1. Department of Physics, School of Science, University of Management and Technology, Lahore, Pakistan;
2. Optics Laboratories, Nilore, Islamabad, Pakistan;
3. Nanosciences and Technology Department, National Centre for Physics, QAU Campus, Islamabad, Pakistan;
4. Department of Experimental Physics, National Centre for Physics, QAU Campus, Islamabad, Pakistan;
5. Department of Physics, Islamia College, Peshawar, Pakistan;
6. Department of Nanosciences and Technology, National Centre for Physics, QAU Campus, Islamabad 45320, Pakistan