Breadboard model assembly and characterization of a sapphire achromatic half-wave plate for LiteBIRD low-frequency telescope

Mitsuharu Kusama; Kosuke Aizawa; Ryosuke Akizawa; Teruhito Iida; Kiyoshi Ikuma; Kuniaki Konishi; Asuka Maeda; Tomotake Matsumura; Haruyuki Sakurai; Yuki Sakurai; Ryota Takaku

doi:10.1117/12.3019752

16 August 2024 Breadboard model assembly and characterization of a sapphire achromatic half-wave plate for LiteBIRD low-frequency telescope

Mitsuharu Kusama, Kosuke Aizawa, Ryosuke Akizawa, Teruhito Iida, Kiyoshi Ikuma, Kuniaki Konishi, Asuka Maeda, Tomotake Matsumura, Haruyuki Sakurai, Yuki Sakurai, Ryota Takaku

Author Affiliations +

Proceedings Volume 13102, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XII; 131020A (2024) https://doi.org/10.1117/12.3019752
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Abstract

We present the development of a breadboard model achromatic half-wave plate (AHWP) for the LiteBIRD Low-Frequency Telescope (LFT). LiteBIRD is a JAXA-led strategic L-class satellite mission to probe the cosmic microwave background polarization. The breadboard model (BBM) polarization modulator unit (PMU) of the LFT uses an AHWP, which achieves an observational frequency coverage 34-161 GHz using a five-layer sapphire stack with a diameter of 330 mm based on the Pancharatnam recipe. The sub-wavelength structures on both end surfaces mitigate the reflection over broadband frequencies. The designed single sapphire plate thickness is 4.95 mm, with a corresponding half-wave shift center frequency of 97.5 GHz. We use hydro-catalysis bonding to glue the sapphire surfaces and assemble the five-layer AHWP. The AHWP is successfully assembled and measured. The transmittance and polarization properties are consistent with the theoretical prediction that neglects the effect of the bonding interfaces. In this work, we present the AHWP design, the assembly process, and the polarimetric characterization. We also discuss the path-forward for this BBM AHWP including the cryogenic and vibrational tests, and the development plan for the flight-size engineering model.

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Mitsuharu Kusama, Kosuke Aizawa, Ryosuke Akizawa, Teruhito Iida, Kiyoshi Ikuma, Kuniaki Konishi, Asuka Maeda, Tomotake Matsumura, Haruyuki Sakurai, Yuki Sakurai, and Ryota Takaku "Breadboard model assembly and characterization of a sapphire achromatic half-wave plate for LiteBIRD low-frequency telescope", Proc. SPIE 13102, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XII, 131020A (16 August 2024); https://doi.org/10.1117/12.3019752

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