Electro-optic beam shaping with a PPLN-bulk LiNbO3 boundary and its use for active Q-Switched operation of an intracavity frequency-doubled Nd3+:YVO4 laser

The authors have experimentally observed an intense electro-optic alteration of the transversal beam-shape of a Gaussian beam passing through a PPLN crystal where the domain patterned region is sandwiched between two mono-domain (unpoled) regions. The effect is strong enough to lead to low voltage driven electro-optic Q-switch when the PPLN crystal is placed intracavity to a 1064 nm Nd³⁺:YVO₄ laser. By heating the crystal to a suitable QPM temperature, Q-switching and efficient intracavity frequency doubling to 532 nm may be realized simultaneously. As compared with previous schemes based on polarization rotation with intra-cavity PPLN crystals, this novel Q-switching technique requires no additional intracavity optical elements such as Brewster plates. It may be implemented in simple composite miniature lasers based on bonding a laser crystal to a PPLN crystal and depositing dielectric mirrors on both laser ends, as all that is required is deposition of electrodes in the crystal and application of an external voltage.