All nonlinear crystals are xray oriented and cut for a specific angle range and temperature at manufacture. You can find anything from room temperature to 60'c in a system.
Low cost, low precision, short lifetime systems are near room temp by design . Hence the horrible drift in mode and stability on most green dpss. Better stuff has very warm, if not hot, KTP.
Again. Its a function of the design, and near room temperature for Type Ii SHG in Ktp is used to save cost. not for optimal prrformance,
Steve
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...