BACKWARD 2ND-HARMONIC GENERATION IN PERIODICALLY POLED LITHIUM-NIOBATE

For periodically poled LiNbO3 with a 3.3-mu m domain period we observe d backward second-harmonic generation using nanosecond laser pulses. W e measured phase-matching spectra at the 16th, 17th, 18th, 19th, and 2 0th orders of the spatial grating. The peak wavelength of each order i s in good agreement with the theoretical prediction. The quadratic dep endence of the backward second-harmonic output pulse energy on the pum p pulse energy was confirmed in our experiments. The quadratic depende nce of the conversion efficiency on the domain length was also confirm ed. Using nanosecond pulses, we achieved a maximum conversion efficien cy of 0.296% for the 16th-order grating. (C) 1998 Optical Society of A merica [S0740-3224(98)02305-4].