Lateral mode discrimination in AlGaInP selectively buried ridge waveguide lasers

The guiding mechanism of (Al_xGa_1-x)_0.5 In_0.5P visible lasers is analysed using a simple effective index approach and is found to be analogous to that of AlGaAs channelled substrate planar lasers. Outside the ridge, the bound mode is leaky, resulting in a real lateral index guide. Furthermore, the loss outside the ridge provides good discrimination against oscillation of higher order modes. The best ridge widths, based on the tradeoff of low loss in the fundamental mode along with high lateral mode discrimination, are in the range 5-7 μm