基于热调谐的窄线宽多通道干涉可调谐半导体激光器的研究

Tunable lasers can be used in many fields, such as, optical detection, optical sensing and optical fiber communication, which have important research value and market application value. Narrow-linewidth tunable lasers are indispensable key devices in high-speed coherent optical communication systems. Foreign optical device manufacturers have developed products of narrow-linewidth tunable semiconductor lasers, while it is still vacant in our country. In October 2017, the Ministry of Industry and Information Technology listed narrow-linewidth tunable light sources as key technologies in the field of optical fiber communication. In this proposal, we study the thermally-tuned narrow-linewidth tunable semiconductor lasers, especially a new scheme of monolithically integrated widely tunable semiconductor lasers: Multi-channel interference (MCI) lasers. Due to electrical tuning, the linewidths of the MCI lasers are at the MHz level, which can’t meet the requirement of high-speed coherent optical communication systems. We plan to use AlGaInAs MQWs and thermal tuning to reduce the linewidths of the MCI lasers. To meet the limitation of power consumption of small form-factor package, suspended thermal tuning waveguides are utilized to increase thermal impedance so as to reduce heat power consumption. We will make the MCI lasers achieve a tuning range of more than 40 nm, side mode suppression ratios higher than 48 dB, fiber coupled power greater than 16 dBm and linewidths less than 100 kHz.

可调谐激光器可用于光检测、光传感以及光通信等领域，具有重要的研究和市场应用价值。其中，窄线宽可调谐激光器是高速相干光通信系统必不可少的关键器件。近几年国外各大光器件厂商都研发出了相应的单片集成的窄线宽可调谐半导体激光器产品，国内尚无相应的产品。2017年10月，工信部将窄线宽可调光源列为了光通信领域的关键技术。本项目对基于热调谐的窄线宽可调谐半导体激光器展开研究，涉及一种新型的单片集成的大范围可调谐半导体激光器——多通道干涉激光器。基于电调谐的多通道干涉激光器的线宽在MHz级别无法满足高速相干光通信系统的应用需求。本项目将采用AlGaInAs量子阱材料和热调谐来降低多通道干涉激光器的线宽。为了满足小尺寸封装的功耗限制，拟采用悬空的热调谐波导来增加热阻从而降低热功耗。预期使多通道干涉激光器的调谐范围> 40 nm，边模抑制比> 48 dB，入纤功率> 16 dBm以及线宽< 100 kHz。

多通道干涉激光器是一款新型的InP基波长大范围可调谐半导体激光器。相比于基于光栅的大范围可调谐半导体激光器，多通道干涉激光器具有制作简单和容差大等优点。在前期研究中，多通道干涉激光器是采用电注入进行波长调谐的。通过延时自外差法测试的电调谐的多通道干涉激光器的线宽在MHz级别。因此，为了满足长距离高速光通信系统对激光器线宽的需求，我们需要降低多通道干涉激光器的洛伦兹线宽。降低多通道干涉激光器洛伦线宽的方法主要有三个：第一个是优化多通道干涉激光器的设计和制作工艺；第二个是采用AlGaInAs量子阱材料；第三个是采用热调谐代替电调谐。。为了增加热电极的加热效率，我们在脊波导与衬底之间制作了一层空气绝热层。我们采用了周期性的结构来支撑悬空波导，可以实现任意长度的悬空波导的制作。支撑结构还可以增加悬空波导的机械强度。为了放大激光器的输出光功率，我们通过双端口的多模干涉反射器实现了激光器与半导体光放大器的集成。150微米长带支撑的悬空波导产生π相移所需的热电极加热功率大约为3mW。经测试，激光器实现了大于45nm的调谐范围，并且在整个调谐范围内边模抑制比大于46dB，入纤光功率大于16dBm，洛伦兹线宽小于100kHz以及总的热调谐功耗小于50mW。