Pendar Technologies, LLC

Romain Blanchard

Daryoosh Vakhshoori

Tobias Mansuripur

Masud Azimi

Peili Chen

Arran M Bibby

Fred R Huettig, Iii

Gokhan Ulu

Greg Vander Rhodes

Kalyani Krishnamurthy

A compact, portable Raman spectrometer makes fast, sensitive standoff measurements at little to no risk of eye injury or igniting the materials being probed. This spectrometer uses differential Raman spectroscopy and ambient light measurements to measure point-and-shoot Raman signatures of dark or highly fluorescent materials at distances of 1 cm to 10 m or more. It scans the Raman pump beam(s) across the sample to reduce the risk of unduly heating or igniting the sample. Beam scanning also transforms the spectrometer into an instrument with a lower effective safety classification, reducing the risk of eye injury. The spectrometer's long standoff range automatic focusing make it easier to identify chemicals through clear and translucent obstacles, such as flow tubes, windows, and containers. And the spectrometer's components are light and small enough to be packaged in a handheld housing or housing suitable for a small robot to carry.

Methods and devices for standoff differential Raman spectroscopy with increased eye safety and decreased risk of explosion

In quartz-enhanced photoacoustic spectroscopy (QEPAS), an analyte (typically in gas phase) generates a pressure wave in response to incident laser light. A quartz tuning fork (QTF) resonant at the frequency of the pressure wave transduces the pressure wave into an electrical signal. Pulsing the laser briefly reduces the amount of thermal chirp and increases the fraction of time that the laser emits at the wavelength(s) of interest. This increases the measurement efficiency. Pulsing the incident laser light with bursts of short pulses at the QTF resonant frequency increases signal strength. Exciting the sample with a two pulses at different laser wavelengths, separated by a half QTF period yields signal and background acoustic waves that partially cancel when integrated by the QTF, producing a differential measurement. Pulsing the incident laser light at a frequency faster than the gas response cut off frequency can improve the noise performance of a QEPAS measurement.

Devices and methods for quartz enhanced photoacoustic spectroscopy

Methods and devices for standoff differential Raman spectroscopy decreased risk of explosion

We present here systems and methods for generating a heterodyne signal using the naturally occurring chirp of a pulsed single-mode laser. The electrical square-wave pulse used to drive the laser heats the laser cavity, causing the laser frequency to change or chirp during the emission of the optical pulse. This chirped optical pulse can be split into a chirped signal pulse that interacts with a sample and a chirped reference pulse that interferes with the chirped signal pulse on a detector to produce a heterodyne modulation whose instantaneous phase and amplitude depend on the sample's dispersion and absorption, respectively. The chirp is reproducible, so the heterodyne modulation, instantaneous phase, and/or instantaneous amplitude can be average over many measurements, either with multiple pulses from the same laser or multiple pulses from different lasers, each emitting at a different wavelength.

Devices and methods for coherent detection using chirped laser pulses

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Lexington, MA, United States of America

Romain Blanchard