What is the Mark on the NLO crystal Surface: There is a dot mark on the NLO crystal which is the axis for angle tilting to achieve phase matching. Laser polarization should be parallel to the doted axis for type I or 45deg. for type II phase matching. If you are not sure of your laser polarization, try it with different angles.
Some optical crystal has an arrow mark if the optical coating is different on the input and output surface.
NLO Crystals Applications
BBO Nonlinear Crystals
KTA crystals for OPO laser
Frequency doubling crystal
electro optic crystal
A-Star’s NLO Crystals include BBO Crystal, LBO Crystal, LiNbO3 Crystal, MgO:LiNbO3 Crystal, DKDP&KDP Crystal, KTP Crystal and KTA Crystal etc.