EOC supplies a wide range of optical filters for the infrared spectrum. These filters are normally combinations of thin film deposition interference filters. Out of band blocking can be achieved by the proper choice of substrate, reflectance filter stacks or by adding absorption glass.
The thin film filters comprise of stacks of thin layers (of different optical materials) in controlled thicknesses. Light is reflected at each film interface and by the correct choice of parameters can be made to interfere with that from other interfaces, constructively, for certain wavelengths giving high reflectance and destructively, for others giving high transmittance. Long wave pass, short wave pass and band pass filters can be designed and manufactured in this way.