[1] S. N. Bose National Centre of Basic Sciences, Salt lake, Kolkata 700098, India
[2] Techno India, Salt Lake City, Kolkata 700091, India
[3] Metropolitan Institution (Main), 39, Sankar Ghosh Lane, Kolkata 700006, India
[4] Department of Applied Physics, Birla Institute of Technology Mesra, Ranchi 835215, India