Experiments with Downconverted Photons: The Quantum Nature of Light

Naomi Courtemanche

Advisor: Dr. Enrique Galvez

This project investigates the wave-particle duality of light. Using a BBO crystal, pairs of single photons are generated using parametric downconversion. These photons observe the laws of conservation of momentum and energy. By rotating the crystal, the degenerate beams are separated and detected using avalanche photodiodes. Placing a lens in the path of each beam and displacing detectors both horizontally and vertically maximizes coincidence rates to approximately 260 counts per second. One beam is passed through a Mach-Zehnder interferometer. By changing the lengths of the two paths of light in the interferometer, an interference pattern is sought, thus demonstrating that single photons interfere with themselves.