Observations of Parametric Fluorescence and Oscillation in the Infrared

Measurements of infrared optical parametric fluorescence are reported for the first time. Using a pump wavelength of 1.064 µ in LiNbO_3 , observations of the fluorescence power, bandwidth, and angular dependence at 1.63 µ are in good agreement with a plane-wave theory. The operating characteristics of two pulsed, internal, doubly resonant parametric oscillators are also reported and compared with predictions of the fluorescence measurements. With measured thresholds on the order of 400–700 W, the two oscillators provided nearly continuous tuning from 1.51 µ to 3.55 µ with average powers of 6 mW and peak powers of 600 W. These powers represent available pump conversion efficiencies of 10% and 50%, respectively. Oscillating bandwidths were only 10% of the fluorescence bandwidth and ranged from 1.7 cm^(-1) to 45 cm^(-1), depending on the output wavelength. Longitudinal mode structure and multiple pulsing of the oscillators were observed

Utilizing public scientific web lectures to teach contemporary physics at the high school level: A case study of learning

This paper describes a teaching experiment designed to examine the learning (i.e., retention of content and conceptual development) that takes place when public scientific web lectures delivered by scientists are utilized to present advanced ideas in physics to students with a high school background in physics. The students watched an exemplary public physics web lecture that was followed by a collaborative generic activity session. The collaborative session involved a guided critical reconstruction of the main arguments in the lecture, and a processing of the key analogical explanations. Then the students watched another exemplary web lecture on a different topic. The participants (N=14) were divided into two groups differing only in the order in which the lectures were presented. The students’ discussions during the activities show that they were able to reason and demonstrate conceptual progress, although the physics ideas in the lectures were far beyond their level in physics. The discussions during the collaborative session contributed significantly to the students’ understanding. We illustrate this point through an analysis of one of these discussions between two students on an analogical explanation of the Aharonov-Bohm effect that was presented in one of the lectures. The results from the tests that were administered to the participants several times during the intervention further support this contention