Synthesis of optical waveguide with complicated cross-section shape and 3D waveguide structures in glass

Abstract

Physics and mathematical modeling of multi-step processes of waveguide structures fabrication in glass K-8 with complex form of it cross-section, based on the combined, solution of two-dimensional nonlinear diffusion equation, electrostatic equation and wave equation has been made. The equations were solved by finite-difference method. With the help of calculated values of silver ion concentration in glass the refractive index profile (proportional to concentration) was determined and, as a next step, optical characteristics of waveguide was calculated by analysis of it mode structure. Model of partially buried waveguide has been made, which has asymmetric refractive index profile. The experimental sample of such waveguide has been made. The model describes the fabrication of waveguide channel in K-8 type glass, where the burial process is performed with the taper-shape mask covering the part of waveguide surface, which leads to different value of burial depth along waveguide longitudinal axis. It was shown that lateral shift of waveguide concentration profile, caused by direction and density of electrostatic flux at angle between waveguide axis and mask edge, having the value less than 1,5 degree, doesn't affect the optical energy loss in the waveguide. Also the modeling of technological processes of single-mode optical waveguides fabrication in two vertically placed toward each other layer in order to build 3D integrated-optic circuit. The simulation was made in order to select technological parameters with similar values, with the working wavelength 1.55 micrometer. The results of calculation showed that according to this purpose the concentration of melt for the second ion exchange must be half of it value for the first one; the gap width in mask for the first step - 2 micrometer, for the second exchange - 5 micrometer.