Backward second-harmonic generation in submicron-period ion-exchanged KTiOPO₄ waveguide

Abstract

For the first time, we demonstrated backward second-harmonic generation (SHG) in a submicron-period ion-exchanged KTiOPO4 (KTP) waveguide. Such a period is the shortest ever achieved in ferroelectric materials. The characteristics of backward quasi-phase-matching at the 6th and 7th orders were investigated. Our analyses on the backward SHG show that the second-harmonic linewidth and conversion efficiency are very sensitive to the grating period error. According to our measurement on the backward SH linewidth, we determined the period error to be approximately 4.5×10-3 μm for our sample, which is close to the value of approximately 7×10-3 μm measured by other techniques.