It was shown here that there was possibility of optical quasi-phase matched secondary harmonic generation in crystalline quartz that was a non-ferro-electric crystal. By utilizing a twinning phenomenon, periodic modulation of the non-linear coefficient was achieved for the first time by fabricating via hot pressing. In this method, stress was applied vertically on a quartz surface. A special press system was also developed. The numbers of twins achieved were 10 for 500μm and 17 for 250μm periods, and the depth of the twinned area was about 50μm. The results suggested that the twinned regions could be controlled artificially, and a twinned depth of more than a few tens of microns could be obtained.

Periodic Twinning in Crystal Quartz for Optical Quasi Phase-Matched Secondary Harmonic Conversion. M.Harada, K.Muramatsu, Y.Iwasaki, S.Kurimura, T.Taira: Journal of Materials Research, 2004, 19[4], 969-72