光学 精密工程, 2014, 22 (1): 50, 网络出版: 2014-02-18
微型铷原子钟专用795 nm垂直腔表面发射激光器
795 nm VCSELs for 87Rb based miniaturized atomic clock
垂直腔面发射激光器 铷原子钟 高温 非闭合台面 Vertical Cavity Surface Emitting Laser(VCSEL) 87Rb atom clock high-temperature unclosed mesa
摘要
针对铷(87Rb)原子钟激励光源微型化和高温工作的特殊需求,设计并制备了对应铷原子能级跃迁的795 nm垂直腔面发射激光器(VCSEL)。首先,根据k·p理论计算了InAlGaAs/AlGaAs量子阱的价带能级和材料增益,得到最优的量子阱组分和厚度; 然后,采用一维传输矩阵方法设计了795 nm波段的布拉格反射器(DBR),根据完整结构VCSEL器件的驻波场分布设计了掺杂分布; 最后,采用金属有机气相外延(MOVPE)技术生长了优化的795 nm VCSEL外延结构,并制备了氧化限制型非闭合台面结构的795 nm顶发射器件。实验显示: 封装后的75 μm口径器件可在室温至85 ℃范围内连续工作,最高功率为17 mW,激光光束呈圆形,发散角为15°,激射波长的温漂系数为0.064 nm/℃; 在温度为52 ℃、注入电流为100 mA时,激射波长位于794.7 nm(对应铷原子钟需要的波长),基本满足铷原子钟激励光源对波长稳定和高温工作的要求。
Abstract
For the special requirements of the exciting source of a 87Rb based atomic clock for the miniaturization and high temperature conditions, a 795 nm Vertical Cavity Surface Emitting Laser(VCSEL)corresponding to the Rb atom energy level transition was designed and fabricated. Firstly, the energy levels and material gains of the InAlGaAs/AlGaAs Multiple Quantum Wells (MQWs) were calculated by the k·p method to optimize the compositions and thicknesses of the quantum wells. Then, a Distributed Bragg Reflectors(DBRs) at 795 nm were designed and their reflection characteristics, longitudinal optical fields and averaged doping profiles were calculated and optimized using a one-dimensional transfer matrix method. Finally, the epitaxial structure of the 795 nm VCSEL with optimized MQWs and DBRs were grown on a GaAs substrate by Metal Organic Vapor Phase Epitaxy (MOVPE) and the oxide-confined 795 nm top-emitting VCSELs with unclosed-mesa structures were fabricated and characterized. Experimental results indicate that the packaged VCSELs can keep lasing under a cw current from 25 ℃ to 85 ℃ with power decreasing from 17 mW to 1.8 mW, the far field profiles are circular with a divergence angle of 15° and the temperature-shift of the lasing wavelength is 0.064 nm/℃. Moreover, the lasing wavelength moves to the wavelength required by 87Rb atoms at an ambient temperature of 52 ℃ and a current of 100 mA. The 795 nm VCSELs satisfy the basic requirements of 87Rb based miniaturized atom clocks for stable operation in a special wavelength and high-temperatures.
张建, 宁永强, 张建伟, 张星, 曾玉刚, 王立军. 微型铷原子钟专用795 nm垂直腔表面发射激光器[J]. 光学 精密工程, 2014, 22(1): 50. ZHANG Jian, NING Yong-qiang, ZHANG Jian-wei, ZHANG Xing, ZENG Yu-gang, WANG Li-jun. 795 nm VCSELs for 87Rb based miniaturized atomic clock[J]. Optics and Precision Engineering, 2014, 22(1): 50.