Gratings in indium oxide film overlayers on ion-exchanged waveguides by excimer laser micromachining

摘要

Relief Bragg gratings were imprinted by 248nm interferometric excimer laser ablation on potassium ion-exchanged channel waveguides in BK-7 glass overlaid with athin high-index InOx film. Using five pulses of energy density 60mJ/cm2, a spectral transmittance notch of depth 66% and Delta.lambda 0.1nm was obtained at 1547nm in the TE polarisation for a waveguide having a nominal width of 8µm and a 135nm thick InOx overlayer. In waveguides coated with 100nm InOx, with widths increasing from 3µm to 8µm, the reflection wavelength shifted by 0.12nm/µm and the reflectivity increased monotonically.