Analysis of an integrated twin-guide laser with coupled-wave theory

The integrated twin-guide (ITG) laser consists of two parallel waveguides for the laser gain and the light output. Light-wave coupling between the two waveguides is analyzed with the help of coupled-wave theory, and the frequency-dependent oscillation conditions are obtained in an explicit form. It is concluded that single axial-mode oscillation is more realizable in an asymmetrical structure with shorter cavity length than in a symmetrical structure. This method of analysis can be applied to integrated optical circuits consisting of twin-guide structures.