Wavelength-tunable spectral filters based on the optical rotatory dispersion effect

An optical arrangement for constructing wavelength-tunable spectral filters is presented that makes use of a set of dispersive polarization rotations to select wavelengths. A filter in the arrangement is initially mechanically tunable, requires no achromatic retarder, and can be further electrically tunable, switchable, or both, depending on the elements selected. Test measurements and results are presented and described. Modified arrangements with additional retarder(s) or liquid-crystal polarization rotator(s) are suggested and discussed.