The conventional chip-on-board light-emitting diodes (COB-LEDs) with flat encapsulant layer present low light efficiency due to the total internal reflection (TIR) happens at the encapsulant-air interface. In this study, microlens array was realized on the flat encapsulant layer of COB-LEDs to diminish the TIR at the encapsulant-air interface. The microlens array was fabricated by selectively exposing

Optical frequency combs (OFC) have revolutionized the field of optics ranging from metrology to radio-frequency photonics. One of the main advantages of an OFC is its spectral purity and broadband phase coherence. An increase in comb linewidth corresponds to elevated phase noise and system performance degradation that mandates larger processing complexity. A specialized processing scheme relying on

Physical layer encryption based on digital chaos emerged as a promising methodology for securing data transmission. Discrete multi-tone (DMT) is a widely investigated advanced modulation format in intensity modulation and direct detection (IM/DD) systems, because of its high spectral efficiency, low cost and high dispersion tolerance. In this letter, we successfully performed a physical layer chaotic

This letter presents an experimental study comparing the relative impact of turbulence induced scattering on coherent and non-coherent light propagating through water. It is shown that the scintillation index increases with increasing temperature inhomogeneity in the underwater channel. Our results indicate that a light beam from a non-coherent source has a greater resilience to temperature inhomogeneity

We investigate on bound-state mode-locking in the close-to-zero dispersion regime of an Er-fiber laser. A two-soliton bound state with 82 fs pulse duration and 0.58 ps pulse separation is achieved. Compound 2+1 type bound state solitons with ~100 fs pulse duration has also been observed. Both the double-pulse and the 2+1 type bound states could experience period-doubling bifurcations and exhibit the

Multiple microelectromechanical system (MEMS) phased arrays in optical conjugation enable scanning over extended angular ranges beyond what is possible with a single device. We demonstrate this method for random access beam steering at 250 kHz using a MEMS phased array and a switchable grating modulator, achieving 4,352 resolvable lines from 2,176 line pairs over a field of view (FOV) of ±3.74° in

We report a method of precise chemical sensing by using on-chip external cavity lasing technology, in which a photonic micro-disk resonator acting as a sensing element is embedded into a laser’s external cavity. The bandwidth of resonance peak of the passive resonator is greatly reduced. The lasing technology improves the quality factor of the system and the detection limitation in chemical sensing

We propose a $1\times2$ electro-optic miniature optical switch based on mode deflection of lithium-niobate (LN) annealed proton exchange waveguides with microstructured electrodes. Our fabricated device consists of LN waveguides covered with isosceles-triangle-shaped array electrodes, a horn-shaped input waveguide, and two tapered output waveguides. At a driving voltage of 40 V, the two-modes can switch

A new multi-functional crystal has been implemented by combining the acousto-optic (A/O) modulation with Raman laser output, which has never reported before. Notably, the $\alpha $ -BTM displaying an adequate A/O figure of merit of $10.18\times 10^{-18}\,\,\text{s}^{3}$ /g using the comparison method is originally tailored to fabricate an A/O modulator that exhibits a high diffraction angle and diffraction

We demonstrate a dual-wavelength, compact femtosecond optical parametric oscillator (OPO) with high-repetition-rate, which is harmonically pumped by a ~101 MHz Yb-doped fiber laser system. The dual-wavelength output is realized by exploiting the bidirectional off-axis pumping technique, and the multiplication of repetition rate is derived by placing a nonlinear crystal in a miniaturized V-type cavity

Thin film optical elements exhibiting translational invariance, and thus robustness to optical misalignment, are crucial for rapid development of compact and integrated optical devices. In this letter, we experimentally demonstrate a beam-shaping element that generates an annular beam by spatially filtering the fundamental Gaussian mode of a laser beam. The element comprises of a one-dimensional photonic

We study the trade-off between energy harvesting and data communication for a two-meter wireless gallium-arsenide vertical-cavity surface-emitting laser and photovoltaic link. The use of orthogonal frequency-division multiplexing with adaptive bit and power loading results in a peak data rate of 1041 Mb/s at a bit-error ratio (BER) of $2.2\times 10^{-3}$ under short-circuit conditions. The receiver

A low power and compact thermo-optic switch based on $1\times 1$ Mach-Zehnder interferometer structure is demonstrated with the thermal isolation structure fabricated with a new backside etching process. The adjacent SiO 2 and underlying silicon around phase arm are removed to suppress the thermal diffusion. Benefiting from the backside anisotropic etching process and front protecting photoresist used

A new cascaded structure based on two long-period fiber gratings (LPFGs) for simultaneous measurement of strain and temperature is proposed and studied. The proposed structure is cascaded by a LPFG and a S-type long-period fiber grating (S-LPFG). The LPFG is fabricated using the CO 2 laser by etched method. The S-LPFG is fabricated using the CO 2 laser by polished method. The grooves of the S-LPFG

This paper introduces a method to do simultaneous temperature estimations of multiple gratings in an FBG array. The method involves training a multi-layer neural network using simulated training data. The network is then used to estimate the temperature changes of multiple gratings simultaneously using only the experimentally obtained spectrum of the FBG array. The versatility of the method is seen

A cascaded optical modulator topology for detecting the phase difference of two microwave signals is presented. It operates based on mixing of two microwave signals. The phase difference of two microwave signals can be obtained from the system output DC voltage. The phase detector is designed to eliminate the problems of DC offset and phase offset, which are present in reported structures. Experimental

A microwave photonic phase shifter based on four cascaded tunable silicon nitride microring resonators is proposed. The phase shifts and RF power variations of the microwave photonic phase shifter were investigated theoretically and experimentally. Good overall performances with full phase tuning range of 400°, low RF power variations of ± 1.5 dB with a broad bandwidth of 11 GHz, fiber to fiber insertion

This letter proposes an electrically controlled non-polarizing optical bandpass filter based on prism coupled planar optical waveguide (POW) structure that incorporates a liquid crystal layer, which works in the electrically controlled birefringent (ECB) mode and makes the central wavelength for TM passband tunable. The measured passband of TM wave, tuned from 526 nm to 599 nm, overlaps with that of

Silicon photonic sensors are promising candidates for lab-on-a-chip solutions with versatile applications and scalable production prospects using complementary metal-oxide semiconductor (CMOS) fabrication methods. However, the widespread use has been hindered because the sensing area adjoins optical and electrical components making packaging and sensor handling challenging. In this work, a local back-side

An integrated design of ultra-high-speed Fiber Bragg Grating (FBG) interrogation system is illustrated and experimentally demonstrated. A Fourier Domain Mode Locked (FDML) laser is employed as a high-speed wavelength-swept light source. The use of the Mach-Zehnder interferometer (MZI) and the single-peak filter (SPF) overcomes the nonlinear effect and the scanning wavelength drift problem. A signal

A high-power InAlGaAs/InP tapered distributed Bragg reflector laser diode with narrow linewidth emission at $1.5~\mu \text{m}$ is reported. The laser has a monolithic waveguide architecture comprising a third-order grating section for longitudinal mode selection, an index-guided gain section for lateral mode filtering, and a gain-guided tapered section for power scaling. An output power of 770 mW is

In this article, we present for the first time to our knowledge, a DWDM $16\times 16$ silicon photonic cyclic-frequency AWGR device. The AWGR features a channel spacing of 1.06 nm (189 GHz), a free spectral range of 17.80 nm (3.16 THz) and a 3-dB channel bandwidth of 0.65 nm (116 GHz). Its proper cyclic-frequency operation was experimentally verified for all $16\times 16$ channels with channel peak

Compact unbalanced splitters are a key constitutive block to achieve flexibility in future multimode applications relying on silicon-on-insulator technology. Their design, however, poses significant challenges as it has to combine high performance for the different supported modes, a compact size, and compliance with fabrication constraints. In this letter, we employ topological derivative to optimize

A transmission model for a mode group division multiplexing system is presented. The model is used to model a two mode group system with either 10 Gbit/s NRZ modulation or 25 Gbit/s PAM4 modulation. Influence of wavelength separation between the channels, detector bandwidth and component crosstalk is examined.

We propose a photonic radio-frequency (RF) channelization scheme which can slice the frequency spectrum into different subchannels through shaping the optical sampling pulse of each subchannel. An optical pulse shaper, which is composed of two cascaded multi-tap optical pulse shapers, is used in each subchannel to shape the sampling pulse. The principle of proposed scheme is theoretically analyzed

In this letter, we present the design of two-cascaded cavities, used as sensing head, for improving the performance of a fiber refractometer. The sensing system makes use of the Coherent-OFDR technique. Using the proposed method, only 15 % length of the sensing signal is used to calculate the refractive index (RI) of the sample under test. Due to reduction of the scanning range used for RI calculation

As a nonorthogonal mode, faster-than-Nyquist (FTN) signaling transmission can effectively improve the spectrum efficiency of a system. However, FTN signaling inevitably causes inter-symbol interference (ISI). The ISI hinders traditional synchronization methods from operating accurately, and this makes the carrier synchronization of FTN systems more complex. To overcome this issue, we propose an iterative

The data communications industry has begun transitioning from electrical to optical interconnects in datacenters in order to overcome performance bottlenecks and meet consumer needs. To mitigate the costs associated with this change and achieve performance for 5G and beyond, it is crucial to explore advanced photonic devices that can enable high-bandwidth interconnects via wavelength-division multiplexing

Digital backpropagation (DBP) is an electronic scheme for compensating nonlinear distortions in fiber transmission systems. Due to the nonlinearity-induced spectral broadening, the data must be oversampled to avoid aliasing, which increases the complexity and power consumption of the scheme. In this work, we show that aliasing can alternatively be prevented by distributed antialiasing filters, at a

A multi-wavelength Brillouin-Raman random fiber laser (BRRFL) with wavelength spacing of double Brillouin frequency shift (BFS) has been proposed for the first time, to the best of our knowledge. This BRRFL has an extremely simple full-open cavity configuration made up of only one roll of fiber, where bidirectional stimulated Raman/Brillouin scattering (SRS/SBS) and Rayleigh scattering based random

A compact hybrid structure of silica taper-assisted dual micro-bubbles is proposed and fabricated for broadband ultrasound sensing. UV-cured adhesive is dripped on silica taper to form dual elliptic microbubbles at preselected position. Scattering and reflected light in each microbubble converges at the two focal points of the ellipse to form two new point light sources, enhancing the emergence of

In this experiment, we generate PAM4 signals based on a dual-polarization Mach-Zehnder modulator (DP-MZM) without DAC. Two high-speed binary OOK signals with different driving voltages are used to modulate a DP-MZM. After modulation, the intensity of the optical OOK signal in a polarization state is 0.7 times of the other. In this way, up to 200-Gbit/s PAM4 signals can be successfully generated. We

We present numerical and experimental analysis of bi-directionally, dual-wavelength pumped extended L-band erbium-doped fiber amplifiers (EDFAs) that use a standard 1480 nm laser diode as the forward pump source and a high-power C-band light source as the backward pump source. When using a ~1535 nm backward pump, efficient amplification can be obtained over the extended L-band with no penalty to the

Intermodal nonlinear signal distortions in a graded-index three-mode fiber are experimentally investigated in a recirculating loop transmission over distances up to 684 km. Transmitting a 24.5 GBaud 16-quadrature-amplitude-modulated spatial super channel as channel under test together with an interfering channel band that is swept by more than 20 nm across the C-band, we find a Q-factor penalty of

Spectroscopic properties of Nd 3+ -doped phosphate glass for three-level laser were investigated for the first time. A 60 nm blue-shift of the three-level transition fluorescence spectrum was achieved by changing the host material from traditional silica glass to phosphate glass. An 880-nm all-fiber laser with a world-record slope efficiency of 42.8% was demonstrated with 25-cm-long 0.25-wt.% Nd 3+

A novel compact polarization beam splitter (PBS) based on a triple-waveguide directional coupler is presented. Among these three waveguides, the middle one is regarded as an input where the contrast of effective refractive index between fundamental modes is enhanced with dielectric-loaded waveguide. Confined into the waveguides with coupling lengths of $8.3~\mu \text{m}$ (TM) and $9.9~\mu $ m (TE)

We propose and experimentally demonstrate a simple and elegant modulation format shifting (MFS) scheme by continuously changing the modulation formats between OOK and Manchester signal for optical camera communication (OCC) using a commercially available mobile phone. Leveraging the MFS scheme, extra data bits are delivered without reducing the pixel width of each bit, resulting in higher transmitted

A novel secure optical 3D probabilistic shaping carrier-less amplitude and phase (3D-PS-CAP) system based on spherical constellation masking is proposed in this letter. In order to improve the bit error rate (BER) performance of the system, probabilistic shaping (PS) is given full play. By employing different masking vectors in different cubes, masking for the constellation points is realized. We successfully

The 2 $\mu \text{m}$ waveband, specifically near $1.9~\mu \text{m}$ , is an imperative resource that could possibly be exploited in future communications systems. This is due to the promising infrastructural developments at the wavelength region (hollow-core photonic bandgap fiber, thulium-doped fiber amplifier) near $1.9~\mu \text{m}$ . In this work, we report the 1 $\times N$ selector switch based

Due to the multipoint excitation and simultaneous detection strategy applied, spinning-disk confocal microscopy (SDCM) results in an increased imaging speed compared to conventional confocal microscopy. Additionally, the super-resolution radial fluctuations (SRRF) approach can further improve the imaging resolution of SDCM in 3D imaging at the cost of imaging time due to the large amounts of data acquisition

We have demonstrated a monolithic semiconductor passively mode-locked Bragg waveguide laser (PMBRL) based on a two quantum well active region. The lasers showed a threshold current of ~33 mA at a saturable absorber reverse bias of 0 V in continuous wave operation (CW), with emission wavelength of ~785 nm. A systematic study of a two section PMBRLs showed that these devices can generate pulse widths

In this letter, a strain sensor with high sensitivity enhancement using a special case of Vernier effect is presented. The sensor configuration is composed of two-fiber loop mirrors in a cascaded configuration with opposite strain responses when individually characterized. Thus, the enhanced Vernier effect is explored, which is the most sensitive of three possible cases Vernier effect. Here, the Vernier

In this letter, we designed and experimentally demonstrated a compact mode converter in silicon-on-insulator (SOI) waveguide based on conformal dielectric metasurface, which uses polygonal slot structure to manipulate the wavefront of guided modes. Mode conversion from TE 0 to TE 2 mode can be realized within an ultracompact size ( $\sim 7.66~\mu \text{m}$ ) by designing the arrow-like slot structure

A frequency conversion mixer or single side band modulator using two cascaded MZM is proven experimentally. The operation of the circuit is modelled by a transfer matrix approach and verified by simulation in support of the experiment. A 10 GHz shift of the optical carrier in both left and right direction is demonstrated. The residual sideband suppression relative to the enhanced sideband is 22 dB

High power cladding mode stripper device has been developed in robust configurations, which demonstrated high attenuation and low temperature rise, allowing to remove 2.16 kW of power with efficiency being 21.7 dB. The maximum temperature in packaging did not exceed 55 °C at a room temperature of 20 °C. The signal insertion loss was measured to be below 0.05 dB, indicating the ability to strip the

We propose and experimentally demonstrate tunable microwave photonic filters (MPFs) with all-optical control, low-power consumption, ultra-high rejection ratios and large tuning ranges based on three cascaded silicon opto-mechanical microring resonators (MRRs). By injecting low pump powers, the nonlinear effects (mainly including the opto-mechanical effect) could be efficiently excited to manipulate

An approach for suppressing the abrupt half the wavelength errors in case of spectral interferometric interrogation of optical fiber sensors is proposed. The approach was derived from theoretical analysis of least-squares fitting of interference signal and is based on estimating the additional phase shift in the interference scheme. The approach was experimentally validated through estimation of the

Surface grating couplers are diffractive periodic structures that enable efficient coupling of light between optical fibers and planar waveguides. Conventional grating couplers have polarization specific and limited wavelength operation, because of the intrinsic radiation angle dependency on both wavelength and polarization. In this Letter, we propose, to the best of our knowledge, the first polarization-independent

We propose a novel two-stage blind carrier phase recovery scheme tailored for probabilistically shaped QAM. Our algorithm is based on modifying the classic Viterbi&Viterbi (V&V) and maximum likelihood (ML) phase estimators by optimizing the blind decisions over the received symbols taking into account the probability distribution of the received signal. Our technique improves the standard V&V + ML

We propose and experimentally demonstrate on-chip optical encoder and decoder with ultra-low power consumption. The key device is a silicon photonic crystal (PC) L3 nanocavity with small mode volume. Consequently, the nonlinear effects in the nanocavity are strongly enhanced and could be excited by lower powers. Leveraging different optical power levels, the transmission spectra of the PC nanocavity

A novel optic-fiber torsion and temperature sensor has been proposed and fabricated by sandwiching a segment of a triangular shaped single-mode fiber between two multimode fibers. This structure provides the sensitivity of torsion, which results from the destruction of the rotational symmetry of the optical fiber. Experimental results show that the polished multimode single-mode multimode (MSM) sensor

Visible Light Communication (VLC) systems are more vulnerable to timing synchronization problems due to the employed incoherent modulation scheme. In this work, a blind timing synchronization algorithm is introduced to DC biased Optical Orthogonal Frequency Division Multiplexing (DCO-OFDM) systems, based on cyclostationarity of the received signal that relies on second-order statistics only. It does

An optical filter switchable between bandpass and bandstop responses is proposed by analyzing frequency response in the complex plane. The device is fabricated based on silicon-on-insulator wafer. Experimental results show that the bandstop response has an extinction ration of exceeding 62.5 dB and a full width at half maximum (FWHM) bandwidth of 971 MHz, and the bandpass response has a rejection ration

To combine the individual benefits of probabilistic-shaping (PS) and time-frequency-packing (TFP), we consider for the first time PS-TFP wavelength-division multiplexing (WDM) superchannels. However, TFP introduces inter-symbol interference (ISI) and/or inter-carrier interference (ICI). Moreover, the presence of reconfigurable optical add-drop multiplexers in the fiber links may further degrade the

Subwavelength diameter micro/nanofiber (MNF) provides excellent platform for many applications. In this work, we fabricate subwavelength diameter MNFs with ultra-long waist and analyze the propagation loss origin for such fibers. Transmittance as high as 99.4% is measured for MNF with a waist length of 10 cm and diameter of $1.2\mu \text{m}$ , and the loss is mainly resulted from the modal leakage

This letter reports on InP/GaInP quantum dot mode-locked lasers emitting in the 730 nm wavelength region, extending the spectral range of previously reported monolithic mode-locked edge-emitting lasers. Modal gain and absorption measurements were used to identify a relatively broad spectrum which is utilised to support passive mode-locking in a monolithically integrated two-section ridge laser. The

In this work, we demonstrate an edge coupler (EC) for the coupling between the single mode fiber (SMF) and the silicon photonic waveguide. High coupling efficiency can be achieved by using arrayed waveguides at 1550 nm with an un-patterned cladding. With such a design, the light will be “pulled” to the top cladding, avoid the using of a cantilever structure. Compared to the conventional inverse taper

A new architecture for a widely distributed dual-band coherent multiple-input multiple-output (MIMO) radar system is illustrated, and its implementation and testing are reported. The system consists in a central unit where radar signals are coherently generated and detected, which serves multiple remote sensors connected over transparent WDM optical network. Every remote node operates coherently both

For the first time, demonstrated is the active-mode CAOS (i.e., Coded Access Optical Sensor) camera. The design demonstrated uses a hybrid approach to both optical device engagement and time-frequency CAOS mode operations. Specifically, time-frequency modulation of both the target illumination light source and the Digital Micromirror Device (DMD) combine to deliver the Frequency Modulation (FM)-Code

We demonstrate an ultra-compact optical fiber thermo-hygrometer on the base of a bilayer OA (Optical Adhesive, a kind of polymer) micro-cap covering the entire SMF (Single-Mode-Fiber) facet. In fabrication, two types of OA are dispensed to fiber facet successively and stratified distinctly forming the bilayer micro-cap, which contains a flat and 2 spherical interfaces reflecting emitted light. Hence