Circularly-Symmetric Grating, Surface-Emitting SemiconductorLaser

研究小组将研究圆对称光栅表面发射（CSGSE）半导体激光器的制造和性能。该研究的目的是开发和演示一种发射具有圆形截面的光束的AlGaAs-GaAs半导体激光器。这种激光器有可能提高光耦合到光纤中的效率，从而减少发射光束的发散，并作为二维锁相阵列的基本元件。利用电子束刻写和化学辅助离子束刻蚀技术，在AlGaAs-GaAs半导体激光器结构中制备圆光栅，并进行分子束外延生长。在定向错误的砷化镓衬底上生长的量子阱激光器结构将用于获得最高质量的材料和最低的阈值电流密度。并尽量减少丝状激光的可能性。圆光栅将在波导中产生振荡激光模式，这种模式是径向向内和向外的圆波。二阶光栅的使用将允许一个圆对称光束通过表面耦合出激光器。理论分析将伴随和指导激光器的制作和实验评价。

The research team will investigate the fabrication and performance of circularly-symmetric-grating, surface-emitting (CSGSE) semiconductor lasers. The objective of the research is the development and demonstration of an AlGaAs-GaAs semiconductor laser that emits a beam with a circular cross-section. Such a laser has the potential to improve the efficiency with which light can be coupled into an optical fiber, to reduce the divergence of the emitted beam, and to serve as the basic element in a two- dimensional phase-locked array. Circular grating will be fabricated in AlGaAs-GaAs semiconductor laser structures, grown my molecular beam epitaxy, using electron-beam writing and chemically-assisted ion-beam etching. Quantum-well laser structures grown on misoriented GaAs substrates will be used to obtain the highest quality material and the lowest threshold current density possible, and to minimize the possibility of filamentary lasing. The circular grating will operate to produce oscillating laser modes in the waveguide that are radially inward- and outward-going circular waves. The use of a second-order grating will allow a circularly- symmetric beam to be coupled out of the laser through the surface. The fabrication and experimental evaluation of the laser will be accompanied and guided by theoretical analysis.