Improved midinfrared polarizers using yttrium vanadate

Pure yttrium vanadate crystals (YVO₄) have optical properties ideal for polarizers in the mid-IR spectrum. YVO₄ is highly transmissive from 400 to 3800 nm and is optically useful to 5 micrometers . YVO₄ is a positive uniaxial crystal with a birefringence larger than the negative uniaxial crystal calcite. The positive birefringence of YVO₄ gives ordinary polarization to the beam transmitted by the polarizer, producing a desirable symmetric field-of- view for all standard designs. Glan, Wollaston, and Rochon polarizers were fabricated from YVO₄ and tested. The preferred Glan design for YVO₄ is Glan-Taylor as for calcite. YVO₄ has advantages in large aperture size, excellent optical quality, high laser-damage threshold, and excellent optical working ability with only a slight tendency to cleave. New monolithic crystal polarizer designs will be described. It is also believed that YVO₄ would be an excellent synthetic substitute for calcite in the visible spectrum.