On Wednesday, September 11, 2013 3:58:24 PM UTC-4, Samuel M. Goldwasser wrote:
writes:



On Tuesday, September 10, 2013 5:36:41 PM UTC-4, Roger wrote:

"Cydrome Leader" wrote in message ...

snip

Shaun

Hi Shaun, Certainly the beam profile is better in a HeNe.



I'm not sure what you mean by 'more coherent', but for the few diode lasers I've looked at - compared to the short cavity HeNe that I have, the diode lasers had a longer coherence length.

(Which struck me as a bit weird the first time I saw it... I had this mistaken belief that the coherence length was related to the cavity length.)

I'm not sure if the long cavity HeNe's have a longer or shorter coherence length when compared to the short cavities... Perhaps Sam will educate us.



George H.
It's a crap shoot. Some diodes have exception coherence length but
many/most are very short.

OK that's good to know. It'd be nice if someone had a list of good diode lasers. The one we use is from US lasers M650-5I. ~$33 from digikey. We have a couple of others but I never looked at the coherence length.

George H.



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