Abstract
We analyze the macroscopic effects which are responsible for producing clean isolated pulses lasting few hundreds of attoseconds when starting from multi-cycle fundamental pulses. In particular, we consider a polarization gating scheme and show that, at high fundamental peak intensities, in the range 0.7-1 PWcm(-2), it usually produces three-four main attosecond pulses of radiation at single dipole level, just located in the leading edge of the laser pulse. We describe the physical mechanisms contributing to the formation of a single attosecond pulse by using a three dimensional non-adiabatic model and a quantum trajectory phase calculation. An analysis of the scheme optimization and stability against various parameters is performed in view of an experimental scheme implementation.
Highlights
The first generation of an attosecond pulse train [1] followed by the measurement of a single isolated attosecond pulse (SAP) [2] has paved the way to what has been called attoscience [3], whose aim is the investigation of physical phenomena occurring on a time scale comparable to the electron revolution time around the nucleus in the Bohr’s vision of the atom
Sub-femtosecond pulses have been mainly generated by means of High Harmonic Generation (HHG) in gases, which can be described by the three-step model [7]
The initial stage of investigation was devoted to finding the range of the key parameters which determine the formation of the SAP
Summary
The first generation of an attosecond pulse train [1] followed by the measurement of a single isolated attosecond pulse (SAP) [2] has paved the way to what has been called attoscience [3], whose aim is the investigation of physical phenomena occurring on a time scale comparable to the electron revolution time around the nucleus in the Bohr’s vision of the atom. We proposed a new approach [18] to achieve SAP from multi-cycle pulses delivered by commercial laser systems (Titanium: Sapphire sources with central wavelength at 800 nm), which combines a polarization gating generated in this case on the leading edge of the driving pulse with a subsequent ionization gating [19] whose role is to prevent the emission of additional attosecond pulses from the rest of the pulse Such a method shows to be effective with pulse durations up to 25 fs and can be used with actual intensities as high as 1 PW⋅cm−2 or potentially more, thereby overcoming a technical limitation arising when Spatial Light Modulator [20] is used to generate a polarization gate. The third section has a first part in which the formation mechanism of the SAP and single electron trajectories contributing to the SAP are discussed, followed by a second part in which we analyze the technical limits of the method and estimate the final SAP brightness
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