Date: Wed Oct 14 15:07:05 2009

Author: Bernard Cleyet

Subject: Re: 1/4 wave plates

Post:


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> I get about 30% variation in light intensity with this setup.
> The diode has quite a tail out to about 700nm.

This is why a monochromatic source or "high quality plate is more
useful. My microwave demo doesn't have noticeable variation in
intensity w/ rotation and no fancy electronics necessary. My 1/4
plate was free scrap and a mechanician cut it gratis.

bc thinks making ones own mica plates an educational exercise.

On 2009, Oct 14, , at 08:38, Thomas J. Bauer wrote:

> Hi Dale,
>
> As I recall Edmund sold two different film retarders at the time.
> one was for 640nm and the other was about 800nm?
> They had the wavelengths listed in the catalog. I mounted mine in
> a 1" Newport lens mount. When I looked at the mount this morning
> I see the wavelength I wrote on them is for 640nm.
> I use a 639nm Diode as a light source.
> I set up a polarizer, 1/4 wave plate, to get circular polarized light.
> Then I use a photodide and lockin amp with a chopper to measure the
> light
> intensity as I rotate the analyzing polarizer.
> I get about 30% variation in light intensity with this setup.
> The diode has quite a tail out to about 700nm.
>
> Tom
>


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I get about 30% variation in light intensity with this = setup.
The diode has quite a = tail out to about = 700nm.


This is why a = monochromatic source or "high quality plate is more
useful. My = microwave demo doesn't have noticeable variation in
intensity w/ = rotation and no fancy electronics necessary. My 1/4
plate was free = scrap and a mechanician cut it gratis.

bc = thinks making ones own mica plates an educational = exercise.

On 2009, Oct 14, , at 08:38, = Thomas J. Bauer wrote:

Hi Dale,

As I recall Edmund sold two different film retarders at = the time.
one was for 640nm and = the other was about 800nm?
They had the wavelengths listed in the catalog. I = mounted mine in
a = 1" Newport lens mount. When I looked at the mount this = morning
I see the wavelength I = wrote on them is for 640nm.
I use a 639nm Diode as a light source.
I set up a polarizer, 1/4 wave plate, to = get circular polarized light.
Then I use a photodide and lockin amp with a chopper to = measure
the light
I get about 30% variation in light = intensity with this setup.
The diode has quite a tail out to about = 700nm.

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