Wide-Aperture Liquid Crystal Electro-Optic Modulator of Carbon Monoxide Laser Radiation

Abstract

Liquid crystal electro-optic modulators of mid-IR radiation have been developed, which can control the polarization state of CO laser radiation in the wavelength range of 5.1 to 5.6 μm with light aperture up to 2.5 cm². The use of a ferroelectric liquid crystal as an electrooptic medium located between crossed polarizer and analyzer made it possible to ensure thermally stable electro-optic modulation of CO-laser radiation at a frequency from 1 to 10 kHz and a contrast ratio from 15 : 1 to 25 : 1. The modes of electrically controlled half-wave and quarter-wave plates with switching times of polarization states from 20 to 50 μs are ensured as is the ability to remember the obtained polarization state after switching off control voltage. The minimum polarization state switching time was 1.4 μs, which was observed at a modulation frequency of 40 kHz and rotation of the liquid-crystal optic axis by an angle of a few degrees, which decreased the contrast ratio to 1.3 : 1.