Laser-based atmospheric remote sensing, an essential tool for modern environmental monitoring and meteorological research, leverages the interaction between lasers and atmospheric components to achieve highly accurate, high-spatio-temporal-resolution detection of aerosols, greenhouse gases, and meteorological parameters. 
1. Basic Principles of Laser Atmospheric Remote Sensing Measurement 
　　Laser-based atmospheric remote sensing technology relies on the interaction mechanisms between lasers and atmospheric components, enabling the retrieval of atmospheric property parameters by analyzing backscattered light signals. As laser pulses travel through the atmosphere, they undergo various interactions with gas molecules, aerosol particles, and other constituents—primarily including elastic scattering (such as Rayleigh and Mie scattering), inelastic scattering (like Raman scattering), and absorption effects. These interaction processes carry critical information about the concentration, distribution, and dynamic state of atmospheric components. By detecting and analyzing the returned echo signals, this technology achieves highly accurate remote sensing measurements of the atmospheric environment. 
Laser-based atmospheric remote sensing systems typically consist of three main components: a laser emission unit, an optical reception unit, and a signal acquisition and processing unit. The laser emission unit generates high-repetition-rate, narrow-pulse-width laser pulses, which are directed into the atmosphere after their divergence angle is adjusted by a beam-expanding lens. The optical reception unit employs a large-aperture telescope to collect backscattered light, while a narrow-band filter is used to suppress interference from background light. Meanwhile, the signal acquisition system utilizes either a photomultiplier tube (PMT) or an avalanche photodiode (APD) to convert the optical signals into electrical signals, which are then digitized at high speed before being sent to a computer for further processing. Modern LiDAR systems are also equipped with scanning mechanisms and GPS/INS positioning modules, enabling three-dimensional stereoscopic detection and seamless integration with mobile platforms. 
2. Characteristics of Laser Atmospheric Remote Sensing Technology 
　　High spatiotemporal resolution: Time resolution can reach the minute or even second level, while the vertical spatial resolution is approximately 3–30 meters, and the horizontal resolution can achieve meter-level accuracy. 
　　Wide detection range: The ground-based system can cover altitudes from 0.1 to 30 km, while the spaceborne system achieves global coverage. 
　　Multi-parameter synchronous detection: A single system can simultaneously acquire multi-dimensional information, including aerosol optical properties, concentration, temperature, and wind fields. 
　　Active Remote Sensing Capability: It doesn't rely on solar radiation, enabling continuous day-and-night observations.

Laser–Atmosphere Main Interaction Mechanisms and Applications:

3. Major Technical Challenges in Laser Atmospheric Remote Sensing 
　　Background light interference: During the day, solar radiation significantly reduces the signal-to-noise ratio, requiring the use of narrowband optical filters (with a bandwidth of less than 1 nm) and time-gating techniques for suppression. 
　　Signal attenuation: Atmospheric extinction (scattering and absorption) causes the echo signal to weaken dramatically with distance, making high-energy lasers and efficient receiving systems crucial. 
　　Geometric overlap: The near-field blind zone issue—typically ranging from 50 to 300 meters—needs to be minimized through optimized optical design. 
　　Inversion uncertainty: Under complex conditions, signal interpretation often yields multiple solutions, necessitating the integration of prior knowledge and validation with multi-source data. 
　　With advancements in laser technology, optoelectronic detection, and signal-processing techniques, laser-based atmospheric remote sensing continues to push the boundaries of performance. High-spectral-resolution lidar (HSRL), by precisely separating Rayleigh-Mie scattering signals using atomic or Fabry-Perot etalons, has significantly enhanced the accuracy of aerosol retrieval. Meanwhile, multi-wavelength lidar systems—such as those combining 355 nm, 532 nm, and 1064 nm—enable the inversion of aerosol microphysical properties, including particle size distribution and refractive index, by analyzing differences in scattered signals across various wavelengths. 
4. Classification of Laser Atmospheric Remote Sensing 
　　Laser-based atmospheric remote sensing technology has evolved into a variety of distinctive technical approaches, depending on the detection principles and application objectives, thereby establishing a comprehensive classification system. 
4.1 Differential Absorption Lidar (DIAL) 
　　Differential Absorption Lidar (DIAL) technology measures the concentration distribution of target gas molecules by exploiting their selective absorption characteristics at specific laser wavelengths. The system alternately emits two nearly identical laser pulses: one wavelength (λon) falls within a strong absorption line of the target gas, while the other wavelength (λoff) is positioned in a region of weak or no absorption. By comparing the differences between the echo signals at these two wavelengths and incorporating absorption cross-section parameters, the system can retrieve the spatial distribution of gas concentration as a function of distance. 
4.2-meter Scattering Lidar 
　　Mie-scattering lidar is the most common type of laser-based atmospheric remote sensing system. By detecting the elastic scattering signals of aerosols and cloud particles off laser beams, it retrieves atmospheric optical properties and boundary-layer structures. Unlike DIAL systems, Mie-scattering lidar typically uses a fixed wavelength (such as 532 nm), resulting in a relatively simpler system design that makes it well-suited for long-term, continuous observations. 
4.3 Raman Lidar 
　　Raman lidar measures temperature, water vapor, and aerosol properties by detecting the vibrational-rotational Raman scattering signal (wavelength shift) from atmospheric molecules. Compared to elastic scattering, the Raman scattering cross section is 6 to 10 orders of magnitude smaller, requiring high-energy lasers and highly efficient detection systems. 
4.4 Hyperspectral Resolution Lidar (HSRL) 
　　Hyperspectral-resolution lidar uses an ultra-narrowband optical filter (with a bandwidth of less than 0.1 pm) to separate the aerosol Mie scattering signal (broadband) from the molecular Rayleigh scattering signal (narrowband), enabling direct measurement of the aerosol extinction coefficient and backscatter coefficient. This approach eliminates the uncertainties introduced by the assumption of the extinction-to-backscatter ratio (radar ratio), which is inherent in traditional methods. 
4.5 Doppler LiDAR 
　　Doppler lidar measures three-dimensional wind fields by detecting laser frequency shifts caused by aerosol motion (the Doppler effect). Based on their detection principles, they can be categorized into two types: coherent detection (heterodyne) and direct detection. 
　　4.5.1 Coherent Doppler Lidar: 
　　Using continuous-wave or pulsed lasers (typically 1.5–2 μm), the local oscillator light mixes with the echo light to generate an intermediate-frequency signal. 
　　Doppler frequency shift can be determined with spectral analysis, achieving an accuracy of up to 0.1 m/s. 
　　Suitable for boundary-layer wind field measurements (0.1–3 km), but unable to detect clean atmospheres (lacking aerosols). 
　　4.5.2 Direct-Detection Doppler Lidar: 
　　Using hyperspectral-resolution filters (such as Fabry-Perot interferometers) to directly analyze the echo spectrum enables simultaneous detection of both aerosol and molecular scattering, thereby extending the measurable altitude range.

5. Applications of Laser Atmospheric Remote Sensing 
　　Laser-based atmospheric remote sensing technology, with its high precision, high spatiotemporal resolution, and ability to simultaneously measure multiple parameters, plays an indispensable role in fields such as weather forecasting, environmental monitoring, climate research, and military applications. As technology advances and application demands grow, LiDAR observations have become a vital component of modern atmospheric science research and operational observation systems. 
5.1 Atmospheric Environment Monitoring 
5.1.1 Aerosol and Particulate Matter Monitoring 
　　Leveraging principles such as Mie scattering and Rayleigh scattering, LiDAR can monitor the vertical distribution, concentration, and particle size of atmospheric aerosols in real time, providing crucial data support for pollution events like smog and sandstorms.

532nm Pulsed Laser for Atmospheric Aerosol Detection (EO-532-H)

5.1.2 Greenhouse Gas Detection 
　　Raman lidar, with a laser wavelength of 355 nm, excites Raman signals from nitrogen (387 nm) and water vapor (408 nm), enabling simultaneous detection of temperature and humidity.

Simultaneous Aerosol and Temperature/Humidity Measurement (LPS-355-100mJ)

5.2 Meteorological and Climate Research 
　　Lidar retrieves atmospheric parameters by detecting the resonant fluorescence signal emitted when high-altitude sodium atoms are excited via the Doppler effect or laser-induced fluorescence, ultimately supporting weather forecasting, aviation safety, and climate model optimization.

The 589nm laser is used in sodium fluorescence Doppler lidar (HPL-589-Q).

5.3 Ecological and Resource Survey 
5.3.1 Carbon Cycle and Ecological Monitoring 
　　Monitoring carbon stocks in terrestrial ecosystems and the effectiveness of major ecological projects, as well as atmospheric carbon cycle monitoring.

DPS-1064 532-BS-D	FL-1550-AO

355/532/1064/1550nm pulsed lasers are used for synergistic monitoring of aerosols and vegetation, as well as for 3D modeling of carbon storage.

5.3.2 Ocean and Polar Exploration 
　　The 532nm green laser can penetrate water vapor and aquatic bodies, making it ideal for remote sensing studies of particulates in environmental applications such as atmospheric and oceanic monitoring.

532nm Microchip Laser for Marine Environment Detection (MPL-T-532)

5.4 Urban and Industrial Applications 
5.4.1 3D Modeling and Smart Cities 
　　Lidar scans buildings and terrain to generate high-precision 3D models, which are applied in urban planning, traffic management, and other fields.

A 532nm pulsed laser is used for ranging and terrain mapping.

5.4.2 Industrial Pollution Source Tracing 
　　Real-time monitoring of pollutant dispersion pathways emitted by the factory, combined with adaptive optics technology to enhance data accuracy.

DFB laser  CO2, CO, and other gas detection	3-12μm Quantum-Cascade Lasers for Detecting SO₂, NOₓ, and More	532nm/785nm Narrow-Line-Width Laser  Analyze dust composition	650nm/780nm Laser  Dust and Particulate Matter Detection

6. Development Trends in Laser Atmospheric Remote Sensing Technology 
　　Laser-based atmospheric remote sensing technology holds broad value in both scientific research and practical engineering. With ongoing technological advancements, its coverage and precision are expected to expand even further in the future, for example: 
　　Multi-parameter fusion detection: Shifting from single-wavelength to multi-wavelength and multi-parameter approaches, enhancing data dimensions. 
　　Space-Ground Cooperative Network: Combining satellite and ground-based lidar observations to achieve global coverage. 
　　Quantum technology breakthrough: Av-level sensitivity photon-counting technology overcomes the limits of turbulence-induced interference. 
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