Contrasts in writing photonic structures with ultrafast and ultraviolet lasers

This paper contrasts the photosensitivity responses and processing windows between two extreme approaches in laser structuring of photonic devices: ultrafast and deep-ultraviolet F, lasers. Low-loss single mode waveguides were formed by scanning in fused silica the focused light from a 50-fs Ti:Sapphire laser and a 157-nm 15-ns F, laser. The latter source represents the first known demonstration of writing buried waveguide structures in bulk glass without driving ultrafast-laser interaction physics. For the ultrafast laser, a refractive index change of 1.0 x 10(-3) was noted after an accumulated fluence of similar to10 kJ/cm(2), a high scanning speed of similar to100 mum/s, and 100-kHz repetition rate. Longitudinal and side-writing techniques were employed and waveguides were characterized at 0.633-mum and 1.5-mum wavelengths. For the F, laser, photosensitivity responses were similar in germanosilicate planar waveguides, and similar to10-fold smaller in fused silica. Waveguide writing speeds were similar to100-fold slower than for the ultrafast laser because of the smaller 100-Hz repetition rate. Overall, ultrafast lasers and ultraviolet lasers offer strong photosensitivity responses in silica-based glasses that address niche applications in fabricating complex three-dimensional photonic structures and trimming optical circuits for telecommunication applications.