Optical Nonlinearities Relating to Reverse Saturable Absorption Self Defocussing of Divalent Metal Tungstate Based rGO Nanocomposite for Smart Filtering Optical Radiation

Abstract

The thesis briefly describes the fundamental nonlinear optical processes relating to third order effects. Nonlinear absorption and refraction ascribing to the third order effects can be analyzed using a single beam Z-scan technique. The mechanisms like saturable absorption (SA), reverse saturable absorption (RSA), self-focusing and self-defocusing ascribed to third order effects are also discussed. These mechanisms are responsible for smart filtering optical radiation in various courses of materials. In this thesis work different strategies such as ions doping and reduced Graphene Oxide (rGO) based nanocomposite fabrication are employed to elate the nonlinear optical properties of divalent metal tungstates such as CaWO4 and MnWO4. The optical nonlinearities of pristine CaWO4 and rare earth element such as cerium (Ce3+) ions substituted CaWO4 are synthesized hydrothermally. The morphology of Ce3+:CaWO4 reveals dumbbell shaped superstructures shows elevated optical nonlinear properties compared with that of pristine CaWO4. The Ce3+ ions substituted in Ca2+ and the synthesized Ce3+:CaWO4 nanocomposites with rGO are synthesized. This strategy elates the third order nonlinear optical susceptibility. The pristine bimetallic tungstate CaSrWO4 and CaSrWO4 grown on rGO sheets are fabricated newline