FW: notch dichro=?iso-8859-1?Q?=EFc?= filter: does it exist?

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FW: notch dichro=?iso-8859-1?Q?=EFc?= filter: does it exist?

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*** Commercial Response***

Dear Christophe,

I agree with the following comments from John. One of the primary reasons for the
(standard catalog) unavailability of such notch dichroics is the lack of significant
interest from the customers. However, in terms of technical capability, it is possible
to offer the following notch filter. For example, Semrock has a catalog notch dichroic
that has high transmission between 350 nm to 1600 nm and a notch at 1064 nm
(NFD01-1064-25x36 ).

Also, I would like to add to John's comment on the recommendation of "angle tuning" a
standard normal incidence notch filter. For example, Semrock's NF03-514E-25, when angle
tuned to 31 degrees, the notch shifts to 491 nm (at normal incidence the notch is at 514
nm).

You should be able to verify the compatibility of this filter by generating the angle
dependent filter spectrum using the "MyLight - Model Data" tool (blue button) located at
the top right of the filter spectrum page. This tool can be used to generate the
theoretical filter spectrum as a function of polarization, angle of incidence, cone half
angle, and wavelength range.  As you will notice using this tool, when the angle of a
filter is changed from normal incidence to a higher angle, the edge shifts to a shorter
wavelength.

I will be happy to discuss this further offline.

Sincerely,
Prashant

Prashant Prabhat, Ph.D.
Applications Scientist

Semrock, Inc
3625 Buffalo Road, Suite 6
Rochester, NY 14624
Direct: (585) 594-7064
Cell: (585) 520-8602
FAX: (585) 594-7095
[hidden email]





-----Original Message-----
From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of
John Oreopoulos
Sent: Wednesday, November 30, 2011 9:42 AM
To: [hidden email]
Subject: Re: notch dichroïc filter: does it exist?

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Christophe, it's a good question. I'm not sure why there are so few "notch dichroic"
filters, but I imagine it is because the filter companies don't get a lot of requests
for optics like that. Think about it, the dichroics are usually intended to pass
broadband light (usually fluorescence) to a detector, and the idea is that you would
have also used an exciter and emission filter (positioned normal to the direction of
light) to pass and block the laser light respectively.

Dichroic mirrors are used in laser engines to combine laser beams into one light path,
but long pass and short pass mirrors can be used in succession if your arrange your
lasers in increasing or decreasing wavelengths, so you don't need a notch filter here
either.

Having said that, you can use a notch filter intended for normal incidence of light at
some non-zero incident angle, but the position of the notch band with shift up or down
the spectrum depending on how you turn it, and the transmission efficiency will lower.
There are some newer filters that actually are intended for variable incident angles of
light, though. For example, you could use a filter like this from Semrock (no commercial
interest):

http://www.semrock.com/FilterDetails.aspx?id=TBP02-440/16-25x36

I think Chroma and Omega Optical (no commercial interest) might also make something
similar. Turn this filter about 45 or 50 degrees, and arrange your light sources such
that the arc lamp reflects off the mirror (instead of transmitting) and position your
laser so that it transmits straight through. I think this would do what you want it to
do.

John Oreopoulos
Research Assistant
Spectral Applied Research
Richmond Hill, Ontario
Canada
www.spectral.ca


On 2011-11-30, at 8:32 AM, Christophe Leterrier wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
>
> Hi, 
>
> On a widefield/FRAP setup, I want to combine a laser at 491 nm (fiber coupling) with
an HBO xenon lamp (direct mount) on the back of my scope. The way things are arranged, I
need to put a 45° dichroic mirror so that the lamp light will go through the mirror into
the scope and the laser light will be reflected into the scope. So I'm looking for a
dichroic mirror that would transmit everything (from 400 to 750) but a small window
arround 491 nm. The window has to be narrow so that I don't loose too much GFP
excitation light from the lamp. Is that kind of dichroïc available? I could'nt find one
browsing Chroma or Semrock offers. Of course there is the option of having a custom one
made, but I was wondering if someone had a link to an existing offer.
>
> On a related note, I found lots of notch filters but not a lot of notch dichroics.
What is the difference between a simple filter and a dichroic? What happens to the
blocked light in the case of a filter, isn't it also reflected like for a dichroic?

>
> Thanks for your help,
>
> Christophe
>
> --
> Christophe Leterrier
> Postdoc
> INSERM UMR641 // Ionic channels Lab
> IFR Jean Roche, Mediterranée University
> Marseille, France
> http://www.cleterrier.net

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