University of Central Florida

About: University of Central Florida is a education organization based out in Orlando, Florida, United States. It is known for research contribution in the topics: Laser & Population. The organization has 18822 authors who have published 48679 publications receiving 1234422 citations. The organization is also known as: UCF.

Nonlinear refraction and optical limiting in thick media

Abstract: We experimentally and theoretically investigate optical beam propagation in nonlinear refractive materials having a thickness greater than the depth of focus of the input beam (i.e., internal self-action). A simple model based on the "constant shape approximation" is adequate for analyzing the propagation of laser beams within such media under most conditions. In a tight focus geometry, we find that the position of the sample with respect to the focal plane, z, is an important parameter in the fluence limiting characteristics of the output. The behavior with z allows us to perform a "thick sample Z-scan" from which we can determine the sign and magnitude of the nonlinear refraction index. In CS2, we have used this method to independently measure the negative thermally induced index change and the positive Kerr nonlinearity with nanosecond and picosecond CO2 laser pulses, respectively. We have experimentally examined the limiting characteristics of thick CS2 samples that qualitatively agree with our analysis for both positive and negative nonlinear refraction. This analysis is useful in optimizing the limiting behavior of devices based on self-action.

Lost in state space: are preferences stable?*

Abstract: We use field experiments to examine the temporal stability of risk preferences. Over a 17-month period, we elicited risk preferences from subjects chosen to be representative of the adult Danish population. During this period we revisited many of these subjects and repeated a risk aversion elicitation task. We find some variation in risk attitudes over time, but we do not detect a general tendency for risk attitudes to increase or decrease over a 17-month span. The results also suggest that risk preferences are state contingent with respect to personal finances.