Computing the eigenmodes of lossy field-induced optical waveguides

Slab waveguides which achieve lateral confinement in the guiding region by applying a spatially selective electric field across a multiquantum well cladding region are modeled by solving the appropriate Helmholtz equation. Attention is focused on the effects of absorption in the cladding region of the waveguide, which leads to attenuation along the propagation direction. Galerkin´s method is utilized to compute exact mode propagation constants and intensities of the fundamental mode. It is found that increased absorption in the cladding layer results in increased lateral extent of the guided mode. At a critical absorption strength, the guided mode becomes unconfined in the lateral direction. This transition can be rationalized in part in terms of the effective index method, which provides a simple approximate way to calculate the characteristics of waveguides with two-dimensional index profiles