Channel waveguide array in Ce-doped potassium sodium strontium barium niobate crystal fabricated by He+ ion implantation

The authors report on the fabrication of one dimensional channel waveguide array in photorefractive Ce-doped potassium sodium strontium barium niobate crystal by photographic masking and following direct multiple energy He+ ion implantation. The dark mode spectroscopy is investigated for determining the refractive index modulation of the waveguide. The Floquet-Bloch modes (band transmission spectra) of the light propagating in the array are observed. It is found that the induced optical barriers with reduced refractive indices form semiclosed wedged walls, which confine the enclosed region (together with air) to be channel waveguides. The propagation loss of the waveguide array is determined to be similar to 1.6 dB/cm for ordinary polarized light at 632.8 nm.