@misc{doelman_snik_por_bos_otten_kenworthy_haffert_wilby_bohn_sutlieff_et al._2021, title={Vector-apodizing phase plate coronagraph: design, current performance, and future development [Invited]}, volume={60}, ISSN={["2155-3165"]}, DOI={10.1364/AO.422155}, abstractNote={Over the last decade, the vector-apodizing phase plate (vAPP) coronagraph has been developed from concept to on-sky application in many high-contrast imaging systems on 8 m class telescopes. The vAPP is a geometric-phase patterned coronagraph that is inherently broadband, and its manufacturing is enabled only by direct-write technology for liquid-crystal patterns. The vAPP generates two coronagraphic point spread functions (PSFs) that cancel starlight on opposite sides of the PSF and have opposite circular polarization states. The efficiency, that is, the amount of light in these PSFs, depends on the retardance offset from a half-wave of the liquid-crystal retarder. Using different liquid-crystal recipes to tune the retardance, different vAPPs operate with high efficiencies (
      
	
	  >
	
	96
	%
      
    ) in the visible and thermal infrared (0.55 µm to 5 µm). Since 2015, seven vAPPs have been installed in a total of six different instruments, including Magellan/MagAO, Magellan/MagAO-X, Subaru/SCExAO, and LBT/LMIRcam. Using two integral field spectrographs installed on the latter two instruments, these vAPPs can provide low-resolution spectra (
      
	
	  
	    R
	  
	
	∼
	30
      
    ) between 1 µm and 5 µm. We review the design process, development, commissioning, on-sky performance, and first scientific results of all commissioned vAPPs. We report on the lessons learned and conclude with perspectives for future developments and applications.}, number={19}, journal={APPLIED OPTICS}, author={Doelman, D. S. and Snik, F. and Por, E. H. and Bos, S. P. and Otten, G. P. P. L. and Kenworthy, M. and Haffert, S. Y. and Wilby, M. and Bohn, A. J. and Sutlieff, B. J. and et al.}, year={2021}, month={Jul}, pages={D52–D72} }
 @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{snik_rodenhuis_escuti_brickson_hornburg_kim_kievid_groenhuijsen_roosegaarde_2019, title={Producing true-color rainbows with patterned multi-layer liquid-crystal polarization gratings}, volume={9}, ISSN={["2159-3930"]}, DOI={10.1364/OME.9.001583}, abstractNote={We present the technical design of the art installation Rainbow Station, that projects a 40-m diameter true-color rainbow. The core technology is comprised of a patterned polarization grating that produces the rainbow with the correct shape and correct color order. We achieve an effective grating period as small as 1.55 µm, and obtain high diffraction efficiency over the entire visible spectral range thanks to a multi-layer liquid-crystal implementation. The -1 spectral order is suppressed by circular polarization filtering.}, number={4}, journal={OPTICAL MATERIALS EXPRESS}, author={Snik, Frans and Rodenhuis, Michiel and Escuti, Michael J. and Brickson, Leandra and Hornburg, Kathryn and Kim, Jihwan and Kievid, Chris and Groenhuijsen, Sebastiaan and Roosegaarde, Daan}, year={2019}, month={Apr}, pages={1583–1589} }
 @article{hornburg_xiang_kim_kudenov_escuti_2018, title={Design and fabrication of an aspheric geometric-phase lens doublet}, volume={10735}, ISSN={["1996-756X"]}, DOI={10.1117/12.2322327}, abstractNote={A prior simulation-only study of aspherical phase profiles [Hornburg et al, Proc SPIE 10743, 10743-4 (2018)] in geometric-phase lenses (GPLs) indicated that aspherical doublet lens systems should provide substantially improved off-axis performance than those using spherical phase profiles. In this work, we fabricate a liquid crystal GPL doublet (24.5 mm diameter, 40 mm back focal length at 633 nm) and compare it to with a reference spherical GPL singlet. We characterized the liquid crystal alignment quality, efficiencies, and spot performance. With these compact GP lens systems, we realize improved performance for wider fields of view, while maintaining low loss.}, journal={LIQUID CRYSTALS XXII}, author={Hornburg, Kathryn J. and Xiang, Xiao and Kim, Jihwan and Kudenov, Michael W. and Escuti, Michael J.}, year={2018} }
 @article{hornburg_xiang_kudenov_escuti_2018, title={Optimization of aspheric geometric-phase lenses for improved field-of-view}, volume={10743}, ISSN={["1996-756X"]}, DOI={10.1117/12.2322326}, abstractNote={In optical thin-films and surfaces, geometric phase is utilized to control the phase beyond that possible through optical path differences. Geometric-phase lenses, which are significantly thinner than refractive lenses for the same numerical aperture (NA), most commonly use a spherical phase profile. This is especially effective for normally incident light, but like other thin lenses, the performance degrades noticeably for off-axis incidence and wider fields-of-view. In this study, we investigate whether or not various aspheric designs provide better off-axis performance. We simulate aspheric singlet and doublet liquid crystal geometric-phase lenses (24.5 mm diameter, 40 mm back focal length at 633 nm), aiming to optimize spot size performance at 0, 3, and 7 degrees field angles, using Zemax OpticStudio 16.5. By using Zernike fringe phase expansions, we find conditions which provide improved off-axis performance. We demonstrate improved performance of a compact lens system utilizing these polarization-dependent optics.}, journal={OPTICAL MODELING AND PERFORMANCE PREDICTIONS X}, author={Hornburg, Kathryn J. and Xiang, Xiao and Kudenov, Michael W. and Escuti, Michael J.}, year={2018} }
 @article{otten_snik_kenworthy_keller_males_morzinski_close_codona_hinz_hornburg_et al._2017, title={ON-SKY PERFORMANCE ANALYSIS OF THE VECTOR APODIZING PHASE PLATE CORONAGRAPH ON MagAO/Clio2}, volume={834}, ISSN={["1538-4357"]}, DOI={10.3847/1538-4357/834/2/175}, abstractNote={We report on the performance of a vector apodizing phase plate coronagraph that operates over a wavelength range of 2–5 μm and is installed in MagAO/Clio2 at the 6.5 m Magellan Clay telescope at Las Campanas Observatory, Chile. The coronagraph manipulates the phase in the pupil to produce three beams yielding two coronagraphic point-spread functions (PSFs) and one faint leakage PSF. The phase pattern is imposed through the inherently achromatic geometric phase, enabled by liquid crystal technology and polarization techniques. The coronagraphic optic is manufactured using a direct-write technique for precise control of the liquid crystal pattern and multitwist retarders for achromatization. By integrating a linear phase ramp to the coronagraphic phase pattern, two separated coronagraphic PSFs are created with a single pupil-plane optic, which makes it robust and easy to install in existing telescopes. The two coronagraphic PSFs contain a 180° dark hole on each side of a star, and these complementary copies of the star are used to correct the seeing halo close to the star. To characterize the coronagraph, we collected a data set of a bright (mL = 0–1) nearby star with ∼1.5 hr of observing time. By rotating and optimally scaling one PSF and subtracting it from the other PSF, we see a contrast improvement by 1.46 magnitudes at 3.5 λ / D . With regular angular differential imaging at 3.9 μm, the MagAO vector apodizing phase plate coronagraph delivers a 5 σ Δ mag contrast of 8.3 ( = 10 − 3.3 ) at 2 λ / D and 12.2 ( = 10 − 4.8 ) at 3.5 λ / D .}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Otten, Gilles P. P. L. and Snik, Frans and Kenworthy, Matthew A. and Keller, Christoph U. and Males, Jared R. and Morzinski, Katie M. and Close, Laird M. and Codona, Johanan L. and Hinz, Philip M. and Hornburg, Kathryn J. and et al.}, year={2017}, month={Jan} }
 @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} }