Re: Coherence length of yellow, green, blue lasers?

From: Sam Goldwasser (sam_at_saul.cis.upenn.edu)
Date: 09/28/04 

Date: 28 Sep 2004 11:28:47 -0400

Michael Koch <astroelectronic@gmx.net> writes:

> Hello,
>
> two questions regarding interferometry with unequal path
> length:
>
> 1. Do yellow 594.1nm and green 543.5nm HeNe laser tubes have
> the same coherence length as red 632.8nm tubes, in the tens
> of meters range?

The coherence length of "other color" HeNe lasers should be similar to red
but none are in the 10s of meters range. Without stabilization, it depends
on the number of longitudienal modes oscillating and the tube length, not
the wavelength. I don't know of any commercial stabilized other-color HeNe
lasers. In principle, you could do your own but it would be a substantial
project.

> 2. Do there exist any blue lasers with coherence length
> bigger than 10 meters? I don't need high power, 1mW is
> enough.

There may be long coherence length blue DPSS lasers and etalon stabilized
argon ion lasers. Nothing inexpensive though if that matters.

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