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3 March 2003 Nulling stellar coronagraph using liquid-crystal device
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Nulling stellar coronagraph has been proposed to detect faint objects very close to a bright point-like star, especially extra-solar planets. The principle of the nulling stellar coronagraph is to cause destructive interference for the light from a star. There have been proposed several methods for nulling interferometry. The key point of the nulling interferometry is the way to produce π-phase shift over wide range of wavelength. Here we propose a method for realizing achromatic π-phase shift utilizing polarization interference. The phase difference between two light beams that pass through different polarizers is π radians when these polarizers are placed between mutually orthogonal polarizer and analyzer. We adopt a ferroelectric liquid-crystal (FLC) device to convert the polarization direction of the incident beam. The FLC device is regarded as a birefringent device with retardation π, namely a half wave plate. The FLC device forms four-quadrant structure and is placed between the polarizer and the analyzer. By fixing the optic axes of the four-quadrant FLC suitably, it can rotate the incident linearly polarized light in parts by plus/minus 45°.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Naoshi Murakami, Naoshi Baba, Tsuyoshi Ishigaki, and Nobuyuki Hashimoto "Nulling stellar coronagraph using liquid-crystal device", Proc. SPIE 4860, High-Contrast Imaging for Exo-Planet Detection, (3 March 2003);

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