• Vacuum-Grade Calcium Fluoride Substrate
• Diameter: 1" (25.40 mm)
• Broadband AR Coating for the 3 - 5 µm Range
• Focal Length: 50mm

Thorlabs' Ø1" Calcium Fluoride (CaF₂) Positive Meniscus Lens, which offers high transmission from 0.18 - 8.0 µm, is available with a broadband AR coating optimized for the 3 - 5 µm spectral range deposited on both surfaces. This coating greatly reduces the surface reflectivity of the substrate, yielding an average transmission in excess of 96.8% over the entire AR coating range.

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.

Positive meniscus (convex-concave) lenses, which are thicker in the middle than at the edges and cause light rays to converge, are designed to minimize third-order spherical aberration. When used to focus a collimated beam, the convex side of the lens should face the source to minimize spherical aberration. They are often used in conjunction with other lenses to decrease the focal length, and therefore increase the numerical aperture (NA), of an optical assembly. Since a positive meniscus lens has a greater radius of curvature on the concave side of the lens than on the convex side, real images can be formed.

• Material: Vacuum-Grade Calcium Fluoride
• Wavelength Range: 0.18 - 8.0 µm
• AR Coating Range: 3 - 5 µm
• Reflectance over Coating Range (Avg.): <2.0%
• Diameter Tolerance: +0.00/-0.10
• Thickness Tolerance: ±0.1 mm
• Focal Length Tolerance: ±1%
• Surface Quality: 40-20 Scratch-Dig
• Spherical Surface Power: 3λ/2
• Spherical Surface Irregularity: λ/2
• Centration: ≤3 arcmin
• Clear Aperture: ≥90% of Diameter
• Design Wavelength: 4 µm
• Diameter: 1" (25.40 mm)
• f: 50 mm
• R1: 15.5 mm
• R2: 55.2 mm
• t_c: 7.1mm
• t_e: 2 mm
• f_b: 43.3 mm
• Suggested Mount: LMR1