Posted by
Zdenek Svindrych-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/polarization-and-dichroics-tp7592058p7592060.html
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Hi Antonio,
I never got all the way to actually doing polarization experiments, but I
once used (literally once) some software (FilmStar) to see how interference
filters change polarization. It might not be that useful for you since you
don't know the prescription for the dichroic in question, but you may ask
the manufacturer...
One trick I've seen in some paper (can't find it now) is that the light
passes through two identical dichroics, one at 45° combines/splits the
emission and excitation, and the other one at -45° compensates the
polarization effects of the first one... But i can't really tell how severe
these effects are in the first place.
Another option would be a low incidence dichroic, but that may limit the
useful field of view due to geometrical constraints. Note that at zero aoi
(normal incidence) the interference filter will cause wavelength-dependent
group delay and what not, but no polarization effects, as there is no
preferred axis.
Or, if you can separate the excitation and emission spatially at some
point, you can use 100% mirrors. Alternatively, something like this (
https://drive.google.com/file/d/1OtdjLG31ZhTfTker4XAkis12DIR2dMcl ) - I
don't know what to call it, a "holey mirror"? - might work. This one is
from a dual-cuvette spectrophotometer - spectrally flat and no polarization
effects on transmission, as the light (or 50% of it) is passing through
empty space!
Best, zdenek
On Wed, Mar 31, 2021 at 1:37 PM Antonio Jose Pereira <
[hidden email]> wrote:
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>
> Hi all,
>
> I'm resorting to those of you who are experienced with anisotropy
> measurements or polarization optics in general. I might need a long-pass
> dichroic beamsplitter at 45º, but where the longer wavelengths
> (fluorescence) will pass through the dichroic backwards. I mean that light
> from the source is to be reflected, whereas the fluorescent light is to be
> transmitted back to the source. Polarization preservation upon reflection
> is not important for me, but preservation upon (backwards) transmission is.
>
> I reckon that taming polarization states with dichroics (and virtually all
> optical elements) is already an issue. I wonder how much more it will be by
> using the dichroic in such geometry.
> Or maybe there other optical elements better suited for this purpose?
>
> Thanks in advance for any comment or suggestion,
> Antonio
>
--
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Zdenek Svindrych, Ph.D.
Research Scientist - Microscopy Imaging Specialist
Department of Biochemistry and Cell Biology
Geisel School of Medicine at Dartmouth