From Event: SPIE Optical Engineering + Applications, 2017
Certain wavelengths bands, especially Y, J, H, and K, have become the main measurement pathway for many of the world’s largest telescopes. Additionally, the study of stellar light within of near-infrared (NIR) bands has become the staple in the field of direct imaging. Because of this, there is a growing necessity for customized broadband optics in the near infrared to meet the needs of the astronomers and allow for more precise measurements. We report on complex birefringent films developed for NIR operation, useful to implement wave-plates, vector apodizing phase plates, and polarization gratings. The combination of multi-twist retarders (MTRs) with both direct-write laser scanning or holographic lithography, and allows us to fabricate arbitrary phase patterns via a geometric phase effect and achromatic, super-achromatic, and highly chromatic (dual-band) spectra from 0.5 to 5 microns. MTRs are complex birefringent films with an optic axis variation along 1D/2D/3D. They consist of two or more chiral liquid crystal (LC) layers on a single substrate and with a single photo-alignment layer. Importantly, subsequent LC layers are aligned directly by prior layers, allowing simple fabrication, achieving automatic layer registration, and resulting in a monolithic film with a continuously varying optic axis. MTRs can be used for a wide range of remote optical sensing, both earth- and space-based. Here, we will review our current and prior MTR films being used for NIR astronomical observation, and discuss the realistic opportunities and limitations ahead for improved precision and design-complexity for retardation and wavefront(phase).
Nathaniel Z. Warriner, Michael J Escuti, Shuojia Shi, and Kathryn J. Hornburg, "Achromatic and chromatic liquid crystal polymer films at near-infrared wavelengths (Conference Presentation)," Proc. SPIE 10407, Polarization Science and Remote Sensing VIII, 104070I (Presented at SPIE Optical Engineering + Applications: August 08, 2017; Published: 19 September 2017); https://doi.org/10.1117/12.2276001.5581337592001.
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