Second harmonic generation at 532 and 780 nm in femtosecond laser direct-written LBO waveguides

We report on the frequency doubling properties of femtosecond (fs) laser direct-written lithium triborate (LBO) cladding waveguides. The guiding properties (mode profiles and propagation losses) of these waveguides are experimentally characterized. The maximum conversion efficiency values of 4.8% and 8.6% are achieved for frequency doubling processes of 1064 → 532 nm and 1560 → 780 nm, respectively, in the fabricated depressed-cladding waveguides at room temperature. Our results suggest the potential applications of fs-laser direct writing technique as well as LBO waveguides in constructing compact frequency converters.