ИСТИНА

The carrier-envelope phase (CEP) of near single cycle laser pulses plays an important role in physics of strong field interaction and attosecond optics [1-4]. Our approach of such pulses generation is based on exploring nonlinear optical transformation of the femtosecond laser pulses with the central wavelength near in anti-resonant hollow-core fiber (AR HCF) filled with argon [5]. The supercontinuum generation is leaded by the soliton self-compression (SSC) scenario, with additional enhancement from the self-steepening effect and parametric generation of four-wave components in the blue wing of the soliton spectrum. In such condition it is possible to form very short pulses with the duration less than on cycle of the field with the noticeable influence of CEP. In our investigation we explore the signatures of phase dependence in the visible part of the SC generated during SSC down to single-cycle pulsewidth in an anti-resonant hollow-core fiber (AR HCF) filled with argon. This phenomenon is observed within the small parameter range, when the pulse reaches its maximum compression ratio, but there is still no strong ionization, leading to pulse decay. Theoretical analysis by means of the numerical solution of the generalized nonlinear Schrödinger equation (GNSE) reveals that the phase dependence arises from the broadband third harmonic generation (THG) in the range from 250 nm to 800 nm at the moment of a sub-cycle pulse composition and its spectral interference with the visible part of the SC. The CEP control of this ultrabroadband f-3f interference provides a signature of the sub-cycle pulse synthesis during SSC in the fiber with duration of 0.4 optical cycles and peak power more than 2 GW on the fiber output [6]. By means of such CEP controlled pulses with a duration about one optical period and pump-probe scheme, we experimentally demonstrated the generation of spectral components sensitive to the phase of the carrier relative to the pump pulse envelope on plasma nonlinearity in a thin film of zinc selenide (ZnSe). The probing pulse is scattered by the plasma, generating new phase-sensitive spectral components at the edges of its spectrum. A theoretical analysis of the generation of these components on nonperturbative plasma nonlinearity is carried out.