Determining the waveguide profile using the overlap integral

The determination of the index profile in guiding structures is a central problem in applied photonics, ranging from optical fibers to femtosecond-written waveguides [1]. A non-destructive and relatively easy method consists in the measurement of the index profile by measuring the transmitted field [2]. From the transmitted field, the refractive index profile is computed by direct inversion of the Helmholtz equation. This technique is called near-field method. Here we present a new near-field method based upon the inversion of the overlap integral.