We have expertise in modeling sum- and difference-frequency mixing, optical parametric amplification (OPA), and optical parametric generation (OPG). For any of these nonlinear frequency conversion processes it is necessary to select the appropriate nonlinear crystal based on its effective nonlinearity and its phase matching properties. The bibliography Crystals.pdf lists papers that contain important information on over 100 nonlinear crystals. Phase matching directions for uniaxial crystals form a cone around the optic axis. For biaxial crystals the phase matching loci form more complicated shapes.
Once the phase matching loci are found it is usually desirable to maximize the effective nonlinearity by choosing one direction from among the loci of phase matched directions. Alternatively, the propagation direction that gives the largest nonlinearity can chosen and quasi phase matching can be used to achieve phase matching. For short pulses or multimode pulses it is also necessary to choose a crystal with the right group velocities.
The process of calculating phase matching, effective nonlinearity, and group velocities is largely automated in SNLO (functions QMIX, QPM, Bmix, Opoangles, Ref_Ind, GVM) Once a suitable crystal is chosen, it is desirable to analyze its performance to see whether it is possible to achieve your design goals. Other SNLO functions can assist with this. They can model sum- and difference-frequency mixing, OPA, and OPG in any crystal. Mixing inside a cavity can also be modeled, for example cavity enhanced second harmonic generation.
We offer custom models as well as design services. We have many year experience in modeling and laboratory use of nonlinear crystals. We also offer advice/service on characterizing nonlinear crystals including measurements of deff and refractive index. We can help diagnose problems and suggest solutions. We can model thermal problems common in high average power applications.