Backward second-harmonic generation in submicron-period ion-exchanged KTiOPO 4 waveguide

Abstract

For the first time, we demonstrated backward second-harmonic generation (SHG) in a submicron-period ion-exchanged KTiOPO 4 (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 ∼4.5×10 −3 μm for our sample, which is close to the value of ∼7×10 −3 μm measured by other techniques.