In laser gravitational waves detectors optical loss restricts sensitivity. We discuss polarization scattering as one more possible mechanism of optical losses. Circulated inside interferometer light is polarized and after reflection its plane of polarization can turn a little due to reflecting coating of mirror can have slightly different refraction index along axes $x,\, y$ in plane of mirror surface (optical anisotropy). This anisotropy can be produced during manufacture of coating (elasto-optic effect). This orthogonal polarized light, enhanced in cavity, produces polarization optical loss. Polarization map of mirrors is very important and we propose to measure it. Polarization loss can be important in different precision optical experiments based on usage of polarized light, for example, in quantum speed meter.
The DKIST is designed to deliver accurate spectropolarimetric calibrations across a wide wavelength range and large field of view for solar observations. Instruments deliver spectral resolving powers up to 300,000 in multiple cameras of several instrument. 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 60deg retardance per nanometer wavelength and several percent dia…
The detection of VUV scintillation light, e.g. in (liquid) argon detectors, commonly includes a reflector with a fluorescent coating, converting UV photons to visible light. The light yield of these detectors depends directly on the conversion efficiency. Several coating/reflector combinations were produced using VM2000, a specular reflecting multi layer polymer, and Tetratex, a diffuse reflecting PTFE fabric, as reflector foils. The light yield of these coatings was optimised and has been measured in a dedicated liquid argon setup built at the University of Zurich. It employs a small, 1.3 kg …
Polarization aberrations in next-generation Giant Segmented Mirror Telescopes (GSMTs). II. Influence of segment-to-segment coating variations on high-contrast imaging and polarimetry
We outline polarization fringe predictions derived from a new application of the Berreman calculus for the Daniel K. Inouye Solar Telescope (DKIST) retarder optics. The DKIST retarder baseline design used 6 crystals, single-layer anti-reflection coatings, thick cover windows and oil between all optical interfaces. This new tool estimates polarization fringes and optic Mueller matrices as functions of all optical design choices. The amplitude and period of polarized fringes under design changes, manufacturing errors, tolerances and several physical factors can now be estimated. This tool compar…
We outline polarization performance calculations and predictions for the Daniel K. Inouye Solar Telescope (DKIST) optics and show Mueller matrices for two of the first light instruments. Telescope polarization is due to polarization dependent mirror reflectivity and rotations between groups of mirrors as the telescope moves in altitude and azimuth. The Zemax optical modeling software has polarization ray-trace capabilities and predicts system performance given a coating prescription. We develop a model coating formula that approximates measured witness sample polarization properties. Estimates…
The increasing scale of cryogenic detector arrays for sub-millimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n = 3.4, low loss, and relatively high thermal conductivity is a nearly optimal material for these purposes, but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a cust…
Measuring the faint polarization signal of the cosmic microwave background (CMB) not only requires high optical throughput and instrument sensitivity but also control over systematic effects. Polarimetric cameras or receivers used in this setting often employ dielectric vacuum windows, filters, or lenses to appropriately prepare light for detection by cooled sensor arrays. These elements in the optical chain are typically designed to minimize reflective losses and hence improve sensitivity while minimizing potential imaging artifacts such as glint and ghosting. The Primordial Inflation Polariz…
The daytime sky has been recently demonstrated as a useful calibration tool for deriving polarization cross-talk properties of large astronomical telescopes. The Daniel K Inouye Solar Telescope (DKIST) and other large telescopes under construction can benefit from precise polarimetric calibration of large mirrors. Several atmospheric phenomena and instrumental errors potentially limit the techniques accuracy. At the 3.67m AEOS telescope on Haleakala, we have performed a large observing campaign with the HiVIS spectropolarimeter to identify limitations and develop algorithms for extracting cons…
We study the impact of the loss of axial symmetry around the optical axis on the polarimetric properties of a telescope with segmented primary mirror when each segment is present in a different aging stage. The different oxidation stage of each segment as they are substituted in time leads to non-negligible crosstalk terms. This effect is wavelength dependent and it is mainly determined by the properties of the reflecting material. For an aluminum coating, the worst polarimetric behavior due to oxidation is found for the blue part of the visible. Contrarily, dust -- as modeled in this work -- …
Silver is a metal which provides the highest reflectivity in the very broad wavelength range as well as the lowest polarization splitting. However, it is not very stable chemically and silver mirrors are easily damaged in a corrosive or oxidizing environment, leading first to the drastic drop in reflection followed by the complete disintegration of a silver layer. For this reason aluminum is much more in use. The problem of protection of silver layer is a very important one for number of applications, requiring the front side reflection, such as telescopes mirrors, reflective IR imaging optics…
The LAMP (Lightweight Asymmetry and Magnetism Probe) X-ray telescope is a mission concept to measure the polarization of X-ray astronomical sources at 250 eV via imaging mirrors that reflect at incidence angles near the polarization angle, i.e., 45 deg. Hence, it will require the adoption of multilayer coatings with a few nanometers d-spacing in order to enhance the reflectivity. The nickel electroforming technology has already been successfully used to fabricate the high angular resolution imaging mirrors of the X-ray telescopes SAX, XMM-Newton, and Swift/XRT. We are investigating this consol…
The polarization effect of the 31 reflections within the mirror train of an auxiliary telescope of the Very Large Telescope Interferometer is calculated as a function of pointing direction and rotator angle. With a rough estimate of the mean complex index of refraction of the reflecting surfaces, their Jones matrices are concatenated while tracing a ray from M1 up to the feeding mirror in front of an instrument. The net effect is summarized in terms of the axis ratio of the polarization ellipse of star light that was circularly polarized above the primary mirror.
Optics and broadband anti-reflection coatings for the BA4-90/150 receiver
Harvard & Smithsonian（哈佛-史密森尼天体物理中心）；Harvard University（哈佛大学）；Cardiff University（卡迪夫大学）；Stanford University（斯坦福大学）；SLAC National Accelerator Laboratory（斯坦福直线加速器国家实验室）；University of British Columbia（不列颠哥伦比亚大学）；California Institute of Technology（加州理工学院）；University of Cincinnati（辛辛那提大学）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；University of Chicago（芝加哥大学）；National Institute of Standards and Technology（美国国家标准与技术研究院）；Argonne National Laboratory（阿贡国家实验室）；University of Minnesota（明尼苏达大学）；University of Iceland（冰岛大学）；University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；University of Cambridge（剑桥大学）；Boston University（波士顿大学）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
A fraction of the light observed from edge-on disk galaxies is polarized due to two physical effects: selective extinction by dust grains aligned with the magnetic field, and scattering of the anisotropic starlight field. Since the reflection and transmission coefficients of the reflecting and refracting surfaces in an optical system depend on the polarization of incoming rays, this optical polarization produces both (a) a selection bias in favor of galaxies with specific orientations and (b) a polarization-dependent PSF. In this work we build toy models to obtain for the first time an estimat…
Radio-glaciological parameters from Moore's Bay, in the Ross Ice Shelf, have been measured. The thickness of the ice shelf in Moore's Bay was measured from reflection times of radio-frequency pulses propagating vertically through the shelf and reflecting from the ocean, and is found to be $576\pm8$ m. Introducing a baseline of 543$\pm$7 m between radio transmitter and receiver allowed the computation of the basal reflection coefficient, $R$, separately from englacial loss. The depth-averaged attenuation length of the ice column, $<L >$ is shown to depend linearly on frequency. The best fit (95…
Proof of Concept Measurements of Laterally Graded Multilayers for Soft X-ray Spectropolarimetry
Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology（卡弗里天体物理学与空间研究所，麻省理工学院）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
