ИСТИНА

We show that an individual droplet of liquid metal can be a source of coherent terahertz (THz) radiation, when it is excited by two femtosecond laser pulses of the same frequency. We describe the experimental results with the model of dynamic gain control, which considers the interaction of both laser pulses with the droplet and explains the THz generation process taking into account the dynamics of electrons and ions after photo-ionization of the metal droplet. The spatial distribution of THz radiation has a forward directed contribution, whose polarization proper-ties are well described by a nonlinear susceptibility of the second order.