Abstract: A heterodyning interferometric monitoring apparatus for simultaneously measuring in situ and in real time the optical and physical thicknesses of a sample during a deposition process. A linearly polarized monochromatic light beam is passed through a frequency shifter which produces therefrom a dichromatic light beam having two orthogonally linearly polarized components at respective different frequencies. The dichromatic beam is applied to a modified Twyman-Greene interferometer, from which two heterodyne light beams emerge. The first of the two light beams is a combination of light at the first frequency reflected from the sample and light at the second frequency reflected from a reference plate, from which the physical thickness of the sample can be determined using a heterodyne signal detector.

Abstract: A method for fabricating graded refractive index (rugate, optical filters as well as complex rugate filters having prespecified refractive index verses thickness profiles is disclosed. A plurality of at least two different compatable thin film deposition source components of different refractive index, which are stoichiometrically combinable in variable proportion, such as silicon nitride and silicon oxide, or zinc sulfide and zinc selenide, are used to form a thin film material with a refractive index which varies as a function of the proportions of the components. Each source component is separately laser flash evaporated and codeposited on a substrate to form a coating while monitoring the physical and optical thicknesses of the coating, to allow adjustment of the respective laser flash evaporation rates of the source components.