Optical filters based on integrated phase-shifted Bragg gratings (PSBGs) have attracted considerable interest because they feature a Lorentzian-shaped resonance, along with strong out-of-band rejection across a broad stopband region. The extent of the stopband can be conveniently adjusted by modifying the grating coupling coefficient [1]. Fabricating PSBGs on a thin-film lithium niobate (TFLN) platform enables the selection and modulation of specific wavelengths at ultra-fast speeds [2]–[3], offering substantial advantages in applications like datacom, sensing, and microwave-photonics systems [4]. In this abstract, a monolithic PSBG based on TFLN is proposed. The low waveguide propagation losses combined with the strong grating coupling coefficient of these devices, enable a narrow wavelength selection combined with a large stopband and effective electro-optic tunning capabilities.

We have developed an integrated dual-band microwave photonic filter utilizing equivalent chirped four-phase-shifted sidewall sampled Bragg gratings on an SOI platform. By employing the reconstruction equivalent- chirp technique, we designed linearly chirped four-phase-shifted sampled Bragg gratings with two pi phase shifts positioned at 1/3 and 2/3 of the cavity, introducing two passbands in the +1(st) channel. Leveraging the significant thermo-optic effect of silicon, dualband tuning is achieved via micro-heaters integrated on the chip surface. By tuning the injection currents into the microheaters, distinct optical frequency divisions from 100 GHz to 400 GHz, are demonstrated using a 100 GHz, 1535 nm semiconductor passive mode-locked laser as the light source.

We present a four-wavelength mode-locked 1.55 μm DFB laser with a chirped four-phase-shifted sampled Bragg grating, delivering transform-limited pulses with high spectral purity—ideal for DWDM and multi-channel photonic applications.

We propose mode-locked distributed Bragg reflector (DBR) and distributed feedback (DFB) lasers based on multiple phase-shift gratings (MPSGs) for terahertz (THz) signal generation, with the latter incorporating an equivalent pi-phase shift. By integrating optimized MPSGs, we achieve multi-channel lasing with uniform reflectivity and dense channel spacing. Mode-locked DBR lasers operating at THz frequencies of 150 GHz, 400 GHz, 800 GHz, and 1.2 THz have been demonstrated, as confirmed by second harmonic generation measurements. Additionally, a 200 GHz mode-locked DFB laser was realized. Amplified by an erbium-doped fiber amplifier (EDFA), the mode-locked DFB laser output was injected into a photoconductive antenna (PCA) to generate THz signals, with the measured power reaching 19.6 mu W. These results highlight the potential of MPSG-based mode-locked lasers for compact and efficient THz generation systems.

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.

All-optical control of silicon photonic integrated devices is crucial for on-chip applications such as signal processing, computing, and switching. A key limitation of current integrated devices is high power consumption, stemming from the weak nonlinear effects of silicon. An alternative nonlinear effect in deformable platforms is the mechanical Kerr effect (MKE), which arises from the optical gradient force (OGF) generated by highly localized optical fields that can deflect freestanding waveguides near a dielectric substrate. In this work, we present a hybrid optomechanical cavity design, driven by OGF, which integrates a compact microring resonator (MRR) with a radius of 10.08 µm and a quadratically tapered photonic crystal nanobeam cavity (PCNC). This design results in two distinct types of resonant modes, enabling mode-dependent wavelength routing. Due to strong localization and intensity enhancement, the tuning range and efficiency are significantly improved compared to conventional MRRs. An experimental 1.98 nm redshift is achieved in the probe PCNC mode, corresponding to a tuning efficiency of 142 GHz/mW. Additionally, substantial mode splitting is observed due to the mode-dependent tuning capability of the device. This design holds great potential for wavelength routing applications, particularly in advanced all-optical tunable optical filtering systems.

We demonstrate, for the first time to the best of our knowledge, a monolithic multi-wavelength mode-locked distributed feedback (DFB) laser based on waveguide Bragg grating microcavities, achieving simultaneous three-wavelength lasing near 1.55 μm within a single cavity. The device exhibits a uniform free spectral range of 0.46 nm (57.4 GHz), a side mode suppression ratio exceeding 30 dB, and near-transform-limited pulses (6.25 ps, time-bandwidth product = 0.359). The structure requires only one metalorganic vapor phase epitaxy growth and a single III-V material dry etching step, significantly simplifying fabrication and enhancing reproducibility. By halving and doubling the central cavity length, we also demonstrate dual- and six-wavelength operation with free spectral ranges of 0.75 nm and 0.27 nm, respectively highlighting the design versatility in tailoring the channel count and repetition frequency. This compact platform enables seamless photonic integration with semiconductor optical amplifiers, electroabsorption modulators, and other on-chip components, making it suitable for dense wavelength division multiplexing, coherent optical communications, and photonic sensing.

A monolithic optical injection-locked distributed-feedback (MOIL-DFB) laser is experimentally demonstrated, achieving a locking current range of 90–150 mA, a side-mode suppression ratio (SMSR) exceeding 45 dB, and a linewidth of 2.7 MHz.

We have developed an integrated dual-band photonic filter (PF) utilizing equivalent chirped four-phase-shifted sidewall-sampled Bragg gratings (4PS-SBG) on a silicon-on-insulator platform. Using the reconstruction equivalent-chirp technique, we designed linearly chirped 4PS Bragg gratings with two π-phase shifts (π-PSs) positioned at 1/3 and 2/3 of the grating cavity, introducing two passbands in the + first order channel. Leveraging the significant thermo-optic effect of silicon, dual-band tuning is achieved through integrated microheaters (MHs) on the chip surface. By varying the injection currents from 0 to 85 mA into the MHs, the device demonstrates continuous and wide-range optical frequency division performance, with the frequency interval between the two passbands adjustable from 52.1 to 439.5 GHz. Four notable frequency division setups at 100, 200, 300, and 400 GHz were demonstrated using a 100 GHz, 1535 nm semiconductor passive mode-locked laser as the light source.

We demonstrate an integrated dual-band microwave photonic filter using equivalent chirped four-phase-shifted Bragg gratings on an SOI platform. Optical frequency division from 100 GHz to 400 GHz is achieved with tunable microheaters and a mode-locked laser.

We report a 4-channel DWDM DFB laser array using four-phase-shifted sampled Bragg grating and asymmetric twin-waveguide technologies, achieving 0.873 nm spacing, >45 dB SMSR, and> 10 dB electro-absorption modulator extinction ratio.

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.

We have developed a photonic filter featuring dual independently tunable passbands. Employing the reconstruction equivalent-chirp technique, we designed linearly chirped sampled Bragg gratings with two equivalent phase shifts positioned at 1/3 and 2/3 of the cavity, thus introducing two passbands in the +1 st channel. Leveraging the significant thermo-optic effect of silicon, dual-band tuning is achieved via micro-heaters integrated on the chip surface. By tuning the injection currents ranging from 0 to 35 mA into the micro-heaters, the filter exhibits a wide range of dual-wavelength filtering performance, with the frequency interval between the two passbands adjustable from 37.2 GHz to 186.1 GHz.

This study proposes and experimentally demonstrates a distributed feedback (DFB) laser with a distributed phase shift (DPS) region at the center of the DFB cavity. By modeling the field intensity distribution in the cavity and the output spectrum, the DPS region length and phase shift values have been optimized. Experimental comparisons with lasers using traditional π-phase shifts confirm that DFB lasers with optimized DPS lengths and larger phase shifts (up to 15π) achieve stable single longitudinal mode operation over a broader current range, with lower threshold current, higher power slope efficiency, and a higher side mode suppression ratio (SMSR). Furthermore, the minimum optical linewidth is reduced significantly, from 1.3 MHz to 220 kHz.

An optomechanical hybrid photonic crystal microring resonator, driven by optical gradient force, achieves controllable, mode-dependent tuning with a maximum 1.98 nm redshift and a tuning efficiency of 142 GHz/mW.

Narrow linewidth lasers are indispensable for coherent optical systems, including communications, metrology, and sensing. Although compact semiconductor lasers with narrow linewidths and low noise have been demonstrated, their spectral purity typically relies on hybrid or heterogeneous external cavity feedback. Here, we present a theoretical and experimental demonstration of a heterogeneous free optical injection locking (HF OIL) semiconductor laser. By integrating a topological interface state extended (TISE) laser with a micro ring resonator (MRR) on an AlGaInAs multiple quantum well platform,we achieve monolithic photon injection and phase locking, thereby reducing the optical linewidth. We fabricated and characterized a 1550 nm sidewall HF OIL laser, achieving stable single mode operation over a broad current range (65 to 300 mA) and a side mode suppression ratio (SMSR) over 50 dB. Under injection locking, the devices Voigt fitted linewidth narrowed from over 1.7 MHz (free running) to 4.2 kHz, representing a three order of magnitude improvement over conventional distributed feedback lasers. The intrinsic linewidth of 1.4 kHz is measured by correlated delayed self-heterodyne frequency noise power spectrum density (FN PSD) method. Moreover, the HF OIL laser demonstrated high phase stability and the ability to transition from a random phased to a phase locked state. These results underscore the potential of HF-OIL lasers in advancing coherent optical communications and phase encoders in quantum key distribution (QKD) systems.

All-optical control of silicon photonic devices is vital for on-chip signal processing, computing, and switching, but remains limited by silicon's weak nonlinearities and high-power demand. Here, we propose, fabricate, and demonstrate a 1D optomechanical photonic crystal nanobeam utilizing the Mechanical Kerr Effect (MKE), achieving a 6.84 nm wavelength shift with just 1.85 mW input power, corresponding to a record tuning efficiency of 486.5 GHz/mW. The device exhibits fast dynamics, with a 1.25 μs rise time and a 0.24 μs fall time. This approach offers a low-power, tunable platform for integrated photonic functions like switching, routing, and filtering.

We have developed a series of dual-wavelength DFB lasers (DWLs) based on different sidewall grating designs. These include DWLs utilizing uniform Bragg gratings (UBG), conventional sampled Bragg gratings (C-SBG), two-phase shifted sampled Bragg gratings (2PS-SBG), and four-phase shifted sampled Bragg gratings (4PS-SBG) for THz signal generation. Additionally, we have explored the use of 4PS-SBG combined with equivalent chirp technology, lateral modulation of the grating coupling coefficient kappa, and four-phase-shifted sampled Moire gratings (4PS-SMG) for millimeter-wave (MMW) signal generation. All the DWLs were fabricated in the AlGaInAs/InP system operating around 1550 nm. For DWLs using UBG, even employing e-beam lithography at its resolution limit of 0.5 nm, the smallest frequency separation is constrained to approximately 400 GHz. C-SBG designs allow precise control of the frequency separation, down to 1.1 GHz, but the effective grating coupling coefficient is only 1/pi of that of UBG. Utilizing 2PS-SBG technology can automatically produce DWLs while maintaining the same sampling periods on both sides of the ridge waveguide. The 4PS-SBG demonstrates a higher effective kappa (approximately 0.9x that of UBG) compared to the 2PS-SBG (approximately 0.64x that of UBG). To ensure single longitudinal mode operation and mitigate longitudinal mode competition, an equivalent pi phase shift (EPS) is inserted at 1/3 of the DFB cavity length on one side, and another EPS is placed at 2/3 of the DFB cavity length on the opposite side. Using equivalent chirp methodology, the two peaks of the photon distributions of the two lasing modes are separated, significantly reducing the overlap region and ensuring stable dual-wavelength operation. Moreover, the wavelength separation can be adjusted by changing the chirp rate. Lateral modulation of the grating coefficient kappa allows tuning of the dual-wavelength separation by adjusting the DWL cavity length and the kappa value. We show that 4PS-SMG exhibits perfect apodization with a cosine profile and two pi phase shifts in the cavity, eliminating the need for intentional insertion of two pi phase shifts in the DWL cavity to achieve dual-wavelength operation. All the aforementioned DWLs serve as compact pumping sources for generating THz/MMW signals.

report, for the first time, a monolithic multi-wavelength passively mode-locked distributed feedback (DFB) laser operating simultaneously at four wavelengths near 1.55 mu m. The device incorporates two chirped sampled Bragg grating (SBG) designs within a single cavity: 1) chirped conventional SBG (C-SBG) and 2) chirped four-phase-shifted SBG (4PS-SBG). Both configurations achieve uniform 0.96 nm (similar to 120 GHz) wavelength spacing using a single DFB section electrode and monolithically integrated saturable absorber (SA) for synchronized passive mode-locking. This shared-cavity architecture ensures intrinsic stability of the frequency comb against environmental perturbations, as all longitudinal modes experience identical phase variations. The lasers exhibit high spectral purity with side-mode suppression ratios (SMSR) >20 dB, with the 4PS-SBG design offering wider bias current operation. Pulse characteristics include near-transform-limited performance for both designs: C-SBG yields 2.84 ps pulses (time-bandwidth product [TBP] = 0.334), while 4PS-SBG generates 2.79 ps pulses (TBP = 0.337). Fabrication employs a simplified ridge waveguide sidewall grating approach requiring only one metalorganic vapor phase epitaxy (MOVPE) step and a single III-V etch process, enhancing manufacturability. We further demonstrate the design's versatility by extending operation to six wavelengths using the 4PS-SBG structure. This integrated platform shows strong potential for dense wavelength division multiplexing (DWDM), coherent communications, and photonic sensing applications requiring compact, environmentally stable multi-wavelength sources.

Multi-wavelength mode-locked distributed feedback (DFB) lasers are among the simplest and most efficient devices for applications such as telecommunications and spectroscopy [1]. However, achieving stable mode-locked lasing across multiple wavelengths is challenging due to mode competition and temperature sensitivity [2]. Chirped conventional sampled Bragg gratings (C-SBGs) enhance wavelength stability, while reconstruction-equivalent chirp (REC) technology provides precise spectral control [3]. This work demonstrates the first DFB mode-locked laser incorporating chirped SBGs, achieving stable and simultaneous four-wavelength mode-locking, with promising potential for dense wavelength division multiplexing (DWDM) and advanced photonic technologies.