Current Research Projects

Interference of Partially-Coherent Light

We have examined Young’s double-slit experiment using a partially coherent light source consisting of a helium-neon laser incident on a rotating piece of white paper.  The resulting interference pattern is observed to disappear and return, depending on the angular size of the source (as expected). Interestingly, while the standard theoretical prediction for the light intensity agrees quite well with experimental data when the fringe visibility is high, the prediction is noticeably off when the visibility is low. A first-principles calculation of the light intensity agrees extremely well with the experimental results for all visibilities.  The research results for this project can be found in the following paper, while a more pedagogical discussion can be found in this article.

High-speed Pulse Shaping

We have constructed an ultrafast pulse shaper capable of rapid pulse switching that also self-characterizes the output pulses.  An acousto-optic modulator (AOM) directs the incoming light to different locations on a two-dimensional liquid crystal display (LCD) located in the Fourier plane of a 4-f pulse shaper.  By programming different pulse shapes onto distinct portions of the LCD, we can rapidly switch between pulses by changing the drive frequency of the AOM.  The output pulses are overlapped with the undiffracted portion of the beam in a spectrometer to automatically characterize the pulses using spectral interferometry.  The device, which is capable of switching rates of up to 100 kHz, is designed for use in quantum-control spectroscopy experiments.  A full description of the device can be found in this article.

Single Photons in the Undergraduate Lab

We use spontaneous parametric downconversion (SPDC) to generate entangled pairs of photons that can be used with a host of experiments aimed at bringing experimental quantum mechanics into the undergraduate curriculum.  A number of senior physics majors have assisted with the development of the experiments, which include proving the photon exists (Grangier experiment), single-photon interference and the quantum eraser, and Hardy’s test of Bell’s inequality.  Many of the experiments are used in our sophomore-level modern physics course.  More details can be seen in the following article.