Abstract

A phase retardation plate so placed as to occupy partially the aperture of a spectroscope produces dark bands in the spectrum of white light. These have been called in the literature¹ as Talbot bands and are characterized uniquely by the phase plate parameters and the wavelengths of light. We propose to present the concept of a novel tunable bandpass filter based on this phenomenon. We have obtained the tunable Talbot bands by replacing the phase plate with an electrically controlled nematic liquid crystal film. As the velocity or the refractive index of the extraordinary beam depends on the angle between the direction of the wave normal and the optic axis, there results the desirable variable phase retardation.

© 1986 Optical Society of America