[Laser] Re: Laser Digest, Vol 11, Issue 10

[wa4qal at ix.netcom.com]

> Message: 7
> Date: Mon, 14 Mar 2005 01:21:17 EST
> From: TWOSIG at aol.com
> Subject: [Laser] Laser Rod
> To: laser at mailman.qth.net
> Message-ID: <13e.ef8c2ed.2f66875d at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
> 
> I saw an ad in Electronic Goldmine for the rods from a military laser range  
> finder.  I think it said that they were pumped by flash tubes.
>  
> The thought came to me that if it was build to be "pumped" by a flash tube,  
> would white LEDs provide the stimulus easier and cheaper than a flash?  
>  
> I really don't know about such things, but I thought it would be worth  
> posting.
>  
> James
> N5GUI

It's VERY HIGHLY DOUBTFUL that this would work.  The instantaneous
energy output from a flash tube is incredibly high (For example, a 50
Watt-Second (aka Joule) tube, which discharges in 1 microsecond,
represents an energy of 50 megaWatts.).  The light output from a LED,
even in pulsed mode, is going to be about 7 or 8 orders of magnitude
less.  The problem is that the older rod type lasers require a population
inversion of the active molecules in order to lase.  This requires a 
certain amount of energy.  And, the amount of energy present from 
even a large array of LEDs is almost certainly going to fall 6 to 8 
orders of magnitude short of the amount necessary to achieve the
population inversion.  

It might be interesting to see what the rods are, though.  The early
flash-tube pumped lasers used ruby rods, and, at one point, this 
temporarily pushed the price of rubies above that of diamonds.  Of
course, many things lase, so it's possible that the rods may be something
else.

Dave
WA4QAL