Nlo, beam deflection
In order to fully understand the third order nonlinear optical response of materials under high irradiance excitation it is necessary to study the temporal and polarization dependence of nonlinear refraction and absorption. There are several existing approaches such as Z-scan and pump-probe techniques to determine those responses. As part of this work, these approaches will be briefly outlined before presenting beam deflection, applied from photothermal beam deflection, as an alternative experimental technique to determine the nonlinear refraction with its temporal and polarization dynamics. This technique measures the angle of the probe beam deflected via the index gradient of the material induced by strong excitation beam, to determine both the sign and magnitude of the nonlinear refraction. The temporal and tensor properties of the nonlinear refractive index can be determined by introducing a delay line, and by varying the polarization of the excitation and probe beam, respectively. To demonstrate the practicality of the beam deflection technique, we performed measurements on Fused Silica, Carbon Disulfide and Zinc Oxide. Each of these samples shows quite different nonlinear responses. Amorphous fused silica exhibits nonlinear refraction purely from instantaneous electronic contribution; while Carbon Disulfide shows a much slower response, originating not only from the electronic contribution but also from non-instantaneous nuclear movements (e.g. molecular orientation). These two contributions can be separated by varying the polarization direction of the excitation and probe beam. By introducing lock-in detection technique, a sensitivity of λ/5500 can be achieved. In Zinc Oxide, a wide-bandgap semiconductor, we measure both nonlinear refraction and two-photon absorption simultaneously. Therefore the beam deflection is a sensitive technique, which can be used to measure the time and polarization dynamics of the nonlinear response of the material
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Hagan, David J.
Master of Science (M.S.)
College of Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Masters Thesis (Open Access)
Dissertations, Academic -- Optics and Photonics, Optics and Photonics -- Dissertations, Academic
Münnich,, Matthias, "Beam Deflection" (2013). Electronic Theses and Dissertations. 2654.