By employing a GaN-based series-biased micro-light emitting diode ( $\mu $ LED) array and orthogonal frequency division multiplexing modulation format, a high-speed free-space visible light communication system for long-distance applications has been demonstrated. The blue series-biased $\mu $ LED array, which consists of $3\times 3$ , 20 $\mu \text{m}$ -diameter $\mu $ LED elements, presents promising

We experimentally demonstrate a passively mode-locked all-fiber Tm laser with an all-fiber saturable absorber (SA) which operates based on the nonlinear multimode interference (NL-MMI) effect in a tapered graded-index multimode fiber (GIMF). The tapered GIMF SA demonstrates the nonlinear characteristics of modulation depth of 21.15%, and saturation fluence of $89.04~\mu \text{J}$ /cm 2 . We obtain

A linear regression algorithm is applied to a digital-supermode distributed Bragg reflector laser to optimise wavelength switching times. The algorithm uses the output of a digital coherent receiver as feedback to update the pre-emphasis weights applied to the laser section currents. This permits in-situ calculation without manual weight adjustments. The application of this optimiser to a representative

Dispersion distribution and optical gain dynamics introduce vivid pulse evolution in fiber lasers. Here, we report on a multi-output fiber laser mode-locked by nonlinear polarization rotation (NPR) in net normal-dispersion regime. In particular, the asymmetry settings of the laser parameters can introduce the spectral reshaping and pulse breathing process at different output ports. Both the transformation

In this letter, highly reliable white light-emitting diodes (WLEDs) were fabricated by using an all-inorganic packaging structure with a phosphor-in-glass (PiG) converter. The PiG was soldered on a three-dimensional substrate to realize the hermetic structure for WLEDs. The packaging structure displays the reliable and dense bonding layer between the PiG and the substrate. The thickness of phosphor

A system containing spectral-domain phase microscopy and fluorescence microscopy has been developed to decode and detect thickness-encoded suspension arrays. The spectral-domain phase imaging path is used for decoding the thickness of the micro glass pieces while the fluorescence imaging path is used for quantifying the targeted analytes. The spectral-domain phase microscopy uses a spectral domain

In this article, a highly sensitive surface plasmon resonance (SPR) based concave shaped refractive index sensor (CSRIS) is designed and analyzed using silver (Ag) nanowire. The SPR effect between the surface plasmon polariton (SPP) and core guided modes of the concave shape (CS) designed sensor is used to measure the variation in refractive index (RI) of analytes ( $\text{n}_{\mathbf {a}}$ ). The

In this work, we present the fabrication process of a $3~\mu \text{m}$ -thick AlGaInAs-based vertical p-i-n laser diode structure grown on a directly bonded InP-SiO 2 /Si (InPoSi) substrate. High-quality epitaxial growth on InPoSi is reported. Based on these structures, the fabrication process of Fabry-Perot broad lasers is presented. Device performance is compared to the ones obtained from the same

A phase demodulation algorithm in phase-sensitive optical time domain reflectometry ( $\Phi $ -OTDR) with self-interference balance detection is proposed. With a simple differentiate-and-cross-multiply (DCM) operation to acquire the perturbation waveform, and a further second-order operation to compensate the amplitude fluctuation of the phase, the phase can be extracted accurately. The self-interference

We experimentally demonstrate a silicon photonic Mach-Zehnder modulator (MZM) assisted by phase-shifted Bragg gratings. Coupled resonators are inserted in the Bragg grating structure to significantly enhance the phase modulation efficiency, while maintaining a wide optical bandwidth compared to other resonator-based modulators. Fabricated using a CMOS-compatible foundry process, the device achieved

We present a dispersive interferometry of optical frequency comb for simultaneous measuring absolute distance and angle. The reconfigured Michelson interferometer can emit two parallel measured beams and one reference beam. The three pulse beams interfere with each other, and the interference spectrum is sampled by a spectrometer. It is simultaneously modulated by the three optical path differences

InAs/GaAsSb type-II superlattice (T2SL) materials grown at a higher temperature and lattice-matched to InAs substrates are considered to have significant advantages in long wavelength infrared (LWIR) detection. In this work, an InAs/GaAsSb T2SL LWIR focal plane array (FPA) was fabricated and evaluated. The FPA has a format of $320\times256$ with a pixel pitch of 30 $\mu \text{m}$ and exhibits a 100%

A novel coupling device composed of a combination of microlens and pillar having an approximately $8~\mu \text{m}$ diameter and $20~\mu \text{m}$ height and grown from single-mode fiber (SMF) core end is proposed. This device was successfully fabricated by using a self-written waveguide and dipping method with UV-curable resin. Theoretical and experimental studies were done. A high coupling efficiency

We demonstrate an optical hitless wavelength-selective switch using a single microring resonator assisted with a symmetric Mach-Zehnder interferometer (MZI). A part of the ring waveguide and its symmetrical waveguide are designed to be an equally armed MZI as an on-off switch for the resonant state of the microring. The symmetric MZI is insensitive to the spectrum and it avoids free spectral range

In this letter we present new results on high power 970 nm ridge waveguide lasers based on an extreme double asymmetric epitaxial design. Due to an improved lateral-longitudinal design an M 2 -value below 1.1 and efficiency over 60% could be maintained at power levels slightly above 2 W. The lasers consist of a narrow mode-filter section at the back facet, a relatively broad section at the front facet

We report a high speed directly modulated widely tunable dual wavelength distributed feedback (DFB) laser for THz communication application. The wavelength separation between the two modes can be thermally tuned between 96 GHz and 1510 GHz. The device can be directly modulated by high speed data at up to 25 Gb/s data rate, which facilitates high speed data modulation in a THz communication system.

This letter reports a novel fused silica microfluidic device with pressure sensing capability that is fabricated by integrated additive and subtractive manufacturing (IASM) method. The sensor consists of a capillary and a 3D printed glass reservoir, where the reservoir volume change under pressure manifests liquid level deviation inside the capillary, thus realizing the conversion between small pressure

High-quality helical long-period fiber gratings (HLPFGs) with a coupling strength greater than 30 dB and an insertion loss less than 0.5 dB are formed by applying CO 2 laser to expose an optical fiber that is simultaneously translated and rotated to relieve the residual stress of the fiber along a helical pathway, rather than twisting the fiber under a high-temperature condition. The mode coupling

We report on the study of optical properties of mist CVD grown $\alpha $ -Ga 2 O 3 with the observation of excitonic absorption in spectral responsivity measurements. 163 nm of Ga 2 O 3 was grown on sapphire using Ga-(acac) 3 as the starting solution at a substrate temperature of 450°C. The film was found to be crystalline and of $\alpha $ -phase with an on-axis full width at half maximum (FWHM) of

The performance of high-speed intensity-modulation (IM)/direct-detection (DD) system implemented by using O-band directly modulated laser (DML) could be limited by the waveform distortions induced by nonlinear modulation dynamics of DML. The conventional polynomial nonlinear equalizer (PNLE) can be used at the receiver to compensate for such waveform distortions. However, this nonlinear equalizer suffers

We report on the spectral characteristics of the phase noise enhancement of continuous-wave (CW) optical signals passing through a semiconductor optical amplifier (SOA) operating in the saturation regime and used for relative intensity noise (RIN) reduction. We show that the known effect of phase noise enhancement, attributed to the linewidth enhancement factor of the device, happens only at a limited

We demonstrate a high power two-dimensional vertical-cavity surface-emitting laser (VCSEL) array cooled by liquid metal. An output power of 1.1 kW at 808 nm with 39% power conversion efficiency (PCE) is obtained under continuous-wave (CW) operation. To the best of our knowledge, this is the highest output power reported for a laser diode array with liquid metal cooling. Moreover, the wavelength drift

We investigated how the performance and reliability of AlGaInP-based red (620 nm) micro-light-emitting diodes (micro-LEDs) ( $25\times 17\,\,\mu \text{m}^{2}$ ) were influenced by the use of $n$ -AlInP ohmic layer and distributed Bragg reflector (DBR). The AlGaAs-based DBR showed reflectivity of 94.9% at 622 nm with a 14 nm-stopband width. The micro-LEDs with $n$ -GaAs gave slightly lower forward voltages

We report on the development of a compact (volume $\approx ~100$ cm 3 ), multimode diffraction-limited Raman spectrograph and probe designed to be compact as possible. The spectrograph uses ‘off the shelf’ optics, a custom 3D-printed two-part housing and harnesses a multi-core fibre (MCF) photonic lantern (multimode to few-mode converter), which slices a large 40 $\mu $ m multimode input into a ne

An InP-based Vertical-Cavity Surface-Emitting Laser (VCSEL) with a liquid crystal (LC) microcell monolithically integrated on its surface for spectral tuning is investigated. Unlike tunable VCSELs integrating a movable membrane, here the physical length of the cavity remains unchanged and only the voltage applied on the LC ensures a refractive index modification for a particular polarization emitted

We experimentally demonstrate a 56-Gb/s vestigial sideband (VSB) modified duobinary (MDB) 4-level pulse amplitude modulation (PAM4) signal transmission over an 80-km single-mode fiber (SMF) in an intensity-modulation and direct-detection (IM/DD) system without optical dispersion compensation. Compared to the conventional PAM4 signal without pulse shaping, the MDB PAM4 signal exhibits a higher spectral

This letter theoretically proposes and experimentally demonstrates a high-security optical access network (OAN) scheme based on carrier-less amplitude and phase modulation (CAP). The double chaotic map is used to perform the floating probabilistic shaping (PS), so as to encrypt data in the physical layer. 20 Gb/s encrypted data transmission was successfully realized employing 16-CAP modulation. The

We propose and demonstrate an integrated reconfigurable fiber-chip mode converter with multi-mode coupling functionality. The converter is composed of an inverse taper array, a cascaded Y-junction and a waveguide crossing, as well as a heater to control the mode conversion states. The fundamental and first-order modes can be coupled and converted simultaneously between fiber and chip without additional

A parallel differential confocal method (PDCM) is proposed to obtain rapid surface height measurements with nanoscale precision with a conventional optical microscope. In contrast to existing differential surface profiling methods where multiple sensors are required and either pixel-by-pixel horizontal or layer-by-layer vertical scanning is necessary, the PDCM uses only a single sensor without scanning

In this paper, a real-time software-reconfigurable orthogonal frequency division multiplexing based non-orthogonal multiple access (OFDM-NOMA) scheme with dynamic power allocation is proposed and experimentally demonstrated for hybrid in-house access over single-mode fiber (SMF) and visible light communication (VLC). Such hybrid access can provide both wired and wireless transmission, which can accommodate

We demonstrate a superluminescent diode fabricated on a nonpolar ${m}$ -plane GaN substrate by employing a linearly tapered waveguide design. A high electrical −3dB modulation bandwidth ( $f_{\mathbf {3dB}}$ ) of 2.5 GHz at a current density of 30 kA/cm 2 is achieved. The high modulation bandwidth is attributed to the shorter carrier recombination lifetime, the linear gain curve in the nonpolar ${m}$

We assess the performance of a modular photonic integrated circuit (PIC) for space and time optical switching as an optical add-drop node for metro-access network applications. The PIC based on semiconductor optical amplifier (SOA) technology enables the implementation of compact, low cost and lossless add-dropping through fast optical switching. Data integrity measurements demonstrate error-free switching

In this paper, we proposed a kind of novel optical time-domain reflectometer (OTDR) which employed the linear frequency modulation (LFM), the fractional Fourier transform (FrFT), and electrical domain frequency division multiplexing (FDM) technologies. In our proposed OTDR, the intensity of the probe pulse was modulated by the LFM signal. At the receiver of the OTDR, the LFM signal was recovered through

In this paper, a calibration process for position-sensitive detector (PSD) systems is proposed. In a PSD system using a quadrature detector (QD), various error sources including the QD, circuit components, and mechanical misalignment that appear in actual implementation introduce inaccuracies in the beam position estimation. The error pattern can be non-linear in the beam power, and non-uniform in

In this paper, we present a detailed investigation of three types of tapered distributed feedback (DFB) quantum cascade lasers (QCLs) emitting at $7.2~\mu \text{m}$ . The sampling gratings with different sampling duty cycles were fabricated by holographic lithography combined with the conventional optical photolithography. High output power of more than 550mW with excellent beam quality was achieved

It is well known that higher diffraction order suggests a stronger dispersion for gratings with the same period. Here, a broadband high-efficiency three-layer all-dielectric rectangular-groove transmission grating operating at the −2 nd order is designed under second Bragg incidence. An initial solution of the grating parameters is obtained quickly by using the simplified modal method (SMM). Moreover

Tunable coherent light source emitting at the visible region has long been recognized as a key asset, especially with a monolithic design involved, for the increasing number of emerging applications in the scientific research and industrial manufacturing. Here, an efficient 640 nm solid-state laser is used as a pump source, and the fiber end-facet mirrors construct a fiber laser resonator. We experimentally

The growing demand for wireless communications services means that RF systems are increasingly unable to support user’s requirement. Consequently, there is a growing interest in using visible light communication (VLC), including interest in sensitive VLC receivers. Since they have the potential to detect single photons, silicon photomultipliers (SiPMs) could potentially be used to create the most sensitive

Polarized low-coherence interferometry (PLCI) is a promising technology to absolute displacement measurement and sensor demodulation. To avoid jump errors induced by dispersion and achieve a high response, a dispersion compensation method based on fringe peak position estimation and polynomial fitting is proposed to get rid of the dependence on the priori model and birefringence parameters, and make

Fiber-optic ultrasound transmitters can be used in structural health monitoring, material characterization, and biomedical imaging. However, the bandwidth of current fiber-optic ultrasound transmitters is tens of MHz which prevents the ultrasound image on cells with resolution of $\mu \text{m}$ level. Here, ultra-compact in-fiber ultrasound transmitter is proposed by using the multi-mode interference

Persistent photoconductivity (PPC) in solution-processed pristine CuO and Au coated CuO thin films have been studied. Long-lasting PPC has been observed in Au coated CuO thin films with stable current levels even for 7 days. For the first time, long-lasting PPC effect in Au/CuO has been utilized for non-volatile optical memory. We have established both the SET and RESET processes using optical excitation

We present a regenerative amplifier (RA) based on Yb:YAG single-crystal fiber (SCF) and nonlinear amplifying loop mirror (NALM) fiber oscillator. The home-made all-fiber NALM oscillator is constructed with polarization maintaining (PM) fibers for improved environmental stability, delivering a stable pulse train. The seed is directly amplified in a single stage without using CPA technique. 21 W, $105~\mu

In this letter, an enhanced thermally tunable filter design based on a stack of three layers and a long external sleeve at the tip of a single mode fiber is presented. Here, two of these layers and the sleeve are thermo-sensitive. Moreover, it is shown that by using the sleeve with a large length compared with the thicknesses of the layers, the thermal tuning mechanism can be considerably enhanced

We experimentally demonstrate a high-speed intensity modulation and direct-detection (IM/DD) system with four wavelength division multiplexing (WDM) channels. With the aid of semiconductor optical amplifier (SOA) and probabilistic shaping (PS) technique, 1T (280Gbit/ $\text{s}\times 4$ ) PS-PAM8 signals can be successfully transmitted over 40-km standard single mode fiber (SSMF). As a more precise

A watt-level directly diode-pumped continuous-wave (CW) Ti:Sapphire oscillator was demonstrated for the first breakthrough by a high-power green laser-diode-pumped module employing the technologies of beam shaping, beam collimation, polarization beam combining, and fiber coupling. A 1.36-W output power and 10.6% of slope efficiency were obtained based on the double-concave (DC) cavity configuration

Metalens as one of the most popular applications of emerging optical metasurfaces has raised widespread interest recently. With nano structures fully controlling phase, polarization and transmission, metalens has achieved comparable performance of commercial objective lenses. While recent studies seeking for the accomplishment of traditional focusing behaviors through metalens are successful, in this

This letter demonstrates the stabilization of an external cavity semiconductor laser at 1550 nm on an ultra-high Q factor fiber ring resonator (FRR). Based on a Pound-Drever-Hall technique, our system is optimized in order to take into account the properties of the FRR which features a large Q factor ( $2\times 10^{9}$ ) but a relatively small free spectral range (2 MHz). The measured performances

We demonstrated an Yb-doped mode-locked fiber laser system delivering both dissipative-soliton-resonance (DSR) and noise-like pulse (NLP) simultaneously. The pulse widths of DSR and NLP were 7.1 ns and 4.3 ns, respectively. Meanwhile, the spectrum widths at 1056 nm of DSR and NLP were 0.5 nm and 21.5 nm, respectively. In this dual mode-locking state operation, the intracavity laser powers (DSR, NLP)

We propose a novel low complexity two-stage frequency offset estimation (FOE) scheme based on modified Zoom-FFT for square 16/64-quadrature amplitude modulation (QAM) coherent optical systems. The first stage roughly estimates the frequency offset through a small size FFT. After frequency shifting, the modified Zoom-FFT can select and reconstruct the spectrum of interest by time domain average. Since

Precise diameter control is critical for many optical micro/nanofiber (MNF) applications. We demonstrate real-time MNF diameter control with improved accuracy and precision. Different from earlier works, a white light source is applied to monitor the transmittance during fiber pulling process. Terminated directly by the transmission intensity drops that indicate the cutoff of TE01 mode at particular

We experimentally demonstrate a 2- $\mu \text{m}$ free-space data transmission system in a simulated atmospheric turbulent device with an actively mode-locked holmium-doped fiber laser. The central wavelength can be adjusted from 2035.6 nm to 2050.2 nm with optional repetition rates of 1.01 GHz and 2.02 GHz, respectively, and the pulse is stabilized by adding a fiber Fabry-Perot filter in the laser

We demonstrate a double-layer Si 3 N 4 multi-ring resonator system, where an $S$ -bend waveguide is cross-coupled with a ring cavity loaded with two sub-ring resonators. The device performance is analyzed by using the transfer matrix method. The alignment-error-induced device performance variations are also discussed. The measured spectra coincide well with the simulated results. The device has high

A nearly transform-limited, single-frequency $2~\mu \text{m}$ laser system with multi-stage of double-pass Tm:Ho:LuLiF 4 slab amplifiers was demonstrated. An amplified pulse energy up to 5.6 mJ at central wavelength of 2051.9 nm was achieved successfully with around 429.7 ns pulse width at a repetition rate of 10 Hz. The line-width of the laser spectrum detected by a heterodyne technique was about

A compact augmented reality (AR) combiner using Pancharatnam-Berry phase (PBP) lens and holographic optical element (HOE) is proposed. PBP lens is activated as a convex lens or a concave lens according to the polarization state of the input light wave. By using this characteristic, a thin AR eyepiece with a large numerical aperture (NA) is constructed. The AR eyepiece operates as a convex lens for

A photonics-assisted approach to dual-functional analog signal transmitter that can simultaneously generate radio-frequency (RF) signal and linear frequency modulation (LFM) signal is proposed and experimentally demonstrated. Two types of beat notes can be independently generated by heterodyning of two lasers in a photodiode using a 4-channel monolithic integrated distributed feedback (DFB) laser array

We demonstrate the transmission of beyond-100 Gb/s Nyquist half-cycle 16-quadrature-amplitude modulation (16-QAM) subcarrier modulation (SCM) signals with a compact silicon-based GeSi electro-absorption modulator. In combination with nonlinear compensation, the measured bit-error rate (BER) after 2 km standard single-mode fiber (SSMF) transmission is below the 20% hard-decision forward error-correction

We have proposed and experimentally demonstrated an ultrasensitive all-fiber angular displacement sensor based on in-fiber polarizing gratings and half waveplate (IFHWP), in which the polarizing gratings are based on 45°-tilted fiber gratings (45°-TFGs) and the IFHWP is constructed by bending-induced birefringence in single mode fiber (SMF). Compared with the existing angular displacement sensors,

We experimentally demonstrated a high-performance frequency upconversion detector for telecom-band photons based on a passively synchronized fiber laser system. The involved coincidence pumping technique enabled to spectrally convert the pulsed infrared photons into the visible regime with a conversion efficiency of 72%. The overall detection efficiency of the upconversion detector reached to 30% with

An integrated in-fiber coupler for excitation of whispering-gallery modes (WGMs) of a microsphere resonator is proposed. The device is fabricated by embedding a microsphere into an optical fiber inner air-cavity through an open micro-channel to excite various WGMs via evanescent field coupling. The asymmetric Fano resonance line shape and the symmetrical Lorentzian line shape with a slope of −13.88

A silicon-based four-channel coarse wavelength- division multiplexing (CWDM) (de)multiplexer working in the O-band is proposed and realized. The present on-chip four-channel CWDM (de)multiplexer is composed of four cascaded optical filters with flat-top spectral responses, which are realized by combining a multimode waveguide grating (MWG) and a two-channel mode (de)multiplexer. For the realized flat-top