Chemical detection with hyperspectral lidar using dual frequency combs

Abstract

High-resolution spectral lidar measurements using dual frequency combs as a source is presented. The technique enables the range-resolved measurement of fine spectral features, such as gas absorption lines, provided that a suitable scatterer is present in the scene. Measurements of HCN absorption lines at 20 meters are presented, with a water droplet cloud and a diffusely reflective surface as scatterers.

High sensitivity stand-off detection and quantification of chemical mixtures using an active coherent laser spectrometer (ACLaS)

“…A fully versatile instrument should have the flexibility to work at short (< 1 m) and far stand-off distances (> 1000 m). 4) Rapid temporal response: rapid update times (seconds to minutes) are needed to allow high screening throughput, fast spatial information gathering, and real-time identification and reaction to threats. 5) Eye-safe operation: operational laser spectrometers deployed in public open areas should meet laser emission limits for a class 1 laser and must pose no risk of harm to the public.…”

“…Laser spectroscopy is a far more promising tool to fulfill the requirements previously mentioned 1 . Recently developed instruments for active stand-off detection include resonance Raman scattering in the UV region 2 and absorption in the infrared region (1-12 µm) using a variety of laser sources including parametric oscillators 3 , ultrafast laser frequency combs 4 and semiconductor lasers 5 . The common underlying architecture is the active transmission of light towards a distant target (cooperative or topographic), the collection and detection of the backscattered or reflected radiation and its analysis to provide chemical identification and quantification.…”

“…Following the definition given in Equation 1, the measured spectrum y is related to the concentrations to be retrieved x and to the fixed parameters of the detection scenario b by Equation 4. This is similar to Equation 1 with the difference that here the function f is assumed to be ideal and describes the full physics of the problem, unlike F which was the actual forward model we have knowledge about.…”

Tracing part-per-billion line shifts with direct-frequency-comb Vernier spectroscopy

“…Actually, demonstrations in almost all electromagnetic spectral regions, from UV [2], through visible-NIR [3][4][5][6][7] and mid-IR [8][9][10], up to the THz range [11], may open new opportunities in physics, chemistry, biology, and industry. Indeed, DCS-based instrumentation developed for multiple trace gas sensing [9,12], hyperspectral lidar [13], scanning near-field optical microscopy (SNOM) [14], and/or coherent Raman spectroimaging [15] are just a few examples of DCS applicability, spanning from environmental and climatic change monitoring to single-virus vibrational mapping as well as chemical recognition of nanomaterials.…”

Autonomous Chemical Vapour Detection by Micro UAV

“…Currently, standoff chemical detection for environmental, industrial and emergency response applications are attempted using technologies, such as multispectral imaging [1,2] or laser based systems, such as LIDAR [3,4] or laser absorption [5]. Challenges with methodologies such as these relate to optical aberrations from the background environment.…”