A new, non-invasive analytical tool has been developed using third
harmonic generation (THG) in pulsed lasers. Scientists from the CNRS
"Centre de physique moléculaire optique et hertziennne"
(CPMOH, Center for Molecular Optic and Radio Physics) have developed
a new type of microscope that can produce a three-dimensional image
of an object by observing third harmonic generation signals following
a laser pulse. The tool is non-invasive, making it ideal for studying
biological systems.
The
instrumentation is based on non-linear optics, an emerging technology,
and uses an ultra short impulse laser that is scanned across a sample
as it is drawn through the focal point of the laser, enabling a three-dimensional
image of the sample to be created as a photo-multiplier picks up third
generation harmonic signals (three times the frequency of the light
of the original pulse) generated at the focal point. The intensity
of the signal depends on the medium traversed and is highly sensitive
to interfaces, and the resolution is about 0.5 mm.
The
microscope has been used to study glial cells, which are of particular
importance in understanding Kreutzfeld-Jakob Disease or Alzheimer's
disease, for example. The diffusion dynamics of intracellular calcium
flow has also been studied and has allowed direct measurement of calcium
flow and migration time. The non-invasive nature of the technique
avoids any complications of added chemicals affecting cell dynamics.
CPMOH
is in discussion with industry regarding further development and applications
of the technique.
