Exploration for adequate non-diffractive beam generation in dense scattering media.

The propagation methods of a non-diffractive beam (NDB) for optical sensing in scattering media have been extensively studied. However, those methods can realize the high resolution and long depth of focus in the viewpoint of microscopic imaging. In this study, we focus on macroscopic sensing in living tissues with a depth of a few tens centimeters. An experimental approach for generating adequate NDB in dense scattering media based on the linear relationship between propagation distance and transport mean free path is reported. For annular beams with different diameters, the same changes of the center intensity ratio of NDB are obtained from the experiment results. They are discussed with theoretical analysis. As a result, the maximum center intensity ratio of the adequate generated NDB can be estimated at arbitrary propagation distance in the dense scattering media.

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. By applying this method to the continuous data obtained from November to December 2018 at Chiba, Japan, we elucidate the temporal variations of near-surface aerosol properties, including the complex refractive index, single scattering albedo, and Angstrom exponent. The results indicate how aerosol particles change their properties between the dry, instrumental conditions and relatively humid setting of the ambient atmosphere.