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Estimation of polarization aberrations and its effect on the point spread function of the Thirty Meter Telescope

Anche, Ramya M. and Anupama, G. C. and Sriram, S. and Sankarasubramanian, K. and Skidmore, Warren (2018) Estimation of polarization aberrations and its effect on the point spread function of the Thirty Meter Telescope. In: Adaptive Optics Systems VI. Proceedings of SPIE. No.10703. Society of Photo-optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 107034K. ISBN 9781510619593.

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The Thirty Meter Telescope (TMT) is a future generation telescope proposed to be located in Mauna Kea, Hawaii or in La Palma in the Canary Islands. The telescope will have a segmented primary and an inclined tertiary mirror. The segmentation of the primary mirror and the inclination in the tertiary mirror can introduce significant polarization aberrations. Typically, the polarization aberrations, introduced due to the mirror coating and the high incident angles cause small modifications to the Point Spread Function (PSF). Here, we perform the polarization ray tracing for TMT using the optical design software Zemax for different input polarizations for a point source (on-axis). We calculate the diattenuation and retardance aberration maps for all the three mirrors of TMT. The coating induced astigmatism obtained from the retardance of the primary and secondary mirror is found to be of the order of 0.048 radians, whereas, the polarization induced tilt by the retardance of the tertiary mirror is in the order of 0.29 radians. The Jones pupil maps are estimated at two of the instrument ports, Wide Field Optical Spectrograph (WFOS) and Narrow Field Infrared Adaptive Optics System (NFIRAOS).The Amplitude Response Matrix (ARM) estimated at the WFOS port show the presence of ghost PSF's. The magnitude of the ghost PSF components is of the order of 2.5 x 10^(-5) at 1μm at WFOS port. The ARM and the Point Spread Matrix (PSM) are estimated at the focus of the NFIRAOS instrument. The Stokes PSF is shown for horizontal and vertical polarization as inputs. The Huygen's point spread function obtained from Zemax shows the variations in FWHM for unpolarized and polarized inputs. These estimations would help in the design aspects of a high contrast imaging instrument for the TMT in the future.

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Additional Information:© 2018 Society of Photo-optical Instrumentation Engineers (SPIE). Authors would like to thank Prof. Jayant Murthy and Mr. Joice Mathew of Indian Institute of Astrophysics for the Zemax software license.
Group:Thirty Meter Telescope
Subject Keywords:Instrumental polarization, Point spread function, Polarization aberrations, Jones Pupil map, Point Spread Matrix, Thirty Meter Telescope, NFIRAOS
Series Name:Proceedings of SPIE
Issue or Number:10703
Record Number:CaltechAUTHORS:20190110-081206164
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Official Citation:Ramya M. Anche, G. C. Anupama, S. Sriram, K. Sankarasubramanian, Warren Skidmore, "Estimation of polarization aberrations and its effect on the point spread function of the Thirty Meter Telescope," Proc. SPIE 10703, Adaptive Optics Systems VI, 107034K (11 July 2018); doi: 10.1117/12.2312506
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92191
Deposited By: Tony Diaz
Deposited On:10 Jan 2019 20:33
Last Modified:16 Nov 2021 03:47

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