用体布拉格光栅(VBG)作为反馈元件与瓦级半导体激光器(LD)以及快轴准直柱透镜构成一个可以将半导体激光器的工作波长稳定在体布拉格光栅布拉格波长处的外腔激光器。测量了体布拉格光栅外腔激光器的波长稳定性与其工作电流、热汇温度、激光束准直装置等因素的关系。分析了波长稳定效果与半导体激光器增益谱特性、外腔结构参量等因素的关系。研究表明,在相同的工作电流、热汇温度下,当准直柱透镜直径为0.4 mm时的波长稳定效果较好;在此情况下,当热汇温度控制在30 ℃,工作电流从0.5 A增加到1.5 A的测量范围内,以及当工作电流固定在1.5 A,热汇温度从20 ℃增加到35 ℃时,测得的光谱特性表明,半导体激光器的工作波长可以很好地稳定在体布拉格光栅的布拉格波长处。与该激光器在同样条件下自由运转的光谱比较,可以看到,自由运转激射波长与体布拉格光栅的布拉格波长差值小于2.6 nm情况下,可以获得很好的波长稳定效果。实验也表明,当该值大于4.8 nm时波长稳定效果变差。

An external-cavity semiconductor laser was built by using a semiconductor laser, collimating cylindrical column lens for fast axis beam and a volume Bragg grating (VBG) as a feedback element to get semiconductor lasers wavelength locked to the Bragg wavelength of the VBG. Its spectral characteristics varied with pump current, heat-sink temperature and different beam collimation optics were measured experimentally. The dependence of the spectral stabilization on gain spectrum of the laser and the parameters of the external cavity were analyzed. The results indicated that good wavelength stabilization could be obtained when a collimating cylindrical lens with diameter of 0.4 mm was used. In the case semiconductor lasers wavelength was measured to be locked at the Bragg wavelength of VBG in the driving current range from 0.5 A to 1.5 A when the heat-sink temperature kept at 30 ℃, and in the temperature range between 20 ℃ and 25 ℃ when the driving current applied at 1.5 A. Compared with spectra of the semiconductor laser at free running, it means that wavelength stabilization can be obtained when difference between the VBG peak and the laser wavelength at free running is smaller than 2.6 nm. The experiment showed also that wavelength stabilization became degraded when the difference increased to larger than 4.8 nm.