Manhattan Professor and Student Develop Ways
to Measure Property Changes of Optical Materials
When optical materials are subject to cold and heat their properties can change. This impacts the performance of all types of optical instruments, such as cameras telescopes and lasers, to name a few. Dr. Bruce Liby, associate professor of physics and chair of the physics department, and his student Ryan Scholl ’09, are developing ways to measure these changes. One important parameter is the index of refraction, which affects how light propagates through a medium. Liby and Scholl measure refractive index temperature dependence by using a method they developed in the Hayden Hall laboratory.
The pair constructed a novel dual-optical interferometer, which produces measurable optical interference fringes by splitting and recombining beams of light, measurable optical interference fringes. These fringes are patterns of dark and light that can be recorded as they cyclically shift when the sample material is heated or cooled. The team uses a frequency-stabilized Helium-Neon laser to provide light to probe the materials. The interferometer is constructed with mirrors, beam splitters, polarizers, lenses and an optical chopper. The data is collected with the Labview data acquisition system.
Accurately counting the net optical fringes produced in an interferometric system of this sensitivity is a major challenge. To better count the fringes, Scholl, as part of his senior thesis, is developing a photodiode-based fringe detection system to reveal the position of fringes over time.
Liby and Scholl have worked on this project and related research since March 2007. Scholl received an Undergraduate Summer Student Research Award from the Dean’s Council of the school of science for 2007 and 2008. The team presented their earlier work at a undergraduate research conference at CUNY called Einsteins in the City 2. More recently, their manuscript was accepted for publication in The Physics Teacher. They hope to publish the results of additional research in 2009.
