Polarization modeling and predictions for DKIST part 3: focal ratio and thermal dependencies of spectral polarization fringes and optic retardance

Harrington, David M.; Sueoka, Stacey R.

doi:10.1117/1.jatis.4.1.018006

Cited by 15 publications

(65 citation statements)

References 78 publications

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“…In H18, 13 we applied the Berreman calculus 14,15 to polarization fringes formed in multi-layer crystals with predictions and data collected in the lab and at a solar telescope. We then extended this calculus in HS18 16 to converging and diverging beams. Fringes were measured at various focal ratios and compared to simulations in converging beams at solar and night time telescopes as well as in the laboratory.…”

Section: Dkist Optics and Polarization Models For Calibrationmentioning

confidence: 99%

“…We also showed thermal models for the DKIST retarders along with thermal perturbation models for the polarization fringes. 16 We recently have investigated spatial variation of retardance across multi-layer retarders made of polished crystals, stretched polycarbonate and ferro-electric liquid crystals in HS18b. 17 This variation was then included in the DKIST optical model to show polarization calibration errors as functions of field angle and wavelength.…”

Section: Dkist Optics and Polarization Models For Calibrationmentioning

confidence: 99%

“…The Cryo-NIRSP feed optics and modulator properties are described in our prior references. 16,17,57,65 For the rest of the polarimetric instruments, the beam must propagate through the AO system as shown in Equation 4. The DL-NIRSP, ViSP and VTF all see M7, M8 and M9 as well as the tenth mirror as the adaptive optics system deformable mirror (DM = M10).…”

Section: Mirror Grouping Models Polarization and System Mueller Matricesmentioning

confidence: 99%

“…The optics are at 15 • incidence angle which does create polarization through the complex dichroic coatings on the front surfaces and also the broad-band anti-reflection coatings on the back surfaces. We modeled polarization fringes in two recent papers 13,68 and do not expect to observe significant fringing given the 0.5 • wedge angle in each of the FIDO beam splitters. There are presently five dichroics planned for fabrication as shown in Table 6.…”

Section: Dichroic Coatings: Polarization Performance and Fido Designsmentioning

confidence: 99%

“…Knowing the range of expected polarization properties also helps validate any DKIST-derived calibrations when using our custom retarders we have mapped spatially and assessed for thermal instabilities. 13,16,17 In September of 2018, we had acquired witness samples for every telescope mirror in the DKIST path that has been coated to date. This includes the optics M2 through M10.…”

Section: A Dkist System Model For Polarization and Throughputmentioning

confidence: 99%

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Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 5: impacts of enhanced mirror and dichroic coatings on system polarization calibration

Harrington

Sueoka

White

2019

J. Astron. Telesc. Instrum. Syst.

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The Daniel K. Inouye Solar Telescope (DKIST) is designed to deliver accurate spectro-polarimetric calibrations across a wide wavelength range and large field of view for solar disk, limb and coronal observations. DKIST instruments deliver spectral resolving powers up to 300,000 in multiple cameras of multiple instruments sampling nanometer scale bandpasses. We require detailed knowledge of optical coatings on all optics to ensure we can predict and calibrate the polarization behavior of the system. Optical coatings can be metals protected by many dielectric layers or several-micron thick dichroics. Strong spectral gradients up to 60 • retardance per nanometer wavelength and several percent diattenuation per nanometer wavelength are observed in such coatings. Often, optical coatings are not specified with spectral gradient targets for polarimetry in combination to both average and spectral threshold type specifications. DKIST has a suite of interchangeable dichroic beam splitters using up to 96 layers. We apply the Berreman formalism in open-source Python scripts to derive coating polarization behavior. We present high spectral resolution examples on dichroics where transmission can drop 10% with associated polarization changes over a 1 nm spectral bandpass in both mirrors and dichroics. We worked with a vendor to design dichroic coatings with relatively benign polarization properties that pass spectral gradient requirements and polarization requirements in addition to reflectivity. We now have the ability to fit multi-layer coating designs which allow us to predict system level polarization properties of mirrors, anti-reflection coatings and dichroics at arbitrary incidence angles, high spectral resolving power and on curved surfaces through optical modeling software packages. Performance predictions for polarization at large astronomical telescopes requires significant metrology efforts on individual optical components combined with systems-level modeling efforts. We show our custom-built laboratory spectropolarimeter and metrology efforts on protected metal mirrors, antireflection coatings and dichroic mirror samples.

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Section: Dkist Optics and Polarization Models For Calibrationmentioning

confidence: 99%

Section: Dkist Optics and Polarization Models For Calibrationmentioning

confidence: 99%

Section: Mirror Grouping Models Polarization and System Mueller Matricesmentioning

confidence: 99%

Section: Dichroic Coatings: Polarization Performance and Fido Designsmentioning

confidence: 99%

Section: A Dkist System Model For Polarization and Throughputmentioning

confidence: 99%

See 3 more Smart Citations

Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 5: impacts of enhanced mirror and dichroic coatings on system polarization calibration

Harrington

Sueoka

White

2019

J. Astron. Telesc. Instrum. Syst.

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The Daniel K. Inouye Solar Telescope – Observatory Overview

et al. 2020

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We present an overview of the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), its instruments, and support facilities. The 4 m aperture DKIST provides the highest-resolution observations of the Sun ever achieved. The large aperture of DKIST combined with state-of-the-art instrumentation provide the sensitivity to measure the vector magnetic field in the chromosphere and in the faint corona, i.e. for the first time with DKIST we will be able to measure and study the most important free-energy source in the outer solar atmosphere – the coronal magnetic field. Over its operational lifetime DKIST will advance our knowledge of fundamental astronomical processes, including highly dynamic solar eruptions that are at the source of space-weather events that impact our technological society. Design and construction of DKIST took over two decades. DKIST implements a fast (f/2), off-axis Gregorian optical design. The maximum available field-of-view is 5 arcmin. A complex thermal-control system was implemented in order to remove at prime focus the majority of the 13 kW collected by the primary mirror and to keep optical surfaces and structures at ambient temperature, thus avoiding self-induced local seeing. A high-order adaptive-optics system with 1600 actuators corrects atmospheric seeing enabling diffraction limited imaging and spectroscopy. Five instruments, four of which are polarimeters, provide powerful diagnostic capability over a broad wavelength range covering the visible, near-infrared, and mid-infrared spectrum. New polarization-calibration strategies were developed to achieve the stringent polarization accuracy requirement of 5×10−4. Instruments can be combined and operated simultaneously in order to obtain a maximum of observational information. Observing time on DKIST is allocated through an open, merit-based proposal process. DKIST will be operated primarily in “service mode” and is expected to on average produce 3 PB of raw data per year. A newly developed data center located at the NSO Headquarters in Boulder will initially serve fully calibrated data to the international users community. Higher-level data products, such as physical parameters obtained from inversions of spectro-polarimetric data will be added as resources allow.

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The Diffraction-Limited Near-Infrared Spectropolarimeter (DL-NIRSP) of the Daniel K. Inouye Solar Telescope (DKIST)

et al. 2022

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The Diffraction-Limited Near-Infrared Spectropolarimeter (DL-NIRSP) is one of the first-light instruments for the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST). DL-NIRSP is an integral-field, dual-beam spectropolarimeter intended for studying magnetically sensitive spectral lines in the Sun’s photosphere, chromosphere, and corona with high spectral resolution and polarimetric accuracy. Two novel fiber-optic integral-field units (IFUs), paired with selectable feed optics and a field-scanning mirror provide great flexibility in spatial sampling ($0.03^{\prime\prime}$ 0.03 ″ , $0.08^{\prime\prime}$ 0.08 ″ , and $0.5^{\prime \prime}$ 0.5 ″ ) and field coverage ($2^{\prime} \times 2^{\prime }$ 2 ′ × 2 ′ ). The IFUs allow DL-NIRSP to record all the spectra from a 2D field of view simultaneously, enabling the instrument to study the evolution of highly dynamic events. The spectrograph is an all-reflecting, near-Littrow design, which achieves a resolving power of approximately 125,000. Multiple wavelengths can be observed simultaneously using three spectral arms: one for visible wavelengths (500 – 900 nm) and two for infrared wavelengths (900 – 1350 nm and 1350 – 1800 nm). Each supporting camera sub-system is capable of a 30-Hz frame rate, making it possible to track dynamic phenomena on the Sun.

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Polarization modeling and predictions for DKIST part 3: focal ratio and thermal dependencies of spectral polarization fringes and optic retardance

Abstract: , "Polarization modeling and predictions for DKIST part 3: focal ratio and thermal dependencies of spectral polarization fringes and optic retardance," J. Astron.

Cited by 15 publications

References 78 publications

Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 5: impacts of enhanced mirror and dichroic coatings on system polarization calibration

Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 5: impacts of enhanced mirror and dichroic coatings on system polarization calibration

The Daniel K. Inouye Solar Telescope – Observatory Overview

The Diffraction-Limited Near-Infrared Spectropolarimeter (DL-NIRSP) of the Daniel K. Inouye Solar Telescope (DKIST)

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