1. Department of Electronics, Asutosh College, 92, Shyamaprasad Mukherjee Road, Kolkata 700026, India
2. Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 B. T. Road, Kolkata 700108, India
3. Central Instrumentation, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata 700032, India
4. Department of Physics, Anna University, Chennai 600 025, India
5. Department of Physics, Indian Institute of Science Education and Research, Mohali, Knowledge City, SAS Nagar, Manauli PO 140306, India