Lijun Yuan

4-lambda InGaAsP-Si distributed feedback evanescent lasers with varying silicon waveguide width

A four-wavelength silicon hybrid laser array operating at room temperature is realized by evanescently coupling the optical gain of InGaAsP multi-quantum wells to the silicon waveguides of varying widths and patterned with distributed feedback gratings based on selective-area metal bonding technology. The lasers have emission peaks between 1539.9 and 1546.1 nm with a wavelength spacing of about 2.0 nm. The single laser has a typical threshold current of 50 mA and side-mode suppression ratio of 20 dB. The silicon waveguides are fabricated simply by standard photolithography and holographic lithography which are CMOS compatible.

EPITAXIAL-GROWTH OF DIAMOND FILMS ON THE (221) AND (100) SURFACES OF C-BN WITH MICROSTRUCTURES FULL OF (100) FACETS

Diamond films on surfaces of cubic boron nitride substrate grown by microwave plasma chemical vapor deposition are investigated. Deposited films are characterized by scanning electron microscopy, reflection high‐energy electron diffraction, and micro‐Raman spectroscopy. We found a new stacking growth mode of the epitaxial diamond films which is distinguished from the previous observed modes. The morphologies of diamond (100) facets formed on the {221} and {100} surfaces of cubic boron nitride are steps and/or stages, respectively. This is beneficial to growing a fair perfect single‐crystal films of diamond.

High-power InGaAs/GaAs quantum-well laser with enhanced broad spectrum of stimulated emission

We report the demonstration of an InGaAs/GaAs quantum well (QW) broadband stimulated emission laser with a structure that integrated a GaAs tunnel junction with two QW active regions. The laser exhibits ultrabroad lasing spectral coverage of ∼51 nm at a center wavelength of 1060 nm with a total emission power of 790 mW, corresponding to a high average spectral power density of 15.5 mW/nm, under pulsed current conditions. Compared to traditional lasers, this laser with an asymmetric separate-confinement heterostructure shows broader lasing bandwidth and higher spectral power density.

A Hybrid Single-Mode Laser Based on Slotted Silicon Waveguides

An InGaAsP-Si hybrid single-mode laser based on etched slots in silicon waveguides was demonstrated operating at 1543 nm. The InGaAsP gain structure was bonded onto a patterned silicon-on-insulator wafer by selective area metal bonding method. The mode-selection mechanism based on a slotted silicon waveguide was applied, in which the parameters were designed using the simulation tool cavity modeling framework. The III-V lasers employed buried ridge stripe structure. The whole fabrication process only needs standard photolithography and inductively coupled plasma etching technology, which reduces cost for ease in technology transfer. At room temperature, a single mode of 1543-nm wavelength at a threshold current of 21 mA with a maximum output power of 1.9 mW in continuous-wave regime was obtained. The side mode suppression ratio was larger than 35 dB. The simplicity and flexibility of the fabrication process and a low cost make the slotted hybrid laser a promising light source.

1550-nm Evanescent Hybrid InGaAsP–Si Laser With Buried Ridge Stripe Structure

An evanescently coupled InGaAsP-Si hybrid laser with a buried ridge stripe (BRS) structure based on a selective area metal bonding method is demonstrated. There are the advantages of good optical field, high thermal performance, and improved carrier and photon confinement by adopting this BRS laser structure. The III-V waveguide with the first-order grating corrugations is fabricated by conventional holographic lithography and standard photolithography. A threshold current as low as 5 mA at room temperature in continuous-wave operation and a side-mode suppression ratio as high as 40 dB with mode-hop free higher than 45 °C were achieved.

A Single Mode Hybrid Laser Based on Graphene Bragg Gratings

We developed a single mode hybrid laser based on graphene Bragg gratings (GBGs). This hybrid laser achieves single-mode, continuous-wave operation at 1540nm with a remarkable side-mode suppression ratio (SMSR) of 48dB.

Fabrication of InGaAs/InP DBR laser with butt-coupled passive waveguide utilizing selective wet etching

We investigated the etching process especially for the integrated InGaAs/InP multiquantum-well laser. Two different ways of etching process were demonstrated, which are RIE followed by selective wet etching and selective wet etching only. The latter one showed ideal interface between active region and passive waveguide after regrowth. This etching process is simpler and more effective than the first one. Using this process, we also fabricated a 1.79-μm DBR laser with 350-μm active region and 400-μm passive waveguide. The output power and threshold current and were demonstrated as a function of temperature. The wavelength tuning characters were investigated with current and temperature changes. It is demonstrated that this etching process can be successfully used to fabricate integrated photonic devices with InGaAs/InP materials and the DBR laser can be a candidate for gas sensing system due to the single mode and large tuning range.

Hybrid integrated InGaAsP-Si laser using selective area metal bonding method for optical interconnection

An evanescently-coupled, hybrid InGaAsP-Si laser operating at 1.55 μm is presented by selective area metal bonding (SAMB). The III-V laser, fabricated on a p-InP substrate with a semi-insulating InP:Fe buried heterostructure (BH), serves to provide optical gain. On the SOI wafer, a 3-μm wide and 500-nm high Si waveguide is formed and the bonding metal (AuSn alloy) is selectively deposited in the regions 6 μm away from the Si waveguide on each side. The InGaAsP gain structure is flip-chip bonded onto the patterned SOI wafer using SAMB method which separates laterally the optical coupling area and the metal bonding area to avoid strong light absorption by the bonding metal. The hybrid laser runs with a maximum single-sided output power of 9 mw at room temperature. The slope efficiency of the hybrid laser is about 0.04 W/A, 4 times that of the laser before bonding which indicates that the light confinement is improved after the bonding. The hybrid laser has achieved 10 °C contimuous wave (CW) lasing. A near-field image of the hybrid laser is studied. As the inject current increases, the light spot markedly shifts down to the Si waveguide and covers the Si waveguide region, which demonstrates that the light generated in the III-V active region is coupled into the Si waveguide. This method allows for different III-V devices to be bonded onto any desired places on a SOI substrate. The simplicity and flexibility of the fabrication process and high yield make the hybrid laser a promising light source.

Near-Infrared Distributed-Feedback Laser Sources and System for Gas Sensing Based on TDLAS Techniques

Near-infrared distributed-feedback laser sources and system for measuring the concentration of different gases are reported. This gas sensing system can be applied to environmental and industrial process monitoring using tunable diode laser absorption spectroscopy (TDLAS).