1. Optical Nanomaterials Lab, Department of Physics, Maulana Azad National Institute of Technology, Bhopal, India
2. Department of Physics, Deen Dayal Upadhyaya Gorakhpur University, Gorakhpur, India
3. Optical Nanomaterials Lab, Department of Physics, Maulana Azad National Institute of Technology, Bhopal, India; Department of Physics, Barkatullah University, Bhopal, India