Determination of Coupling Coefficient in Large Optical Cavity Distributed Feedback Laser Structure with Metal Surface Grating

The paper provides simulation studies for the optimization of the ridge profile which is required to achieve a single and well-confined mode in ridge waveguide with an asymmetrical large optical cavity (LOC) edge-emitting lasers emitting at 976 nm. Optimized ridge waveguide parameters are then used for the design of laterally coupled distributed feedback (LC DFB) laser structure with chromium metal surface grating. The theory of coupled modes for coupling coefficient calculations and the non-uniform Finite Difference Method for mode solving is used. These 2D simulations have been performed using the commercial simulation tool Fimmwave. The residual thickness of 447 nm (etch depth 1 µm) can provide better flexibility in terms of coupling the grating with the mode field. The dependence of the coupling coefficient on structural parameters of gratings is also investigated.