低阈值单横模852nm半导体激光器

基于波导理论、等效折射率方法,设计并制备了非对称波导隔离双沟结构脊型边发射激光器,最终获得了低闽值单基侧模852 nm激光器.详细研究了不同脊型台深宽比参数设计对激光器侧向模式特性的影响规律,实现了腔面未镀膜情况下脊型波导边发射激光器的单基侧模稳定输出,同时激射波长可以精确调谐到852 nm;工作电流达到150 mA,工作温度30℃;斜率效率最高可达0.89 nW/mA,光谱半宽小于1 nm.研究结果为进一步实现超窄线宽激光器提供了参考和借鉴,并且为实现激光器稳定输出提供了实验基础.

A low threshold single transverse mode 852 nm semiconductor laser diode

A 852 nm ridge waveguide edge emitting laser has important applications. But lateral mode instability leads to its poor beam quality because of its ridge structure. Such a structure gives rise to two guidance mechanisms (gain-guide and index-guide), whose change leads to “kink” effect. So, the control of the single fundamental lateral mode is more difficult. There is no well-informed study in these aspects for ridge waveguide edge emitting lasers. In this paper we study how to improve the beam quality for achieving a stable fundamental lateral mode output experimentally. We are to investigate the influence of lateral mode characteristics of the laser with different ridge depth-to-width ratios in detail by waveguide theory and equivalent refractive index method. Depth and width of the ridge are two key parameters influencing lateral mode. The depth can control lateral guidance mechanism, and the width can control lateral mode order. We find that the ratio must be in a limited range to ensure the single fundamental lateral mode steady. Through theoretical analysis of waveguide theory and equivalent refractive index method, we obtain a limited range of depth-to-width ratio. Then we conduct an experimental comparison, where we adjust the ridge depth, with the width fixed, to control the ratio. Meanwhile we improve the fabrication technology to ensure the accuracy of the structure. We design and fabricate an asymmetric waveguide ridge waveguide edge emitting laser with isolation grooves, whose active region is the core of asymmetric waveguide epitaxy structure. The key structural parameters are 5 μm in ridge width, 500 nm in ridge depth, 2 μm in isolation grooves depth, 10 μm in width, 30 μm in spacing between the grooves, and 1 mm in cavity length. Isolation grooves are very useful for improving the performance of the laser: threshold decreased by 50%, output power raised by 44%, and slop efficiency increased by 17%. And the equally crucial role of grooves is to avoid being damaged at packaging process to maintain laser structure. Finally we achieve a stable single fundamental lateral mode output and an accurate tuning wavelength at 852 nm of ridge waveguide edge emitting laser without cavity surface coated at working current 150 mA, working temperature 30 ℃ (working conditions can be changed in a small range). The slope efficiency is on average 0.7 mW/mA (its maximum value is 0.89 mW/mA), and the full wave at half maximum is less than 1 nm. Although we improve the performance of ridge waveguide edge emitting laser and beam quality for stable output, there is still a need to further study the stable output over a wide range. The results in this paper will provide a useful reference for realizing the stable output ridge waveguide edge emitting lasers and the ultra-narrow line-width lasers.