The generation of beams with a double frequency (i.e. half wavelength) or other multiple frequencies is done with so-called nonlinear crystals.
Various crystal materials are available. These materials vary in the wavelength range that can be used, crystal structure, and thermal properties. The most common ones are BBO, LBO, KTP, LiNbO3, KDP, KD*P, RTP and BiB3O6. Our product specialists would be more than happy to assist you when choosing an appropriate crystal for your application.
Typical applications for nonlinear crystals:
Frequency multiplication (SHG, THG, …)
Frequency mixing (SFM, DFM)
Optical parametric oscillators/amplifiers (OPO/OPA)
Electro-optical components (Pockels cells, Q-switches)