Wang Tianfang, Yang Chengao, Zhang Yi, Chen Yihang, Shang Jinming, Zhang Yu, Xu Yingqiang, Niu Zhichuan
Opt Express. 2021 Oct 11;29(21):33864-33873. doi: 10.1364/OE.439255.
In this article, we present a tunable GaSb-based blazed grating external cavity laser (BG-ECL) with high spectral purity and high output power single-mode operation around 1940nm. The drastic increase in spectral selectivity and optical power results from the employment of a single-transverse-mode operating narrow ridge waveguide laser diode with an optimized AR coating on the front facet. The stable fundamental spatial mode output beam from the laser diode enables efficient collimation and high coupling efficiency with the blazed grating, leading to stronger wavelength-selective feedback. The AR coating with proper low reflectivity on the straight waveguide effectively suppresses the internal cavity mode lasing without causing extra optical loss. As a result, the BG-ECL device exhibits excellent comprehensive performance with a side mode suppression ratio (SMSR) over 50 dB with optical power exceeding 30 mW within a 70 nm tuning range. A maximum SMSR of 56.26 dB with 35.12 mW output power was observed in continuous-wave operation. By increasing the working temperature of the diode laser, the tuning range can be further extended to over 100 nm without noticeable degradation in spectral and output power performance.
在本文中，我们展示了一种基于GaSb的可调谐闪耀光栅外腔激光器（BG - ECL），其在1940nm附近具有高光谱纯度和高输出功率单模运行特性。光谱选择性和光功率的显著提高源于采用了具有优化前表面增透膜的单横向模式运行窄脊波导激光二极管。激光二极管输出的稳定基模空间模式光束能够实现与闪耀光栅的高效准直和高耦合效率，从而产生更强的波长选择性反馈。在直波导上具有适当低反射率的增透膜有效地抑制了内腔模式激射，而不会造成额外的光学损耗。因此，BG - ECL器件表现出优异的综合性能，在70nm调谐范围内边模抑制比（SMSR）超过50dB，光功率超过30mW。在连续波运行中观察到最大SMSR为56.26dB，输出功率为35.12mW。通过提高二极管激光器的工作温度，调谐范围可以进一步扩展到超过100nm，而光谱和输出功率性能不会有明显下降。
