Laser irradiance in the sea: Theory and experiment

Laser beam spreading due to the air/sea interface, volume scattering, and initial beam divergence is modeled. Beam steering is considered for the case in which the laser beam diameter is small compared to the length of the refracting wave. An expression is developed for the irradiance as a function of depth into the ocean. A comparison of the terms in this expression shows that the surface spreading effect is small compared with bulk scattering. Wavetank experiments were performed. The height, slope, and frequency content of wind-driven capillary waves are reported for wind speeds in the range 2.2 m/sec to 7.6 m/sec.