1 research outputs found
Photon Correlation Spectroscopy for Observing Natural Lasers
Natural laser emission may be produced whenever suitable atomic energy levels
become overpopulated. Strong evidence for laser emission exists in astronomical
sources such as Eta Carinae, and other luminous stars. However, the evidence is
indirect in that the laser lines have not yet been spectrally resolved. The
lines are theoretically estimated to be extremely narrow, requiring spectral
resolutions very much higher (R approx.= 10**8) than possible with ordinary
spectroscopy. Such can be attained with photon-correlation spectroscopy on
nanosecond timescales, measuring the autocorrelation function of photon arrival
times to obtain the coherence time of light, and thus the spectral linewidth. A
particular advantage is the insensitivity to spectral, spatial, and temporal
shifts of emission-line components due to local velocities and probable
variability of 'hot-spots' in the source. A laboratory experiment has been set
up, simulating telescopic observations of cosmic laser emission. Numerically
simulated observations estimate how laser emission components within realistic
spectral and spatial passbands for various candidate sources carry over to
observable statistical functions.Comment: Paper presented at the conference 'High Time Resolution
Astrophysics', held in Edinburgh, Scotland, September 2007. To appear in
D.Phelan, O.Ryan & A.Shearer, eds.,'The Universe at sub-second timescales',
AIP Conf.Proc., in press, 2008 (American Institute of Physics,
http://www.aip.org/proceedings). 9 pages, 3 figures, 36 reference