Mr. Hiroshi Sasago Profile

Hiroshi Sasago

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Publications (4)

Proceedings Article | 23 August 2024 Poster + Paper

Development of the CdZnTe immersion grating spectrometer for the detection of snow-lines with high-resolution spectroscopy

Takao Nakagawa, Hideo Matsuhara, Umi Enokidani, Toyoaki Suzuki, Shunsuke Baba, Yasuhiro Hirahara, Hidehiro Kaneda, Ryoichi Koga, Li Yuan, Biao Zhao, Daiki Takama, Hiroshi Sasago, Takehiko Wada, Toshihiro Nakaoka, Taiki Eda, Ryota Kakihara, Yoshinori Shiomitsu, Takuya Hosobata, Noboru Ebizuka, Yutaka Yamagata, Shota Notsu, Hideko Nomura

Proceedings Volume 13092, 130923D (2024) https://doi.org/10.1117/12.3019636

KEYWORDS: Spectroscopy, Crystals, Absorption, Antireflective coatings, Refractive index, Optical gratings, Transmittance, Mid infrared, Cryogenics, Prototyping

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Proceedings Article | 23 August 2024 Poster + Paper

Transmittance measurement of high-resistivity CdZnTe at cryogenic temperature for material selection of the immersion grating for the next-generation infrared telescope GREX-PLUS

Yuan Li, Yasuhiro Hirahara, Biao Zhao, Hiroshi Sasago, Umi Enokidani, Hideo Matsuhara, Takao Nakagawa, Ryoichi Koga, Takehiko Wada

Proceedings Volume 13092, 130923E (2024) https://doi.org/10.1117/12.3019645

KEYWORDS: Transmittance, Absorption, Temperature metrology, Cryogenics, Lamps, Linear filtering, Refractive index, Mid infrared, Infrared radiation, Signal intensity

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Proceedings Article | 23 August 2024 Poster + Paper

Development of the broadband Fourier transform IR imaging spectrometer with common path wavefront division phase-shift interferometry for compact satellite payload

Biao Zhao, Yasuhiro Hirahara, Yuan Li, Shohei Negishi, Hiroshi Sasago, Yasumasa Kasaba, Ryoichi Koga, Takao Nakagawa, Hideo Matsuhara, Umi Enokidani, Takehiko Wada

Proceedings Volume 13092, 130922X (2024) https://doi.org/10.1117/12.3019640

KEYWORDS: Mirrors, Spectroscopy, FT-IR spectroscopy, Phase interferometry, Phase shifts, Imaging systems, Optical design, Diffraction, Cameras, Infrared imaging

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We have developed a compact broadband infrared imaging Fourier transform spectrometer, referred to as the 2D FTIR, employing common path wavefront division phase-shift interferometry. The system comprises a 3-reflector point-topoint optical setup with overlapping paths, incorporating two free-form mirrors and a pair of 20 mm high and 40 mm wide planar mirrors. Initially, we establish a one-dimensional multi-slit object plane with spacing tailored to match the FPA detector pixel size, effectively preventing destructive interference. Through precise optimization of the parameters of the two free-form mirrors (Mirror 1: 4th-order Zernike polynomial; Mirror 2: 6th-order Zernike polynomial), we achieve precise beam collimation, reflection through a phase shifter, and subsequent refocusing onto the FPA detector. Utilizing a commercial uncooled bolometer camera with a resolution of 640x480 pixels and a pixel size of 17μm, we attain optimal performance across the 4-20μm wavelength range, coupled with a generous 6mm diameter field of view. The spectrometer boasts a remarkable wavenumber resolution of 2.7 cm^-1, with R (λ=4μm) ≈ 1000, alongside a spatial resolution of 34μm. All components seamlessly fit within a 170x150x80 mm vacuum frame. The 2D FT-IR enables the acquisition of spectral maps post-image capture and offers a broad measurement wavelength range of 4-20 μm. After completion of development, we plan to employ it to study the generation mechanisms of cryogenically frozen organic matter simulating Titan's haze and to measure the low-temperature continuous spectral transmittance and refractive index of the GREX-PLUS spectroscopic components. Additionally, due to its high vibration resistance and compact design, we intend to deploy it as a spectrometer for compact satellites developed by JAXA. Lastly, it will serve as a pivotal test instrument for the PLANETS telescope, facilitating the evaluation of the telescope's resistance to atmospheric disturbances.

Proceedings Article | 23 August 2024 Poster + Paper

Development of a mid-infrared refractive index measurement system at cryogenic temperature for the development of an immersion grating to be onboard next-generation infrared space telescope GREX-PLUS

Umi Enokidani, Hideo Matsuhara, Takao Nakagawa, Yasuhiro Hirahara, Ryoichi Koga, Yuan Li, Biao Zhao, Daiki Takama, Hiroshi Sasago, Takehiko Wada

Proceedings Volume 13092, 130923F (2024) https://doi.org/10.1117/12.3019753

KEYWORDS: Refractive index, Temperature metrology, Infrared radiation, Angle measurement, Prisms, Infrared telescopes, Cryogenics, Spectrographs, Mid infrared, Optical testing

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