Refractive index reconstruction of graded-index buried channel waveguides from their mode intensities

The refractive index distribution has been determined for a number of graded-index, single-mode, buried channel waveguides, formed by irradiation with a high energy focused ion beam. The refractive index has been calculated from the waveguide's mode field intensity at a wavelength of 670 nm, via an inversion of the scalar wave equation. Waveguides with doses in the range 0.7/spl times/10/sup 15/-4.1/spl times/10/sup 15/ ions/spl middot/cm/sup -2/ exhibited a peak refractive index change increasing linearly with ion dose, in the range 0.01-0.08%, and the results are consistent with profiles derived from TRIM simulations.