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Methods and apparatus for mid-infrared sensing

United States Patent

June 2, 2015
View the Complete Patent at the US Patent & Trademark Office
A chip-scale, air-clad semiconductor pedestal waveguide can be used as a mid-infrared (mid-IR) sensor capable of in situ monitoring of organic solvents and other analytes. The sensor uses evanescent coupling from a silicon or germanium waveguide, which is highly transparent in the mid-IR portion of the electromagnetic spectrum, to probe the absorption spectrum of fluid surrounding the waveguide. Launching a mid-IR beam into the waveguide exposed to a particular analyte causes attenuation of the evanescent wave's spectral components due to absorption by carbon, oxygen, hydrogen, and/or nitrogen bonds in the surrounding fluid. Detecting these changes at the waveguide's output provides an indication of the type and concentration of one or more compounds in the surrounding fluid. If desired, the sensor may be integrated onto a silicon substrate with a mid-IR light source and a mid-IR detector to form a chip-based spectrometer.
Lin; Pao Tai (Brighton, MA), Cai; Yan (Stoughton, MA), Agarwal; Anuradha Murthy (Weston, MA), Kimerling; Lionel C. (Concord, MA)
The Massachusetts Institute of Technology (Cambridge, MA)
14/ 076,655
November 11, 2013
GOVERNMENT SUPPORT This invention was made with government support under Contract No. DE-NA000421 from the Department of Energy. The government has certain rights in this invention.