2010 CAP Congress - University of Toronto (Toronto, Ontario)

Toronto, Ontario

Year: 
2010
Date: 
June 7, 2010 - June 11, 2010
Venue: 
University of Toronto
Past Congress
Attendance: 
855
Keynote Speaker: 
Dr. Charles Townes, University of California at Berkeley
Keynote Title: 
50th Anniversary of the Laser

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 2010 Congress poster

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Abstract for Herzberg Public Lecture :

CHARLES TOWNES, UNIVERSITY OF CALIFORNIA AT BERKELEY

50th Anniversary of the Laser

In the early 1950s I thought and worked hard at trying to find a way to obtain an oscillator for frequencies higher than those available from known electronics, in order to do very high resolution spectroscopy. Finally, I suddenly had the idea to put enough excess atoms or molecules in an upper state, and provide stimulated emission. My student Jim Gordon and I made this work first in the microwave range, primarily as a test. The resulting maser (for microwave amplification by simulated emission of radiation) generated an exciting field and many people jumped into it to make microwave oscillators and amplifiers. But after a few years I pushed myself to move on to much shorter wavelengths. Arthur Schawlow and I then wrote a paper on how such stimulated emission oscillators could be produced at wavelengths as short as those of light – we called it an optical maser, but it soon was renamed the laser (light amplification by stimulated emission of radiation). After publication of our theoretical discussion, many scientists were excited and the first working system was made by Theodore Maiman at the Hughes Labs, a pulsed ruby laser. The first continuously oscillation system was made by one of my former students, Ali Javan, with Wm. Bennett and Don Herriot at the Bell Telephone Labs. Industry by then recognized the importance of this field, and all the first lasers were built in industrial labs. Lasers are now a wonderful field for science and for a wide variety of technical applications -- all an outgrowth of spectroscopy, a field Herzberg helped develop importantly.

I presently use lasers to do infrared interferometry on stars with three separate telescopes. Lasers have helped astronomy in many ways, in particular producing a rapid growth of interferometry for measurement of stellar sizes and shapes. Our interferometer is the only one, however, which uses heterodyne detection, provided by laser local oscillators, which hence allows interferometry in very narrow bandwidths which can avoid spectral lines due to surrounding gas. This allows measurement of old and active stars quite directly, without interference from their emitted gases. I will report some of the measurements, showing the changes in size of some stars, the dust shells they have blown off and expansion of these shells, along with other details not seen until such techniques became possible.