Silicon (Si)
Plano-Convex Lenses

Plano-convex (PCX) lenses have a positive focal length and can be used to focus a collimated beam to the back focal point, to collimate light from a point source, or reduce the divergent angle of a diverging source. To minimize the introduction of spherical aberration, a collimated light source should be incident on the curved surface of the lens when using a PCX to focus a collimated light source; Similarly, the diverging light rays should be incident on the planar surface of the PCX lens when collimating a point source of light. These lenses are used in infinite and finite conjugate applications.

When deciding between a plano-convex lens and a bi-convex lens, both of which cause collimated incident light to converge, it is usually more suitable to choose a plano-convex lens if the desired absolute magnification is either less than 0.2 or greater than 5. Between these two values, bi-convex lenses are generally preferred.

Silicon offers high thermal conductivity and low density. However it has a strong absorption band at 9 microns, it is not suitable for use with CO2 laser transmission applications. Paralight Optics offers Silicon (Si) Plano-Convex Lenses are available with a broadband AR coating optimized for the 3 µm to 5 μm spectral range deposited on both surfaces. This coating greatly reduces the surface reflectance of the substrate, yielding high transmission and minimal absorption over the entire AR coating range. Check the Graphs for your references.