Achromatic polarization gratings as highly efficient thin-film polarizing beamsplitters for broadband light

Chulwoo Oh; Michael J. Escuti

doi:10.1117/12.735370

13 September 2007 Achromatic polarization gratings as highly efficient thin-film polarizing beamsplitters for broadband light

Chulwoo Oh, Michael J. Escuti

Author Affiliations +

Proceedings Volume 6682, Polarization Science and Remote Sensing III; 668211 (2007) https://doi.org/10.1117/12.735370
Event: Optical Engineering + Applications, 2007, San Diego, California, United States

Abstract

We introduce and experimentally demonstrate an achromatic polarization grating (PG), which manifests high diffraction efficiency (> 99.5%) over a broad range of spectrum. Unlike conventional phase gratings, this family of PGs has unique diffraction properties including three non-zero diffraction orders (m = 0,±1) with up to 100% efficiency and strongly polarization sensitive first-order diffraction. It has long been recognized that these diffractive optical elements are useful for beamsplitting, polarimetry, displays, and more. A conventional (Circular-type) PG implemented with a spiraling, in-plane, linear birefringence has a modest spectral range (Δλ/λ₀ congruent to 6.8%) over which it possesses > 99.5% efficiency. We have identified a two-layer twisted PG structure that achieves achromatic diffraction that achieves a five-fold improvement of the high efficiency bandwidth (Δλ/λ₀ congruent to 34.3%). We have successfully implemented this structure with reactive mesogens (polymerizable liquid crystals) with a small amount of left- and right-hand chiral agents, and here report on its operation over nearly the entire range of visible light. We also investigated the behavior of the achromatic PG with the finite-difference time-domain method using an Open Source software package WOLFSIM, developed at NC State University, in order to evaluate the angular selectivity and the paraxial limit.

Citation Download Citation

Chulwoo Oh and Michael J. Escuti "Achromatic polarization gratings as highly efficient thin-film polarizing beamsplitters for broadband light", Proc. SPIE 6682, Polarization Science and Remote Sensing III, 668211 (13 September 2007); https://doi.org/10.1117/12.735370

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