16-channel 200-GHz-spacing RW-DFB laser array with low noise and high output power.

We experimentally demonstrated a ridge waveguide (RW) distributed feedback (DFB) continuous-wave (CW) laser array with high output power, low relative intensity noise (RIN) and narrow linewidth for all 16 channels with 200-GHz-spacing. The ridge waveguide is formed above an offset-quantum-well structure to increase single transverse mode waveguide width to 8-µ;m for higher output power and lower noise. A relatively long cavity length of 800-µm as well as a backup laser technique are introduced to achieve good single mode stability.

High-performance PCW-DFB laser diodes using offset quantum well epitaxial structures.

We demonstrated a high-performance partially corrugated waveguide distributed feedback (PCW-DFB) laser with high output power, low relative intensity noise (RIN) and narrow linewidth. By introducing offset quantum-well structure that provides enough threshold gain difference for single transverse mode operation, the laser can achieve single mode behavior with an 8-µm-wide ridge waveguide. The laser has been designed by the simulation model based on the coupled wave equations, and the fabricated PCW-DFB laser with the cavity length of 1.

Turn-key Kerr soliton generation and tunable microwave synthesizer in dual-mode SiN microresonators.

This study investigates the thermal compensation mechanism in dual-mode SiN microresonators that demonstrates the ease of generation of single-solitons with nearly octave-wide spectral bandwidth. The deterministic creation of soliton frequency combs is achieved by merely switching the wavelength of a tunable laser or a semiconductor diode laser in a single step. The pump frequency detuning range that can sustain the soliton state is 30 gigahertz (GHz), which is approximately 100 times the resonance linewidth.

Versatile octave-spanning soliton crystals with high conversion efficiency in a SiN microresonator.

Microresonator-based soliton crystals are a key recent advancement in the study of the rich nonlinear dynamics of soliton states. The soliton crystals are self-organized temporal pulses filling the microresonator cavity and have strong comb lines with wide spacing making them of great interest in many potential applications such as communication and meteorology. However, achieving a broad spectrum, tunable repetition rates, and high conversion efficiency are still a challenge.

Narrow linewidth electro-optically tuned multi-channel interference widely tunable semiconductor laser.

A narrow linewidth electro-optically tuned multi-channel interference (MCI) widely tunable semiconductor laser based on carrier injection is demonstrated in this paper. The MCI laser with a common phase section and a semiconductor optical amplifier (SOA) is packaged into a 16-pin butterfly box. The laser is characterized by a strategy: shifting the longitudinal mode and then aligning the reflection peak, which obtains a quasi-continuous tuning range over 48 nm.

Low-power consumption InP-based optical phase arrays with non-uniformly spaced output waveguides.

Optical Phase Arrays (OPAs) are expected to be an ideal solution to achieve beam shaping, laser radar (LIDAR), free-space optical communications, and spatially resolved optical sensors, etc. We demonstrated a low-power consumption 32-channel OPA with non-uniformly spaced waveguides based on InP substrate. The phase shifters are based on a p-i-n structure which are operated with reverse bias and have a low power consumption.

Wide-waveguide high-power low-RIN single-mode distributed feedback laser diodes for optical communication.

We present an 8-µm-wide 800-µm-long high-power, single-mode and low RIN DFB laser using a dual-waveguide structure. The introduced passive lower waveguide has weakenes the lateral optical confinement for the ridge waveguide, and thus reduces losses caused by the p-doped layers and maintains single mode stability of the laser. The fabricated laser exhibited an output power higher than 170 mW and a relative intensity noise (RIN) below -157 dB/Hz along with a side-mode suppression-ratio (SMSR) over 55 dB.

Demonstration of high output power DBR laser integrated with SOA for the FMCW LiDAR system.

We demonstrated a high output power distributed-Bragg-reflector (DBR) laser integrated with semiconductor optical amplifier (SOA) for the frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR) system. In order to acquire higher output power, different from the conventional SG-DBR laser, the front mirror in this work is a section of uniform grating to get higher transmissivity. Therefore, the output power of the laser reaches 96 mW when the gain current and SOA current are 200 mA and 400 mA, respectively.

Near-octave-spanning breathing soliton crystal in an AlN microresonator.

The soliton crystal (SC) was recently discovered as an extraordinary Kerr soliton state with regularly distributed soliton pulses and enhanced comb line power spaced by multiples of the cavity free spectral ranges (FSRs), which will significantly extend the application potential of microcombs in optical clock, signal processing, and terahertz wave systems. However, the reported SC spectra are generally narrow. In this Letter, we demonstrate the generation of a breathing SC in an aluminum nitride (AlN) microresonator (FSR ∼374), featuring a near-octave-spanning (1150-2200 nm) spectral range and a terahertz repetition rate of ∼1.

1.3 μm wavelength tunable single-mode laser arrays based on slots.

Two twelve-channel arrays based on surface-etched slot gratings, one with non-uniformly spaced slots and another with uniformly spaced slots are presented for laser operation in the O-band. A wavelength tuning range greater than 40 nm, with a side-mode suppression ratio (SMSR) > 40 dB over much of this range and output power greater than 20 mW, was obtained for the array with non-uniform slots over a temperature range of 15 °C - 60 °C. The introduction of multiple slot periods, chosen such that there is minimal overlap among the side reflection peaks, is employed to suppress modes lasing one free spectral range (FSR) from the intended wavelength.

Narrow-linewidth thermally tuned multi-channel interference laser integrated with a SOA and spot size converter.

A narrow-linewidth thermally tuned multi-channel interference (MCI) laser integrated with a semiconductor optical amplifier (SOA) and spot size converter (SSC) is demonstrated in this paper. A MCI laser integrated with SOA through chirped grating is successfully realized for the first time, which achieves a tuning range of more than 42.5 nm with side-mode suppression ratios (SMSRs) higher than 48 dB and Lorentzian linewidth below 100 kHz.

Butterfly-packaged multi-channel interference widely tunable semiconductor laser with improved performance.

A multi-channel interference (MCI) widely tunable semiconductor laser is described in detail with improved performance in this paper. The MCI laser without the common phase section was packaged into a standard 14-pin butterfly package. The device realized a tuning range of more than 40 nm with side mode suppression ratios (SMSRs) higher than 48 dB and about 7 dBm fiber power.

Low V thin-film lithium niobate modulator fabricated with photolithography.

Thin-film lithium niobate (TFLN) modulators are expected to be an ideal solution to achieve a super-wide modulation bandwidth needed by the next-generation optical communication system. To improve the performance, especially to reduce the driving voltage, we have carried out a detailed design of the TFLN push-pull modulator by calculating 2D maps of the optical losses and V for different ridge waveguide depths and electrode gaps. Afterwards the modulator with travelling wave electrodes was fabricated through i-line photolithography and then characterized.

Octave-spanning Kerr frequency comb generation with stimulated Raman scattering in an AlN microresonator.

Octave-spanning optical frequency combs (OFCs) are essential for various applications, such as precision metrology and astrophysical spectrometer calibration. In this Letter, we demonstrate, for the first time to our knowledge, the generation of octave-spanning Kerr frequency combs ranging from 1150 to 2400 nm in aluminum nitride (AlN) microring resonators, by pumping the modes at 250 mW on-chip power. By simply adjusting the pump detuning, we observe the transition and coexistence of Kerr OFC and stimulated Raman scattering.

Photolithography allows high-Q AlN microresonators for near octave-spanning frequency comb and harmonic generation.

Single-crystal aluminum nitride (AlN) possessing both strong Pockels and Kerr nonlinear optical effects as well as a very large band gap is a fascinating optical platform for integrated nonlinear optics. In this work, fully etched AlN-on-sapphire microresonators with a high-Q of 2.1 × 10 for the TE mode are firstly demonstrated with the standard photolithography technique.

Single-mode surface-emitting DFB lasers with a large-area oxidized aperture based on the surface grating.

We propose and experimentally demonstrate an 850 nm single-mode surface-emitting distributed feedback laser based on the surface grating. The laser composes a second-order grating section sandwiched by two first-order grating sections. The second-order grating provides not only surface emission, but also phase shift to remove the emission degeneracy.

Concentric microcavities for cylindrical vector beam lasers.

Cylindrical vector (CV) beams with polarization singularities have attracted intense research interest because of their important applications in optical trapping and manipulation, imaging, and high-speed optical communication. In this Letter, we propose a high-speed integrated device designed to emit fundamental CV beams, including both radially and azimuthally polarized beams. The device is composed of two grating-assisted concentric microcavities based on an InP platform.

850 nm GaAs/AlGaAs DFB lasers with shallow surface gratings and oxide aperture.

We present and experimentally demonstrate a novel oxide-confined ridge-waveguide distributed feedback (DFB) laser with the first-order surface grating using only a single growth step. The metal contacts are laterally offset from the ridge waveguide to inject current thus avoiding unwanted light absorption from the electrodes. The oxide aperture is defined by selective wet oxidation of aluminium-rich material, which confines the injection current from the electrodes to the active layer under the ridge waveguide.

Single-mode surface-emitting microcylinder/microring laser assisted by a shallowly-etched top grating.

Semiconductor lasers based on microcylinder/microring cavities supporting high-quality factor modes are promising candidates of optical sources for optical interconnect. However, their multi-mode lasing performance and non-directional emission characteristic restrict their applications. In this paper, a single mode surface-emitting laser at O-band based on a second-order grating shallowly etched on the top of the microcylinder/microring cavity is proposed and demonstrated.

High-performance InP-based Mach-Zehnder polarization beam splitter with a 19 dB extinction ratio across C-band.

A high-performance InP-based polarization beam splitter (PBS) using a symmetrical Mach-Zehnder interferometer is experimentally demonstrated. The waveguides are aligned along the [011] direction, which results in a small reverse bias required and easy adjustment to realize the PBS. The experimental results indicate that the polarization extinction ratio (PER) is over 19 dB in the wavelength range from 1525 to 1570 nm with one arm injected with a 4.

Experimental demonstration of DFB lasers with active distributed reflector.

We experimentally demonstrated DFB lasers containing an active distributed reflector that has the same waveguide core as the active section. Although without current injection, the distributed reflector will be optically pumped to near transparency by the laser itself, and therefore can provide relatively high reflection to the laser. The laser, fabricated with processing steps similar to standard DFB lasers, has achieved 10-mA threshold current, 0.

1 × 8 MMI based multi-channel interference laser integrated with SOA through a 2-port multimode interference reflector.

A 1 × 8 multimode interferometer (MMI) based multi-channel interference (MCI) widely tunable laser integrated with semiconductor optical amplifier (SOA) through a 2-port multimode interference reflector (MIR) is reported in this paper. The 2-port MIR can be fabricated with deeply etched waveguides of the MCI laser with no extra fabrication process, which decreases the fabrication complexity greatly. To reduce the loss arising from mode mismatch between surface and deep ridge waveguides, a tapered shallow-deep transition structure is designed and fabricated with a loss of 0.

Highly fabrication tolerant InP based polarization beam splitter based on p-i-n structure.

In this work, a novel highly fabrication tolerant polarization beam splitter (PBS) is presented on an InP platform. To achieve the splitting, we combine the Pockels effect and the plasma dispersion effect in a symmetric 1x2 Mach-Zehnder interferometer (MZI). One p-i-n phase shifter of the MZI is driven in forward bias to exploit the plasma dispersion effect and modify the phase of both the TE and TM mode.

Optimization algorithm based characterization scheme for tunable semiconductor lasers.

In this paper, an optimization algorithm based characterization scheme for tunable semiconductor lasers is proposed and demonstrated. In the process of optimization, the ratio between the power of the desired frequency and the power except of the desired frequency is used as the figure of merit, which approximately represents the side-mode suppression ratio. In practice, we use tunable optical band-pass and band-stop filters to obtain the power of the desired frequency and the power except of the desired frequency separately.