LF1988-C 25.4 mm Dia. N-BK7 Negative Meniscus Lens; EFL=-500mm 1050-1700nm

The LF1988-C is a high-quality spherical lens from Thorlabs, featuring a negative meniscus shape and a diameter of 25.4 mm. This lens is designed for use in the 1050-1700nm wavelength range, making it suitable for a variety of applications in the near-infrared spectrum.

The lens is made from N-BK7, a popular optical glass known for its excellent optical properties and wide transmission range. This material is particularly suitable for use in the near-infrared region, where it offers high transmittance and low dispersion.

The lens has a focal length of -500mm, as indicated by its effective focal length (EFL). This negative focal length indicates that the lens is a diverging lens, which spreads out light rays that pass through it. The lens has a center thickness of 3mm and an edge thickness of 3.3mm, providing a robust and durable construction.

The lens is coated with Thorlabs' proprietary AR coating, which is designed to reduce surface reflections and improve transmission. This coating, denoted as 'tho c bbar', is applied to both the front and back surfaces of the lens.

The lens's geometry is defined by its inner and outer radii, which are both 0 in this case. The radii of curvature for the front and back surfaces are 250mm and 126.3mm, respectively. These parameters, along with the lens's refractive index and Abbe number, determine its optical performance.