http://confocal-microscopy-list.275.s1.nabble.com/Near-IR-luminescence-observed-from-Microscope-Objectives-tp4759825p4807804.html
> 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 <
[hidden email]> 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:
[hidden email]]
>> On Behalf Of Arnold Estrada
>> Sent: Friday, 19 March 2010 9:01 AM
>> To:
[hidden email]
>> 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
>>