2015 BFY II Abstract Detail Page

Previous Page  |  New Search  |  Browse All

Abstract Title: W19 - Using an LED as a Low-Efficiency Single Photon Avalanche Diode
Abstract: In this experiment, a very inexpensive GaP light-emitting diode (LED) is reverse-biased and used to detect individual photons. In this mode, the LED behaves as a Geiger-mode avalanche photodiode, albeit one with an extremely low quantum efficiency. Students construct a simple op-amp circuit that lets them control the time constant of the circuit, the height of the output pulse, and a user-controlled discriminator. The experiment is simple and inexpensive, but very rich in interesting physics for students to explore, and can be appropriate for electronics, optics, semiconductor, and advanced lab courses. Students can investigate the statistics of random (or nearly random) events, diode and avalanche diode behavior, as well as the temperature and spectral sensitivity of the device. The experiment could be used as a 'safe' introduction to single-photon detection, before students use expensive, and much more sensitive commercial sensors.

The LED, comparator, resistors and potentiometer used in this experiment all total to less than $2 per setup. However the standard lab equipment required includes: a basic breadboard, three DC regulated power supplies (5V, 15V, 0-30V), a 2 channel oscilloscope, and a way to count pulses and the time between pulses. The latter device could be a Vernier LabQuest interface, National Instruments LabView and DAQ, a pulse counter/interval timer similar to the one sold by TeachSpin ($650), or any similar device.
Abstract Type: Workshop

Author/Organizer Information

Primary Contact: Lowell McCann
University of Wisconsin – River Falls

Workshop Documents

Workshop Doc 1: Download the Workshop Doc 1
Workshop Doc 2: Download the Workshop Doc 2
Workshop Doc 3: Download the Workshop Doc 3
Workshop Doc 4: Download the Workshop Doc 4