Colloquium: Dr. Deric Gray, Naval Research Lab

Abstract: Almost as soon as the laser was invented, oceanographers have been using it to learn more about the ocean. From the earliest applications of bathymetry measurements from aircraft, lidars are used for the detection of oil, fish schools, and even temperature and salinity of the water. In this talk I will discuss some of the current uses of lidar in oceanography. We will begin by introducing the basic concepts and ideas of light propagation in the ocean. Ocean water contains a continuum of particles - from the very small - water molecules themselves - to the very large - fish, dolphins, and whales, and all of them can have an effect on lidar propagation in the ocean. We will then discuss the basic components of an oceanographic lidar and some of challenges in their design and operation - from wavelength consideration, laser repetition rate and receiver characteristics. Signals from some typical lidars will be shown to illustrate the types of signals we can get in different environments. We will then look at some of the more unique research using lidars in the ocean: Raman and Brillouin scattering to determine water temperature and salinity, linear and circular polarization to determine particle shape and orientation, and multi-wavelength lidars to characterize particle types.