Abstract

A comparative theoretical and experimental study of the diffraction characteristics of aluminum strip gratings in the infrared region is presented. The gratings were made on ZnSe and ZnS substrates by means of standard photolithographic techniques and reactive-ion etching. We used a grating period of 3 m and a fill factor of approximately 0.33. The grating thicknesses varied from 2400 Å to 9500 A. Transmittance measurements were carried out in the 713 m wavelength band, in which only the forward and backward zeroth-order waves propagate. The gratings exhibit a long-wavelength bandstop, i.e., a high-pass filtering characteristic in transmission in which the transmission decreases with increasing grating thickness.

© 1990 Optical Society of America