A new method for the determination of complex refractive index spectra of transparent solids in the far-infrared spectral region: Results of pure silicon and crystal quartz

The complex refractive index spectrum of a solid material in the far infrared region ( approximately 5-500 cm -1 ) is determined from a single dispersive interferometric measurement of a plane parallel specimen. This method uses essentially the measured (frequency-dependent) transmission of electromagnetic radiation through the specimen and is based on the interferometric formalism developed by the authors. The method is especially suited for transparent solids, which are used as window materials in far-infrared spectroscopic experiments. Results on hyperpure silicon and on crystal quartz are presented as an illustration of this new method.