Wave propagation in inhomogeneous slab waveguides embedded in homogeneous media

A uniform asymptotic technique is developed for analyzing the wave propagation of inhomogeneous slab waveguides embedded in homogeneous media. The effect of the refractive-index profiles with various core and cladding structures on the guided modes is accurately evaluated by this technique. The guided-modes of waveguides with asymmetric claddings and with a near-parabolic profile core or a quasi-Gaussian profile core were calculated. It is found that the third-order asymptotic solution is accurate for all the guided modes for the near-parabolic profile core and for modes far from cutoff in the quasi-Gaussian profile core. The numerical results show that the propagation modes in strongly asymmetric profiles correspond to almost all of the odd-order modes of propagation in the symmetric profile waveguide. In addition, the fundamental modes in the asymmetric structure waveguides have finite cutoff frequencies.