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Multilayer Etched Antireflective Structures for Silicon Vacuum Windows

Macioce, T. and Defrance, F. and Jung-Kubiak, C. and Rahiminejad, S. and Sayers, J. and Connors, J. and Chattopadhyay, G. and Golwala, S. R. and Radford, S. J. E. (2020) Multilayer Etched Antireflective Structures for Silicon Vacuum Windows. Journal of Low Temperature Physics, 199 (3-4). pp. 935-942. ISSN 0022-2291. doi:10.1007/s10909-019-02294-4.

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Future instruments employing cryogenic detectors for millimeter and submillimeter astronomy applications can benefit greatly from silicon vacuum windows with broadband antireflection treatment. Silicon is an ideal optical material at these wavelengths due to numerous attractive properties, including low loss, high refractive index, and high strength. However, its high index (n = 3.4) necessitates antireflection (AR) treatment, which has proven a major challenge, especially for the multilayer treatments required for wide spectral bandwidths. We address this challenge by developing a wide-bandwidth integral AR structure for silicon vacuum windows using a novel fabrication technique, tuning the effective refractive index of each AR layer using deep reactive ion etching (DRIE) and using wafer bonding to assemble the structure. We present the progress we have made in designing and fabricating such vacuum windows from 100-mm-diameter silicon wafers. We have previously demonstrated a two-layer AR structure for windows over a 1.6:1 bandwidth and are currently fabricating a four-layer coating designed for a 4:1 bandwidth. We have also converged on a design for a six-layer structure optimized to give − 20 dB reflection between 80 and 420 GHz (5.25:1 bandwidth), which will be useful for future multicolor Sunyaev–Zel’dovich (SZ) observations.

Item Type:Article
Related URLs:
URLURL TypeDescription ReadCube access
Macioce, T.0000-0002-3156-6627
Defrance, F.0000-0002-3746-5296
Jung-Kubiak, C.0000-0003-2745-6342
Rahiminejad, S.0000-0001-8094-7189
Sayers, J.0000-0002-8213-3784
Connors, J.0000-0002-6094-2943
Chattopadhyay, G.0000-0001-7942-5025
Golwala, S. R.0000-0002-1098-7174
Radford, S. J. E.0000-0001-9113-1660
Additional Information:© 2019 Springer-Verlag. Received 21 August 2019; Accepted 02 December 2019; Published 14 December 2019. This work was supported by a NASA Space Technology Research Fellowship. This work was also supported by a NASA APRA Grant.
Group:Astronomy Department
Funding AgencyGrant Number
Subject Keywords:Antireflective coating; Vacuum window; Silicon optics; Deep reactive ion etching
Issue or Number:3-4
Record Number:CaltechAUTHORS:20191220-102933374
Persistent URL:
Official Citation:Macioce, T., Defrance, F., Jung-Kubiak, C. et al. Multilayer Etched Antireflective Structures for Silicon Vacuum Windows. J Low Temp Phys 199, 935–942 (2020).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100391
Deposited By: Tony Diaz
Deposited On:20 Dec 2019 19:18
Last Modified:16 Nov 2021 17:53

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