Renu Appl. PhyB lasers & optics (original) (raw)
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Comparison of indigenously developed micro pulse polarization lidar with EZ lidar profiles
Applied Physics B, 2011
A Micro Pulse Polarization LIDAR (MPPL) has been designed and developed for aerosol and cloud studies at National Physical Laboratory, New Delhi, India (28°35 N, 77°12 E) using a low-energy pico-second pulsed Nd:YAG laser at 532 nm and single PMT detector. This has been used for detecting depolarization characteristics with back-scatter coefficient of atmospheric aerosols and clouds. The backscattered signals are detected at the emitted wavelength with co-polarization and cross-polarization discrimination with a mirror on stepper motor for aerosols and cloud. Data are obtained by MPPL and are inter-compared with a wellestablished commercial Leosphere made EZ LIDAR, industry standard at the same site and time, and the results are found to be in good agreement. In the present communication the back-scattered coefficient, aerosols optical depth, depolarization ratio etc. obtained using MPPL & EZ LIDAR are discussed in detail.
We present a newly designed Compact Cloud and Aerosol LIDAR (ComCAL) that was built for the de ployment in field campaigns on ground and on mobile platforms like aboard the research vessel Polarstern. The automated system is particularly suited for tropo spheric aerosol research within the altitude range from 0.7 to 20 km. As emitter it uses a frequency doubled and tripled Nd:YAG laser. It measures elastic backscat ter and the depolarization at 532 nm and 355 nm as well as inelastic scattering with a 32-channel spectro graph. Recently, it was shown that biomass burning aerosol fluoresces when irradiated by a UV laser beam while other aerosol types do not fluoresce [1]. Beside the detection of N2 and H2O Raman scattering, fluores cence of aerosols can be detected by the new optical set-up of our lidar system. The measurement of wave lengths dependent backscatter, extinction, depolariza tion, and fluorescence makes a detailed study of atmo spheric aerosols possible. The new li...
A four-wavelength depolarization backscattering LIDAR for polar stratospheric cloud monitoring
Applied Physics B Photophysics and Laser Chemistry, 1992
A four wavelength backscattering depolarization LIDAR designed for polar stratospheric cloud and stratospheric aerosol measurement is described. The system uses the following wavelengths: 355 nm, 532 nm, 750 nm, and 850 nm. These wavelengths, obtained by means of the third-and secondharmonic of a Nd:YAG laser and by means of a tunable Ti:Sapphire laser, are chosen in a way to better characterize the particel size of such stratospheric aerosols. They are not emitted simultaneously as the LIDAR system is designed with only two detection channels permitting to detect, in the analog and in the photon counting mode, both the direct and the depolarized backscattered signal. The system has been operational in northern Finland since the end of November 1991.
Polarization lidar at 1.54μm and observations of plumes from aerosol generators
Optical Engineering, 2007
The ability to detect relative changes in backscatter polarization from a scanning high-pulse-energy lidar system at 1.54-m wavelength is demonstrated. The new capability was tested during the dissemination of various biological aerosol simulants and other particulate emissions at the U.S. Army's Dugway Proving Ground. Results demonstrate that the lidar is sensitive to different types of aerosols, and departures from the atmospheric background depolarization ratio are consistent with the limited amount of information available on the degree of particle sphericity. We conclude that the polarization-sensitive coatings of the beam-steering unit mirrors are presently the largest source of error and that this error is minimized when scanning with a near-zero elevation angle. This is an encouraging result for aerosol source surveillance applications, where the depolarization information may be useful in determining the aerosol generation mechanism or provide an additional scalar variable for use in delineating the plume from the background.
LIDAR investigation of properties of atmospheric aerosol
The European Physical Journal Special Topics, 2007
In the paper application of lidars for investigation of aerosol particle size distribution and for observation of aerosol consisting of solid state particles is presented. For size distribution the multiwavelength lidar and original method of data analysis was applied. For registration of dust transported to Central Europe from Sahara and Middle East deserts analysis of depolarization of the backscattered signals was used. In order to solve the lidar equation measurements of total atmospheric optical depth by means of Microtops sun photometer was done. Mean size and the aspect ratio of dust particles were determined by comparing of lidar observations with data from T-matrix calculations.
Multiwavelength micropulse lidar for atmospheric aerosol investigation
2010
Multiwavelength micropulse lidar (MML) designed for continuous atmospheric sounding is presented. In its optical emitter, a diode pumped pulsed Nd:YAG laser is used. The laser generates three wavelengths: 1064, 532 and 355 nm. Energies of light pulses are about 30, 15 and 7 μJ, respectively, while their repetition rate is 2 kHz. Returning light is collected by a Cassegrain telescope with the mirror of 170 mm in diameter. Then, the signal is spectrally separated by a polichromator built with dielectric interference and colour filters. Detection of the signals is performed with three photomultipliers and a multiscaling photon counter. Preliminary results of investigation of aerosol properties during COAST 2009 experiment on the Baltic Sea are presented.
Implementation Of Micropulse Lidar at 4.5 μm and 1.5 μm for Aerosol and Cloud Study
EPJ Web of Conferences, 2016
Identifying and quantifying ambient aerosols and their interactions with clouds are important for air-quality and climate studies. Advances in infrared technologies on fiber lasers, quantum cascade lasers and IR detectors have made developing micro-pulse (low energy) IR lidar systems operating in the infrared spectral range feasible. We present in this contribution a micropulse dual channel (IR wavelength) lidar system for studying aerosol and cloud optical properties. The system operates at 1.545 µm (6472.5 cm-1) and at 4.55 µm (2197.8 cm-1) with high repetition rates and microjoule pulses. The system is intended to be coupled with an existing UV, visible, near infrared lidar system at the city college of New York, part of the CREST lidar network Preliminary backscattered signals from this system are here presented and compared to SNR simulation.