CaF2 Plano-Concave Lenses, Uncoated
|Substrate Material||Vacuum-Grade Calcium Fluoride|
|Wavelength Range |
|0.18 - 8.0 μm|
|Diameters Available||1/2" or 1"|
|Diameter Tolerance||+0.00/-0.10 mm|
|Thickness Tolerance||±0.1 mm|
|Focal Length Tolerance||±1%|
|Surface Quality||40-20 (Scratch-Dig)|
|Spherical Surface Power|
(Peak to Valley)
|Clear Aperture||>90% of Diameter|
|Design Wavelength||588 nm|
*These lenses are also available with an AR coating for the 3 - 5 µm range.
**Much like surface flatness for flat optics, spherical surface power is a measure of the deviation between the surface of the curved optic and a calibrated reference gauge, typically for a 633 nm source, unless otherwise stated. This specification is also commonly referred to as surface fit.
Custom Coatings are also available. Please contact our technical support staff for a quote.
- Uncoated Vacuum-Grade Calcium Fluoride Substrate
- Ø1/2" and Ø1" Versions Available
- Focal Lengths from -18.0 to -500.0 mm
Thorlabs' Ø1/2" and Ø1" Calcium Fluoride (CaF2) Plano-Concave Lenses offer high transmission from 0.18 - 8.0 μm. CaF2 is commonly used for applications requiring high transmission in the infrared and ultraviolet spectral ranges. Its extremely high laser damage threshold makes it useful for use with excimer lasers. The material exhibits a low refractive index, varying from 1.35 to 1.51 within its usage range of 180 nm to 8.0 μm. Calcium fluoride is also fairly chemically inert and offers superior hardness compared to its barium fluoride, magnesium fluoride, and lithium fluoride cousins.
Like all plano-concave lenses, these lenses have negative focal lengths and can be used to diverge collimated beams; in this case, the curved surface should face the source in order to minimize spherical aberration. In addition, they can be employed to offset the effects of spherical aberration caused by other lenses in an optical system.
Total Transmission of Optic (CaF2 Substrate, Uncoated)
The table below gives the approximate theoretical transmission of these uncoated optics for a few select wavelengths in the 0.18 - 8.0 μm range. To see an excel file that lists all measured transmission values for this wavelength range, please click here.
|Wavelength (μm)||Total Transmission|
Wavelength-Dependent Focal Length Shift
The paraxial focal length of a lens is wavelength dependent. The focal length listed under the Specs tab for a given lens corresponds to the value at the design wavelength (i.e., the focal length at 588 nm). Since CaF2 offers high transmission from 0.18 - 8.0 μm, users may wish to use these lenses at other popular wavelengths. Below is a table that gives the focal length (in millimeters) for each lens at fifteen popular wavelengths within the 0.18 - 8.0 μm range.
The first column lists the fifteen wavelengths for which the focal length was calculated. The first row lists the item numbers. Trace across the row of choice to the column of choice to find the focal length corresponding to that lens and that wavelength. For example, the focal length of an LC5749 plano-concave lens when used with 3000 nm light is -25.94 mm. Note that the row denoting the focal lengths at the design wavelength is highlighted in orange.
Ø1/2" Plano-Concave Lenses
| 248 nm||-16.67 mm||-23.16 mm|
| 405 nm||-17.67 mm||-24.55 mm|
| 488 nm||-17.85 mm||-24.81 mm|
| 532 nm||-17.92 mm||-24.90 mm|
| 588 nm||-17.98 mm||-24.99 mm|
| 633 nm||-18.02 mm||-25.04 mm|
| 780 nm||-18.11 mm||-25.17 mm|
| 850 nm||-18.14 mm||-25.21 mm|
| 1064 nm||-18.20 mm||-25.30 mm|
| 1310 nm||-18.26 mm||-25.38 mm|
| 1550 nm||-18.31 mm||-25.44 mm|
| 3000 nm||-18.67 mm||-25.94 mm|
| 4000 nm||-19.04 mm||-26.46 mm|
| 5000 nm||-19.55 mm||-27.17 mm|
| 8000 nm||-22.30 mm||-30.99 mm|
Ø1" Plano-Concave Lenses
| 248 nm||-37.07 mm||-69.53 mm||-92.69 mm||-185.39 mm||-463.51 mm|
| 405 nm||-39.30 mm||-73.71 mm||-98.26 mm||-196.54 mm||-491.39 mm|
| 488 nm||-39.71 mm||-74.47 mm||-99.28 mm||-198.58 mm||-496.49 mm|
| 532 nm||-39.85 mm||-74.74 mm||-99.64 mm||-199.30 mm||-498.29 mm|
| 588 nm||-39.99 mm||-75.00 mm||-99.99 mm||-200.00 mm||-500.04 mm|
| 633 nm||-40.08 mm||-75.17 mm||-100.21 mm||-200.45 mm||-501.15 mm|
| 780 nm||-40.28 mm||-75.54 mm||-100.71 mm||-201.44 mm||-503.64 mm|
| 850 nm||-40.34 mm||-75.67 mm||-100.87 mm||-201.77 mm||-504.46 mm|
| 1064 nm||-40.49 mm||-75.94 mm||-101.24 mm||-202.51 mm||-506.30 mm|
| 1310 nm||-40.62 mm||-76.18 mm||-101.55 mm||-203.13 mm||-507.86 mm|
| 1550 nm||-40.73 mm||-76.38 mm||-101.83 mm||-203.67 mm||-509.22 mm|
| 3000 nm||-41.52 mm||-77.87 mm||-103.82 mm||-207.66 mm||-519.18 mm|
| 4000 nm||-42.35 mm||-79.44 mm||-105.90 mm||-211.82 mm||-529.59 mm|
| 5000 nm||-43.49 mm||-81.56 mm||-108.73 mm||-217.49 mm||-543.77 mm|
| 8000 nm||-49.59 mm||-93.01 mm||-124.00 mm||-248.03 mm||-620.11 mm|