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Proceedings Paper

Breakthroughs in silicon grism and immersion grating technology at Penn Stat Univ
Author(s): Jian Ge; Daniel Ludlow McDavitt; Shane Miller; John Luther Bernecker; Abhijit Chakraborty; Junfeng Wang
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Paper Abstract

Fabrication of silicon grisms up to 2 inches in dimension has become a routine process at Penn State thanks to newly developed techniques in chemical etching, lithography and post-processing. The newly etched silicon grisms have typical rms surface roughness of ~ 9 nm with the best reaching 0.9 nm, significantly lower than our previous attempts (~ 20-30 nm). The wavefront quality of the etched gratings is high. Typical wavefront error is ~ 0.035 wave at 0.6328 micron, indicating diffraction-limited performance in the entire infrared wavelengths (1.2-10 microns) where silicon has excellent transmission. These processes have also significantly eliminated visible defects due to grating mask breaks during chemical etching. For the best grisms, we have less than 1 defect per cm2. The measured total integrated scatter is less than 1% at 0.6328 micron, indicating similar or lower scatter in the IR when grisms are operated in transmission. These new generation grisms are being evaluated with our Penn State near IR Imager and Spectrograph (PIRIS) in cryogenic temperature. We are applying the new techniques in etching an 80x40 mm2 grating on 30 mm thick substrate to make an anamorphic silicon immersion grating, which can provide a diffraction-limited spectral resolution of R = 220,000 at 2.2 micron. We plan to put this immersion grating in a modified PIRIS to measure magnetic field strength using the Fe I line at 1.56 micron among hundreds of nearby solar type stars to investigate the probability of the Maunder Minimum using the Mt. Wilson 100inch with adaptive optics in 2003.

Paper Details

Date Published: 7 March 2003
PDF: 10 pages
Proc. SPIE 4841, Instrument Design and Performance for Optical/Infrared Ground-based Telescopes, (7 March 2003); doi: 10.1117/12.461163
Show Author Affiliations
Jian Ge, The Pennsylvania State Univ. (United States)
Daniel Ludlow McDavitt, The Pennsylvania State Univ. (United States)
Shane Miller, The Pennsylvania State Univ. (United States)
John Luther Bernecker, The Pennsylvania State Univ. (United States)
Abhijit Chakraborty, The Pennsylvania State Univ. (United States)
Junfeng Wang, The Pennslyvania State Univ. (United States)

Published in SPIE Proceedings Vol. 4841:
Instrument Design and Performance for Optical/Infrared Ground-based Telescopes
Masanori Iye; Alan F. M. Moorwood, Editor(s)

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