1. Fiber Optics and Photonics Division; CSIR-Central Glass and Ceramic Research Institute; 196, Raja S. C. Mullick Road Kolkata 700032 India
2. Centro de Investigaciones en Optica; Loma del Bosque 115; Col. Lomas del Campestre; Leon 37150 Guanajuato Mexico
3. Electron Microscopic Section; Material Characterization Division; CSIR-Central Glass and Ceramic Research Institute; 196, Raja S. C. Mullick Road Kolkata 700032 India