摘要
We report optical parametric generation from a 532-nm-pumped periodically poled lithium niobate with a wavelength spectrum covering the sodium D/sub 1/, D/sub 2/ wavelengths 589.6 and 589.0 nm. Despite the 8 cm/sup -1/ attenuation at the 5.45 /spl mu/m idler wavelength, the PPLN generates a 9 /spl mu/J/pulse energy near the 589-nm sodium wavelength when pumped by a 130 /spl mu/J/pulse frequency-doubled Nd:YAG Q-switched laser. The observed effective nonlinear coefficient is about 40% higher than its value at the visible and near infrared wavelengths. We believe that this is the first observation of ionic susceptibility enhanced parametric gain in the mid-infrared absorption region of lithium niobate