Frequency Combs Advance Biomedicine
DENVER, June 15, 2012 — Laser frequency combs, first a curiosity but now a practical research tool, are moving beyond physics and optics to advance biomedicine by helping evalulate a novel instrument that kills harmful bacteria without liquid chemicals or high temperatures.
Generated by ultrafast lasers, frequency combs precisely measure individual frequencies of light. As with many new measurement tools, the laser frequency comb seemed at first an oddity but has found more practical uses than originally imagined. Researchers at JILA, operated jointly by the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder, are using such a comb to identify specific molecules in gases based on which frequencies, or comb "teeth," are absorbed by the gas, and in what amounts.
These comb measurements help explain, for the first time, how his sterilization technique inactivates bacteria, said Mark Golkowski, assistant professor of electrical engineering and bioengineering at the University of Colorado at Denver, and will help clinics address the growing problem of multidrug-resistant bacteria.
This apparatus is a key part of the JILA frequency comb instrument
used to measure trace gases for biomedical applications. The beam from a
powerful fiber laser is converted by a special crystal and other optics into
two lightwaves at lower frequencies. The system can detect and measure the
concentration of many different molecules based on how they absorb mid-infrared
light. (Image: JILA)
The extremely sensitive instrument "also yields information about the interaction dynamics, since many molecules can be simultaneously observed on short time scales," Golkowski said.
Golkowski and colleagues conducted a variety of tests with an instrument that delivers an air stream of free radicals — highly reactive molecules — to quickly kill bacteria up to three meters away. The system achieved high-level disinfection of Staphylococcus aureus (a cause of pneumonia and other diseases) and Pseudomonas aeruginosa (often found on medical equipment) on surfaces such as plastic ID badges — a major source of pathogen transmission. The method also proved effective against difficult-to-eradicate spores of Bacillus atrophaes (found in soil) and biofilms of Escherichia coli (E. coli, a cause of food poisoning).
The remote sterilization system kills bacteria as quickly as competing treatments that use bulky and expensive equipment, while also offering the advantages of low-cost hardware and flexibility of application, according to the team.
JILA/NIST Fellow Jun Ye and two members of his research group used one of their frequency comb systems to measure the concentrations of reactive molecules in the airstream-ozone, hydrogen peroxide, nitrous oxide and nitrogen dioxide. He and his team also generated the first extreme -ultraviolet laser frequency comb (See: EUV Frequency Comb Debuts).
Measuring hydrogen peroxide is important because the presence and concentration of this chemical is key to effective sterilization. But the comb technique also captures the complex chemical reactions in the sterilization system in real time.
"The multiple and simultaneous reactions make numerical modeling of the chemical dynamics difficult; hence the need for direct measurement of simultaneous concentrations, a capability that the frequency comb spectroscopy uniquely provides," the researchers said.
The JILA measurements are funded by NIST and the Air Force Office of Scientific Research. The work, now published online, will appear in IEEE Transactions on Plasma Science.
For more information, visit: www.nist.gov
- fiber laser
- A laser in which the lasing medium is an optical fiber doped with low levels of rare-earth halides to make it capable of amplifying light. Output is tunable over a broad range and can be broadband. Laser diodes can be used for pumping because of the fiber laser's low threshold power, eliminating the need for cooling.
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