Lanthanum gallium silicate (La₃Ga₅SiO₁₄, LGS) crystal belongs to tripartite crystal system, point group 32, space group P₃₂₁ (No.150). LGS has many effects such as piezoelectric, electro-optical, optical rotation, and can also be used as laser material through doping. In 1982, Kaminsky et al. reported the growth of doped LGS crystals. In 2000, LGS crystals with diameter of 3 inch and length of 90 mm were developed by Uda and Buzanov.

LGS crystal is an excellent piezoelectric material with cutting type of zero temperature coefficient. But different from piezoelectric applications, electro-optic Q-switching applications require higher crystal quality. In 2003, Kong et al. successfully grew LGS crystals without obvious macroscopic defects by using Czochralski method, and found that the growth atmosphere affects the color of the crystals. They acquired colorless and gray LGS crystals and made LGS into E-O Q-switch with size of 6.12 mm × 6.12 mm × 40.3 mm. In 2015, one research group in Shandong University successfully grew LGS crystals with diameter 50~55 mm, length 95 mm, and weight 1100 g without obvious macro defects.

In 2003, the above mentioned research group in Shandong University let laser beam pass through the LGS crystal twice and inserted a quarter wave plate to counteract the optical rotation effect, thus realized the application of the optical rotation effect of LGS crystal. The first LGS E-O Q-switch thereupon was made and successfully applied in laser system.

In 2012, Wang et al. prepared a LGS electro-optic Q-switch with size of 7 mm × 7 mm × 45 mm, and realized the output of 2.09 μm pulsed laser beam (520 mJ) in the flash- lamp pumped Cr,Tm,Ho:YAG laser system. In 2013, 2.79 μm pulsed laser beam (216 mJ) output was achieved in the flash-lamp pumped Cr,Er:YSGG laser, with pulse width 14.36 ns. In 2016, Ma et al. used a 5 mm × 5 mm × 25 mm LGS E-O Q switch in Nd:LuVO4 laser system, to realize repetition rate of 200 kHz, which is the highest repetition rate of LGS E-O Q-switched laser system reported publicly at present.

As an E-O Q-switching material, LGS crystal has good temperature stability and high damage threshold, and can work at high repetition frequency. However, there are several problems: (1) The raw material of LGS crystal is expensive, and there is no breakthrough in replacing gallium with aluminum which is cheaper; (2) The E-O coefficient of LGS is relatively small. In order to reduce the operating voltage on the premise of ensuring the enough aperture, the crystal length of the device needs to be linearly increased, which not only increases the cost but also increases the insertion loss.

LGS Crystal – WISOPTIC TECHNOLOGY