Physics / mechanism
Atmospheric sensing detects and quantifies gas-phase species, aerosols, and meteorological parameters in the open atmosphere. Core modalities: differential absorption lidar (DIAL) using tunable laser pulses to exploit species-specific absorption cross-sections at paired wavelengths; Fourier-transform infrared spectrometry (FTIR) for broadband fingerprinting; cavity-enhanced techniques (CRDS, CEAS) reaching sub-ppb detection limits via effective path lengths >10 km in a compact cell; and photoacoustic spectroscopy for portable mid-IR sensing. Key parameters: sensitivity (NEA ~10⁻¹⁰ cm⁻¹ Hz⁻½ for CRDS), selectivity (spectral resolution <0.001 cm⁻¹), range (lidar to 30+ km), and SWaP. Mid-IR quantum cascade lasers (QCLs, 3–12 µm) are the dominant photon source for molecular fingerprinting; interband cascade lasers (ICLs) cover lower power budgets. GHG monitoring, air quality, industrial leak detection, and defence CBRN drive deployment.
Competitive landscape
Competing and adjacent approaches split by range, cost, and analyte class. Electrochemical and metal-oxide sensors dominate low-cost point detection but lack selectivity and drift. Satellite remote sensing (Sentinel-5P, GHGSat) provides global coverage at coarse resolution (>1 km). Passive FTIR competes with active lidar for standoff. Raman lidar resolves aerosol backscatter independent of absorption. Miniaturised photonic integrated circuit (PIC) spectrometers on Si or SiN wafer platforms are the near-term disruptive vector.
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Connected ideas
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Frontier (open questions)
- To be added.