Presents
Light with a twist: simple generation and
applications of light with
orbital angular momentum
Wednesday, February 17, 2016
4:00 PM
F.W. Olin Hall Room 105
2190 E. Iliff Avenue
Presented by
Dr. Mark Siemens
Assistant Professor
University of Denver
Department of Physics & Astronomy
We normally think of light as traveling straight between points in space, but beams of light can
rotate as they travel. In the simplest rotating beams, individual light particles (photons) spin as they
travel and this “spin angular momentum” has been well understood for about 100 years. But less
than 20 years ago, the “orbital angular momentum” form of rotation was discovered that leads to a
“vortex” beam with a helical phase. These crazy-quantum vortex beams have many exciting
applications, including controlling tiny micromachines, measuring star rotation, enabling superhigh-resolution imaging, and allowing communication with theoretically-unlimited bandwidth.
Conventional methods for generating and measuring twisted light involved either expensive and
fixed-wavelength optics or computer-controlled electro-optics such as a spatial light modulator. In
this talk, I will 1.) provide a tutorial explaining the basic concepts of twisted light, 2.) discuss very
simple methods for generating and measuring the orbital angular momentum of light, and 3.) share
our recent questions about possible subluminal speed of twisted light and how this twisted light
interacts with semiconductor nanostructures like quantum dots.
Biography: Dr. Mark Siemens is an Assistant Professor in the Department of Physics and Astronomy at DU. His
research group uses lasers to study important questions related to energy and health, such as understanding energy
transport in nanostructures for improving the conversion efficiency of next-generation photovoltaics. He is the faculty
advisor for the Society of Physics Students, which was recognized as DU’s student organization of the year in 2014,
and won multiple national awards in 2015.
HOST: Dr. Mark Siemens, (303) 871-3541, [email protected]
Join us for refreshments & follow-up discussions in Physics Building Room 116, 5:00-6:00 PM