Waveguide Design Optimization for Long Wavelength Semiconductor Lasers with Low Threshold Current and Small Beam Divergence

• 作者: Abdelmajid Salhi Abdullah Alharbi Abdulrahman Al-Muhanna
• 来源期刊: 现代物理(英文)
• 学科: 工学
• 关键词: SEMICONDUCTOR LASER FAR-FIELD Simulation
• 年，卷（期）: 2011,（4）
• 页码范围: 225-230
• 页数: 6页
• 分类号: TN2

摘要

Long wavelength GaSb-based quantum well lasers have been optimized for high coupling efficiency into an optical system. Two approaches were used to reduce the vertical far-field. In the first approach we showed the use of V-shaped Weaker Waveguide in the n-cladding layer dramatically reduces vertical beam divergence without any performance degradation compared to a conventional broad-waveguide laser structure. Starting from a broad waveguide laser structure design which gives low threshold current and a large vertical far-field (VFF), the structure was modified to decrease the VFF while maintaining a low threshold-current density. In a first step the combination of a narrow optical waveguide and reduced refractive index step between the waveguide and the cladding layers reduce the VFF from 67? to 42?. The threshold current density was kept low to a value of ~190 A/cm2 for 1000 × 100 μm2 devices by careful adjustment of the doping profile in the p-type cladding layer. The insertion of a V-Shaped Weaker Waveguide in the n-cladding layer is shown to allow for further reduction of the VFF to a value as low as 35? for better light-coupling efficiency into an optical system without any degradation of the device performance. In the second approach, we showed that the use of a depressed cladding structure design also allows for the reduction of the VFF while maintaining low the threshold current density (210 A/cm2), slightly higher value compare to the first design.