction. Although excellent results can be achieved by using this technique, the number of training and label data must be the same and strict paired relationship is required. Here, we present a new end-to-end learning-based framework to reconstruct noise-free images in absence of any paired training data and prior knowledge

In this work, a metasurface with the symmetrical double C-shaped narrow ring connected with the central cross structure is investigated by simulation, theory and experiment, which can near-perfectly convert linearly polarized electromagnetic waves into their orthogonal components in the frequency ranges from 9.38 to 13.36 GHz and 14.84 to 20.36 GHz. And the corresponding fractional bandwidths within

A simple method to regulate the single-mode lasing intensity of semiconductor lasers without wavelength shift is demonstrated in this paper. The basic component is a digital micro-mirror device (DMD), which can be taken as an adjustable two-dimensional grating by its special structure. The lasing peak wavelength and peak intensity are respectively regulated by the DMD angular position and the DMD setting

In this paper, time-domain finite element methods for the full system of Maxwell's equations with cubic nonlinearities in 3D are presented, including a selection of computational experiments. The new capabilities of these methods are to efficiently model linear and nonlinear effects of the electrical polarization. The novel strategy has been developed to bring under control the discrete nonlinearity

Terahertz biosensing provides a suitable method to identify biomolecules due to their rich spectral fingerprint in this electromagnetic region. However, owing to the limitations of terahertz sources and detectors, the signal is weak and requires to be enhanced by particular technologies. In this paper, we propose a terahertz plasmonic biosensor based on Goos-Hänchen effect in graphene. Sample sensing

Biomedical applications such as pathology and hematology expect microscopes with high space-bandwidth product (SBP) which is difficult to achieve with conventional microscope setup. By applying a deep neural network, we demonstrate a high space-bandwidth product microscopic technique termed multi-angle super-resolution microscopy (MASRM) to achieve high-resolution imaging with the low-magnification

We proposed and experimentally demonstrated a novel and simple method to realize D-band millimeter-wave (mm-wave) single-sideband (SSB) vector signal generation using cascaded one single-drive Mach-Zehnder modulator (MZM) and one push-pull MZM. After the first MZM driven by a radio frequency (RF) signal of 20-GHz, an optical frequency comb (OFC) with six flat carriers was successfully generated. Using

We put forward and experimentally demonstrate a second order machine-learning (ML) based visible-light-positioning (VLP) system using simple linear interpolation algorithm to reduce the training samples required in the ML algorithm. Algorithms of the second order regression ML model using 2,430 training samples; and using the reduced training samples of 570 with and without the proposed linear interpolation

Digital coherent combining (DCC) technique can increase the free space optical signal collection area by combining the signals received by an array of small apertures in a coherent manner. To realize DCC the different versions of signals must be aligned in phase by the digital phase alignment algorithm (PAA). Low computation complexity is imperative for the PAA because the main obstacle to implement

Two types of GaN vertical-cavity surface-emitting lasers (VCSELs), with and without lateral optical confinement (LOC) structure, were fabricated and their performances were compared. Compared with the VCSEL without LOC, the device with LOC showed a great improvement in threshold current, slope efficiency, output power and differential quantum efficiency, which was mainly due to the reduction of internal

We demonstrate a compact all-fiber Er-doped chirped pulse amplification (CPA) system that can produce ∼344 fs pulses with an average power of up to 1.02 W and a repetition rate of 40.6 MHz at 1.56 μm (corresponding to an energy of 25.1 nJ). The pulse compressor in the CPA system is based on a hollow core photonic crystal fiber which is directly butt-coupled to the silica fiber. A mismatched negative

Polarization-maintaining (PM) all-fiber cavity is always essential to realize stable ultrafast-pulse generation. With the help of five sections of PM fibers with independently specific splicing angles, we successfully obtain a femtosecond pulse output from a PM Ytterbium-doped fiber laser (YDFL) mode-locked by the nonlinear polarization evolution (NPE) technique. Using a hybrid component, the PM all-fiber

A new method for fabricating a high-quality buried-heterostructure optical waveguide using quantum well intermixing (QWI) has been demonstrated. By patterning a SiO 2 thin film on top of a multiple quantum well (MQW) heterostructure, rapid thermal annealing (RTA) could induce laterally local QWI, resulting in a bandgap blueshift and a simultaneous decrease in the refractive index. Both lateral bandgap

We experimentally demonstrate spatial beam self-cleaning in an Yb-doped graded-index multimode fiber taper, both in passive and active configurations. The input laser beam at 1064 nm was injected for propagation from the small to the large core side of the taper, with laser diode pumping in a counterdirectional configuration. The Kerr effect permits to obtain high-beam quality amplification with no

In this paper, a new distributed fiber optic sensor system based on dual sensing directions by polarization optical time-domain reflectometer (POTDR) is proposed. Using a single POTDR scheme, the system is able to detect signals in the forward direction and backward direction simultaneously. It can detect more perturbations applied on the fiber simultaneously than a traditional POTDR. It can also improve

Polarization de-multiplexing becomes challenging in Stokes vector-direct detection (SV-DD) systems, especially when the rotation of state of polarization (RSOP) and fiber chromatic dispersion (CD) are induced. To address this issue, an adaptive blind RSOP equalizer based on Stokes space is proposed. After theoretical analysis, it is found that the distribution of transmitted signals in Stokes space

We experimentally demonstrate the transmission performance of the bit-loading discrete multi-tone (DMT) signal in intensity modulation and direct detection (IM-DD) system with a transmission distance of 2km and a net data rate of 108-Gb/s by two different shaping methods. A detailed comparison between the application of geometric shaping (GS) and probabilistic shaping (PS) in bit-loading DMT is presented

High-order soliton in anomalous-dispersion ultrafast fiber lasers is rarely researched due to its intrinsic instability in dissipative systems. For the first time, we numerically demonstrate the ultrafast pulse in fiber lasers will deviate from the fundamental soliton under strong pulse energy before splitting into multiple pulses. High-order soliton effect results in the single-pulse splitting into

Images acquired under sand-dust weather conditions are severely degraded, with low contrast and severe color shift. The reason is that, due to the influence of sand-dust particles, light is scattered and absorbed, resulting in a blurred image and low contrast; the color shift is caused by the rapid attenuation of blue light. Therefore, to solve the problem of color shift and poor visibility in sand-dust

We propose a method for implementing nanoscale optical logic circuits via single-step Förster resonance energy transfer (FRET). Use of single-step FRET enabled circuits with simple design and high expandability. Two kinds of FRET gates, a YES gate and a NOT gate, were used to modulate fluorescence output signals based on light inputs. Various logic circuits could be implemented by connecting FRET gates

In this paper, we report a two-layer five-port diffraction grating by a polarization-independent design under normal incidence. To be different from conventional five-port gratings, initially, we design a novel two-layer grating with operation in transmission. Next, we firstly design a polarization-independent grating with five-port splitting output. On the one hand, the accurate grating vector parameters

A generalized Lugiato-Lefever equation in frequency domain for the modeling of Kerr frequency combs, including full-order frequency dependence of all parameters, is derived and solved without sacrifice of computational time. The proposed model shows high accuracy and efficiency in simulations, agreeing well with previous reports. Based on the proposed model, the influence of parametric frequency dependence

A switchable polarization beam splitter utilizing GST-on-silicon waveguides is introduced and comprehensively investigated in this paper. Based on the phase matching and mode hybridization, structural parameters of the presented device are optimized by using the particle swarm optimization algorithm and finite difference time domain method, so that the output fundamental transverse-electric (TE 0 )

The ever-growing machine-to-machine traffic in data centers has stimulated the increase of transceiver data rate from 25 Gb/s/λ to 100 Gb/s/λ and beyond. It is believed that advanced modulation formats and digital-to-analog converters (DACs) will be employed in next generation short-reach transceivers. Digital pre-emphasis techniques are widely employed in DAC-based transceivers to compensate for the

Tetrahedral chromium (Cr 4+ )-ions is the main contributor to gain in the broadband single-mode Cr-doped crystalline core fibers (SCCFs). We have demonstrated a gross gain of 8-dB on a length of 27-cm for a 300-nm broadband SCCF using a thermal annealing technique. Gross gain and fiber length are the highest yet reported for the SCCF. The record gain is mainly due to both the longer fiber by aligned

We propose a novel approach for microwave and optical fields entanglement using an electrical capacitor loaded with graphene plasmonic waveguide. In the proposed scheme, a quantum microwave signal of frequency $\omega _{m}$ drives the electrical capacitor, while an intensive optical field (optical pump) of frequency $\omega _1$ is launched to the graphene waveguide as a surface plasmon polariton (i

In this article, a novel method for constructing a pre-equalizer by optimized filter synthesis with vector fitting is proposed to broaden the bandwidth of a visible light communication (VLC) system. By using the proposed method, an active-passive hybrid equalization circuit is constructed, and it is demonstrated that the 3-dB bandwidth of the VLC system with commercially available phosphorescent white

Broadband image-reject mixing using a dual-channel polarization-modulated photonic microwave phase shifter is proposed and experimentally demonstrated. The polarization-modulated photonic microwave phase shifter is realized by an orthogonal circularly-polarized wavelength generator, an optical coupler, two polarizers, and two photodetectors (PDs). When a local oscillator (LO) signal, a radio-frequency

We propose and realize a bandwidth and wavelength-tunable all-optical filter with high tuning efficiency based on double opto-mechanical microring resonators (MRRs) assisted Mach-Zehnder interferometer (MZI) structure, which is beneficial to achieve high extinction ratio and shape factor. As the optical field gradient is largely enhanced in the free-hanging MRRs, the opto-mechanical effect could be

High speed wireless communications are highly desirable for many industrial and scientific underwater applications. Acoustic communications suffer from high latency and limited data rates, while Radio Frequency communications are severely limited by attenuation in seawater. Optical communications are a promising alternative, offering high transmission rates (up to Gb/s), while water has relatively

In this article, we study the polarization coupling in a Faraday magnetooptical microcavity. Due to Faraday effect, the polarization coupling can be achieved between the intrinsic left and right elliptically-polarized modes. The mode characteristics of the Faraday microcavity, such as the dispersion curve, mode distribution and polarization evolution, are studied. And the supermodes can generate the

A demodulation method of spatial domain based on low-coherence interferometry is proposed. The original signal of spatial domain acquired by linear CCD is filtered with all-phase filter to obtain the fringe pattern, and the phase signal of the spatial frequency domain is retained after filtering. The fringe pattern analysis is employed to avoid phase ambiguity and realize large measurement range in

A switchable multi-wavelength thulium-doped fiber laser (TDFL) using a four-mode fiber based Sagnac loop filter was proposed and demonstrated. The Sagnac loop, incorporating a 4.8 m long four-mode step-index fiber, acting as a comb filter was analyzed theoretically and experimentally. By adjusting two polarization controllers, eight stable single-wavelength operations and five stable dual-wavelength

We present a novel concept for the stabilization of the carrier-envelope offset (CEO) frequency of femtosecond pulse trains from thin-disk laser oscillators by exploiting gain depletion modulation in the active gain region. We shine a small fraction of the laser output power back onto the thin disk allowing the population inversion in the gain medium to be controlled. We employ this technique in our

An ultrafine frequency linearly tunable single-frequency fiber laser based on the intracavity active tuning is demonstrated. Single-frequency operation can be achieved by an ultrashort cavity and ultranarrow polarization-maintaining fiber Bragg grating. A sub-nanometer-accuracy piezoelectric ceramic actuator with closed-loop mode has been employed to realize the cavity-length active tuning scheme,

We propose and demonstrate a cladding-pumped, erbium-ytterbium co-doped fiber amplifier (EYDFA) scheme based on dual wavelength auxiliary signal injection technique to solve the issue of the backward Yb-ASE self-lasing under strong pumping for the high-power fiber amplification of 1.5-μm kHz-linewidth linearly-polarized laser signal. With the dual wavelength auxiliary signal of 1030 and 1040 nm injection

A D-band vector millimeter wave (mm-wave) signal generation and propagation scheme employing cascaded intensity modulator (IM) and in-phase/quadrature (I/Q) modulator is proposed and implemented. In experiment, both the IM and I/Q modulator are operating on optical-carrier-suppressing (OCS) mode to generate two pairs of dual single-sideband (SSB) signals, and the undesired optical sidebands are not

Optical imaging/tracking through scattering medium is a difficult challenge. We demonstrate a method using speckles with multiple bit depths to image objects through scattering medium. The image of the object can be reconstructed even if the speckles are binary. Speckles with different bit depths are obtained by quantifying the original speckle. And we discuss the application of binarized speckles

The performances of quantum-dot (QD) based photoluminescent devices are highly restricted by the application environment, especially the moisture and oxygen. However, current external encapsulation structures are not applicable to the devices with discrete QD distribution, especially for some rough profiles. To address this issue, an encapsulation method for discretely distributed quantum-dot arrays

Agile mode switching between LP 01 and LP 11 modes in an all-fiber laser is demonstrated by exploiting an acoustically induced fiber grating within the laser cavity. The laser exploits a cladding pump configuration and can deliver up to 5.85 W of stable output power in LP 11 mode at 1070.07 nm and 6.06 W in LP 01 mode at 1070.48 nm, with a slope efficiency near 50%. Complete mode-switching speed with

In this paper, a passively mode-locked Tm-doped fiber laser by employing lead sulfide (PbS) nanoparticles as the saturable absorber (SA) is successfully demonstrated in the 2 μm region for the first time, to the best of our knowledge. Measured by a home-made balanced twin-detector setup at 2 μm, the PbS SA was characterized by the modulation depth of 10.69%, the non-saturable loss of 74.27%, and the

Here we report on the exfoliation of graphene by using femtosecond pulsed laser with the highly oriented pyrolytic graphite (HOPG) immersed in water. The size of the graphene flakes was demonstrated to be well regulated by controlling the peak-power density of the femtosecond laser irradiation on the HOPG. The transmission electron microscopy (TEM) and Raman spectroscopy were used to identify the morphology

A high power Ho:YAP laser in-band pumped by a home-constructed Tm doped all fiber master oscillator power amplifier (MOPA) is reported. The optically polished and uncoated Ho:YAP laser yielded over 107 W of output power at ∼2117.1 nm with 215.4 W of absorbed pump power, corresponding to a slope efficiency of 50.6% with respect to the absorbed pump power. The beam quality M 2 parameter was measured

The experiment reports a kind of L-band dissipative soliton resonance (DSR) nanosecond Er-doped fiber laser. The passive mode-locked L-band DSR pulse is achieved in a figure-eight structure by using the nonlinear-amplifying-loop-mirror (NALM). The repetition rate of pulse is 468 kHz. At the maximum pump power of 398 mW, the output power is 25 mW with a pulse energy of 45 nJ. By adjustment of polarization

Recent research on nonlinear multimode interference (NL-MMI) based mode-locking method provides a new approach for ultrafast all-fiber lasers. Here, we report on the polarization dynamics of group velocity locked vector solitons (GVLVSs) and noise-like vector pulses (NLVPs) in a graded-index multimode fiber (GIMF) based all-fiber laser. Due to the non-polarization sensitive characteristic of the NL-MMI

We experimentally demonstrated a novel repetition rate adjustable SBS-based Q-switched fiber laser. An inserted Fabry-Perot interferometer formed by two non-contact end faces of two FC/PC fiber connectors was inserted to help the system stabilize the random output of SBS-based Q-switching. By mechanically fine-tuning the length of the inserted Fabry-Perot interferometer, a linear and continuous repetition

We propose designs of silicon nitride (Si 3 N 4 ) waveguides with enhanced nonlinear parameter and engineered anomalous group velocity dispersion (GVD) by addition of tellurium oxide (TeO 2 ) top-coating layers of various thicknesses. The proposed waveguides have calculated nonlinear parameters of up to three times that of stoichiometric Si 3 N 4 and exhibit anomalous GVD at near infrared wavelengths

The phenomenon of resonant reflection from a grating-coupled waveguide mode is conceptually, technologically, and experimentally transposed from a planar corrugated waveguide structure under plane wave excitation to a circularly symmetrical waveguide at the inner wall of a tube under cylindrical wave excitation. The mode coupling element is an azimuthally periodic wall corrugation having an integer

This study presents an automated registration method based on optical flow for an adaptive optics scanning laser ophthalmoscope. The method was designed to align and average images to obtain a higher signal-to-noise ratio image. A correlation based optical flow image registration method, which has large registration degrees of freedom, is adopted as a local registration method. By comparing the images

Image quality is degraded in the out-of-focus region because of the depth-variant (DV) point spread function (DV-PSF) of a fluorescence microscope. Either non-blind or blind deconvolution for restoration results in limited improvement. In this work, we propose a two-step learning-based DV deconvolution (LB-DVD) to restore the out-of-focus image. In the first step, DV-PSF is predicted by a defocus level

The authors have proposed an Ultrabroadband Metamaterial Microwave Absorber. The authors have claimed that the proposed structure is metamaterial absorber. We have recognized that the designed structure is not a metamaterial absorber because of ignorance of cross-polarized reflection coefficient. The designed structure is polarization convertor because the proposed unit cell has an-isotropic geometry

Beam splitters, especially those with tunable split ratios, play significant role in interferometers, spectrometers, and communication systems. To this end, we proposed a polarization-controllable beam splitter based on dielectric metasurface composed of an array of dielectric pillars. The dielectric metasurface presents phase gradients along two orthogonal directions, say, x- and y- axis, with each

Wave plates as important polarization control devices are widely used in the applications of biomedical imaging, fiber optical communication, astronomy, semiconductor industry and aerospace etc. To make the wave plate actively tunable, we propose a rectangular antenna-based metasurface based on the phase-changing material Ge 2 Sb 2 Te 5 (GST) with high transmittance and polarization conversion rate

We propose a novel optical spatial differentiator to perform the differentiation computation in terahertz region based on the graphene metalines, which consist of graphene layers with different widths and chemical potentials. The numerical simulation results show that when beam waist size w>1.9λ, the metalines perform the first-order differentiation in the reflection spectrum with efficiency>97%, which

We report on an ultra-compact, low loss and broadband TM-pass polarizer, which is constructed by two interleaved subwavelength-gratings (SWGs) waveguides inserted in the center of the strip waveguide on a silicon-on-insulator (SOI) platform. The device structure is optimally engineered to support Bloch mode for fundamental TM polarization only. Therefore, the TM mode transmits along the strip waveguide

A microwave photonics interferometric (MWPI) method for measuring the beat length in high birefringence polarization-maintaining fiber (PMF) is proposed. The approach is based on the radio frequency (RF) interference between the two polarization modes propagating on the polarization axis in the PMF. The period of the RF interference spectral is determined by the optical path difference of the two polarization

We present temporal quadratic solitons in doubly resonant temporal dispersive optical parametric oscillators without a walk-off in numerical simulations. In frequency domain, these cavity solitons correspond to coherent dual-combs with smooth envelopes in half-harmonic and pump fields. We also investigate the soliton existence region, and the soliton behavior with parameters in this cavity system.

In this paper, a new image encryption system based on joint transformation correlation principle and ptycholographic iterative engine is proposed. When the encryption is performed, the original image can be divided into several parts by using the scanning movement of the probe. Each part is encrypted by the joint transformation correlation technology, and the ciphertexts are finally transmitted in

We demonstrate a tunable band-stop optical filter on a germanium-on-insulator photonic platform operating at 1.95 μ m wavelength. The band-stop filter is implemented using parallel-coupled microring resonators with the number of microring resonators varied from one to. three. Through the use of a heating stage, the thermo-optic coefficient of germanium is measured to be +3.55 × 10 −4 /°C. The high