We did check that by putting a black box on the stage. This wouldn't
eliminate the effect.
On Sat, Mar 27, 2010 at 12:02 AM, Martin Wessendorf <[log in to unmask]> wrote:
> What happens if you remove the transmitted-light condenser?
>
> Vladimir Gukassyan wrote:
>>
>> Hello Arnold,
>>
>> I can just share a similar obervation on our system. We were using
>> multiphoton excitation in the range of 800 and 960 nm when we were
>> trying to calibrate the system for the FCS experiments. What we
>> observed was that there was a signal in case of no sample above the
>> objective, (inverted) there was a well - expressed fluorescence there.
>> However, whenever just a glass slide was put, the signal was
>> diminished almost to the background level. We still don't know what
>> was the exact source of this phenomena.
>>
>> With regards,
>> Vladimir
>>
>> On Fri, Mar 19, 2010 at 1:36 AM, Arnold Estrada <[log in to unmask]>
>> wrote:
>>>
>>> It scales approximately linearly.
>>>
>>> Thanks for a response
>>> -Arnold E.
>>> On Mar 18, 2010, at 11:32 PM, Guy Cox wrote:
>>>
>>> Interesting. Does the luminescence intensity scale linearly or
>>> quadratically with excitation?
>>>
>>> Guy
>>>
>>> -----Original Message-----
>>> From: Confocal Microscopy List [mailto:[log in to unmask]]
>>> On Behalf Of Arnold Estrada
>>> Sent: Friday, 19 March 2010 9:01 AM
>>> To: [log in to unmask]
>>> Subject: Near IR luminescence observed from Microscope Objectives.
>>>
>>> In the process of trying to make phosphorescent lifetime measurements
>>> from a very week signal, I have observed that all of my microscope
>>> objectives seem to luminesce in the near-infrared. My research involves
>>> using two-photon excitation of phosphorescent probes with very small
>>> two-photon action cross-sections. Consequently my excitation source is
>>> a gated Ti:Sapphire (@ 800 nm) such that the excitation reaches the
>>> sample (or objective in this case) for 20 microseconds out of every two
>>> milliseconds. The laser power reaching the objective is about 400 mW
>>> while the gating is on. Using a spectrometer, I have confirmed that
>>> this luminescence extends from ~ 700nm to greater than 850 nm. The
>>> presence of the anti-stokes shifted light implies some sort of
>>> multi-photon absorption mechanism. However, I observe this luminescence
>>> whether the laser is mode locked or not. I have also observed that the
>>> luminescence process appears to have a lifetime of ~ 60-80 uS. Has
>>> anyone else ever observed this? I have observed this with other lenses
>>> (not microscope objectives) as well. Is it possible that the high laser
>>> power used is causing a multi-step absorption process followed by
>>> luminescence from the metal dopants in the high index glass in the
>>> objective?
>>>
>>> Any help would be greatly appreciated.
>>>
>>> ---
>>> Arnold D. Estrada.
>>>
>>> Doctoral Candidate
>>> Department of Biomedical Engineering
>>> The University of Texas at Austin
>>> Biomedical Engineering Bldg, 1.324
>>> 107 W. Dean Keaton Street
>>> Austin, TX 78712
>>>
>>> Office Phone (512) 471-2071
>>> Lab Phone (512) 471-1532
>>> Cell Phone: (512) 731-4298
>>>
>
>
> --
> Martin Wessendorf, PhD (612) 626 0145 (office)
> Associate Professor (612) 624 2991 (lab)
> Dept Neuroscience (612) 624 8118 (FAX)
> Univ Minnesota e-mail: martinw(at)umn.edu
>
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