Quantum Cascade Laser Sensor

QCL-NO-1001 5.2 Micron NO Sensor

Description

Physical Sciences Inc. (PSI) has developed a stand-alone, fully automated sensor for ultra-sensitive detection of Nitric Oxide (NO). The sensor uses room-temperature Distributed FeedBack Quantum Cascade Laser (DFB-QCL) and Balanced Ratiometric Detection (BRD) technology to achieve a detection sensitivity at ambient temperature and pressure of 10 ppb-m. Higher sensitivity may be achieved at lower pressure or with longer absorption pathlengths. The QC laser is mounted in a custom-fabricated housing, complete with thermo-electric cooler, beam-shaping optics, and pulsed current supply. The sensor includes all optical components necessary to setup absorption measurements in a typical laboratory environment.

Example Rack-Mount QCL Sensor produced for the NASA Ames Research Center. The multi-pass cell and gas control system shown are not included in the basic system described below.

Schematic of sensor components.

Features

• Fully automated operation based on Pentium-class computer
• Graphical user's interface
• Thermo-electrically-cooled laser mount
• Single mode laser operation with average linewidth <0.3 cm^-1
• Quasi-cw operation with 1 mW minimum average power (5 ns pulse width, 1 MHz pulse-repetition-rate)
• Optimized for absorption measurements using 1900 cm^-1 NO transition to minimize interference by water vapor and other common atmospheric or industrial gases.
• 10 Hz continuous concentration reporting rate
• Standard 19-in. rackmounting components
• Compact QCL-mount
• Matched InSb detectors in liquid-nitrogen-cooled dewars

Compact, thermo-electrically-cooled QCL mount with integral current pulser

Specifications

• Minimum detectable NO concentration - 10 ppb at 1 atm air pressure, 300 K, and 1 m absorption pathlength
• Laser wavelength - 1900 cm^-1
• Laser operating temperature (at 1900 cm^-1) - between 280 and 320 K
• Laser current tuning range - 0.5 cm^-1
• Laser temperature tuning range (280 to 320 K) - 5 cm^-1
• Minimum average power - 1 mW (at 0.5% duty cycle)
• Detectors - matched signal and reference InSb detectors with 4 A/W and D* [ 2.3 x 10¹¹ cmHz^1/2W^-1]
• Bandwidth - continuous 10 Hz concentration data update

Applications

• Atmospheric monitoring
• Pollution emissions monitoring
• Exhaled human breath monitoring

PSI's QCL-series sensors represent the state-of-the-art in advanced laser-based sensor technology. They have been developed to provide laboratory sensor configurations for researchers in university, government, and industrial laboratories evaluate this revolutionary technology for specific applications. Customized units are available on request. Please see related publications list at the left for links to detailed descriptions of PSI's various QCL sensor prototypes and recent laboratory, field, and industrial applications.

Example measurements of trace NO in ambient air with 50 ppb-m detection limit

Contact

Mark G. Allen
Physical Sciences Inc.
20 New England Business Center
Andover, MA 01810-1077

Telephone: (978) 689-0003
Fax: (978) 689-3232
allen@psicorp.com