OPTICAL-PROPERTIES OF BISMUTH-GERMANATE [BGO(2/3)] WAVE-GUIDES FORMED BY ION-IMPLANTATION

The planar optical BGO(2:3) waveguides formed by He+ ion implantation have been studied. Ion implantation causes a high optical index well in both electronic and nuclear stopping power regions, which is stable at T less-than-or-equal-to 200-degrees-C. Annealing at this temperature results in a low loss (0.2 dB/cm) waveguide. A gradual recovery in the waveguide was observed at T less-than-or-equal-to 400-degrees-C, and for heavily implanted samples the well is replaced by a low index barrier if it is annealed at 425-degrees-C < T < 450-degrees-C. Furthermore, this material becomes optically active by ion implantation, and annealing to 450-degrees-C strengthens the rotary power up to approximately 90-degrees/mm at 633 nm. The optical activity is also mode order dependent, which suggests that there is a non-uniformity across the waveguide. This assumption is confirmed by intensity distribution calculations. Overall, it is proposed that the implantation causes a relaxation into a new optically active crystal phase.