碟型量子阱微腔激光器的低阈值激射

利用反应离子刻蚀(RIE)和湿法腐蚀方法在InGaAs/InGaAsP多量子阱材料上研制出直径为8μm、4.5μm和2μm的碟型半导体微腔激光器。其中2μm直径的微碟在液氮温度下其光泵浦激射阈值仅为3μW左右。对高光功率密度下泵浦时出现的多模激射、跳模和激射光谱强度饱和现象进行了研究。并对微碟激光器的激射光谱线宽特性进行了初步的分析。

Low Threshold Lasing in Microdisk Quantum Well Laser

Microcavity lasers have been attracting much more attention recently. Microdisk lasers represent a novel class among them. The disk thickness is typically only a half of an optical wavelength in the materials. Whispering gallery modes near the disk edge account for the low loss resonator modes. InGaAs/InGaAsP MQW microdisk lasers based on this disk resonator were fabricated by using standard photolithography, reactive ion etching (RIE) and wet chemical etching. The MQW materials were grown on InP substrates by gas source MBE technique. The diameters of the disk laser we had made were 8μm, 4.5μm and 2μm, respectively. The optical properties of the disk were characterized by optical pumping at liquid nitrogen temperature. The lasing threshold of the disk with a diameter of 2μm was only about 3μW when pumped by 514.5nm line of Ar ion laser. To our knowledge, this threshold of 3μW is the lowest one up to now. Multiple mode lasing, mode chirping and output saturation were investigated when pumped at high optical pump density. It was observed that the structure of the photoluminescence spectra became sophisticated with increasing the pump power. New lasing peaks appeared and became dominated in the spectra. It was also observed that the intensity of lasing lines became saturated with increasing the pump power. The linewidth of lasing peak was of the order of about 1.3nm. It was also observed that microdisk lasers showed anomalous linewidth behavior compared with ordinary semiconductor laser. This characteristic was usually explained with many-body effect induced by the non equilibrium carrier distribution when optically pumped.