Massachusetts Institute of Technology

Shawn Michael Redmond

Thomas H Jeys

Alexander Stolyarov

William D Herzog

Ryan Sullenberger

Brian G Saar

David Crompton

Patrick Hassett

Salvatore Di Cecca

Alexander M Stolyarov

A two-layer hybrid solid wedged etalon was fabricated and combined with a traditional imager to make a compact computational spectrometer. The hybrid wedge was made of NbOand Infrasil 302 and was designed to operate from 0.4-2.4 &#x3bc;m. Initial demonstrations used a CMOS imager and operated from 0.4-0.9 &#x3bc;m with spectral resolutions &#x3c;30 cmfrom single snapshots. The computational spectrometer operates similarly to a spatial Fourier Transform infrared (FTIR) spectrometer with spectral reconstruction using a non-negative least squares fitting algorithm based on analytically computed wavelength response vectors determined from extracted physical thicknesses across the entire two-dimensional wedge. This computational technique resulted in performance and spectral resolutions exceeding those that could be achieved from Fourier techniques. With an additional imaging lenses and translational scanning, the system can be converted into a hyperspectral imager.

Compact computational spectrometer using solid wedged low finesse etalon

A device, and corresponding method, can include a pump light source configured to irradiate a target specimen. The device can also include a sensor configured to observe a probe speckle pattern based on light from a probe light source reflected from the target specimen. The device further may include a correlator configured to determine a material property of the target specimen by analyzing changes in images of the probe speckle pattern as a function of the irradiation with the pump light source. Advantages of the device and method can include much higher sensitivity than existing methods; the ability to use visible probe wavelengths for uncooled, low-cost visible detectors with high spatial resolution; and the ability to obtain target material properties without detecting infrared light.

Material property determination using photothermal speckle detection

A device, and corresponding method, can include a pump light source configured to be modulated at a pump modulation and to irradiate a target specimen. The device can also include a probe light source arranged to generate a speckle pattern from the target specimen, as well as a sensor configured to detect changes in at least one of position and intensity of one or more speckle lobes of the speckle pattern having correlation with the pump modulation. The device and method can be used for non-contact monitoring and remote sensing of surfaces, gases, liquids, particles, and other target materials by analyzing speckle pattern changes as a function of pump light irradiation. Advantages can include much higher sensitivity than existing methods; the ability to use visible probe wavelengths for uncooled, low-cost visible detectors with high spatial resolution; and the ability to obtain target material properties without detecting infrared light.

Devices and methods for sensing targets using photothermal speckle detection

A system includes a build-up cavity to locally increase the power of light beams within the build-up cavity, where the light beams interact with samples to sense a substance of interest. The build-up cavity is disposed within a main cavity that includes a gain material to amplify the light beams. A portion of the light beams oscillating in the build-up cavity propagators through the build-up cavity and functions as a feedback to control the linewidth of the light beams. The two cavities can function as two separate 'filters' and light beams at wavelengths that propagate through both of these 'filters' can be preferentially amplified. The combination of the build-up cavity and the main cavity can achieve high power and narrow linewidth for the light beams without complex electronics, thereby decreasing the size, weight, and power (SWaP) of the system.

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Lexington, MA, United States of America

Shawn Michael Redmond