“…CSP is optically negative uniaxial chalcopyrite so that non-critical type-I (oo-e) phasematching is possible in contrast to the positive ZnGeP 2 (ZGP) which is the only commercially available II-IV-V 2 type chalcopyrite. The birefringence, (n e -n o ), of CSP was found to be -0.06 approaching a wavelength of 6 µm [2], -0.051 near 2 µm [7], -0.05 at 1 µm [5], and -0.045 at 840 nm [3] in earlier work. An isotropic point, i.e.…”