CHEMISTRY & BIOCHEMISTRY
Lasers and Materials:
How Do They
Interact?
By John Toon
A NEW RESEARCH LABORATORY launched recently at the Georgia Institute of Technology will use the latest in laser analytical techniques to study how photons interact with materials of all types, including the human body.
Equipment in the Georgia Tech Laser Dynamics Laboratory
can study phenomena that occur in as few as 100 femtoseconds -- the
time required for light to travel the width of a human hair.
|
The Laser Dynamics Laboratory, supported in part by funds from the National Science Foundation (NSF), will provide a shared resource for researchers, encourage collaboration across disciplines and facilitate the use of laser spectroscopic techniques in new areas of study, says director Dr. Mostafa El-Sayed.
"We are establishing collaborative programs in many research areas in which lasers interface with materials," he explains. "We know about photons and what they will do. We want to extend that knowledge into other applications that are helpful to us and to other researchers. This combination of expertise from different areas can lead to many new developments."
Part of Georgia Tech's School of Chemistry and Biochemistry, the Laser Dynamics Laboratory operates a series of laser systems and related analytical equipment configured for use in spectroscopic techniques. The equipment can study phenomena that take place in as short a time scale as 100 femtoseconds -- the amount of time required for light to travel the width of a human hair.
Such analytical techniques can be used to investigate a wide range of phenomena, including the dynamics of molecular dissociation, energy relaxation and transformation; molecular mechanisms of the primary processes of photosynthesis; and electronic and energy transport in various materials ranging from nanoparticles to disordered solids to photobiological systems.
El-Sayed says the facility would be of interest to researchers studying the detailed structural changes in molecules or materials following linear or non-linear laser excitation in the 100 femtosecond to millisecond time domain. The laser-induced changes can be followed by observing the optical absorption, fluorescence, Raman or infrared spectra of the transients.
At Georgia Tech, the new facility could boost existing research into the properties of optical, electro-optical and non-linear optical materials -- key technologies in developing new generations of fast optical switches, new memory devices, and techniques useful in interfacing high-bandwidth optical systems to computers.
"This adds to Georgia Tech a facility that can measure the properties of materials using lasers, which is one of the most important capabilities today," El-Sayed explains. "As we get deeper and deeper into studying materials and their application to the field of communications, this will become more important."
But while study of inorganic materials may provide the laboratory's primary near-term benefit, El-Sayed believes laser spectroscopic techniques also offer great long-term potential in the diagnosis of human disease processes. There, unique "signatures" of cancerous tissue or disease organisms could provide physicians with immediate diagnosis without the need for time-consuming laboratory clinical analytical techniques.
El-Sayed expects the new research laboratory, built with NSF and Georgia Tech support, will encourage collaboration and help researchers make efficient use of the costly laser equipment, which is already used extensively in his own research program. This availability also could encourage research into new areas where these analytical techniques are helpful to understanding complex issues.
"At a time when national resources are limited, a facility like this will help stretch the ability [of] researchers to get their work done and allow them to study these phenomena without having to invest in their own laser equipment," he explains.
Systems and techniques available at the laboratory include transient optical absorption spectroscopy, time- resolved Raman Spectroscopy, time-resolved IR spectroscopy (TRIR), time-resolved Fourier Transform Infrared (TRFTIR) spectroscopy, fluorescence spectroscopy and time-correlated single photon counting.
Available equipment includes:
A Clark-MRX Amplified Ti:sapphire system that pumps two
Quantronix TOPAS-POP, producing two femtosecond pulses each with a
wavelength that can be changed independently from the UV to the infrared
range.
An Antares/Satori coherent picosecond system and a
SpectraPhysics MOPO 730 nanosecond laser that can provide wavelengths in
the UV to the infrared range.
A flash photolysis system combining laser pumping and Xenon
flash or CW lamps for time-resolved spectral measurements in the
nanosecond to millisecond time scales.
A Bruker time-resolved FTIR system is available to measure
changes in IR spectra in the nanosecond to millisecond time range.
The laboratory was formally inaugurated with a symposium and open house in late November 1996. El-Sayed holds the Julius Brown Chair in chemistry and is editor-in-chief of the Journal of Physical Chemistry, a publication of the American Chemical Society.
Further information is available from Dr.
Mostafa El-Sayed, School of Chemistry and Biochemistry, Georgia
Institute of Technology, Atlanta, GA 30332-0400.
Send questions and comments regarding these pages to Webmaster@gtri.gatech.edu
Last updated: May 30, 1997