Courtesy Photo | Schematic of the interleaved difference generation (iDFG) dual-comb spectroscopy (DCS)...... read more read more
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New developments in photonics-based technologies are being used to develop highly sensitive chemical sensors the size of computer chips that will reduce the physical burden on the Joint Force while increasing the detectability of trace levels of toxic chemical threats in a complex mixture. Photonics is the science of the generation, detection, and manipulation of both light particles—or photons—and light waves. Current optical detection systems have bulky setups with moving mirrors that make them heavy, expensive, and fragile.
The Defense Threat Reduction Agency’s (DTRA) Chemical and Biological Technologies Department in its role as the Joint Science and Technology Office (JSTO) for the Chemical and Biological Defense Program has invested with researchers at the University of Arizona and the California Institute of Technology (Caltech) to use technical advancements in integrated photonics research to create small, lightweight, and low-power chemical sensors.
The Frequency-Locked Optical Whispering Evanescent Resonator (FLOWER) developed at the University of Arizona uses light from a laser that internally reflects around microtoroid resonators, which are glass, mushroom-shaped devices. When chemicals or small biomolecules interact with the surfaces of the microtoroid resonators, the refractive index—the amount the path of light is bent—causes a frequency shift in the light spectrum. FLOWER uses peak-locking feedback control, noise reduction, and data analysis to be able to detect down to a single macromolecule (large molecule containing many atoms) without having to label the molecule of interest.
FLOWER was adapted for selective trace gas detection using synthesized polymer coatings developed at Caltech. As gas molecules diffuse through the polymer layer, they cause an index of refraction change and swelling of the polymer that result in a change in resonance frequency. A nerve agent simulant, ammonia, and formaldehyde were detected at part-per-trillion concentrations, extremely more sensitive than existing technologies tested in an ambient environment and offering chemical selectivity. Lowering the detection limit for chemical threats helps keep warfighters safe by providing them more time to don the proper protective equipment and avoid a contaminated area before experiencing an adverse effect of the chemical exposure.
While the initial FLOWER prototype is a bench-scale instrument, researchers plan to design a small, low-cost sensor prototype. Microtoroids can be fabricated on a chip, significantly reducing size, and facilitating future experiments. To realize these possibilities, researchers at the University of Arizona are developing free-space coupling methods, which would enable the parallel read out of multiple microtoroids coated with different capture agents, which will aid DTRA JSTO’s goal to have the Joint Force ready to fight and win in a CB-contested environment.
Another research effort at Caltech, the University of Rochester, and the University of Victoria developed a new detection method based on an interleaved difference frequency generation (iDFG) dual-comb spectroscopy (DCS) approach. This work successfully integrated the electro-optic modulators directly with the comb resonator on a single microchip, which should result in small sensors that can be cost-effectively produced.
A high spectral resolution allows the technique to be sensitive to the molecular rotations and vibrations of both gas and vapor molecules. This helps differentiate between toxic compounds of interest versus ambient contaminants, which is critical for detecting threats in a complex chemical environment and reducing false alarm rates. Current efforts on this project have included designing a microcontroller with an efficient machine-learning code to provide real-time spectral analysis to identify the presence of different gas molecules and quantify their concentration with the goal of making it easier for end users to interpret results.
Together, FLOWER and the iDFG DCS technologies, while still early in development, offer the promise of photonics-based chemical sensors to detect threats in a complex mixture, all in a smaller and lighter format that reduces the physical burden on the Joint Force.
POC: Tyler Miller, tyler.c.miller.civ@mail.mil
| Date Taken: | 12.02.2022 |
| Date Posted: | 12.02.2022 16:51 |
| Story ID: | 434409 |
| Location: | FT. BELVOIR, VIRGINIA, US |
| Web Views: | 345 |
| Downloads: | 3 |
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