http://confocal-microscopy-list.275.s1.nabble.com/Shearing-Interferometer-with-Ti-Sapph-tp7585684p7585688.html
> Am 21.09.2016 15:21 schrieb
[hidden email]:
>> ***** To join, leave or search the confocal microscopy listserv, go
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>> posting. ***** Hi Tim,
>> no experience with shearing interferometry, but few thoughts:
>> As pointed out, 100 fs pulse has 'physical length' (s=c*t) of some 30
>> um. With the mentioned interferometer (more than 20 mm path difference
>> according to Thorlabs specs!) you end up with two copies of the pulse
>> separated by 70 ps. They will only interfere if you watch them through
>> extremely narrow-band filter (just a theory, probably not practical at
>> all).
>> Even in CW, as suggested by Mark (not all Ti:saphs can be easily
>> forced to CW) the coherence length may not be enough to see fringes,
>> depending on the laser.
>> One solution would be zero path difference interferometer, which can
>> be constructed with common path geometry:
>>
http://www.sciencedirect.com/science/article/pii/S0030402605002226>>
>> But I'm not aware of it being available commercially.
>> There are other options to measure collimation, like wavefront sensors
>> (quite costly) or watching the far field of the beam (needs lots of
>> space or some already collimated optics)...
>> Good luck!
>>
>> --
>> Zdenek Svindrych, Ph.D.
>> W.M. Keck Center for Cellular Imaging (PLSB 003)
>> University of Virginia, Charlottesville, VA
>>
http://www.kcci.virginia.edu/>> tel: 434-982-4869
>> Annual FRET Workshop:
http://kcci.virginia.edu/workshop-2017>>
>> ---------- Původní zpráva ----------
>> Od: Joshua Vaughan <
[hidden email]>
>> Komu:
[hidden email]
>> Datum: 21. 9. 2016 0:40:55
>> Předmět: Re: Shearing Interferometer with Ti-Sapph
>>
>>> ***** To join, leave or search the confocal microscopy listserv, go
>>> to:
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>>> images on
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>>> posting. *****
>>>
>>> Here's a shot in the dark here for you, since I have never tried
>>> doing what you asked about.
>>>
>>> Short pulse lasers only interfere over a short distance called their
>>> coherence length. It might only be 10-30 microns or so depending on
>>> the laser's bandwidth. If the path length difference of the two
>>> interfering beams is more than this 10-30 microns, then no fringes.
>>>
>>> If the interferometer works by beam 1 reflecting off the front of
>>> the glass wedge (going through no glass) and beam 2 reflecting off
>>> the back surface of the glass at a little different angle (going
>>> through the glass twice), then the optical path length of beam 2 is
>>> quite a bit more than that of beam 1. Probably by much more than
>>> 10-30 microns since the wedge is probably at least 1 mm thick where
>>> you use it. I would guess no fringes.
>>>
>>> Basically, I am asking whether your interferometer is designed for
>>> short pulse lasers. I bet the Thorlabs folks could weigh in on it if
>>> you email them.
>>>
>>> Anyway, isn't it easier to check collimation by shooting the beam
>>> across the room and checking the diameter is constant?
>>>
>>> On Tue, Sep 20, 2016 at 9:07 PM, Tim <
[hidden email]> wrote:
>>>
>>>> *****
>>>> To join, leave or search the confocal microscopy listserv, go to:
>>>>
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>>>> Post images on
http://www.imgur.com [2] and include the link in
>>>> your posting.
>>>> *****
>>>>
>>>> Hello, we recently purchased a shearing interferometer from
>>>> Thorlabs (Part # SI254) to test collimation after beam expansion
>>>> in our two-photon microscope setup. The strange thing is we cannot
>>>> seem to get an interference pattern either before or after beam
>>>> expansion (varying the distance between the lenses in the beam
>>>> expander). We do see the pattern clearly if we try on a simple
>>>> laser diode. Does anyone have experience looking at the shearing
>>>> interferometer pattern with a Ti-Sapphire laser or have any ideas
>>>> what may be causing our problem?
>>>>
>>>> Thanks for any help,
>>>> Tim
>>>
>>> --
>>>
>>> Joshua C. Vaughan
>>>
>>> Assistant Professor
>>> Department of Chemistry
>>> Box 351700
>>> University of Washington
>>> Seattle, WA 98195
>>> 206-543-4644
>>
>>
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