Re: Near IR luminescence observed from Microscope Objectives.

Posted by Guy Cox-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Near-IR-luminescence-observed-from-Microscope-Objectives-tp4759825p4761120.html

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

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