Physics Fall 2019 Seminar Series: Tim Thomas
Monday, November 18, 2019 - 3:15pm

“Introduction to Gemstone Optics,” or “Optics of Bling,” will cover the basic elements of gemstone optical performance.   Colored gems absorb light at various wavelengths to produce the color we see, or disperse it to produce the flashes observed in faceted diamonds.  The type of light, such as indoor or outdoor lighting, as well as how the stone was cut can make a substantial difference in the beauty of the gemstone.  The presentation will cover gemstone sample orientation for spectroscopic purposes, spectroscopy of gemstone materials, leading to how we calculate what the expected color will be.  Knowing the color, the approximate optical path in the gem, and the absorption cross-section for the color centers in a gem, it is possible to approximate the chemical concentration of the color centers.  Also discussed are total internal reflection, pleochroism, birefringence, and dispersion…along with pretty example photos.

Tim Thomas is a Portland State University alumni with an undergraduate degree in mechanical engineering, a master of science degree in electrical engineering from the Oregon Graduate Institute of Science and Technology, and is a graduate gemologist.  He is the director of engineering for Applied Materials at the laser facility in Hillsboro, Oregon, and prior to that was the technical director for optical systems at the Gemological Institute of America (GIA).

Date: November 18th, 2019

Time: 3:15pm

Location: SB1-107

Event is free and open to the public.