• Material: BK7 or SF11
• Wavelegnth Range: BK7: 350 nm - 2.0 μm, SF11: 420 nm - 2.3 μm

Thorlabs BK7 and SF11 Plano-Concave lenses are popular for many applications. Plano-Concave lenses diverge a collimated beam to a virtual focus as used in a Galilean type beam expander (see Drawing tab for reference). Plano-Concave lenses have a negative focal length and negative spherical aberration. Negative spherical aberration can be used to balance out aberrations of other lenses in the system.

BK7 has an Abbe Number of 64.17, while SF11 has an Abbe Number of 25.76. A lower Abbe Number means the lens is made from material with a higher dispersion. SF11 lenses have a higher dispersion than BK7 lenses.

An Antireflection Coating reduces the amount of light reflected from each surface of the lens. Thorlabs BK7 and SF11 Lenses are available with our standard -A, -B, -C Broadband Antireflection Coating (please see Graphs tab for coating details).

Lens kits are available. Please click here for information.