FABRICATION OF PLANAR OPTICAL WAVE-GUIDES IN LIB3O5 BY 2-MEVHE+ ION-IMPLANTATION

Planar optical waveguides have been fabricated in LiB3O5 for the first time. Using 2 MeV He-4+ implantation with a dose of 1.5 x 10(16) ions/cm2 at 300 K, the refractive indexes of a 0.2 mum thick layer 5.1 mum below the crystal surface are reduced to form optical barrier guides. For this ion dose the maximum change from the bulk values of refractive index at a wavelength of 0.488 mum are 1.5%, 5.25% and 4% for n(x), n(y), and n(z), respectively. The refractive indexes of the guiding region change by less than 0.02% from the bulk values. The dose dependence of the optical barrier height has been measured. A threshold ion dose of about 0.75 x 10(16) ions/cm2 is required to form a refractive index barrier and ion doses higher than about 2.5 x 10(16) ions/cm2 saturate the refractive index decrease. Waveguide propagation losses for annealed single energy implants of dose 1.5 x 10(16) ions/cm2 are dominated by tunnelling and are estimated to be approximately 8.9 dB/cm for our z-cut waveguides. Multiple energy implants broaden the optical barrier and losses < 4 dB/cm have been observed.