A new spectroscopic technique for remote molecular detection is presented. Chirped Laser Dispersion Spectroscopy
(CLaDS) uses a two-color dynamic interferometric heterodyne detection to measure optical dispersion caused by
molecular transitions. The dispersion sensing is based on measurement of instantaneous frequency of an optical
heterodyne beatnote which provides high immunity to optical power fluctuations. Thus CLaDS is well suited to long
distance remote sensing and open-path monitoring. In this work we present CLaDS experimental setup for remote
sensing of nitric oxide using 5.2 μm quantum cascade laser. System performance as well as advantages and limitations
are discussed.
A basic wireless laser spectroscopic sensor network for monitoring of trace-gases will be presented. The prototype lowpower
sensor nodes targeting carbon dioxide are based on tunable diode laser absorption spectroscopy and operate using
a 2 μm VCSEL and a 3.5 m Herriott multi-pass cell. The sensor system, which employs real-time wireless
communications, is controlled by custom electronics and can be operated autonomously. The sensor core electronics
performs molecular concentration measurements using wavelength modulation spectroscopy with an active laser
frequency locking to the target transition. The operating sensor node consumes approximately 300 mW of electrical
power and can work autonomously for up to 100 hours when powered by a 10.5 Ah Lithium-ion polymer battery.
Environmentally controlled long term (12 hours) stability tests show sensor node detection limit of ~0.286 ppm with 1
second integration time and the ultimate minimum detectable fractional absorption of 1.5x10-6 is obtained after 3500
seconds averaging time. The sensor node performance results and preliminary tests in a basic network configuration are
discussed.
We describe our novel instrumentation architectures for infrared laser spectrometers. Compact, power
efficient, low noise modules allow for optimized implementation of cell phone sized sensors using
VCSELs, diode, and quantum cascade laser sources. These sensors can consume as little as 0.3W with full
laser temperature (<0.001K/Hz1/2) and current control (<2ppm/Hz1/2 noise), photodiode preamplification
(<2pA/Hz1/2 noise floor, 1MΩ transimpedance), and digital lock-in amplification with 3 independent
channels. We have implemented sensors based on laser absorption spectroscopy, photoacoustic
spectroscopy, and Faraday rotation spectroscopy using the openPHOTONS systems, with performance
rivaling standalone laboratory measurement instrumentation. Additionally, as openPHOTONS is an open
source software repository, this instrumentation can be quickly adapted to new optical configurations
and applications. Such modules allow the development of flexible sensors, whether implementing
closed path spectrometers, open path perimeter monitoring, or remote backscatter based sensors. This
work is also the enabling technology for wireless sensor networks (WSN) of precision sensors, a
desirable sensing paradigm for long term, wide area, precision, temporally and spatially resolved
studies. This approach can complement existing remote sensing and mapping technologies including
satellite observations and sparse networks of flux towers.
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