Description:
Simultaneous Ranging and Remote Chemical Sensing Utilizing Optical Dispersion or Absorption Spectroscopy
(Princeton Docket # 14-3039)
Inventors: Gerard Wysocki, Andreas Hangauer
Princeton researchers have developed a novel methodology that enables simultaneous ranging and spectroscopic chemical detection, combining capabilities that are not achievable with current state-of-the-art continuous wave laser-based spectrometers. This system employs a continuous-wave laser modulated by a time-varying radio frequency signal to produce spectral sidebands that encode chemical spectral information and range data. The modulated light passes through an optical path—potentially encountering multiple reflections or scattering—and is then detected and down-converted into a complex baseband signal. The resulting signal is demodulated to extract instantaneous frequency shifts that correspond directly to changes in optical path lengths. Integrated with real-time signal processing techniques such as phase correction and harmonic analysis, the technology delivers both accurate chemical concentration data and precise range measurements using only a single laser source and detector for multiple cascaded sensing paths. This approach is differentiated by its ability to combine remote chemical sensing with simultaneous optical path length determination in a continuous-wave system, bypassing the typical limitations found in pulsed methods like Raman LIDAR. By leveraging chirped radio frequency modulation and specialized signal processing, the system simplifies calibration and enables multi-path analysis, offering high chemical sensitivity and extensive range capabilities that are particularly valuable for applications such as gas plume monitoring and complex optical environments.
A continuous-wave laser system uses RF modulation to produce sidebands that encode spectroscopic and range information via frequency chirp. It demodulates a complex baseband signal, applying phase corrections, harmonic analysis, and path separation filtering to extract precise chemical concentrations and optical path lengths. This technique supports single or cascaded sensor layouts, offering simultaneous high-sensitivity remote chemical sensing with robust multipath resolution even under low light-return conditions.
|
APPLICATIONS
|
ADVANTAGES
|
- Remote and open-path chemical sensing
- Closed-path sensing applications that utilize multi-mode/scattering-based gas cells for which the pathlength is not known a-priori (e.g., integrating spheres)
- Potential usage in multi-path chemical sensing for tomographic chemical detection with a single laser-based instrument
- Enhancement of conventional spectrometers (e.g., based on CLaDS, FM spectroscopy, or WMS)
- Usage in optical gas cells, where the invention can address the enduring problem of slowly drifting effective optical pathlength simultaneous with spectroscopic detection
- Multiple cascaded sensors (measurement cells) in one optical train
|
- Enables simultaneous chemical sensing and distance measurement in one system.
- Increased system reliability through active monitoring of the optical pathlength
- Supports robust multipath and cascaded sensor configurations for advanced applications.
- Provides high sensitivity and accurate remote sensing even over long optical paths.
- Improves calibration and monitoring by extracting precise optical path length information.
- Simplifies sensor infrastructure by using a single laser and detector for multi-path analysis.
|
Stage of Development
Experimental verification has been completed in the following publication, where the observed behavior was as theoretically predicted:
Chirped laser dispersion spectroscopy for spectroscopic chemical sensing with simultaneous range detection
Contact
Renee Sanchez
New Ventures & Licensing Associate • (609) 258-6762 • renee.sanchez@Princeton.edu
