A carbon monoxide sensor developed by researchers at Rice University in Houston, Lucent Technology Inc.'s Bell Labs in Murray Hill, N.J., and Physical Sciences Inc. in Andover, Mass., may find applications in the continuous monitoring of the pollutant. Based on a 4.6-µm quantum cascade distributed feedback laser, the spectroscopic sensor displays a sensitivity of 12 ppb; the current technique, which was approved by the Environmental Protection Agency, offers a sensitivity of up to 1 ppm.According to their calculations, the new sensor should have a sensitivity of 6.5 ppb, but the researchers believe that frequency drift in the laser source affects its precision. In subsequent tests, they plan to replace the current source and data acquisition electronics in the sensor to enable it to complete a sampling run in 1.5 s. Today's CO detectors have response times of 30 s.The researchers reported the work in the Feb. 20 issue of Applied Optics.