RAY OPTICS DETERMINATION OF THE DFB COUPLING COEFFICIENT IN SEPARATE-CONFINEMENT AND MULTI-QUANTUM-WELL LASER STRUCTURES

A ray optics technique is used to derive a closed-form expression for the first-order backward coupling coefficient kappa in a generic five- layer separate confinement distributed feedback laser configuration wi th sinusoidal, triangular, or rectangular gratings. The expression is applicable to multiquantum-well structures as well as strong coupling configurations, and can be evaluated without using any numerical techn iques. For the weak perturbation configurations normally encountered i n such devices, the ray optics kappa values are in good agreement with those obtained using the standard overlap integral technique.