Two-laser generation of extended underwater plasma

A method for remotely generating an underwater acoustic pulse having a controlled anisotropic waveform and pulse duration, comprising:

• at time t1, firing a first laser pulse into a body of water, the first laser pulse being focused to a first intensity and being configured to generate an optical filament in the water, the intensity of the first laser pulse further being configured to generate a low-energy plasma coincident with the optical filament;
• and
• at time t2, firing a second laser pulse into the body of water targeted at the low-energy plasma coincident with the optical filament, the second laser pulse being focused to a second intensity and being configured to deposit its energy into the low-energy plasma so as to achieve a desired heating of the low-energy plasma, causing formation of an superheated extended underwater plasma having a desired spatial profile and energy density;
• wherein the extended underwater plasma generates an underwater acoustic pulse having a first desired pulse duration τ∥ in a direction parallel to the optical filament a second desired pulse duration τ⊥ in a direction orthogonal to the optical filament.