Performance Improvement Of Mid-infrared Semiconductor Lasers Based On Lateral Microstructure

Mid-infrared semiconductor lasers(MSLs)have many advantages over other midinfrared lasers,such as small size,long lifetime and high efficiency.Hence,MSLs shows the promising applications in gas sensing,LiDAR,medical treatments and defense as a high efficiency laser.However,the heat dissipating capability of MSLs is poor due to the issues of material and epitaxial structure,which proposes the crucial challenge to the package and temperature control.In addition,the broad area waveguide in MSLs results in a poor lateral beam quality.These issues have limited the realistic applications of MSLs.In this paper,in order to solve above problems,the lateral microstructure was applied in the MSLs and the influence on the performance of MSLs was studied.The investigation contents and achievements were as follows:(1)The finite element method was used to study the thermal and electrical properties of quantum cascade lasers.The effects of different waveguide structures on the thermal and electrical properties were analyzed.A structure with high efficient lateral heat dissipation was proposed.The temperature of active region was compared with that of traditional dual-trench structure.The temperature at active region shows a significant decrease,and the current injection efficiency is improved as well.(2)An on-chip beam combination structure based on angled cavities was designed.The software was used to calculate the resonance and reflectivity of lateral modes in the angled cavity.It is theoretically proved that the structure proposed can suppress effectively the lasing of high-order lateral modes and improve the beam quality.The mechanism of deterioration in threshold current density was analyzed.(3)The on-chip beam combination structure based on angled cavities had been applied to the GaAs-based near-infrared lasers and GaSb based MSLs,and the devices with the included angle of 10° and 15° were fabricated.The significant enhancement of the lateral beam quality and brightness were demonstrated.(4)A kind of GaSb-based micro-strip broad area laser was proposed,the thermal and electrical properties were simulated by COMSOL Multiphysics.The results show that the current injection efficiency and the heat dissipation have been improved noticeably compared with the GaSb based broad area lasers.(5)The GaSb-based micro-strip broad area lasers emitting near 1.96?m at room temperature had been demonstrated.Compared with the broad area GaSb based lasers,the injection efficiency,heat dissipation and characteristic temperature of the device were greatly improved.The threshold current density was reduced over 50%,and the wall plug efficiency had also been increased to as high as 30.5%.Better beam quality was realized.These experimental results demonstrated that the micro-strip structure was an efficient approach to improve the performance of MSLs.