Current Research Projects

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.

Detection of Enzyme Binding

In this project we use shaped, ultrafast laser pulses to detect changes in enzyme binding in the biomolecule NADH (reduced nicotinamide adenine dinucleotide) using two-photon absorption.  Lasers pulses are directed into solutions containing either NADH alone or NADH along with the enzyme MDH (malhydrate dehydrogenase), and the fluorescence from each solution is recorded on a PMT.  We find the response of the enzyme-bound form to changes in pulse shape differs from NADH alone, and by examining the ratio of fluorescence we can determine changes in the binding fraction as low as 3%.  We are interested in monitoring changes in the binding in real-time due to modifications in the local molecular environment.  These experiments were carried out during a sabbatical in the lab of Prof. Thomas Weinacht at Stony Brook University.  For more information on this research please see the following 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.