ИСТИНА

The carrier-envelope phase (CEP) of single-cycle laser pulses plays an important role in the strong field physics and attosecond optics [1-4]. Our approach to the generation of such pulses is based on the study of nonlinear optical conversion of femtosecond laser pulses with a central wavelength of about 2 μm in an antiresonant hollow fiber (AR HCF) filled with argon [5] under pressure. The supercontinuum is generated according to the soliton self-compression (SSC) scenario with additional gain due to the self-steepening effect and parametric generation of four-wave components in the blue wing of the soliton spectrum. Such conditions allow to obtain very short pulses with a duration of less than one field cycle with a noticeable influence of CEP. In our study, we study the phase dependence of the visible part of the supercontinuum generated during the SSC of the ultrashort pulses down to the single-cycle duration in an antiresonant hollow fiber filled with argon. This phenomenon is observed in the range of small parameters, when the pulse reaches the maximum compression ratio, but there is no strong ionization yet, leading to pulse attenuation. Theoretical analysis using the numerical solution of the generalized nonlinear Schrödinger equation shows that the phase dependence arises due to the broadband generation of the third harmonic in the range from 250 nm to 800 nm at the moment of formation of the sub-cycle pulse and its spectral interference with the visible part of the supercontinuum. The CEP control of the by this ultra-wideband f-3f interference indicates the generation of a sub-cycle pulse at the SSC in the fiber with a duration of 0.4 optical cycle and a peak power of more than 2 GW at the fiber output [6]. Using such CEP-controlled single-cycle pulses and a pump-probe scheme, we experimentally demonstrated the generation of spectral components sensitive to the carrier-envelope phase on plasma nonlinearity in a thin zinc selenide (ZnSe) film. The probe pulse is scattered by the plasma, generating new phase-sensitive spectral components at the edges of its spectrum. A theoretical analysis of these components generation on plasma nonlinearity is carried out.