Epoxy-based broadband antireflection coating for millimeter-wave optics

Rosen, Darin; Suzuki, Aritoki; Keating, Brian; Krantz, William B.; Lee, Adrian T.; Quealy, E.; Richards, P. L.; Siritanasak, P.; Walker, William C.

doi:10.1364/ao.52.008102

Cited by 37 publications

(24 citation statements)

References 10 publications

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“…A copper sample holder, which is cooled with liquid nitrogen, clamps the alumina filter and cools it to 81 K by conduction. The same cooling method is used elsewhere 17 . At each incident frequency, we measure the output voltage with and without the sample and obtain the transmittance as their ratio.…”

Section: Experiments and Resultsmentioning

confidence: 99%

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Cryogenic infrared filter made of alumina for use at millimeter wavelength

et al. 2014

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We propose a high thermal conductivity infrared (IR) filter using alumina for use in millimeter wave detection systems. We constructed a prototype two-layer anti-reflection (AR) coated alumina filter with a diameter of 100 mm and a thickness of 2 mm, and characterized its thermal and optical properties. The transmittance of this filter at 95 GHz and 150 GHz is 97 % and 95 % while the estimated 3 dB cutoff frequency is at 450 GHz. The high thermal conductivity of alumina minimizes thermal gradients. We measure a differential temperature of only 0.21 K between the center and the edge of the filter when it is mounted on a thermal anchor of 77 K. We also constructed a thermal model based on the prototype filter and analyzed the scalability of the filter diameter. We conclude that temperature increase at the center of alumina IR filter is less than 6 K even with a large diameter of 500 mm, when the temperature at the edge of the filter is 50 K. This is suitable for an application to a large-throughput next-generation cosmic microwave background (CMB) polarization experiment, such as POLARBEAR-2 (PB-2).

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Section: Experiments and Resultsmentioning

confidence: 99%

“…The two-layer AR coating consists of the epoxy glues, Stycast 2850 FT and Stycast 1090, manufactured by Emerson and Cuming [15][16][17] . We measure their indices and the losses as shown in Table II.…”

Section: B Alumina Propertiesmentioning

confidence: 99%

Cryogenic infrared filter made of alumina for use at millimeter wavelength

et al. 2014

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“…High thermal conductivity of the alumina helps with overall cryogenic performance [14]. Alumina lenses are anti-reflection coated with two-layer epoxy coating, thermal sprayed ceramic coating and expanded kapton coating [14,15,16]. The Optical design achieves a strehl ratio greater than 0.90 over entire 365 mm diameter focal plane.…”

Section: Instrumentmentioning

confidence: 99%

“…Bandpass filters on the wafer split the signal into two separate bands, then transition edge sensor (TES) bolometers detects the signal [17]. Silicon lenslet array is anti-reflection coated with two layers of epoxy based coating [15,18]. Readout electronics are assembled behind the detector array for a modular design.…”

Section: Instrumentmentioning

confidence: 99%

The Polarbear-2 and the Simons Array Experiments

et al. 2016

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We present an overview of the design and status of the POLARBEAR-2 and the Simons Array experiments. POLARBEAR-2 is a Cosmic Microwave Background polarimetry experiment which aims to characterize the arc-minute angular scale B-mode signal from weak gravitational lensing and search for the degree angular scale B-mode signal from inflationary gravitational waves. The receiver has a 365 mm diameter focal plane cooled to 270 milli-Kelvin. The focal plane is filled with 7,588 dichroic lenslet-antenna coupled polarization sensitive Transition Edge Sensor (TES) bolometric pixels that are sensitive to 95 GHz and 150 GHz bands simultaneously. The TES bolometers are read-out by SQUIDs with 40 channel frequency domain multiplexing. Refractive optical elements are made with high purity alumina to achieve high optical throughput. The receiver is designed to achieve noise equivalent temperature of 5.8 µK CMB √ s in each frequency band. POLARBEAR-2 will deploy in 2016 in the Atacama desert in Chile. The Simons Array is a project to further increase sensitivity by deploying three POLARBEAR-2 type receivers. The Simons Array will cover 95 GHz, 150 GHz and 220 GHz frequency bands for foreground control. The Simons Array will be able to constrain tensor-to-scalar ratio and sum of neutrino masses to σ (r) = 6 × 10 −3 at r = 0.1 and ∑ m ν (σ = 1) to 40 meV.

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“…At mid-IR/optical wavelengths, the AR layer can be applied using a thin film deposition, however at far-IR/millimeter wavelengths the AR layer becomes macroscopic and difficult to apply. Plastic coatings have been explored at millimeter wavelengths [7][8][9][10]. Laser milling and laser ablation have been proposed to make simulated dielectric metamaterial AR coatings [11][12][13] but custom high-power optical setups are needed.…”

Section: Introductionmentioning

confidence: 99%

Deep reactive ion etched anti-reflection coatings for sub-millimeter silicon optics

et al. 2017

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Refractive optical elements are widely used in millimeter and sub-millimeter astronomical telescopes. High resistivity silicon is an excellent material for dielectric lenses given its low loss-tangent, high thermal conductivity and high index of refraction. The high index of refraction of silicon causes a large Fresnel reflectance at the vacuum-silicon interface (up to 30%), which can be reduced with an anti-reflection (AR) coating. In this work we report techniques for efficiently AR coating silicon at sub-millimeter wavelengths using Deep Reactive Ion Etching (DRIE) and bonding the coated silicon to another silicon optic. Silicon wafers of 100 mm diameter (1 mm thick) were coated and bonded using the Silicon Direct Bonding technique at high temperature (1100 C). No glue is used in this process. Optical tests using a Fourier Transform Spectrometer (FTS) show sub-percent reflections for a single-layer DRIE AR coating designed for use at 320 microns on a single wafer. Cryogenic (10 K) measurements of a bonded pair of AR-coated wafers also reached sub-percent reflections. A prototype two-layer DRIE AR coating to reduce reflections and increase bandwidth is presented and plans for extending this approach are discussed.

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Epoxy-based broadband antireflection coating for millimeter-wave optics

Cited by 37 publications

References 10 publications

Cryogenic infrared filter made of alumina for use at millimeter wavelength

Cryogenic infrared filter made of alumina for use at millimeter wavelength

The Polarbear-2 and the Simons Array Experiments

Deep reactive ion etched anti-reflection coatings for sub-millimeter silicon optics

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