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Mid-Infrared Chip-scale Trace Gas Sensors


TECHNOLOGY AREA(S): Chem Bio_defense 

OBJECTIVE: To develop trace gas sensors on a chip with mid-infrared laser based spectroscopy techniques such as absorption spectroscopy with a broad wavelength span of 3-15 microns and sub-ppm sensitivity. 

DESCRIPTION: Mid-infrared trace-gas sensing in the molecular fingerprint region is a rapidly developing field with a wide range of applications including detection of explosives and hazardous chemicals, control of industrial processes and emissions, breath analysis for medical diagnostics, and environmental and atmospheric monitoring. Mid-infrared spectral range (3-15 micron wavelength) hosts fundamental vibrational-rotational transitions of virtually any chemical compound. These transitions are strong and characteristic of molecular structure which allows performing chemical detection and identification of chemical and biological compounds with high sensitivity and specificity. Quantum cascade lasers (QCLs) have dramatically affected the field of trace-gas sensing by providing narrowband tunable continuous-wave room-temperature emission in the entire mid-infrared spectral range [1,2]. Currently, mid-infrared trace gas sensing systems based on based on ring-down spectroscopy, absorption spectroscopy, or photoacoustic spectroscopy are developed around bulky gas cells and free-space optics [3]. However, these systems require relatively large and expensive optical elements. These systems have significant size and weight that place constraints on their applications in the field, particularly for airborne or handheld platforms. Additionally, the use of free-space optics makes these systems inevitably sensitive to stress and vibration. Recently, several groups demonstrated integration of QCLs, photodetectors, and optical cells on the same solid-state platform [4,5] using plasmonic [4] or dielectric [5] waveguides. Unlike systems based around free-space optics, integrated-photonics gas sensors are expected to be light, highly compact, and inherently robust to vibrations and physical stress. Dielectric platforms based on silicon or germanium materials [7] may offer low optical loss and high effective propagating distances for mid-infrared light to produce an equivalent of a multi-pass cell within a solid-state platform. Slow-light-enhanced mid-infrared sensing has been demonstrated recently in silicon-on-sapphire platform with 10 ppm sensitivity using an 800 micron long photonic crystal waveguide [6]. However, silicon-on-sapphire system is not suitable for operation in the entire mid-infrared band (3-15 microns) and monolithic integration of light sources and detectors with the passive photonics platform is required to enable a compact trace gas sensing system that is robust to vibrations and physical stress. Suitable approaches therefore need to be developed to integrate sources, detectors, and waveguides on a single photonic platform and enable monolithic mid-infrared chip-scale trace gas sensors operable in the entire 3-15 microns spectral range for the detection of chemical warfare agents, explosives, narcotics and other chemicals of interest to Army. All electronics, while not necessarily on the same chip, must be packaged into a compact handheld, or field-portable unit. 

PHASE I: Propose a packaged design that can detect a selected gaseous substance or substances of interest to Army at sub-ppm levels by mid-infrared absorption spectroscopy in the 3-15 micron wavelength range, with all components including light source, detector and sensor transducer integrated on the same chip. Two example analyte gases desired to sense in Phase I would be methane and ammonia gas (3.3 and 6.1 micron absorption lines) for dual-use Army and civilian sensing applications. Preliminary experimental data showing the feasibility of the proposed approach will be needed to validate transition to Phase 2. 

PHASE II: Deliver a packaged handheld prototype mid-infrared spectrometer, with the integrated light source, detector and sensor, to Army detecting at least 3 selected substances of interest to sub-ppm levels by mid-infrared absorption spectroscopy in the 3-15 micron wavelength range. The gaseous analyte examples given for Phase I (methane and ammonia) should be expanded upon to demonstrate feasibility across the entire range. Examples of substances desirable to detect includes (or simulants of the substances) nerve and blister agents such as Tabun (GA), Sarin (GB), Soman (GD), Vx (VX), S-Mustard (HD), etc. and explosives such as RDX, PETN, TNT, HMX, Ammonium Nitrate, etc. 

PHASE III: Further research and development during Phase III efforts will be directed towards 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 the U.S. Army and end-user requirements. Potential commercial applications include detection of dangerous and greenhouse gases in the environment, contraband and narcotics for use in Homeland Security applications. 


1: Y. Yao, A.J. Hoffman, and C.F. Gmachl, "Mid-infrared quantum cascade lasers," Nature Photon. 6, 432 (2012).

2: J.M. Wolf, S. Riedi, M.J. Suess, M. Beck, and J. Faist, "3.36 µm single-mode quantum cascade laser with a dissipation below 250 mW," Opt. Express 24, 662 (2016).

3: A. Kosterev, G. Wysocki, Y. Bakhirkin, S. So, R. Lewicki, M. Fraser, F. Tittel, R.F. Curl, "Application of quantum cascade lasers to trace gas analysis," Appl. Phys. B 90, 165 (2008).

4: D. Ristanic, B. Schwarz, P. Reininger, H. Detz, T. Zederbauer, A.M. Andrews, W. Schrenk, and G. Strasser, "Monolithically integrated mid-infrared sensor using narrow mode operation and temperature feedback," Appl. Phys. Lett. 106, 041101 (2015).

5: Y. Zou, K. Vijayraghavan, P. Wray, S. Chakravarty, M.A. Belkin, R. T. Chen, "Monolithically integrated quantum cascade lasers, detectors and dielectric waveguides at 9.5 µm for far-infrared lab-on-chip chemical sensing,"CLEO Technical Digest, paper STu4I.2 (2015).

6: Y. Ma, G. Yu, J. Zhang, X. Yu, R. Sun, and F.K. Tittel, "Quartz enhanced photoacoustic spectroscopy based trace gas sensors using different quartz tuning forks," Sensors 15, 7596 (2015).

7: J. P. Waclawek, H. Moser, and B. Lendl, "Compact quantum cascade laser based quartz-enhanced photoacoustic spectroscopy sensor system for detection of carbon disulfide," Opt. Express 24, 6559 (2016).

8: Y. Zou, S. Chakravarty, P. Wray, R. T. Chen, "Mid-Infrared holey and slotted photonic crystal waveguides in silicon-on-sapphire for chemical warfare simulant detection," Sensors and Actuators B 221, 1094 (2015).

9: R. Soref, "Mid-infrared photonics in silicon and germanium," Nat. Photon. 4, 495 (2010)


KEYWORDS: Mid-infrared, Absorption Spectroscopy, Integrated Photonics, Trace Gas Sensing 

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