400 nm laser that emits 1-photon-per-second -- possible?

[Green Xenon]

Hi:

 

Is it possible to design and build a laser that emits 400 nm light at the extremely low intensity of 1-photon-per-second.

 

This is one extremely low power laser!

 

 

Thanks,

 

Green Xenon

[calbiterol]

Out of curiosity, why?

[D H]

Something that emits one 400 nm photon per second could not be called a "laser". Lasers emit coherent light. With what is that well-isolated photon coherent?

[swansont]

You'd have to do this by filtering the output.

[Green Xenon]

Out of curiosity, why?

 

Most lasers tend to be high-intensity [all give warning not to stare into]. I was wondering if it is possible to have an extremely-low intensity laser [one which the eye could look right into at close range without experiencing any damage/discomfort]

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With what is that well-isolated photon coherent?

 

The next photon?

[swansont]

Lasers amplify light, by definition — there is gain from stimulated emission. Low intensity is hard to reconcile with that requirement. If all you are getting is the occasional photon, they must be from spontaneous emission events, which means you aren't lasing.

[John Cuthber]

I can't imagine why you would bother but...

Imagine you have a normal dye laser that emits somewhere near 400nm and you tune it with a grating or whatever to exactly 400nm (as near as you want).

This laser will have an output mirror that reflects very nearly all the photons that hit it back into the cavity in order to maintain the oscillation.

Imagine that you coat a bit more silver onto that mirror so it reflects slightly more- the system will still work as a laser. You might have to drop the input power to keep things balanced but that's not difficult.

Keep raising the reflectance of the output mirror and you will get to a point where, on average, you get one photon a second from it.

Pointless, but possible.

[swansont]

I have a hard time with independent spontaneous emission events occurring infrequently enough for that to happen and still consider it a laser.

[Green Xenon]

I have a hard time with independent spontaneous emission events occurring infrequently enough for that to happen and still consider it a laser.

 

Couldn't stimulated emission also result in an intensity of 1-photon-per-second?

 

Also, is it possible to have coherent light [not necessarily a laser] whose intensity is only 1-photon-per-second?

[John Cuthber]

I have a hard time with independent spontaneous emission events occurring infrequently enough for that to happen and still consider it a laser.

 

There would be a vast number of photons bouncing about coherently inside the laser. Almost all lasers act this way; most photons don't get out.