K. T. Lu

What is LIDAR ? Everything you wanted to know but were afraid to ask !

LIDAR is the abbreviated word for Laser Radar (laser light detection and ranging). It combines the advantages of laser's ability to detect atoms and molecule and radar's ability for remote sensing. Because of these unique features, LIDAR has gaining more attention as a valuable high-tech tool in remote sensing. The marriage between high power pulsed laser with photonics imaging technology has developed new types of LIDAR system capable of detecting toxic and radioactive chemicals and metals not in gas form and not exposed in air such as in underground water and subsurface soil. The high power laser is used to vaporize the target material and generate a plasma. Optical fiber is often used to deliver the laser beam and to collect the emission for imaging. The combination of spectroscopy with advanced photonics imaging techniques can study both the chemical components of samples in-situ under ambient conditions and spatial distribution of different chemicals in remote operation without requiring sample preparation or extensive sample handling. The latest high-tech innovation greatly enlarged the horizon of traditional capability of remote sensing. Examples of different LIDAR systems for detection of pollutants in air, ground water and subsurface soil will be present.

LIDAR relies on the detection of "finger prints" induced by laser excitation and ablation of the elements or chemicals. However, these "finger prints" can be interfered by the laser induced plasma and environmental matrix effects such as air pressure, water or solid phases. Computational technique based on non-equilibrium dynamic method is required to deal with the expanding plasma and to disentangle these interference effects and to enhance the quantitative analytical capability to achieve the real-time decision making as required by the LIDAR technique. Highlights of the mechanisms and their experimental manifestations will be presented which include: