Tiny, tunable lasers key to palm-sized sensors

Sept. 15, 2005
Most organic molecules have a distinctive absorption pattern in the mid-infrared band between about 3 and 20 m.

Boris Mizaikoff displays a prototype of the gas-phase sensor, while graduate student Christy Charlton holds the liquid-phase prototype.


Illuminating the molecules with a laser tuned to the correct frequency makes them vibrate and absorb the light, the amount of which depends on concentration.

So-called quantum-cascade lasers are key to scaling down mid-infrared chemical-sensing tools to palm size, says Boris Mizaikoff, an associate professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology.

"These diode lasers are roughly the size of those in laser pointers or CD players. They operate at room temperature and can emit nearly across the mid-infrared band."

A photonic-band-gap hollow waveguide — basically a hollow, flexible tube — holds a gas to be sampled. Liquid-phase detectors use a planar, silver-halide waveguide to transmit the laser light. The waveguides efficiently propagate only one wavelength, making them useful for detecting specific molecules. For example, a waveguide coupled to a frequency-matched quantum-cascade laser can detect ethyl-chloride levels down to 30 ppb, on par with gas and liquid chromatography methods. The system needs only 1 ml of sample gas, compared to a few hundred milliliters for conventional multipass gas cells.

Breath diagnostics is a promising application for the technology. Many diseases have specific biomarkers present in breath that rapidly grow in concentration as the disease progresses but remain at extremely low levels, necessitating sensitive and reliable tools to detect the changes. The technology may also bring instruments capable of continuously monitoring water quality with single-digit, parts-per-billion sensitivity.

Sponsored Recommendations

Pumps Push the Boundaries of Low Temperature Technology

June 14, 2024
As an integral part of cryotechnology, KNF pumps facilitate scientific advances in cryostats, allowing them to push temperature boundaries and approach absolute zero.

The entire spectrum of drive technology

June 5, 2024
Read exciting stories about all aspects of maxon drive technology in our magazine.

MONITORING RELAYS — TYPES AND APPLICATIONS

May 15, 2024
Production equipment is expensive and needs to be protected against input abnormalities such as voltage, current, frequency, and phase to stay online and in operation for the ...

Solenoid Valve Mechanics: Understanding Force Balance Equations

May 13, 2024
When evaluating a solenoid valve for a particular application, it is important to ensure that the valve can both remain in state and transition between its de-energized and fully...

Voice your opinion!

To join the conversation, and become an exclusive member of Machine Design, create an account today!