Development progress of diffraction-limited coronagraphs with moderate spectral bandwidths

Satoshi Itoh; Taro Matsuo; Shunsuke Ota; Yuji Ikeda; Reiki Kojima; Toru Yamada; Takahiro Sumi

doi:10.1117/12.2629087

29 August 2022 Development progress of diffraction-limited coronagraphs with moderate spectral bandwidths

Satoshi Itoh, Taro Matsuo, Shunsuke Ota, Yuji Ikeda, Reiki Kojima, Toru Yamada, Takahiro Sumi

Proceedings Volume 12188, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V; 121884D (2022) https://doi.org/10.1117/12.2629087
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Conference Poster

Abstract

Recently, we have proposed a fourth-order coronagraph with inner working angles (IWA) of ∼ 1λ/D applicable with segmented telescopes, by deriving some complex-valued focal-plane mask patterns with the value between the interval [-1,1]. The mask pattern is implementable achromatically with a custom-patterned half-waveplate sandwiched between two linear polarizers orthogonal to each other. To enhance the system’s spectral bandwidth, we are now investigating the methods from various perspectives. One method to widen the system’s spectral bandwidth is to disperse point spread functions (PSF) incident to the focal-plane mask to the direction orthogonal to the mask pattern using a diffraction grating. Because the mask pattern is one-dimensional, we can optimize the mask pattern for each PSF dispersed by each wavelength (spectroscopic coronagraph). Another method focuses on the fact that the stellar leak due to a wide spectral bandwidth is flat at the Lyot stop and thus reducible with the successive use of the multiple coronagraph systems. Because the practical successive use of the multiple coronagraph systems requires a high off-axis throughput of the focal-plane mask, we derived new mask patterns by modifying the original pattern. This method can bring additional enhance of spatial resolution, although the current optimization limits the working angle to the separation angles of 0.7–1.4λ/D (super-resolution coronagraph or double coronagraph). Our fundamental simulation shows that both the methods can deliver a contrast of 10−10 at wavelengths of 650–750nm.

Citation Download Citation

Satoshi Itoh, Taro Matsuo, Shunsuke Ota, Yuji Ikeda, Reiki Kojima, Toru Yamada, and Takahiro Sumi "Development progress of diffraction-limited coronagraphs with moderate spectral bandwidths", Proc. SPIE 12188, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V, 121884D (29 August 2022); https://doi.org/10.1117/12.2629087

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