University of Illinois Postdoctoral Appointment 2004-2006.
Dr. Abjijit Chakraborty specializes in near-IR instrumentation, adaptive optics, substellar dwarfs, young stellar objects, and precision radial velocity spectroscopy. Prior to his appointment at the University of Illinois, Dr. Chakraborty was a postdoctoral researcher at Pennsylvania State Univeristy (2001-2004), and before that at the Tata Institute of Fundamental Research in Bombay (1999-2000). During his Ph.D. studies, Dr. Chakraborty spent 1 year at the Inter University Centre for Astronomy and Astrophysics in Pune. He is now a permanent staff member of the Physical Research Laboratory, Ahmedabad, India.
While at Illinois he worked on the design of Gaussian aperture pupil masks for stellar coronagraphs. His goal was to select the largest possible clear aperture for the pupil mask but still maintain a shape that scatters a large fraction of the diffracted light preferentially into wide sectors thereby leaving other sectors open for the detection of faint nearby sources. His pupil masks were manufactured at the Nanofabriction Laboratory at Penn State University via photolithographic deposition on high quality optical windows. The use of nanofabrication methods is necessary to get a sufficiently smooth edge at the boundary between the clear and opaque areas of the mask. One of his best designs is shown in in the figure below along with its Fourier transform to show the predicted performance in the focal plane.
|Gaussian Aperture Pupil Mask||Theoretical Intensity Distribution in Focal Plane|
This particular design of a Gaussian aperture pupil mask (left) and its Fourier transform (right) were created for use with the UnISIS AO system. Note the effect of the partially obscured pupil mask in selectively redistributing the diffracted light into the upper and lower sectors thereby opening the two sectors on the left and right hand sides for the detection of faint companions.
The home page of Dr. Chakraborty at the Physical Research Laboratory can be found here.