Guided-wave second harmonic generation in hexagonally poled RPE:LiNbO₃

Abstract

Buried waveguides fabricated by reverse proton exchange (RPE) have recently allowed the demonstration of the highest Second Harmonic Generation (SHG) efficiency reported to date in 1D Periodically poled LiNbO3 (PPLN) [1] and appear extremely promising for practical applications of χ(2) nonlinearities. In this communication, we report on efficient SHG at telecom wavelengths in an optimised buried waveguide made by RPE in 2D Hexagonally poled LiNbO3 (HexLN). We demonstrate an RPE:HexLN device (the integrated version of the configuration of Ref.[2]) allowing the simultaneous generation of a pair of guided SH waves by means of two concurrent TM0(ω)+TM0(ω) --&gt; TM0(2ω) processes, quasi-phase-matched by different reciprocal lattice vectors of the HexLN pattern. A full characterisation of the angular and spectral SHG response of the RPE:HexLN device provides us also with additional information on the linear properties of the buried waveguide, difficult to determine via conventional linear measurements.<br/