Tunable optical filter having a large dynamic range

Abstract

A novel (to our knowledge) concept for a tunable birefringent filter with a high dynamic range is proposed and demonstrated by using a stack of liquid-crystal retarders having different thicknesses following an arithmetic sequence. Each retarder is between crossed polarizers with its optic axis oriented azimuthally at 45 degrees to the polarizer axis. The tunable filter was fabricated by using nematic liquid crystals demonstrating tunability over a range of 800 nm, covering the visible and the near IR; hence it has a potential for use in biomedical optical imaging applications.