Effect of a silicone contaminant film on the transmittance properties of AR-coated fused silica

Boeder, Paul; Visentine, James T.; Shaw, Christopher G.; Carniglia, C. K.; Alred, John; Soares, Carlos E.

doi:10.1117/12.560859

Cited by 5 publications

(3 citation statements)

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“…The potential primary contaminants on space telescopes include water ice and a number of non-volatile residuals (nvr), which are currently unidentified. Consequently, in addition to water ice, tetramethyl-tetraphenyl trisiloxane (DC-704) was included in the model as a silicone contaminant analog, the photochemical deposition of which has been commonly studied 25 – 27 DC-704 has been shown to deposit as a smooth, widely-spread film on nonmetallic, cold surfaces for temperatures up to 93K due to inadequate thermal energy to induce the coalescence of molecules 28 .…”

Section: Methodsmentioning

confidence: 99%

“…Consequently, in addition to water ice, tetramethyl-tetraphenyl trisiloxane (DC-704) was included in the model as a silicone contaminant analog, the photochemical deposition of which has been commonly studied. [25][26][27] DC-704 has been shown to deposit as a smooth, widely-spread film on nonmetallic, cold surfaces for temperatures up to 93K due to inadequate thermal energy to induce the coalescence of molecules. 28 Moreover, in a recent study conducted for JWST, DC-704 was identified to be one of the primary potential contaminants, with its origin attributed to silicone fluids used in diffusion pumps for high vacuum systems.…”

Section: Environmental Changes In Spacementioning

confidence: 99%

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Extreme broadband dichroics: Monte Carlo transmission line modeling for astronomical spectroscopy

Thurairethinam,

Savini,

Hawkins

et al. 2024

J. Astron. Telesc. Instrum. Syst.

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Dichroic beamsplitters, or dichroics, rely on the optical interference that occurs within thin-film layers to ensure the separation of the transmission and reflection of selective wavelengths of an incident beam of light at a given angle of incidence. Utilized within the optical systems of numerous space telescopes, they act to separate the incoming light spectrally and spatially into various channels. As space missions increasingly demand simultaneous observations across wavebands spanning extreme wavelength ranges, the necessity for exceedingly complex broadband dichroics has emerged. Subsequently, the uncertainties pertaining to their optical performance have also become more intricate. We use transmission line modeling to evaluate the spectral performance of multilayer coatings deposited on a substrate material for given thicknesses, materials, angles of incidence, and polarization. A dichroic recipe in line with the typical specifications and requirements of a dichroic is designed with the aid of a Monte Carlo simulation. The tolerances of the coating performance to systematic and random uncertainties from the manufacturing process, as well as from environmental changes in space, are studied. With the aid of accurate manufacturing recipes and uncertainty amplitudes from commercial manufacturers, this tool can predict variations in the optical performance that result from the propagation of each of these uncertainties for various hypothetical scenarios and systematic effects.

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Section: Methodsmentioning

confidence: 99%

Section: Environmental Changes In Spacementioning

confidence: 99%

Extreme broadband dichroics: Monte Carlo transmission line modeling for astronomical spectroscopy

Thurairethinam,

Savini,

Hawkins

et al. 2024

J. Astron. Telesc. Instrum. Syst.

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“…In the presence of oxygen with irradiation, the hydrophobic silicone surface is rendered hydrophilic, i.e., a conversion to a SiO x layer occurs [31][32][33][34][35][36][37] . A recent study examined polydimethylsiloxane exposed to three different conditions: 1) Longer wavelength (315-400 nm) UV irradiation in air, 2) VUV irradiation at 185 and 254 nm in air generating atomic oxygen, and 3) oxygen plasma.…”

Section: Silicone/tefzel Contaminant Reaction Chemistrymentioning

confidence: 99%

Characterizing the optical performance of AZ93 with a fluoropolymer overcoat under ultraviolet exposure

Huang

Schmidl

Soares

2008

Optical System Contamination: Effects, Measurements, and Control 2008

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AZ93 with a fluoropolymer overcoat is an option to simplify ground handling of space hardware. The overcoat applied on some on-orbit International Space Station (ISS) hardware provides contamination protection for optically sensitive ceramic thermal control coatings. However, if the fluoropolymer is not eroded on-orbit by atomic oxygen (AO), then it will darken. This will increase the solar absorptance resulting in possible thermal performance degradation. If the fluoropolymer overcoat was not present, optical performance would be significantly improved. To characterize the optical performance of the AZ93 with the fluoropolymer overcoat for modeling the UV degradation, laboratory testing of the coating was performed at Marshall Space Flight Center (MSFC). Sample coupons prepared by AZ Technology were exposed under vacuum to ultraviolet radiation. At periodic intervals, the samples were removed from the testing chamber to acquire images and to measure the solar absorptance. The images showed visible differences between AZ93 with the overcoat and without the overcoat as vacuum ultraviolet (VUV) exposure increased. Darkening is more pronounced in the samples with the fluoropolymer overcoat. This was also evident in the solar absorptance measurements. Optical properties of AZ93 with the fluoropolymer overcoat significantly degraded in comparison to those without the overcoat. A short period of little change followed by an exponential rise in solar absorptance was observed. The optical degradation of the fluoropolymer overcoat is described in terms of surface reaction chemistry and kinetics and is found to follow a pseudo first order reaction rate.

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Charles Keith Carniglia (1944-2006): in memoriam

Ja¹

2007

Appl. Opt.

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Effect of a silicone contaminant film on the transmittance properties of AR-coated fused silica

Cited by 5 publications

References 0 publications

Extreme broadband dichroics: Monte Carlo transmission line modeling for astronomical spectroscopy

Extreme broadband dichroics: Monte Carlo transmission line modeling for astronomical spectroscopy

Characterizing the optical performance of AZ93 with a fluoropolymer overcoat under ultraviolet exposure

Charles Keith Carniglia (1944-2006): in memoriam

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