Time Resolved Measurement of Optical Nonlinearity in Organic Material Using Beam Deflection Method

Akshay, Raj. R. (2019) Time Resolved Measurement of Optical Nonlinearity in Organic Material Using Beam Deflection Method. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Akshay Raj. R. (14MS025)) 14MS025.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

Measurements to estimate the thermally originated nonlinearity or rather nonlinear refractive index in organic samples using a novel Beam De ection method were carried out. The setup was made using CW lasers and checked the nonlinearity due to the thermal effect in organic materials. Experiments were performed with various samples to check the reliability of the setup. Several sets of optimisation have been done through the course of this thesis work. The setup has been optimised to the best possible way including a Quadrant Photo Diode and digitizer to the setup. We have worked on a solution of organic dye Coumari-153 on ethanol to check the reliability of the new setup and compared it with the value we got form the Spatial Self Phase Modulation (SSPM) technique. The results show high similarity and showed us that the Beam Deflection technique is a powerful and accurate qay to measure nonlinear refractive index like SSPM. After this, we worked with a solution of 2-5 Thiophene Rohdanine on methanol which was showing Polymorphism in the linear optical regime. The main motive to work with this sample was to check whether it is showing any interesting properties in the nonlinear regime too. Part of the thesis work also involve the study of polarisation dependence of the sample via beam deflection method towards the end of the work.

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