Remote detection and identification of plastics with hyperspectral Raman imaging lidar.

We report a hyperspectral Raman imaging lidar system that can remotely detect and identify typical plastic species. The system is based on a frequency-doubled, Q-switched Nd:YAG laser operating at 532 nm and an imaging spectrograph equipped with a gated intensified CCD spectrometer. Stand-off detection of plastics is achieved at 6 m away with a relatively wide field of view of 1 × 150 mm, thus providing the groundwork for better solutions in monitoring marine plastic pollution.

Hard-Target Reflection Laser Spectroscopy of Carbon Monoxide Gas Concentration for the Early Detection of Spontaneous Combustion of Coal.

We report on the hard-target reflection spectroscopy of carbon monoxide (CO) gas based on the technique of infrared tunable diode laser absorption spectroscopy aiming at developing a low-cost yet sensitive sensor for the early detection of spontaneous coal combustion. A narrow-band distributed feedback laser emitting around 2333.7 nm is used to monitor CO gas molecules contained in a 5 cm gas cell.

Remote visualization of underwater oil using a flash Raman lidar system.

We propose and experimentally demonstrate a new, to the best of our knowledge, underwater monitoring system that incorporates Raman spectroscopy based on a flash lidar. We have visualized underwater oil at a 5 m distance by illuminating the area of around 15 cm diameter with an expanding laser beam at 532 nm and detecting the oil and water Raman images. By calibrating the oil Raman image with the water Raman image, the detection limit of liquid oil thickness has been estimated to be about 0.

Raman lidar for remote sensing of oil in water.

We describe a portable Raman lidar system that can remotely detect oil leakages in water. The system has been developed based on a frequency-doubled, -switched Nd:YAG laser, operated at 532 nm with a receiver telescope equipped with some filters and photomultipliers. Stand-off detection of oil is achieved in a 6-m-long water tank, which allowed us to considerably increase the survey capability of subsea infrastructures, including both the range observation and target identification.

Comparison of aerosol properties derived from sampling and near-horizontal lidar measurements using Mie scattering theory.

Aerosol optical properties are measured near the surface level using sampling instruments and a near-horizontal lidar. The values of the aerosol extinction coefficient inside the instruments are derived from nephelometer and aethalometer data, while the ambient values are measured from the lidar. The information on aerosol size distribution from optical particle counters is used to simulate extinction coefficients using the Mie scattering theory, with corrections on the humidity growth of hygroscopic particles.