Nonlinear Optical Properties of a Photochromic Material

Jha, Natwar (2017) Nonlinear Optical Properties of a Photochromic Material. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Natwar Jha (12MS075)) 12MS075.pdf - Submitted Version Restricted to Repository staff only Download (901kB)

Abstract

Nonlinear optical properties of photochromatic material, bennzodihydropyrene (BDHP) is studied through open aperture z-scan measurement.Specifically, ring formation due to self phase modulation (a particular type of nonlinear optical phenomenon) of laser beam while passing through Photochromic materials has been described briefy. Two different structural isomers of BDHP shows drastic difference in ring patterns in terms of size and number of rings under identical conditions. Origin of this difference is investigated in terms of their linear and nonlinear absorption properties. Linear absorption for the two forms of BDHP shows no difference while nonlinear absorption is very difference. Closed form of BDHP shows either reverse saturable absorption or two photon absorption. Open form od BDHP shows saturable absorption but at higher intensities, this form also shows some amount of either reverse saturable absorption or two photon absorption. Reason behind two different kind of ring patterns is explained in terms of nonlinear absorption and self phase modulation.

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