Theoretical analysis of passively mode-locked semiconductor ring lasers.

In this paper, the theoretical analysis of the passive mode-locked semiconductor ring lasers (PML-SRLs) is investigated based on a travelling wave model. It is found that both the optical confinement factor and the injection current make great contributions to the operation regime and the performance of PML-SRLs. All operation regimes of PML-SRLs are governed by the transient gain-loss balance.

Stably polarized 795 nm vertical-cavity surface-emitting lasers with anti-phase SiN surface gratings.

795 nm vertical-cavity surface-emitting lasers (VCSELs) with dielectric surface gratings to control the output polarization are designed and fabricated. The calculated results demonstrate that a well-designed surface grating positioned on the surface of an anti-phase VCSEL structure enhances the reflectivity difference between the two polarization modes compared to a conventional GaAs surface grating, consequently resulting in a larger gain anisotropy in VCSELs and a high orthogonal polarization suppression ratio (OPSR). Characterization shows that a peak-to-peak OPSR of 30.

Effects of Thermal-Strain-Induced Atomic Intermixing on the Interfacial and Photoluminescence Properties of InGaAs/AlGaAs Multiple Quantum Wells.

Quantum-well intermixing (QWI) technology is commonly considered as an effective methodology to tune the post-growth bandgap energy of semiconductor composites for electronic applications in diode lasers and photonic integrated devices. However, the specific influencing mechanism of the interfacial strain introduced by the dielectric-layer-modulated multiple quantum well (MQW) structures on the photoluminescence (PL) property and interfacial quality still remains unclear. Therefore, in the present study, different thicknesses of SiO-layer samples were coated and then annealed under high temperature to introduce interfacial strain and enhance atomic interdiffusion at the barrier-well interfaces.

Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser.

We report, to the best of our knowledge, the first demonstration of a 1555-nm stepped-height ridge waveguide polarization mode converter monolithically integrated with a sidewall grating distributed-feedback (DFB) laser using the identical epitaxial layer scheme. The device shows stable single longitudinal mode (SLM) operation with the output light converted from TE to TM polarization with an efficiency of >94% over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The highest TM mode purity of 98.

Robust and Low-Power-Consumption Black Phosphorus-Graphene Artificial Synaptic Devices.

Two-dimensional (2D) black phosphorus (BP) materials, as the most promising building blocks for the development of artificial synapses, have attracted more and more attention. However, the instability of exfoliated 2D BP structures still remains a problem in the development of artificial synapse devices. In this study, the robust and low-power-consumption artificial-synaptic-based BP was successfully manufactured.

Frequency comb with 100 GHz spacing generated by an asymmetric MQW passively mode-locked laser.

A L-band two-section AlGaInAs/InP asymmetric multiple quantum well (QW) passively mode-locked laser has been used to generate a frequency comb with a 100 GHz spacing at a central wavelength of 1610 nm. The comb contains 10 optical lines within a -3 bandwidth of 8.05 nm and 34 optical lines within a -20 bandwidth of 30 nm.

Suppression of substrate mode in GaN-based green laser diodes.

Parasitic substrate mode readily appears in GaN-based laser diodes (LDs) because of insufficient optical confinement, especially for green LDs. Substrate modes affect the behavior of a LD severely, including the laser beam quality, the optical output power, the longitudinal mode stability, and the maximum modulation speed. In this article, systematic studies on the n-cladding layer (CL) design to suppress the substrate mode of GaN-based green LDs were carried out.

Proposal and numerical study of a flexible visible photonic crystal defect cavity for nanoscale strain sensors.

A flexible photonic crystal cavity, consisting of a III-V active layer embedded in a flexible medium, with a line-defect by removing three air holes for nanoscale structural deformation detection is proposed and optimized. The cavity can hold the photonic band-gap modes with the fundamental mode located at approximately 686 nm, overlapping with the photoluminescence spectrum of the InGaP/InGaAlP quantum wells. Results of finite-difference time-domain simulations indicate that the L3 cavity features an ultra-compact mode volume of 10 µm and high quality factor of 10 at a sub-micron footprint within the studied visible wavelength.

Study on DFB semiconductor laser array integrated with grating reflector based on reconstruction-equivalent-chirp technique.

A 4-channel distributed feedback (DFB) semiconductor laser array with incorporation of a grating reflector utilizing reconstruction-equivalent-chirp technique is theoretically studied and experimentally demonstrated. By integrating with a grating reflector, 40% increase of slope efficiency, about 10mA decrease of threshold current and 7dB increase of side mode suppression ratio (SMSR) are achieved with a deviation of wavelength spacing being less than 0.07nm.

High channel count and high precision channel spacing multi-wavelength laser array for future PICs.

Multi-wavelength semiconductor laser arrays (MLAs) have wide applications in wavelength multiplexing division (WDM) networks. In spite of their tremendous potential, adoption of the MLA has been hampered by a number of issues, particularly wavelength precision and fabrication cost. In this paper, we report high channel count MLAs in which the wavelengths of each channel can be determined precisely through low-cost standard μm-level photolithography/holographic lithography and the reconstruction-equivalent-chirp (REC) technique.

Characterization of graphene layers using super resolution polarization parameter indirect microscopic imaging.

We report on the development of super-resolution polarization (parameter) indirect microscopic imaging (PIMI) and its application to visualizing and quantifying graphene layer's morphological and structural features. The PIMI system was built by modifying a conventional optical microscopy such that the variation of the polarization status of incident light can be precisely controlled, imaging was subsequently acquired by analyzing the dependence of the optical intensity transmitted through (or reflected from) the samples on the incident light polarization status. Measurements on the thickness as well as other structural features of graphene samples which had been prepared by different methods were performed.

Low divergence angle and low jitter 40 GHz AlGaInAs/InP 1.55 μm mode-locked lasers.

We demonstrate a novel (to the best of our knowledge) 40 GHz passively mode-locked AlGaInAs/InP 1.55 μm laser with a low divergence angle (12.7°×26.

160 GHz harmonic mode-locked AlGaInAs 1.55 μm strained quantum-well compound-cavity laser.

We characterized the reflectivity and the modal discrimination of intracavity reflectors (ICRs) with different numbers of slots and presented harmonic mode-locking operation of a monolithic semiconductor laser comprising a compound cavity formed by a single deeply etched slot ICR fabricated from 1.55 μm AlGaInAs strained quantum well material. Gaussian pulses were generated at a 161.