抄録
Reported here is the use of the focused beam of an infrared ultrashort pulse laser (150 femtoseconds pulse width, 200 kHz repetition rate, 800 nm wavelength, and 100 μm/s scanning speed) to increase the refractive index of a germanium-doped silica-glass planar waveguide. The increase obtained, Δn, itself increases in proportion to increases in the laser intensity of the surface irradiation, and it saturates to 1.6 ∼ 1.8 × 10-3 at 2.2 TW/cm2, without producing any increase in insertion loss and birefringence. Further, no decay in the refractive index change is observed after annealing at 200 °C for 10 hours. Results show that ultrashort pulse lasers are more suitable than UV lasers as light sources for highly stable adjustment of the optical lengths of waveguide devices.
