针对移频激发拉曼光谱测试系统的小型化需求, 在Littrow结构中, 采用商用的785 nm大功率激光二极管作为增益器件, 构建了一款便携式光栅外腔可调谐半导体激光器。 该激光器通过采用一种新型的波长调谐方法, 即以改变半导体增益器件相对于准直透镜的水平位置来实现波长的连续调谐, 实现了尺寸为140 mm×65 mm×50 mm的小型化结构设计。 相比于传统的旋转衍射光栅改变光线在光栅上的入射角来实现波长调谐的方式, 该方法有效地缩减了增益器件的平移距离, 从而有利于便携式外腔激光器波长的快速宽带调谐。 实验结果表明, 该激光器具有较宽的波长调谐范围, 在340~900 mA注入电流下均可实现10 nm以上的波长调谐, 尤其在900 mA大注入电流下, 其波长调谐覆盖77940~79107 nm, 调谐范围可达1167 nm, 且激射线宽小于02 nm, 单波长输出功率最高可达280 mW, 放大的自发辐射抑制比大于25 dB, 呈现出较优异的输出性能, 满足移频激发拉曼光谱检测系统对光源的基本要求。 此外, 该激光器可采用一微型压电陶瓷驱动器来实现波长的电动调谐, 实验获得了135 nm的波长调谐范围, 证实了所制785 nm便携式光栅外腔可调谐半导体激光器适合作为便携式移频激发拉曼光谱检测系统的光源用于减除原始拉曼光谱中的荧光背景。

Aiming at the miniaturization requirement of shifted excitation Raman spectroscopy test system, a portable grating-coupled external cavity (EC) tunable semiconductor laser in Littrow configuration is designed and fabricated with a commercial 785 nm high-power laser diode as the gain device. By using a new wavelength tuning method, aiming to change the position of gain device relative to the collimating lens in the horizontal direction, a miniaturized device with the size of 140 mm×65 mm×50 mm is designed. Compared to the traditional wavelength tuning method which is to change the light incident angle by rotating the diffraction grating, this new tuning method reduces the translational distance of semiconductor gain device effectively, thus it is conductive to the fast and broad wavelength tuning of portable EC laser. The experimental results show that the EC laser has a wide wavelength tuning range. Under any injection current from 340 to 900 mA, a wavelength tuning range of more than 10 nm can be realized. Especially at 900 mA, good performance including a 1167 nm-wavelength tuning range from 77940 to 79107 nm, a less than 02 nm-spectral linewidth, an up to 280 mW-output power, and a more than 25 dB-amplified spontaneous emission suppression ratio is presented, which fully meets the basic testing requirements of shifted excitation Raman spectroscopy. Moreover, 135 nm-electric wavelength tuning range is achieved by applying a mini-piezoelectric actuator. This indicates that the home-made 785 nm portable grating-coupled EC tunable semiconductor laser is suitable as the light source of portable shifted excitation Raman spectroscopy testing system to eliminate the fluorescence background of Raman spectrum.