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This list shows seminars for May 19 only. [Show all events]
EECS SEMINAR: "Development of a High Power Sum-Frequency Sodium Laser for ‘Laser Guide Star’ Appl.
Monday May 19, 2008 at 11:00 AM — Technological Institute - Room L324
EECS Seminar
Dr. Renu Tripathi
Palomar Observatory at Caltech
“Development of a High Power Sum-Frequency Sodium Laser for ‘Laser Guide Star’ Application”
Adaptive optics (AO) systems require a reference source in order to correct for the atmospheric distortion of light. Sufficiently bright stars are not available in all parts of the sky, which limits the usefulness of natural guide star adaptive optics. However, one can create an artificial guide star by shining a laser into the atmosphere. Lasers that can excite the D2 line in sodium (Na) atoms present in the mesosphere (about 50 km to 80-90 km altitude above Earth's surface) are of significant interest to the astronomical scientific community. The return signal received from backscattering serves as an artificial bright star. When imaged through a ground-based telescope onto a wavefront sensor, this provides a dynamic map of the atmospheric distortion or turbulence. This information is then used to adaptively correct the phase errors through feedback onto deformable mirrors used in the telescope to significantly improve their resolution.
During the talk, I will discuss my efforts to develop a high power sum-frequency sodium laser system based on sum-frequency mixing of two (1064 nm and 1319 nm) diode-pumped, pulsed and mode-locked Nd:YAG lasers. I will describe my continued effort in improving the system to obtain higher average optical power by virtue of better cavity design, efficient mode-locking and nonlinear wave-mixing. Currently, the laser operates with an average power of 8W at 500 Hz repetition rate and with 10% duty cycle. I will show the critical component development in the laser system and briefly discuss the projection from the launch telescope, laser beam quality and the photon number density in the return signal. I will also show some early results obtained using the table-top laser system operating in conjunction with the adaptive optics (AO) system at the Caltech’s Palomar observator
Event URL: http://www.eecs.northwestern.edu/events/
For more information, contact:
Brooke Hildebrand
brooke@eecs.northwestern.edu
847-491-3451
Electrical Engineering & Computer Science
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