Recently, transparent conducting oxides such as indium tin oxide and aluminum-doped zinc oxide have been characterized in their epsilon-near-zero crossover regions due to their strong enhancement of light-matter interaction. A newer technique, known as beam deflection, can be used to enable single-detector measurements that characterizes the complex nonlinear refractive index by detecting the angular deflection and transmission of a probe beam. Here we describe two key nonidealities in beam deflection measurements, 1) the spatio-temporal interaction of the beams with a finite relative angular separation, 2) the apparent angular deviation occurring due to strong spatially non-uniform absorption.
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