Abstract

A liquid crystal Fabry-Perot etalon (LCFPI), in which tuning is achieved via the electrooptic effect, is described. The design is applicable to measurements of the solar emission corona, which requires precise subtraction of the scattered light component from the faint emission signal of the coronal lines. For this, spectral chopping is used, in which the signal from one polarization Fabry-Perot channel positioned in the continuum of the spectrum is subtracted electronically from the tunable orthogonally polarized channel via a polarization modulator. The particular use that we require from the filter established the class of LC material to be used and requires special care in the preparation of the substrates. Applications in the IR are possible preserving the full tunability of the filter with low voltages and low powers. The basic design properties of the LCFPI are discussed, and analysis is performed of its thermal sensitivity, transmittance, and stability.

© 1988 Optical Society of America