Terahertz sound generation at the effect of a femtosecond pulse of laser radiation on a metal.

Sound generation by a femtosecond laser pulse in a metal layer on a dielectric substrate is studied. The excitation of sound caused by the effect of the ponderomotive force, temperature gradients of electrons, and lattice is considered. A comparison is made of these generation mechanisms for various excitation conditions and frequencies of generated sound. It is shown that in the case when effective collision frequencies in the metal are low, sound generation dominates in the terahertz frequency range due to the ponderomotive effect of the laser pulse.

Competition of quasi-cylindrical and surface waves excited at the femtosecond pulse effect on the metal.

Nonlinear generation of the quasi-cylindrical and surface waves in terahertz frequency domain under exposure of a femtosecond laser pulse focused into a strip on a metal was studied. Competition between generated waves is determined by the value of the product of electron collision frequency and laser pulse duration. Comparison of magnetic field pulses of the quasi-cylindrical and surface waves generated on the surface is given for gold, silver, and aluminum. It is shown that far from the focusing strip the surface wave pulse contains oscillations arising due to frequency dispersion.