Remote chemical sensing with quantum cascade lasers

Conference · Fri Oct 15 04:00:00 EDT 2004

OSTI ID:15011338

Harper, Warren W; Strasburg, Jana D

A trailer based sensor system has been developed for remote chemical sensing applications. The sensor uses quantum cascade lasers (QCL) that operate in the long wave infrared. The QCL is operated continuous wave, and its wavelength is both ramped over a molecular absorption feature and frequency modulated. Lock-in techniques are used to recover weak laser return signals. Field experiments have monitored ambient water vapor and small quantities of nitrous oxide, tetrafluoroethane (R134a), and hydrogen sulfide released as atmospheric plumes. Round trip path lengths up to 10 km were obtained using a retro-reflector. Atmospheric turbulence was found to be the dominating noise source. It causes intensity fluctuations in the received power, which can significantly degrade the sensor performance. Unique properties associated with QCLs enabled single beam normalization techniques to be implemented thus reducing the impact that turbulence has on experimental signal to noise. Weighted data averaging was additionally used to increase the signal to noise of data traces. Absorbance sensitivities as low as {approx}1 x 10{sup -4} could be achieved with 5 seconds of data averaging, even under high turbulence conditions.

• Research Organization: Pacific Northwest National Lab., Richland, WA (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 15011338
• Report Number(s): PNNL-SA-41010; NN2001000
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ATMOSPHERIC CIRCULATION
FIELD TESTS
HYDROGEN SULFIDES
INFRARED RADIATION
LASERS
NITROUS OXIDE
POLLUTANTS
REFRIGERANTS
REMOTE SENSING
REMOTE SENSING
LASERS
LIDAR
CHEMICAL DETECTION
QUANTUM CASCADE LASER
TURBULENCE
WATER VAPOR