ISSO Y2005 Annual Report | Contents

Development of Quantum-Cascade Laser Based Biosensor Technology • 27-32
Thomas L. Harman, Frank K. Tittel, John C. Graf, Yury Bakhirkin
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Abstract--The development of new types of sensitive, selective, real-time gas sensors is based on continuous wave and pulsed quantum cascade lasers for various chemical sensing applications, such as medical diagnostics, environmental monitoring, and industrial process control. Tunable laser absorption spectroscopy in the mid-infrared spectral region is a sensitive analytical technique for trace gas quantification. During the past year a nitric oxide (NO) gas sensor was developed based on a novel thermoelectrically cooled, continuous wave, distributed feedback quantum cascade laser operating at 5.45 mm (1835 cm^-1) and off-axis integrated cavity output spectroscopy (OA-ICOS) combined with a wavelength modulation technique. Its purpose is to determine NO concentrations at the sub-ppbv levels that are essential for such applications. The sensor employs a 50 cm-long high-finesse optical cavity that provides an effective pathlength of ~ 700 m. A noise equivalent (SNR = 1) minimum detection limit of 0.7 ppbv with a 1 second observation time was achieved.