Frequency-doubling of a compact femtosecond Cr:LiSAF laser using a periodically-poled KTP waveguide crystal

We have investigated a very simple, extracavity single-pass scheme for frequency doubling in a periodically-poled KTP crystal waveguide. This sample was 11 mm in length and was poled for the frequency doubling of ∼850 nm light. The channel guide had cross-sectional dimensions of ∼4×4 μm and was fabricated by ion exchange technique. The poled section was approximately 8 mm in length followed by a 3 mm Bragg-reflector section. Although the inclusion of this Bragg section, which reflected 26% of the fundamental, was intended for another application, it did not appear to affect the performance of the source laser. The observed saturation of the SHG efficiency in the ppKTP waveguide is attributed to pump depletion.