@article{boehle_doelman_konrad_snik_glauser_por_warriner_shi_escuti_kenworthy_et al._2021, title={Cryogenic characterization of the grating vector apodizing phase plate coronagraph for the enhanced resolution imager and spectrograph at the Very Large Telescope}, volume={7}, ISSN={["2329-4221"]}, DOI={10.1117/1.JATIS.7.4.045001}, abstractNote={Abstract. We present results on the laboratory characterization of the grating vector apodizing phase plate (gvAPP) coronagraph that will be included in the upcoming instrument enhanced resolution imager and spectrograph (ERIS) at the VLT. ERIS will include a 1 to 5  μm adaptive-optics-fed imager, NIX, that will greatly improve the capability of the VLT to perform high-contrast imaging of exoplanets especially in the 3 to 5  μm wavelength range. The gvAPP, one of the coronagraphs in the NIX suite, is a pupil plane coronagraph that uses a thin film of patterned liquid crystals to create two images of a star with a D-shaped dark hole on either side. The gvAPP is manufactured using an innovative direct-write system that produces precise patterns of liquid crystals. We utilized the upgraded infrared cryogenic test bench run by the Exoplanets and Habitability Group at ETH Zurich to measure the morphology of the gvAPP PSF and to test the accuracy of the liquid crystal manufacturing technique in the lab for the first time at contrast levels of ∼10  −  5. We find that the gvAPP can reach raw contrasts below ∼10  −  5 between ∼10 and 13  λ  /  D. This contrast upper limit translates to a writing accuracy of the orientation of the liquid crystal’s fast axis of better than 0.3 deg for the spatial frequencies corresponding to those separations. This is a sufficient accuracy such that the gvAPP will not be the limiting factor in achieving the required contrasts to image exoplanets.}, number={4}, journal={JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS}, author={Boehle, Anna and Doelman, David and Konrad, Bjorn S. and Snik, Frans and Glauser, Adrian M. and Por, Emiel H. and Warriner, Nathaniel Z. and Shi, Shuojia and Escuti, Michael J. and Kenworthy, Matthew A. and et al.}, year={2021}, month={Oct} }
 @article{warriner_escuti_2019, title={Fabrication of Liquid Crystal Binary Polarization Gratings (bin-PGs)}, volume={11092}, ISSN={["1996-756X"]}, DOI={10.1117/12.2530131}, abstractNote={Planar, anisotropic liquid crystal (LC) optics, along with metasurfaces, have shown to be the predominant meth- ods of producing a geometric (or Pancharatnam-Berry) phase hologram (GPH). One of the simplest GPHs, the traditional continuous polarization grating (PG), implements a continuous linear phase ramp. This PG has received significant attention due to its polarization-selective nature and 100% diffraction efficiency. However, when this linear phase is sampled with a 0-π alternating phase profile, theoretical reasoning predicts polarization- independent qualities. In order to distinguish this grating from continuous PGs, we call this a binary polarization grating (bin-PG). Traditional PGs, with a continuously varying nematic director profile, are simple to manufacture with many holographic methods. However, no bin-PG fabricated with patterned LCs have yet been reported. In this work, we experimentally study bin-PGs formed using a photo-aligned LC polymer network. Particular attention is brought to the problematic rotational ambiguity of LC at the phase step. To prevent disclination lines, a rotation biasing pixel of varying size is implemented at the phase transition boundary. We measure the diffraction efficiencies, the input polarization response, and the impact of the non-zero transition region. At the smallest transition pixel size (0.625μm) an average +1-order efficiency of 36% was measured with an input-polarization sensitivity of only ±1.7%.}, journal={LIQUID CRYSTALS XXIII}, author={Warriner, N. Zane and Escuti, Michael J.}, year={2019} }
 @article{warriner_escuti_2019, title={Paraxial Analysis of Binary Polarization Gratings (bin-PGs)}, volume={11105}, ISSN={["1996-756X"]}, DOI={10.1117/12.2530111}, abstractNote={Traditional polarization gratings (PGs) have been studied with increasing intensity since 2005, in part because they can manifest 100% single-order diffraction efficiency and strong sensitivity to input polarization, in both theory and practice. They can be made using patterned anisotropic materials (e.g., liquid crystals) or nanostructures (e.g., metasurfaces). Nearly every prior work on traditional PGs has implemented a linear spatial phase-shift that is either continuous or which samples the 2π phase period with multiple (≥ 4) discrete phase levels. As far as we know, only two prior works (Bhandari et al, Phys. Rep. 281 (1997); and Wang et al, Appl. Phys. Lett. 108 (2016)) have considered the circumstance when the phase is sampled with exactly two phase levels, with π radians between them. We call this a Binary PG (Bin-PG). In this work, we apply Jones calculus and the small angle (i.e., paraxial) approximation to derive the fundamental optical behavior of Bin-PGs: far-field efficiencies, input polarization sensitivity, and output polarizations. We show that Bin-PGs manifest properties that are a compelling and unique mixture of both traditional (non-binary) PGs and standard diffraction gratings (e.g., surface-relief-gratings (SRGs)). Like non-binary PGs, their output polarization is often different than the input and diffraction efficiencies are dependent on the effective retardation of the film or surface. However, like SRGs, they show a maximum of 80% total first-order efficiency and are insensitive to input polarization.}, journal={NOVEL OPTICAL SYSTEMS, METHODS, AND APPLICATIONS XXII}, author={Warriner, N. Zane and Escuti, Michael J.}, year={2019} }
 @inproceedings{doelman_snik_warriner_escuti, title={Patterned liquid-crystal optics for broadband coronagraphy and wavefront sensing}, volume={10400}, booktitle={Techniques and instrumentation for detection of exoplanets viii}, author={Doelman, D. S. and Snik, F. and Warriner, N. Z. and Escuti, M. J.} }