|Acquisition Program: ||JPEO Chemical and Biological Defense|| Objective: ||Develop a monolithic chemical sensor based on laser absorption spectroscopy.
|| Description: ||The Chemical and Biological defense community has the need for a miniature, highly sensitive, and specific sensor for detection of chemical agents and toxic industrial chemicals. Infrared absorption spectroscopy has proven to be a very useful tool in the detection and precise identification of airborne chemicals. Pattern recognition is used to compare the infrared spectrum of library molecules against the infrared spectra of airborne contaminants. Infrared spectrometers have rapid response and clear-down times, which provide utility in cloud tracking and dynamic monitoring experiments.
A miniature monolithic spectrometer that is rugged and consumes very little energy would have utility within the chemical/biological defense community. Several military gas-sensing applications require widespread, networked deployment of many individual low-cost rugged sensors. Some envisioned applications involve dispersing sensor networks from aircraft without using parachutes. Thus a sensor that is rugged enough to survive a freefall from altitude and still function effectively would be of great value.
Tunable diode laser absorption spectroscopy (TDLAS) is a configurable optical technology for highly sensitive and specific chemical vapor detection. TDLAS technology leverages a very large effort by the telecommunications industry in the development of very small, rugged, reliable laser sources. Sensors incorporating mature well-packaged wavelength-stabilized near-infrared lasers, developed for the telecommunications industry, have been successfully used to detect toxic gases. Recently developed mid-IR lasers, particularly quantum cascade devices spanning wavelengths of 3-12 µm, have been used to sense sub-ppm concentrations of hydrocarbons in real-time. Compact TDLAS systems can operate continuously at room temperature, without maintenance, cryogenics, or user attendance.
It has recently become possible to construct a complete chemical sensor using monolithic fabrication techniques. Using monolithic fabrication, the chemical sensor, including laser, sampling element, and detector, can be fabricated as a monolithic unit using established production techniques. A monolithic integrated optic TDLAS platform would significantly reduce costs compared to current commercially available systems while providing the sensitivity and selectivity needed for military missions. The integrated optic TDLAS platform would enable inexpensive mass fabrication and miniaturization. The improved ruggedness of the proposed sensor would significantly improve the utility of the system.
|| ||PHASE I: Design an integrated optic TDLAS chemical sensor platform concept, combining the laser, sampling element, and detector onto a monolithic platform that can be fabricated or assembled using established production techniques. Identify and design means for minimizing and controlling power consumption while maintaining laser wavelength stability. The design will also include an electronic control and processing module, as well as a power supply and packaging with a goal of a final sensor package that is comparable in size to a rugged cellphone. Demonstrate by calculation the ability to detect chemical warfare agent and simulant vapors at relevant concentrations. For this demonstration, the ability to detect the chemical simulant triethylphosphate at a concentration of less than 1 milligram per cubic meter at ambient temperature and pressure should be demonstrated. Validate experimentally the feasibility of meeting the targeted sensitivity.
|| ||PHASE II: Build and test a TDLAS based chemical sensor with an integrated monolithic laser, sampling element and detector. The sensor package should include an electronic control module, power supply, and packaging. The control module should contain all necessary algorithms for detecting chemical agents and simulants. Rigorously test the sensor performance. Use ROC curve analyses to quantify detection sensitivity. Demonstrate sensor ruggedness. Evaluate production costs.
|| ||PHASE III: Further research and development during Phase III efforts will be directed towards refining a final deployable design, incorporating design modifications based on results from tests conducted during Phase II, and improving engineering/form-factors, equipment hardening, and manufacturability designs to meet U.S. Army CONOPS and end-user requirements. There are many environmental applications for a small chemical sensor. A rugged, monolithic chemical sensor will benefit the manufacturing community by providing finely tuned monitoring of chemical processes. Also first responders such as Civilian Support Teams and Fire Departments, have a critical need for a rugged, inexpensive, and versatile sensor that can be transported to the field to test for possible contamination by CW agents and other toxic chemicals.
|| References: ||
1. P. Werle, R. Mücke, and F. Slemr, “The limits of signal averaging in atmospheric trace-gas monitoring by tunable diode-laser absorption spectroscopy (TDLAS)”, Applied Physics B: Lasers and Optics, Volume 57, Number 2, Pages 131-139, August, 1993
2. K. Song, H.K. Cha, V.A. Kapitanov, Yu.N. Ponomarev, A.P. Rostov, D. Courtois, B. Parvitte, and V. Zeninari, “Differential Helmholtz resonant photoacoustic cell for spectroscopy and gas analysis with room-temperature diode lasers”, Applied Physics B: Lasers and Optics, Volume 75, Numbers 2-3, Pages 215-227, September, 2002
3. R. Kormann, H. Fischer, C. Gurk, F. Helleis, Th. Klüpfel, K. Kowalski, R. Königstedt, U. Parchatka and V. Wagner, “Application of a multi-laser tunable diode laser absorption spectrometer for atmospheric trace gas measurements at sub-ppbv levels”, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Volume 58, Issue 11, Pages 2489-2498, September 2002.
4. M. Druy, M.B. Frish, and W.J. Kessler, “From laboratory technique to process gas sensor – The maturation of Tunable Diode Laser Spectroscopy”, Spectroscopy, Volume 21, number 3, pages 14-18, March 2006.
|Keywords: ||Chemical Detection, TDLAS, Monolithic, diode laser, infrared spectroscopy, integrated optics|