Backward second-harmonic generation in periodically poled lithium niobate

For periodically poled LiNbO3 with a 3.3-mu m domain period we observed backward second-harmonic generation using nanosecond laser pulses. We measured phase-matching spectra at the 16th, 17th, 18th, 19th, and 20th orders of the spatial grating. The peak wavelength of each order is in good agreement with the theoretical prediction. The quadratic dependence of the backward second-harmonic output pulse energy on the pump pulse energy was confirmed in our experiments. The quadratic dependence of the conversion efficiency on the domain length was also confirmed. Using nanosecond pulses, we achieved a maximum conversion efficiency of 0.296% for the 16th-order grating. (C) 1998 Optical Society of America [S0740-3224(98)02305-4].