Manufacturers of optical coatings and components

Cold mirrors and hot mirrors are multilayer dielectric coated optics that selectively redirect energy that causes heat in an optical system.  Their advantage over heat absorbing glass is that they are much less susceptible to thermal shock and can be used to direct the offending radiation to a location in the system where dissipation is more convenient.  In addition, multilayer dielectric filters can be made in larger sizes than heat absorbing glass.