Low Propagation Loss of Single-Mode Planar Waveguides on MgF $_{\bf 2}$ Crystals

The single-mode planar waveguides were fabricated on MgF 2 crystals by 6.0 MeV carbon ion implantation with the fluence of $1 \times 10^{15}$ ions/cm 2 . The guiding modes were measured by the prism-coupling method at the wavelength of 632.8 nm. The near-field intensity distributions were obtained by the end-face coupling method, and the simulation of the light propagation process was performed simultaneously for comparison. The thermal stability was investigated by annealing treatment at different temperatures ranging from 260 °C to 400 °C in air. After suitable annealing, the minimum propagation loss of the waveguide can be reduced to 0.4 dB/cm.