@article{hornburg_komanduri_escuti_2019, title={Highly chromatic retardation via multi-twist liquid crystal films}, volume={36}, ISSN={["1520-8540"]}, DOI={10.1364/JOSAB.36.000D28}, abstractNote={Here we study birefringent films with highly customizable chromatic retardation spectra, using multi-twist liquid crystal (LC) films. These are made of two or more layers of chiral nematic LC polymer network materials, also known as reactive mesogens, which form a monolithic thin-film wherein the in-plane orientation of subsequent layers is automatically determined by the single alignment layer on the substrate. The multiple layer thicknesses and twists present many degrees of freedom to tailor the retardation. While prior work examined achromatic spectra, here we show how to use Mueller matrix analysis to create highly chromatic spectra. We experimentally demonstrate both a uniformly aligned retarder as a green/magenta color filter and a “hot” polarization grating (PG) that diffracts infrared while passing visible light. The three-twist color filter shows a contrast ratio in transmittance between polarizers as high as 10:1 between the half- and zero-wave retardation bands. The “hot” PG shows an average first-order efficiency of about 90% for 1000–2700 nm and an average zero-order efficiency of about 90% for 500–900 nm. The principles here can be extended to nearly any chromatic retardation spectra, including high/low/bandpass, and to nearly any LC orientation pattern, in general known as geometric-phase holograms.}, number={5}, journal={JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS}, author={Hornburg, Kathryn J. and Komanduri, Ravi K. and Escuti, Michael J.}, year={2019}, month={May}, pages={D28–D33} }
 @article{xiang_kim_komanduri_escuti_2017, title={Nanoscale liquid crystal polymer Bragg polarization gratings}, volume={25}, ISSN={["1094-4087"]}, DOI={10.1364/oe.25.019298}, abstractNote={We experimentally demonstrate nearly ideal liquid crystal (LC) polymer Bragg polarization gratings (PGs) operating at a visible wavelength of 450 nm and with a sub-wavelength period of 335 nm. Bragg PGs employ the geometric (Pancharatnam-Berry) phase, and have many properties fundamentally different than their isotropic analog. However, until now Bragg PGs with nanoscale periods (e.g., < 800 nm) have not been realized. Using photo-alignment polymers and high-birefringence LC materials, we employ multiple thin sublayers to overcome the critical thickness threshold, and use chiral dopants to induce a helical twist that effectively generates a slanted grating. These LC polymer Bragg PGs manifest 85-99% first-order efficiency, 19-29° field-of-view, Q ≈ 17, 200 nm spectral bandwidth, 84° deflection angle in air (in one case), and efficient waveguide-coupling (in another case). Compared to surface-relief and volume-holographic gratings, they show high efficiency with larger angular/spectral bandwidths and potentially simpler fabrication. These nanoscale Bragg PGs manifest a 6π rad/μm phase gradient, the largest reported for a geometric-phase hologram while maintaining a first-order efficiency near 100%.}, number={16}, journal={OPTICS EXPRESS}, author={Xiang, Xiao and Kim, Jihwan and Komanduri, Ravi and Escuti, Michael J.}, year={2017}, month={Aug}, pages={19298–19308} }
 @article{hornburg_komanduri_escuti_2014, title={Multiband retardation control using multi-twist retarders}, volume={9099}, ISSN={["0277-786X"]}, DOI={10.1117/12.2051170}, abstractNote={We introduce and demonstrate an approach to create highly chromatic retardation spectra across various wave lengths. The design approach is based on Multi-Twist Retarder (MTR) principle where multiple liquid crystal polymer layers are coated on top of each other on a single substrate. Previous MTRs have been applied to develop broadband achromatic retarders, but here we show that MTRs are quite flexible, and their retardation spectrum can be tuned to create arbitrary profiles. As a representative example, we show this tailorability by creating a retarder which produces approximately zero retardation in visible (500-900 nm) and half-wave retardation in near- infrared (1-2.7 μm) wavelength region. This would provide enhancement in remote sensing, telecom, and spectroscopy systems where it is advantageous to have an optical element which affects only one band, but is largely transparent otherwise.}, journal={POLARIZATION: MEASUREMENT, ANALYSIS, AND REMOTE SENSING XI}, author={Hornburg, Kathryn J. and Komanduri, Ravi K. and Escuti, Michael J.}, year={2014} }
 @article{komanduri_lawler_escuti_2013, title={Multi-twist retarders: broadband retardation control using self-aligning reactive liquid crystal layers}, volume={21}, ISSN={["1094-4087"]}, DOI={10.1364/oe.21.000404}, abstractNote={We report on a family of complex birefringent elements, called Multi-Twist Retarders (MTRs), which offer remarkably effective control of broadband polarization transformation. MTRs consist of two or more twisted liquid crystal (LC) layers on a single substrate and with a single 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. In this work, we employ a numerical design method and focus on achromatic quarter- and half-wave MTRs. In just two or three layers, these have bandwidths and general behavior that matches or exceeds all traditional approaches using multiple homogenous retarders. We validate the concept by fabricating several quarter-wave retarders using a commercial polymerizeable LC, and show excellent achromaticity across bandwidths of 450-650 nm and 400-800 nm. Due to their simple fabrication and many degrees of freedom, MTRs are especially well suited for patterned achromatic retarders, and can easily achieve large bandwidth and/or low-variation of retardation within visible through infrared wavelengths.}, number={1}, journal={OPTICS EXPRESS}, author={Komanduri, Ravi K. and Lawler, Kristopher F. and Escuti, Michael J.}, year={2013}, month={Jan}, pages={404–420} }
 @article{kim_komanduri_escuti_2012, title={A compact holographic recording setup for tuning pitch using polarizing prisms}, volume={8281}, ISSN={["0277-786X"]}, DOI={10.1117/12.913952}, abstractNote={We introduce and demonstrate a new holographic recording technique based on birefringent prisms for creating polarization gratings (PGs). Conventional holographic arrangements for creating PGs consist of several polarization and collimating optics that are carefully aligned with each other, and often require substantial physical space. Both the size and the relative distance between these optics increase for large exposure areas, that limit the range of grating period achievable. Moreover, the cost and complexity associated with the mounting of the several elements also increases, and therefore such approaches are not viable for large area PGs and large volume manufacturing. To overcome the above limitations, we propose new approach using multiple polarizing prisms to record PGs that is compact, scalable for large areas, and enables easy tuning of the grating period by simple rotation of at most two elements.}, journal={PRACTICAL HOLOGRAPHY XXVI: MATERIALS AND APPLICATIONS}, author={Kim, Jihwan and Komanduri, Ravi K. and Escuti, Michael J.}, year={2012} }
 @article{kim_komanduri_lawler_kekas_escuti_2012, title={Efficient and monolithic polarization conversion system based on a polarization grating}, volume={51}, ISSN={["2155-3165"]}, DOI={10.1364/ao.51.004852}, abstractNote={We introduce a new polarization conversion system (PCS) based on a liquid-crystal polarization grating (PG) and louvered wave plate. A simple arrangement of these elements laminated between two microlens arrays results in a compact and monolithic element, with the ability to nearly completely convert unpolarized input into linearly polarized output across most of the visible bandwidth. In our first prototypes, this PG-PCS approach manifests nearly 90% conversion efficiency of unpolarized to polarized for ±11° input light divergence, leading to an energy efficient picoprojector that presents high efficacy (12 lm/W) with good color uniformity.}, number={20}, journal={APPLIED OPTICS}, author={Kim, Jihwan and Komanduri, Ravi K. and Lawler, Kristopher F. and Kekas, D. Jason and Escuti, Michael J.}, year={2012}, month={Jul}, pages={4852–4857} }
 @article{komanduri_kim_lawler_escuti_2012, title={Multi-twist retarders for broadband polarization transformation}, volume={8279}, ISSN={["0277-786X"]}, DOI={10.1117/12.913795}, abstractNote={We introduce a family of broadband retarders, comprised of a low number of twisted nematic liquid crystal layers, that accomplishes well-controlled polarization transformation for nearly any bandwidth desired. For example, we show that broadband linear to circular polarization conversion can be achieved with only two twist layers where the performance matches the popular three-waveplate approach by Pancharatnam. Using liquid crystal polymers on a single substrate, we show how these multi-twist retarders are embodied as a monolithic birefringent plate with excellent performance and potentially very low cost.}, journal={EMERGING LIQUID CRYSTAL TECHNOLOGIES VII}, author={Komanduri, Ravi K. and Kim, Jihwan and Lawler, Kristopher F. and Escuti, Michael J.}, year={2012} }
 @article{miskiewicz_kim_li_komanduri_escuti_2012, title={Progress on large-area polarization grating fabrication}, volume={8395}, ISSN={["0277-786X"]}, DOI={10.1117/12.921572}, abstractNote={Over the last several years, we have pioneered liquid crystal polarization gratings (PGs), in both switchable and polymer versions. We have also introduced their use in many applications, including mechanical/non-mechanical laser beam steering and polarization imaging/sensing. Until now, conventional holographic congurations were used to create PGs where the diameter of the active area was limited to 1-2 inches. In this paper, we discuss a new holography setup to fabricate large area PGs using spherical waves as the diverging coherent beams. Various design parameters of this setup are examined for impact on the quality of the recorded PG profile. Using this setup, we demonstrate a large area polymer PG with approximately 66 inch square area, and present detailed characterization.}, journal={ACQUISITION, TRACKING, POINTING, AND LASER SYSTEMS TECHNOLOGIES XXVI}, author={Miskiewicz, Matthew N. and Kim, Jihwan and Li, Yanming and Komanduri, Ravi K. and Escuti, Michael J.}, year={2012} }
 @article{komanduri_lawler_escuti_2011, title={A High Throughput Liquid Crystal Light Shutter for Unpolarized Light using Polymer Polarization Gratings}, volume={8052}, ISSN={["0277-786X"]}, DOI={10.1117/12.887140}, abstractNote={We report on a broadband, diffractive, light shutter with the ability to modulate unpolarized light. This polarizer-free approach employs a conventional liquid crystal (LC) switch, combined with broadband Polarization Gratings (PGs) formed with polymer LC materials. The thin-film PGs act as diffractive polarizing beam-splitters, while the LC switch operates on both orthogonal polarization states simultaneously. As an initial experimental proof-of- concept for unpolarized light with ±7° aperture, we utilize a commercial twisted-nematic LC switch and our own polymer PGs to achieve a peak transmittance of 80% and peak contrast ratio of 230:1. We characterize the optoelectronic performance, discuss the limitations, and evaluate its use in potential nonmechanical shutter applications (imaging and non-imaging).}, journal={ACQUISITION, TRACKING, POINTING, AND LASER SYSTEMS TECHNOLOGIES XXV}, author={Komanduri, Ravi K. and Lawler, Kris F. and Escuti, Michael J.}, year={2011} }
 @article{komanduri_escuti_2009, title={High efficiency reflective liquid crystal polarization gratings}, volume={95}, ISSN={["0003-6951"]}, DOI={10.1063/1.3197011}, abstractNote={We experimentally demonstrate a reflective-mode liquid crystal polarization grating with high reflectance, small grating period, and subms switching times. This switchable optical element can diffract ∼100% into a single order, have highly polarization-sensitive first orders, and have a polarization-insensitive zero order. Here we introduce an absorbing layer that overcomes the reflection of the (ultraviolet) holographic beams, which otherwise prevents high quality fabrication. At a grating period of 2.1 μm, we report 98% diffraction efficiency, 90% reflectance, ∼600:1 contrast-ratio, and ∼3000:1 polarization contrast. These elements can therefore be configured as polarization-independent modulators or switchable polarizing beam splitters, for use in telecommunications, displays, spatial-light modulators, and polarimetry.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Komanduri, R. K. and Escuti, M. J.}, year={2009}, month={Aug} }
 @article{komanduri_escuti_2007, title={Elastic continuum analysis of the liquid crystal polarization grating}, volume={76}, ISSN={["1550-2376"]}, DOI={10.1103/physreve.76.021701}, abstractNote={We apply elastic continuum theory to model critical parameters influencing the free-energy equilibrium configuration and the dynamic performance of a continuous and in-plane liquid crystal profile acting as a polarization grating. We present analytical expressions for the threshold voltage, critical thickness, and the dynamic switching times under strong anchoring conditions, negligible flow, and arbitrary splay, twist, and bend constants. We also study the influence of weak anchoring, and derive expressions describing a dramatic reduction of the critical thickness and voltage threshold, even for modest grating periods and surface anchoring strengths. Good correlation exists with previously reported experimental data, except in the dynamic response; we therefore show that flow effects (backflow and kickback) likely play an essential role in the fall times, presumably due to the prominent splay-bend deformation of the zero-field configuration. We consider the impact of surface pretilt, and validate our entire analysis with numerical simulations. The approximation technique we employ is likely broadly useful for many problems which include nano- or micropatterned surfaces.}, number={2}, journal={PHYSICAL REVIEW E}, author={Komanduri, Ravi K. and Escuti, Michael J.}, year={2007}, month={Aug} }
 @article{komanduri_jones_oh_escuti, title={Polarization-independent modulation for projection displays using small-period LC polarization gratings}, volume={15}, number={8}, journal={Journal of the Society for Information Display}, author={Komanduri, R. K. and Jones, W. M. and Oh, C. and Escuti, M. J.}, pages={589–594} }