Heterodyne indicial refractometer

摘要

A method and apparatus for simply and accurately determining the index of refraction of semiconductor materials, etalon bars and materials transparent to infrared radiation. The channel spectra of the material is obtained by passing through it a portion of radiation from a continuously tuned diode laser. Another portion of the diode laser radiation is heterodyned with radiation from a CO2 laser to obtain heterodyne marker beats. The channel spectra and marker beats are displayed in conjunction whereby the frequency difference between the marker beats can be related to the number of fringes in the channel spectra between the marker beats.