Re: A list of textbook miscon: spatial coherence

[John Gastineau <gastineau@mindspring.com>]

At 02:23 PM 2/13/98 -0500, SCIAMANDA@edinboro.edu wrote:

> (At these wavelengths, even the frequency selectivity of the resonant 
> cavity is not the main contributor to temporal coherence (linewidth).)

Are you saying that a laser linewidth is not determined by the cavity?
In a standard HeNe classroom laser, the linewidth of the emitted light
is a small fraction of the Doppler-broadened spectral profile of the
neon atoms in the laser. In fact, for typical sizes of laser tubes, 25
or 30 cm long, two or three cavity resonance modes fall within the
Doppler profile. The line width for these lasers is determined almost
entirely by the Finesse (technical term) of the mirrors. 

JEG


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