ABSTRACT
Chapter 22, Crystal Polarizers, presents new analyses on common, but misunderstood, optical components – the crystal polarizers, including Glan-Taylor and Glan-Thompson polarizers. The common issues when incorporating Glan-type of polarizers into imaging systems are small field of view (FOV), restricted étendue and vignetting.
Crystal polarizers are commonly used in specialized applications, such as ellipsometry which require high performance. High power laser systems are another application for Glan-Taylor polarizers, because their ability to handle much higher powers than sheet and wire grid polarizers is compelling. Crystal polarizers fabricated from anisotropic materials utilize double refraction, totally internal reflecting (TIR) one eigenmode while transmitting most of the orthogonal mode to achieve a highly polarized beam, resulting the highest performing polarizers with exceptional extinction ratio and diattenuation. Crystal polarizers provide high performance in optical systems at a high penalty: limited aperture and significant length due to TIR, and thus smaller FOV.
Our analysis focuses on several critical performance issues, the small FOV of crystal polarizers, transmission loss and large apodization, and the transmission patterns for undesired modes. The refractive index of the intended extraordinary mode varies with angle, introduces astigmatism, apodization, and polarization aberrations which are daunting for these excellent polarizers. Additionally, at the edge of the small FOV the reflected ordinary rays begin to leak through, rapidly decreasing the degree of polarization of the transmitted light and varying the polarization state in a complex manner across the pupil. The complex behavior of crystal polarizers should be considered when designing or using these polarizers.
