Analysis Of Diffraction For Planar Waveguide And Its Application For Parameters Measurement

With information society on the horizon, the information demand is always increasing dramatically. Planar optical waveguides are the base of the integrated optical circuits, and measurement of their parameters and performance is very imperative for improving the performance of devices, because the data from the measure provide a theoretical base and guidance for the fabrication technique of integrated optical circuits in turn. This paper centers on the measurement of refractive index profile of planar waveguide, and in addition, the total coupling of star coupler is analyzed. Firstly, the far-field diffraction equation of planar waveguide's end-surface is derived from Kirchhoff diffraction integral equation, and its diffractive characteristics are analyzed for the relations between diffraction field and waveguide parameters. Secondly, the coupling efficiency is reviewed and discussed for between the Gaussian beam and planar waveguide, two adjacent planar waveguide and NxN star couplers. Finally, reconstruction of graded refractive index profile of planar wave is presented on the base of inverse matrix algorithm for near-field method, applying discrete Fourier transform and central finite difference method, and herein sampling step of far-field diffraction, inverse Fourier transform and central finite difference method are systematically and detailedly discussed.