用于太赫兹发射的高功率双波长近衍射极限半导体激光器研究

Dual-wavelength semiconductor lasers have extensive applications in the field of THz generation by optical difference-frequency, etc. Currently dual-wavelength semiconductor lasers are usually fabricated by internal DFB grating in the world. However, the manufacturing process of the device is complex, the output power is low, it is difficult to meet the demand for high power terahertz wave. This project presents high power monolithic integrated dual-wavelength near-diffraction-limited semiconductor lasers with a dual distributed Bragg reflector (DBR) Y-branch waveguide coupled amplifier structure, the principle of near-diffraction-limited dual-wavelength output is mainly studied to improve the stability of its dual-wavelength high-power output. The high power near-diffraction-limited semiconductor lasers will be achieved by these steps — fabricating one–step epitaxy, optimizing the design of the device structure, monolithic integrating different cycle dual-DBR with Y-branch coupling waveguiding, and then amplify the dual-DBR with a tapered amplifier. The devices will reach continuous wave total output powers up to 1W and realize dual-wavelength (1064nm) emission. The beam quality factor (M2) of the device will be less than 1.3. Due to its advantages of simple manufacturing technology and high reliability, the semiconductor laser will substantially reduce the cost of high power THz source by optical difference-frequency, thus making a great significance to the high power THz source by optical difference-frequency.

双波长半导体激光器在利用非线性差频法产生太赫兹波等领域具有重要的应用前景。现在国际上通常采用DFB内置光栅的方法研制这种双波长半导体激光器，但是该器件制作工艺复杂、输出功率较低，难以满足产生高功率太赫兹波的需求。本项目提出一种高功率单片集成带有双分布布拉格反射器（DBR）的Y波导耦合放大结构的双波长近衍射半导体激光器，主要研究其双波长高功率近衍射极限输出机理，以提高其双波长高功率输出的稳定性。该器件采用一次外延工艺，通过优化设计器件结构，将两个不同波长的DBR半导体激光器利用Y形波导进行单片集成并在锥形区放大，来获得高功率、近衍射极限输出的双波长半导体激光器。该器件可实现1064nm波段双波长发射，连续输出总功率达到1W，光束质量因子小于1.3。这种半导体激光器具有制作工艺简单、可靠性高等优点，可大幅降低光学差频法研制高功率太赫兹源的成本，对利用非线性差频法研制高功率太赫兹源具有重要意义。

现阶段，由于缺少高功率、高光束质量的双波长半导体激光器，利用差频方法研制出来的太赫兹源的功率都比较低，严重制约了利用光学差频方法产生太赫兹波发射的研究。本项目提出了一种高功率单片集成带有双分布布拉格反射器（DBR）的Y波导耦合放大结构的双波长近衍射半导体激光器, 该器件采用一次外延工艺，通过优化设计器件结构，将两个不同波长的DBR半导体激光器利用Y形波导进行单片集成并在锥形区放大，来获得高功率、近衍射极限输出的双波长半导体激光器。本项目利用RSoft光学设计软件对Y形耦合波导结构参数进行了优化设计并系统地研究了其双波长高功率近衍射极限输出机理，以提高其双波长高功率输出的稳定性。在对半导体激光器外延结构分析的基础上，结合以往DBR半导体激光器外延参数设计的经验，设计并生长出了1064 nm高应变半导体激光器外延材料。利用全息曝光系统曝光，并结合ICP干法刻蚀技术，研制出双波长近衍射极限输出高功率半导体激光器。在25℃室温下，激光器阈值电流约为550mA，在2500 mA注入电流下，连续输出功率达到1.2W。注入电流2500 mA时，峰值波长为1064.10nm和1067.15nm。在2500mA注入电流下，器件的光束质量因子（M2）为1.213。这种工艺简单、高可靠性的双波长半导体激光器在利用差频法研制高功率太赫兹源等领域具有重要的应用前景。