Analytical model of backscattering signals in lidars based on complex modulated photon density waves

Theoretical models of lidar echo signals, which are formed when probing seawater with laser pulses modulated by a broadband high-frequency signal with the use of matched detection (for "compression" of the modulating signal), have been developed. The models are suitable for calculating elastic backscattering signals and fluorescence echo signals; they are constructed based on analytical solutions of the radiation transfer equation in the small-angle approximation. The elastic backscattering signal model has been verified using Monte Carlo statistical simulations. It has been shown that the considered probing method will allow recording vertical profiles of optically active substances contained in water with the same spatial resolution as the ultrashort pulse probing method, however, with lower probing power.