Bonding crystal, optical cement crystal, separated crystal

First introduce the principle of 532nm laser

808nm semiconductor laser diode (LD) of pumping source supplies energy to laser crystal

Most of crystals are Nd:YVO4, some are Nd:YAG, both have Nd3+ ions and can produce 1064nm infrared laser

Infrared laser turns into 532nm green light through KTP nonlinear frequency doubling crystal

So, 532nm has 2 crystals, including laser crystals and frequency doubling crystal, the combination method of these two crystals include bonding, optical cement and separation.

Bonding crystal. UV light adhesives are adopted to bond crystals. If the power is relatively large, the crystals will be heated up quickly, then that would be a tragic if adhesives may come unglued after expansion and contraction. The extreme power of agglutination crystal is 200mw and its stability is poor
Optical cement crystal. A special treatment is conducted to contact surface of crystals (estimated to be highly polished), then crystals will be pressed together, crystals after this treatment will not be easy to come unglued as molecular forces integrate and their stability are relatively high, good for lasers below 300mW

Separated crystal. 2 crystals are separately placed for independent cooling, it can withstand a great power. Its weaknesses is that complex adjustment is needed to change the crystal position to achieve the maximum output and it has complex structure, large volume and high cost.