Frequency locking to the center of a 532 nm iodine absorption line by using stimulated brillouin scattering from a single-mode fiber.

A simple method for frequency locking a frequency-doubled Nd:YAG laser to the center of line 1109 of the iodine absorption spectrum is described. The 31.6 GHz frequency shift provided by stimulated-Brillouin scattering from a single-mode silica fiber provides a probe signal that lies on the edge of line 1105 of the iodine spectrum. We adjust the frequency of the laser to maintain the transmission of a 5 cm iodine absorption cell at a value that places the unshifted laser line in the center of line 1109.

Practical model for the calculation of multiply scattered lidar returns.

An equation to predict the intensity of the multiply scattered lidar return is presented. Both the scattering cross section and the scattering phase function can be specified as a function of range. This equation applies when the cloud particles are larger than the lidar wavelength. This approximation considers photon trajectories with multiple small-angle forward-scattering events and one large-angle scattering that directs the photon back toward the receiver. Comparisons with Monte Carlo simulations, exact double-scatter calculations, and lidar data demonstrate that this model provides accurate results.

Fiber-optic scrambler reduces the bandpass range dependence of Fabry-Perot étalons used for spectral analysis of lidar backscatter.

Lidar systems that analyze backscatter with Fabry-Perot étalons exhibit range-dependent spectral transmission functions. A fiber-optic scrambler is described that reduces this range dependence.

High spectral resolution lidar to measure optical scattering properties of atmospheric aerosols. 1: theory and instrumentation.

A high spectral resolution lidar technique to measure optical scattering properties of atmospheric aerosols is described. Light backscattered by the atmosphere from a narrowband optically pumped oscillator-amplifier dye laser is separated into its Doppler broadened molecular and elastically scattered aerosol components by a two-channel Fabry-Perot polyetalon interferometer. Aerosol optical properties, such as the backscatter ratio, optical depth, extinction cross section, scattering cross section, and the backscatter phase function, are derived from the two-channel measurements.

High spectral resolution lidar to measure optical scattering properties of atmospheric aerosols. 2: calibration and data analysis.

The high spectral resolution lidar (HSRL) measures optical properties of atmospheric aerosols by interferometrically separating the elastic aerosol backscatter from the Doppler broadened molecular contribution. Calibration and data analysis procedures developed for the HSRL are described. Data obtained during flight evaluation testing of the HSRL system are presented with estimates of uncertainties due to instrument calibration. HSRL measurements of the aerosol scattering cross section are compared with in situ integrating nephelometer measurements.

Aerosol size distributions: remote determination from air-borne measurements of the solar aureole.

Aerosol size distributions were determined remotely using an airborne scanning photometer. This instrument consists of a sunshade, optics, and a large dynamic range photodetector-amplifier system that scans about the vertical, recording both the direct attenuated solar beam and the diffuse sky radiance in the almucantar of the sun at an effective wavelength of 0.54 microm. The inversion of the measured radiances determined aerosol radii from approximately 0.2 microm to 8.0 microm. Data were taken during flights in May 1973 over western Lake Superior and southwestern Wisconsin. Inverted aerosol size distributions are compared with results obtained by other methods.