Thermal annealing of implantation-induced compaction for improved silica waveguide performance

The optimum processing parameters for the fabrication of low-loss waveguides in fused silica by ion implantation and annealing have been determined through a comparison of implantation-induced physical and optical properties. The step height at an implanted/unimplanted boundary resulting from Si implantation was measured as a function of the ion dose (2x10(12)-6x10(16)/cm(2)) and energy (1-9 MeV) and the postimplantation annealing temperature (200-900 degrees C) and time (0.1-150 min). For a given ion energy (5 MeV), the step height increased for doses <similar to 10(15)/cm(2) and thereafter, saturated. For a given ion dose (2x10(15)/cm(2)), a near-linear trend was evident for step height as a function of ion energy. Isochronal and isothermal annealing both resulted in a nonlinear reduction in step height, typical of a thermally induced process. In contrast to the continual reduction in step height observed during isochronal annealing, the loss coefficient exhibited a distinct minimum of similar to 0.15 dB/cm at an intermediate temperature of 500 degrees C. This feature was consistent with the removal of a specific defect or color center. (C) 1996 American Institute of Physics.