Backward second-harmonic and third-harmonic generation in a periodically poled potassium titanyl phosphate waveguide

Abstract

We observed backward second-harmonic and backward third-harmonic generation in a periodically poled KTiOPO4 waveguide using nanosecond laser pulses. The highest conversion efficiency achieved for the backward second-harmonic generation, occurring at the 25th-order grating, was ∼0.6%. The backward third-harmonic generation was the result of mixing the pump beam with the forward or the backward second-harmonic beam. Conversion efficiency of ∼0.4% was achieved at a pump wavelength of 1233.7 nm, where the two constituent nonlinear processes are both quasi-phase matched. © 1999 Optical Society of America.