高功率半导体激光器在固体或光纤激光器泵浦、材料加工、医疗、传感、空间通讯和**上有着极其重要的应用, 但传统半导体激光器面临垂直发散角大、椭圆光斑的难题, 限制了其直接应用。为了降低激光器的垂直发散角, 本项目采用布拉格反射波导结构, 利用光子带隙导引替代传统的全反射进行光场限制, 优化设计了多种布拉格反射波导激光器结构, 并制备了高性能的激光器器件。首先, 采用传输矩阵理论和布洛赫波近似的方法计算了布拉格反射波导的模式色散关系, 发现通过控制腔模光场分布, 可实现不同远场的激光输出。接着, 针对布拉格波导光子带隙导引机制, 深入研究了四分之一波长布拉格反射波导激光器、单边布拉格反射波导激光器的光场特性, 弄清了影响此类激光器远场的本质因素, 最终设计并验证了一种布拉格反射波导双光束激光器, 激光器在垂直方向可输出两个对称的、近圆形光束, 单光束垂直和侧向发散角半高全宽分别低至7.2°和5.4°。另外, 通过调控光缺陷层, 使激光器工作在受抑隧穿光子带隙导引机制下, 实现了超窄的单光束激光输出, 激光器单管连续输出功率超过4.6 W, 垂直发散角最低降至4.9°(半高全宽)和9.8°(95%功率)。这种高功率、窄的圆形光束输出可以大幅降低半导体激光器的应用成本, 提高泵浦或光纤耦合效率, 具有广阔的应用前景。

High power diode lasers are widely used for pumping of solid state lasers and fiber lasers, material processing, medical treatment, sensors, free-space optical communication, security and defense. However, the conventional diode lasers usually suffer from a large far-field divergence and strongly elliptical beam, which limit the direct applications. To improve the divergence, diode lasers based on Bragg reflection waveguide(BRW) are studied in this project, which utilizes the photonic bandgap(PBG) effect rather than the total internal reflection(TIR) to provide optical confinement. Several kinds of BRW lasers(BRLs) with different structures are designed and fabricated. First, the mode dispersion equation of the BRW is solved by the transfer matrix method and Bloch theory. The further analysis shows that the far-field distribution of BRW is determined by the mode shape in the cavity. In the case of Bragg form of PBG guidance, the optical field characteristics of a quarter-wave BRL and a single-sided BRL are studied. The essential reason affecting the far-field distribution is investigated. Finally, a twin-beam laser based on BRW is designed and demonstrated. Almost all the emission power of this laser is concentrated in two near-circular lobes in the vertical direction. The full-width at half maximum(FWHM) divergence angles of one beam are as narrow as 7.2° and 5.4° respectively in the vertical and lateral direction. Furthermore, the high brightness BRL with a ultra-narrow circular output beam is demonstrated by controlling the defect layer. The ultra-low vertical divergence of 9.8° with 95% power content and 4.9° with the FWHM definition is realized. The maximum output power exceeds 4.6 W under continuous-wave operation at room temperature. The narrow circular beam emission from the BRL can greatly improve the pumping efficiency and optical fiber coupling efficiency without expensive beam shaping. It is believed that the BRLs have a promising application prospect.