ИСТИНА

Superfilament formation in air by 0.5 TW femtosecond IR pulse was studied. Control of the initial transverse distribution of electromagnetic field was achieved by placing amplitude or phase (so-called diffractive optical element) masks before the loosely focusing lens. Angularly resolved spectra of the radiation inside a filament as well as wideband acoustic signals were detected starting from the focusing lens to the filament termination point. We presented a comparative study for (i) a single filament, (ii) stochastic superfilamentation, (iii) amplitude or (iv) phase controlled superfilamentation. In simulations we apply the Forward Maxwell equation with a carrier wave resolved. Our model includes the diffraction, dispersion, Kerr nonlinearity, self-consistent ionization and transient photocurrent of free electrons. Such the model can describe adequately the spectral transformation and energy absorption.