Date: Fri Oct 16 09:58:58 2009

Author: --- cbettis

Subject: Re: 1/4 wave plates



Thanks, excellent point.


Quoting "Thomas J. Bauer" :

> Cliff,
> "non-polarized" lasers should really be called "randomly polarized" .These
> lasers tend to have
> more than one mode which each have a different polarization. As the laser
> cavity expands and
> contracts with temperature changed it will drift between the different
> modes.
> Imagine a laser with two modes and polarizations at 90 to each other. When
> both modes are equal
> in intensity the laser appears to be non-polarized. 10 minutes later, only
> one of the modes is active and the laser appears totally polarized,....
> I would use a good polarized laser without the first polarizer, however,
> laser intensity typically
> varies by about 5% over times of 10-20 minutes.
> Tom
> writes:
>> Dale,
>> If you do buy a spatial filter, you could use it with a red HeNe laser
>> to illuminate your polarizers and 1/4 wave plate. If the wavelength is
>> really what you think it is for the 1/4 wave plate, that ought to work
>> nicely and be very visible although not as handy as an OHP for a
>> source. Make sure your laser isn't polarized.
>> Cliff