Lidar (light detection and ranging) depolarization measurements were performed simultaneously at three wavelengths using a coherent white light continuum. The white light continuum ranging from the ultraviolet to the infrared region was generated by a focused 0.5 TW/100 fs pulse in a krypton gas cell at the atmospheric pressure. The lidar system consisted of three depolarization channels at 450, 550, and 800 nm. The observed depolarization ratios for each wavelength showed differences for clouds. These depolarization features in wavelength are discussed in terms of particle size and shape using T-matrix computations. The depolarization ratios at three wavelengths can be used to infer information on the size of the particles in clouds, assuming an ice crystal shape a priori. Also, the obtained size distributions from the three-wavelength depolarization ratios correspond with the changes in particle size indicated by changes in the Angstrom coefficient obtained by multiwavelength lidar techniques. This study demonstrated that the three-wavelength depolarization ratios provided additional information about the size and shape of clouds and aerosols.

No abstract

We carried out depolarization light detection and ranging (LIDAR) measurements for the first time using a coherent white light continuum with multi-wavelength backscatter measurements. The white light continuum from the UV to the IR region was generated in Kr gas by a terawatt femtosecond laser system. The LIDAR system consisted of a depolarization channel at 450 nm and the five-wavelength Mie scattering channels at 350, 450, 550, 700, and 800 nm. This technique can potentially open a promising avenue toward simultaneous depolarization LIDAR at multi-wavelength.

No abstract

We have developed a laser Raman spectroscopy technique for assessing the working conditions of transformers by measuring dissolved C2H2 gas concentrations present in transformer oils. A frequency doubled Q-switched Nd:YAG laser (532 nm) was used as a laser source, and Raman signals at ~1972 cm(-1) originating from C2H2 gas dissolved in oil were detected. The results show that laser Raman spectroscopy is a useful alternative method for detecting transformer faults.