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From: mcdonald@uxe.cso.uiuc.edu
Newsgroups: sci.electronics
Subject: Re: Looking for Blue LEDs (Found!)
Message-ID: <44300009@uxe.cso.uiuc.edu>
Date: 25 Sep 88 14:53:00 GMT
References: <1182@nmtsun.nmt.edu>
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Nf-ID: #R:nmtsun.nmt.edu:1182:uxe.cso.uiuc.edu:44300009:000:922
Nf-From: uxe.cso.uiuc.edu!mcdonald    Sep 25 09:53:00 1988



>Frequency multipliers do exist, though.

>One application of their use is to convert  the output of a high power
>laser; eg: a Nd-YAG laser (IR light); to higher frequency, eg, visible light.

>The doubler is grossly inefficient, expensive, and is usable because
>the laser gives off lots of watts (large photon flux so multi photon aborption
>is more probable).  

Doublers are not inefficient. 5 mm long potassium titanyl phosphate

( K TiO PO ) crytsals will double 1.064 micron light with typical
          4

efficiencies of 60 to 75%. With two in series you can get total
90% efficiency. They are expensive ($2700 for a 5x3x3mm crystal).
They do need large powers (say 50 watts to get 60% efficiency).

Multiphoton absorption is to  be avoided like the plague - if it happens,
the crystal EXPLODES! Whoops, $2700 down the drain! 
These things work on nonlinear index of refraction, not absorption.

Doug McDonald