Natural lasers

[Loren Booda]

Besides manmade lasers, from what phenomenon might the coherent light of naturally occurring lasers originate?

[Kane O'Donnell]

It just takes stimulated emission to get two coherent photons. However, to get *heaps* of coherent photons (ie a laser beam) requires some very careful construction. It is unlikely that there are many natural environments in which there is both some gain medium with a sustained population inversion and a stable cavity resonator.

I have been told, however, that the CO2 atmosphere of Mars sustains a population inversion significant enough such that if one established a cavity in the atmosphere (with mirrors) you would get an insta-laser. :smile:

Of course, the academic in question may have been pulling my leg...

Kane O'Donnell

[Pieter Kuiper]

Stimulated emission is observed in the microwave region by radio astronomers. You can google for "maser spots".

[somy]

see it:
http://home.achilles.net/~ypvsj/news/MWC349.html

[Dr Transport]

The only natural source of "partially" coherent light that I know of is starlight. Optical coherence theory says that farther away from a source the more coherent the light becomes. This is why we can do interometry experiments with starlight.

[Pieter Kuiper]

Starlight has good _transverse_ coherence. But it lacks the longitudinal or time-coherence (narrow linewidth) that is characteristic of a laser.

[meteor]

there's some speculation about the existence of laser stars , stars that can emit laser radiation naturally. the idea of lasers stars was proposed by Varshni in the mid 1970s. The laser star hypothesis implies that all or the most part of quasars are laser stars

[NateTG]

I believe that there are 'cosmic masers' which are essentially large excited gas clouds which amplify radio signals that go through them.

There was also speculation that part of the earth's atmosphere (ionosphere?) could get exited by solar radiation, and act as a laser with radio signal.

[meteor]

I believe that there are 'cosmic masers'

Another related concept is the so-called "Megamaser galaxies"

[Creator]

Besides manmade lasers, from what phenomenon might the coherent light of naturally occurring lasers originate?

Mars Pathfinder discovered a single pass natural CO2 laser in the Martian atmosphere. Mechanism described here with references:
http://home.achilles.net/~ypvsj/history/mars.html :bugeye:

Creator