He Rui Optics' Plano-concave lenses diverge a collimated beam from a virtual focus and are commonly used in Galilean-type beam expanders.Given their negative focal length and negative spherical aberration, plano-concave lenses can be used to balance out aberrations of other lenses in the system. He Rui Optics' provides plano-concave lenses fabricated from N-BK7, N-SF11, UV-fused silica, calcium fluoride, and zinc selenide. N-SF11 offers a usage range that is slightly shifted to the red compared to N-BK7. However, N-SF11 glass is associated with more dispersion because it has a lower Abbe Number than N-BK7 glass.
| Material | optical glass,N-BK7 Glass, Fused Silica, sapphire,Si,Ge,CaF2,LiF,BaF2,Crown glass,Pyrex, .. |
| Dimensions | 3-400mm |
| Dimension Tolerance | ±0.01mm |
| Thickness Tolerance | ±0.01mm |
| Center thickness | >1mm |
| Focal Length tol. | ±1% |
| Centration | 3 arc minutes |
| Surface Quality | 80/50 60/40 40-20 20-10 |
| Clear Aperture | >90% |
| Wavelength Range | Substrate Material |
| 180nm-8.0μm | Calcium Fluoride (CaF2) |
| 185 nm-2.1 um | UV Fused Silica |
| 200 nm- 5.0 um | Sapphire |
| 200 nm- 6.0 um | Magnesium Fluoride (MgF2) |
| 220 nm to >50 um | CVD Diamond Windows |
| 230 nm- 1.1 um | UV Fused Silica. Textured Antireflective surface |
| 250 nm- 1.6 um | UV Fused Silica, for 45° AOI |
| 250 nm- 26 um | Potassium Bromide (KBr) |
| 350 nm- 2.0 um | N-BK7 |
| 600 nm- 16 um | Zinc Selenide (ZnSe) |
| 1.2- 8.0 um | Silicon (Si) |
| 1.9- 16 um | Germanium (Ge) |
| 2- 5 μm | Barium Fluoride (BaF2) |