Challenges in optics for Extremely Large Telescope instrumentation

Spanó, P.; Zerbi, F. M.; Norrie, Callum J.; Cunningham, Colin; Strassmeier, K. G.; Bianco, Andrea; Blanche, Pierre Alexandre; Bougoin, M.; Ghigo, M.; Hartmann, Péter; Zago, Lorenzo; Atad-Ettedgui, Eli; Délabre, Bernard; Dekker, H.; Melozzi, Mauro; Snyders, B.; Takke, Ralf; Walker, David D.

doi:10.1002/asna.200610610

Cited by 18 publications

(13 citation statements)

References 45 publications

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“…Among photochromic materials, diarylethenes have a special role since they combine high photochromic performances with the thermal stability of the colored state [2]. The variation of both their extinction coefficient (in the UV-Vis spectral region) and their refractive index (in the NIR spectral region) has been applied to develop rewritable optical elements for optics [3,4] including amplitude elements such as computer generated holograms [5,6], transparency masks for lithography [7][8][9], and astronomical multiobject spectroscopy [10].…”

Section: Introductionmentioning

confidence: 99%

Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index

et al. 2017

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Photochromic polymers have been studied as rewritable systems for optical elements with tunable transparency in the visible and refractive index in the NIR. Six diarylethene monomers have been synthesized to give thin films of photochromic polyurethanes. The absorption properties of the monomers in solution and of the corresponding polymeric films have been evaluated showing that a transparency contrast in the visible spectrum of the order of 10 3 can be obtained by a suitable choice of the chemical structure and illumination wavelength. The change in the refractive index in the NIR have been determined by ellipsometry showing changes larger than 10 −2 . A trend of this variation with the absorption properties has been also highlighted. Fresnel lenses working on the basis of both a change of the transparency and the refractive index (amplitude and phase) have been demonstrated.

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Section: Introductionmentioning

confidence: 99%

Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index

et al. 2017

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“…Such filters, however, have the disadvantage, that they change their filter properties strongly with the angle of the incident light. This effect is much lower with bulk colored glass filters [7]. Fig.…”

Section: Replacement Possibilities For Lead and Cadmium Containing Glmentioning

confidence: 97%

Optical glass and the EU directive RoHS

Hartmann

Hamm

2011

SPIE Proceedings

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Optical glass is part of optical systems, being subject to the EU directive RoHS, restricting the use of certain hazardous substances in electric and electronic equipment. Some special optical and filter glasses contain lead or cadmium, since these elements are essential for some special glass properties needed by high end optical systems. Most lead containing glass for consumer optics has been replaced by lead free versions. A lot of effort has been spent searching for substitute glass types. But for some remaining applications a set of lead or cadmium containing glass types have revealed to be irreplaceable. Even though they are used only in small amounts and are of negligible environmental influence, long and tedious effort was necessary to obtain an exemption from the directive. The optics community has to stay alert to prevent vast damages due to possible non-availability of glass types crucial for very important applications such as fluorescence microscopy. There are tendencies to restrict the use of even more elements, which could endanger the existence of most optical and filter glass types. These materials are key enabling factors of technical civilization as a whole because they are used in all industries and many research fields. They must be taken out of the scope of RoHS in total since exemption procedures will lead to periods of secured availability too short to be acceptable for the design of optical systems, which usually takes years and in high end optics must be valid also for long term deliveries. New regulations improving ecological aspects should assess the consequences on other important goals of society.

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“…At the largest telescopes, challenges in highestresolution spectroscopy stem from the difficulty to optically match realistically-sized grating spectrometers to the large image scales, i.e., to squeeze starlight into a narrow spectrometer entrance slit while avoiding unrealistically large optical elements (Spanò et al 2006). The use of image slicers would limit the number of measurable spectral orders although some remedy could be offered by adaptive optics (Ge et al 2002;Sacco et al 2004).…”

Section: Spectrometers At the Largest Telescopesmentioning

confidence: 99%

High‐fidelity spectroscopy at the highest resolutions

Dravins¹

2010

Astron Nachr

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High-fidelity spectroscopy presents challenges for both observations and in designing instruments. High-resolution and high-accuracy spectra are required for verifying hydrodynamic stellar atmospheres and for resolving intergalactic absorption-line structures in quasars. Even with great photon fluxes from large telescopes with matching spectrometers, precise measurements of line profiles and wavelength positions encounter various physical, observational, and instrumental limits. The analysis may be limited by astrophysical and telluric blends, lack of suitable lines, imprecise laboratory wavelengths, or instrumental imperfections. To some extent, such limits can be pushed by forming averages over many similar spectral lines, thus averaging away small random blends and wavelength errors. In situations where theoretical predictions of lineshapes and shifts can be accurately made (e.g., hydrodynamic models of solar-type stars), the consistency between noisy observations and theoretical predictions may be verified; however this is not feasible for, e.g., the complex of intergalactic metal lines in spectra of distant quasars, where the primary data must come from observations. To more fully resolve lineshapes and interpret wavelength shifts in stars and quasars alike, spectral resolutions on order R = 300 000 or more are required; a level that is becoming (but is not yet) available. A grand challenge remains to design efficient spectrometers with resolutions approaching R = 1 000 000 for the forthcoming generation of extremely large telescopes.

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Challenges in optics for Extremely Large Telescope instrumentation

Cited by 18 publications

References 45 publications

Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index

Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index

Optical glass and the EU directive RoHS

High‐fidelity spectroscopy at the highest resolutions

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