Integrated waveguide frequency-converted laser fabricated by ultrafast laser inscription

We report the fabrication and characterization of a monolithic waveguide-based frequency-converted laser source. An Nd:YAG laser crystal and a periodically poled lithium niobate frequency-doubling chip were permanently bonded on a common fused-silica substrate via ultrafast laser microwelding. A continuous double-track waveguide was then fabricated across the two dissimilar crystals using ultrafast laser inscription to form an integrated, alignment-free frequency-converted laser source. The integrated source was diode-pumped at 808 nm, resulting in lasing at 1064 nm and subsequent second-harmonic generation (SHG) at 532 nm. SHG tuning behavior for different track separations revealed trade-offs between confinement, efficiency, and mode structure. Propagation and vertical-offset losses were studied to determine the optimal waveguide geometry.