Near-field method for refractive-index profiling of optical planar and channel waveguide

Refractive-index profile reconstruction methods for optical slab (direct and inverse analysis methods) and channel (inverse analysis method) waveguides are proposed and compared. Both methods are based on the output near-field measurement at the cleaved edge of a waveguide. Theoretical simulations of each method are demonstrated. Effects of noise and of the optical imaging system are taken into account and are minimized.;As an application, the near-field patterns of planar and channel optical waveguides fabricated by purely thermal K+-Na+ ion-exchange in soda-lime glass substrates are measured using a CCD camera. The resultant refractive-index profiles of the slab waveguide samples are then compared with data obtained by optical characterizations done by others. Index profiles of channel waveguide samples are also reconstructed.;A Runge-Kutta (RK) method and a One-Dimensional Finite-Difference Method (1D-FDM) are used to model planar waveguides, while an Effective-Index Method (EIM) and a variable grid 2D-FDM are implemented to model channel waveguides.