We simulate and demonstrate experimentally an inner-wall grating double slot micro ring resonator (IG-DSMRR) with a center slot ring radius of only 6.72 µm based on the silicon-on-insulator platform. This novel photonic-integrated sensor for optical label-free biochemical analysis boosts the measured refractive index (RI) sensitivity in glucose solutions to 563 nm/RIU with the limit of detection value being 3.7 × 10⁻⁶ RIU (refractive index units). The concentration sensitivity for sodium chloride solutions can reach 981 pm/%, with a minimum concentration detection limit of 0.02%. Using the combination of DSMRR and IG, the detection range is enlarged significantly to 72.62 nm, three times the free spectral range of conventional slot micro ring resonators. The measured Q-factor is 1.6 × 10⁴, and the straight strip and double slot waveguide transmission losses are 0.9 dB/cm and 20.2 dB/cm, respectively. This IG-DSMRR combines the advantages of a micro ring resonator, slot waveguide, and angular grating and is highly desirable for biochemical sensing in liquids and gases offering an ultra-high sensitivity and ultra-large measurement range. This is the first report of a fabricated and measured double-slot micro ring resonator with an inner sidewall grating structure.

We present the first, to our knowledge, demonstration of a 1550 nm multi-wavelength distributed feedback (MW-DFB) laser employing a third-order, four-phase-shifted sampled sidewall grating. By utilizing linearly chirped sampled gratings and incorporating multiple true π-phase shifts within a cavity, we achieved and experimentally validated a four-wavelength laser with a channel spacing of 0.4 nm. The device operates stably and uniformly across a wide range of injection currents from 280 mA to 350 mA. The average wavelength spacing was measured at 0.401 nm with a standard deviation of 0.0081 nm. Additionally, we demonstrated a 0.3 nm MW-DFB laser with a seven-channel output, achieving a wavelength spacing of 0.274 nm and a standard deviation of 0.0055 nm. This MW-DFB laser features a ridge waveguide with sidewall gratings, requiring only one metalorganic vapor-phase epitaxy (MOVPE) step and a single III–V material etching process. This streamlined fabrication approach simplifies device manufacturing and is well-suited for dense wavelength division multiplexing (DWDM) systems.

Advances in 1D topological photonic crystals have enabled robust light‐emitting devices through a topological interface state at the cavity center. In this study, a 1D TIS‐extended photonic crystal (1D‐TISE‐PhC) structure both theoretically and experimentally is demonstrated. a linearly dispersive, zero‐index 1D photonic crystal is integrated with a four‐phase shift (4PS) sampled grating so that photons propagate through the cavity without phase differences, enhancing robustness and extending the TIS. This extension yields a more uniform photon distribution along the laser cavity and mitigates spatial hole burning. This is fabricated and characterized a 1550 nm 1D‐TISE‐PhC semiconductor laser, achieving stable single‐mode operation from 60 to 420 mA, with a side‐mode suppression ratio of 50 dB. The device exhibited a linewidth narrowing effect, with the narrowest Lorentzian linewidth of 126 kHz and a typical linewidth of 150 kHz, nearly an order of magnitude lower than conventional distributed feedback Bragg lasers. Using reconstruction equivalent‐chirp technology with the 4PS grating allowed precise wavelength control in laser arrays, with a spacing of 0.796 nm ± 0.003 nm. This results confirm that the TIS remains intact in the TISE cavity, preserving topological protection and demonstrating improved design simplicity and fabrication tolerance for high‐power, narrow‐linewidth semiconductor lasers.

Narrow-linewidth lasers are essential for coherent optical applications, including communications, metrology, and sensing. Although compact semiconductor lasers with narrow linewidths have been demonstrated, achieving high spectral purity generally necessitates passive external cavities based on photonic integrated circuits. This study presents a theoretical and experimental demonstration of a monolithic optical injection locking topological interface state extended (MOIL-TISE) laser. By monolithically integrating a TISE laser with a micro-ring resonator on an AlGaInAs multiple quantum-well platform, the proposed device achieves efficient photon injection and linewidth narrowing. Experimental characterization indicates stable single-mode operation over a wide injection current range (65 to 300 milliamperes), exhibiting a side-mode suppression ratio exceeding 50 decibels. The laser’s Voigt linewidth was reduced from 2 megahertz to 4.2 kilohertz, with an intrinsic linewidth of 983 hertz extracted from power spectrum density, underscoring the MOIL-TISE laser’s promise for coherent communications and modulation-free quantum key distribution applications.

A novel AlGaInAs/InP electro-absorption modulated laser (EML) with a simple fabrication process is proposed, in which the electro-absorption modulator (EAM) has a 10 nm blueshift induced by quantum well intermixing (QWI) and is monolithically integrated with a sidewall grating distributed-feedback (DFB) laser working at 1.55 μm wavelength. The extent of the QWI process is characterized by a diffusion length. The quantum confined Stark effect (QCSE) is simulated in terms of extinction ratio (ER) and chirp for bias electric fields from 0 kV/cm to 200 kV/cm and for different amounts of intermixing. The results indicate that for a 150 µm-long EAM with a 10 nm blueshift induced by QWI, an ER of 40 dB is obtained at 2.5 V reverse bias with no penalty in chirp compared to an as-grown quantum well (QW) and the insertion loss at 0 V bias is 0.11 dB for 1.55 µm operation wavelength. The simulated –3 dB bandwidth of the electrical to optical power response is 22 GHz.

Polarization control is at the heart of high-capacity data optical communication systems, such as polarization-division multiplexers and Stokes vector modulation transmitters. Despite passive polarization control being mature, the realization of monolithically integrated polarization controllers and single longitudinal mode light sources, such as distributed-feedback (DFB) lasers, is of importance. In this research, we report an AlGaInAs multiple-quantum-well photonic integrated circuit device which can control the state of polarization of the output light source, consisting of a polarization mode converter (PMC), a differential phase shifter (DPS), and a sidewall grating DFB laser. We demonstrate an asymmetrical stepped-height ridge waveguide PMC to realize TE to TM polarization conversion and a symmetrical straight waveguide DPS to enable polarization rotation from approximately counterclockwise circular polarization to linear polarization. Based on the identical epitaxial layer scheme, all the PMC, DPS, and DFB lasers can be integrated monolithically using only a single step of metalorganic vapor-phase epitaxy and two steps of III-V material dry etching. For the DFB-PMC device, a high TE to TM polarization conversion efficiency (98.4%) over a wide range of DFB injection currents is reported at 1555 nm wavelength. For the DFB-PMC-DPS device, a nearly 60° rotation of the Stokes vector on the Poincaré sphere was obtained with a range of bias voltage from 0 to −3.0 V at a laser drive current of 170 mA.