Design considerations of the DBR injection laser and the waveguiding structure for integrated optics

Abstract

In this paper, we analyze the operation of the distributed-Bragg-reflector (DBR) injection laser with an emphasis on compatibility with the integrated-optics concept. First, methods of computing the coupling constant are reviewed and the results are compared. A general agreement is found. Next, the reflection and transmission coefficients for both lossless and lossy Bragg reflectors are examined for their dependencies on the coupling constant, the reflector length, the loss constant in the reflector region, and the operating wavelength. The computed results are then applied to analyzing experimental results on DBR GaAs double-heterostructure (DH) injection lasers. A general agreement between the theory and the experiment is found. From the analysis, it appears possible for the DBR injection laser to operate in single mode with sufficient output power, low threshold, and good efficiency by proper design of the laser structure and significant loss reduction in the reflector region. A waveguiding structure is considered for loss reduction and for eventual incorporation of the laser into an integrated optical circuit. The stress is on a single liquid-phase-epitaxy (LPE) step for the fabrication of the structure. Additional pre-LPE and post-LPE steps are suggested for fabrication and isolation of different optical devices.