http://confocal-microscopy-list.275.s1.nabble.com/polarization-and-dichroics-tp7592058p7592071.html
accurate (let's face it, I was plainly wrong). This is what I had in mind:
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>
> Hi all,
>
> Thank you so much Zdenek, Craig, Peter, for the suggestions and
> literature. I'll certainly try some pre-compensation using l/2 and l/4
> waveplates. I don't have the system built yet, so I'm just anticipating the
> difficulties...
>
> Mirrors are problematic too, not so much for (protected?) metallic ones.
> Regarding the 'mirror pair' that we will use for beam co-alignment (as is
> often needed in general optical setups), I was considering making the two
> reflections define orthogonal planes. Like a periscope 'looking to the
> side', so that an s-component reflection in the 1st mirror becomes a
> p-reflection in the 2nd mirror. I guess this compensation strategy is
> either well-known or just wrong. If it would really work, I might even
> consider dielectric mirrors, maybe.
>
> Anyway, thanks for your help.
> Antonio
> i3S, University of Porto - Portugal
>
>
> ----- Original Message -----
> From: "Peter Brunt AVR" <
[hidden email]>
> To: "CONFOCALMICROSCOPY" <
[hidden email]>
> Sent: Thursday, 1 April, 2021 16:21:55
> Subject: Re: polarization and dichroics
>
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>
> Hi Antonio,
> A quick disclaimer- AVR Optics is the research distributor for Semrock in
> the US and Canada.
>
> This is something we have come across in the past from groups working on
> polarization sensitive projects. Due to the nature of interference
> coatings, different polarization states will behave differently as the
> propagate through the coating lasers. This effect can be controlled but to
> a certain degree but this becomes more challenging at 45 degrees versus
> zero degrees for example. For linear states this tends to manifest in the
> form of a simple efficiency change but for mixed states, this can cause
> ellipticity.
>
> One option that we have suggested in the past where you are seeing a
> polarization change as a result of the dichroic is to pre-compensate for
> the polarization prior to the dichroic. If the effect of the dichroic is
> known, then you can work with that to correct the issue. In your case this
> may be challenging as you're also interested in the return state but this
> could be worth exploring.
>
>
> Best Regards
>
> Peter Brunt
> (he/him/his)
>
>
> Peter Brunt (MPhys)
> VP of Sales
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> -----Original Message-----
> From: Confocal Microscopy List <
[hidden email]> On
> Behalf Of Craig Brideau
> Sent: Wednesday, March 31, 2021 3:47 PM
> To:
[hidden email]
> Subject: Re: polarization and dichroics
>
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> To join, leave or search the confocal microscopy listserv, go to:
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>
> Polarization is actually one of my research focuses. The primary dichroic
> in particular can alter your polarization fairly strongly. This is mainly
> an issue if you don't have pure S or P states (+) relative to the dichroic
> surface. Any 45 or -45 content (x) will be likely ellipticized by the
> coating layers, and if you already have elliptical light then it starts
> becoming very complicated. This is problematic as we discovered that under
> certain conditions fluorophores exhibit "interesting" responses to
> polarized light. We actually observed different fluorescence rises with
> calcium concentration using XRhod using different polarization states for
> excitation. This implies that if you use certain polarization states you
> will get significantly different results with your experiment! Here's a
> couple of our papers on the subject, and a couple additional papers on my
> similar work with polarized CARS microscopy.
>
>
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5459219/>
>
>
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8207/82076C/Polarization-dependent-responses-of-fluorescent-indicators-partitioned-into-myelinated-axons/10.1117/12.908976.short>
>
>
https://www.researchgate.net/publication/258711286_Automated_Control_of_Optical_Polarization_for_Nonlinear_Microscopy>
>
>
https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-24/issue-4/046502/Excitation-parameters-optimized-for-coherent-anti-Stokes-Raman-scattering-imaging/10.1117/1.JBO.24.4.046502.full>
> Enjoy!
> Craig
>
> On Wed, Mar 31, 2021 at 11:37 AM Antonio Jose Pereira <
>
[hidden email]> wrote:
>
> > *****
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> posting.
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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 45ยบ, 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
> >
>