Abstract Details

Name: Krishna Reddy
Affiliation: Aryabhatta Research Institute of Observational Sciences (ARIES)
Conference ID: ASI2020_524
Title : A full-stokes spectro-polarimeter for 3.6-m Devasthal Optical Telescope
Authors and Co-Authors : Amitesh Omar,B.Krishna Reddy,Jaysheekar Pant
Abstract Type : Poster
Abstract Category : Instrumentation and Techniques
Abstract : A spectro-polarimeter for the 3.6-m Devasthal Optical Telescope (DOT) is a desired instrument to add extra dimensions to various science cases already being pursued using the ARIES telescopes. An innovative design for adding a quad-beam spectro-polarimeter mode using double wedged Wollaston prisms in ARIES-Devasthal Faint Object Spectrograph & Camera (AD-FOSC) will be presented. The optical design uses only two 64mm x 34mm x 19mm wedged Wollaston prisms made of Quartz crystal without any rotating half-wave plate. A fixed quarter-wave plate is proposed to be mounted in the slit-mask for circular polarimetry. In addition, spectral order-sorting filters are also proposed to be mounted in the slit-mask itself. Both linear and circular polarimetry observations in imaging and spectroscopy mode will be possible with the proposed augmentation in AD-FOSC. In order to validate design ideas, a sub-aperture spectro-polarimeter using two 25X25 mm Wollaston prisms procured from a small-scale optical manufacturer in India is presently being integrated in the AD-FOSC. This sub-aperture spectro-polarimeter does not require a wedge and the required separation between the four spectrums measuring polarization of light at 0,90,45, and 135 degree angles is obtained by placing two Wollaston prisms at a relative angle of 45 degree and rotating this double Wollaston assembly at an angle with respect to the spectrograph's dispersion axis. The design, test results, and expected performance will be presented.