Cadmium selenide (CdSe) crystals has an infrared transmission from 0.8 to 25 µm, reasonably large nonlinearity and small walk-off angle. CdSe crystals can be employed into difference frequency generation (DFG), optical parametric oscillation (OPO) schemes to generate infrared laser radiation above ZGP absorption edge (>12 µm). For instance, CdSe OPO can potentially be pumped by 2 µm Tm-doped, Ho-doped, Tm and Ho co-doped lasers and produce far infrared idler radiation. Besides nonlinear optic applications cadmium selenide crystal material can be used for IR optical elements: substrates, polarizers, waveplates, etc.
Applications:
Far infrared wavelength radiation generation by DFG, OPO schemes
Material for infrared optical elements: substrates, polarizers, waveplates, etc.
Performance comparison of commonly used mid-infrared birefringent uniaxial crystals:
| Material | ZnGeP2 | AgGaSe2 | CdGaAs2 | CdS | CdSe |
| Energy gap(eV) | 2.02 | 1.83 | 0.67 | 2.42 | 1.73 |
| Absorption Coef, λ=10.6µm | 0.9cm-1 | 0.089cm-1 | 0.14cm-1 | 0.007cm-1 | 0.0015cm-1 |
| Refractive index, λ=10.6µm | no=3.0738 | no=2.5917 | no=3.5054 | no=2.2245 | no=2.4258 |
| ne=3.1137 | ne=2.5585 | ne=3.5922 | ne=2.2376 | ne=2.4437 | |
| Max. light | 55 | 65 | 60 | 70 | 71 |
| Transmittance | 0.7-12µm | 0.7-19µm | 0.7-20µm | 2.5-15µm | 0.8-25µm |
| Mohs hardness | 5.5 | 3-3.5 | 3.5-4 | 3.4 | 3.25 |
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