Carrier-envelope Phase Of Pulses Research Articles

Theoretical investigation of electron dynamics driven by laser pulses in graphene nanoribbons

Control of electron dynamics in graphene nanoribbons (GNRs) is critically important for the future applications of graphene-based nanoelectronic devices. Based on real-time simulations, we investigate the manipulation of electronic transport by femtosecond laser pulses in armchair GNRs. The simulation results show that the multiphoton absorption process can drive the photon-excited electron flow along a GNR. The corresponding transferred charges are determined by the order of multiphoton absorption and depend on the central frequency and energy distribution of few-cycle laser pulses. Furthermore, the transferred charge can be controlled by the carrier-envelope phase of pulses; this dependence vanishes as the duration time of laser pulses increases. These results also provide insights into the manipulation of electron dynamics using lasers and the design of optoelectronic devices based on graphene materials.

Generation of XUV spectral continua from relativistic plasma mirrors driven in the near-single-cycle limit

We present experiments using relativistic-intensity 1.5-cycle laser fields at 1 kHz repetition rate to drive surface high-harmonic generation (SHHG) from surface plasmas with controlled density gradient. As a function of the driving pulse carrier-envelope phase (CEP), we observe a transition from a modulated to a continuous SHHG spectrum, indicating the transition from double to isolated attosecond pulse emission. Single shot-acquisitions of XUV spectral continua support the emission of isolated attosecond pulses with an isolation degree of between 10 and 50 for the majority of the driving pulse CEPs. 2D Particle-in-cell simulations corroborate this interpretation and predict percent-level efficiencies for the generation of an isolated attosecond pulse even without spectral filtering.

Active phase control of terahertz pulses using a dynamic waveguide.

Control over the spectral phase of a light pulse is a fundamental step toward arbitrary signal generation in a spectral band. For the terahertz spectral regime, pulse shaping holds the key for applications ranging from ultra-high speed wireless data transmission to quantum control with shaped fields. In this work, we demonstrate a technique for all-optical and reconfigurable control of the spectral phase of a light pulse in the important terahertz (THz) band. The technique is based on interaction of a guided THz pulse with patterned photoexcited regions within a uniform silicon-filled parallel-plate waveguide. We use this platform to demonstrate broadband and tunable positive and negative chirp of a THz pulse, as well as control of the pulse carrier envelope phase.

Interference of electron wave packets in photoionization of by attosecond ultraviolet laser pulses

We study molecular photoionization of aligned by a sequence of two attosecond ultraviolet laser pulses at frequencies and from numerical solutions of time-dependent Schördinger equations. Results exhibit signature of interference effects of coherent electron wave packets, which is shown to be sensitive to the time delay between the two pulses. It is found that for the photoionization with identical frequencies , same interference distributions are produced in the positive and negative momentum regions whereas for the case of , photoelectron momentum distributions are asymmetric. Influence of the pulse carrier envelope phase is also presented. The attosecond perturbation theory is used to describe these interference phenomena.

Laser pulses for coherent xuv Raman excitation

We combine multi-channel electronic structure theory with quantum optimal control to derive Raman pulse sequences that coherently populate a valence excited state. For a neon atom, Raman target populations of up to 13% are obtained. Superpositions of the ground and valence Raman states with a controllable relative phase are found to be reachable with up to 4.5% population and phase control facilitated by the pump pulse carrier envelope phase. Our results open a route to creating core-hole excitations in molecules and aggregates that locally address specific atoms and represent the first step towards realization of multidimensional spectroscopy in the xuv and x-ray regimes.

Short pulse carrier-envelope phase absolute single-shot measurement by photoionization of gases with a guided laser beam

We present an all optical approach to measure the value of the carrier-envelope phase (CEP) of a short intense laser pulse. This method relies on photo-ionization of gases with a guided laser beam. This approach that provides the absolute value of the CEP, is compatible with single shot characterization, is scalable in wavelength, does not suffer from bandwidth limitation and is largely intensity independent. It has also the potential to provide a full characterization of the pulse profile via high order autocorrelation on a single shot basis.

Measurement of the carrier-envelope phase stability of infrared femtosecond laser pulses by two-path interferometer

We describe a self-referencing two-path interferometer designed to measure the carrier-envelope phase stability. In experiment, we measure the carrier-envelope phase （CEP） stability of a home-made infrared tunable OPA laser pulses with the self-referencing two-path interferometer. When the wavelength of the incident pulses is 1.6 μm, the CEP fluctuation is 115 mrad （rms） in 100 seconds. The interferometer can provide an accurate and quick measurement of the pulse CEP.

Phase-dependent nonsequential double ionization by few-cycle laser pulses

By solving the time-dependent Schrödinger equation, we investigate the phase dependence of nonsequential double ionization of one-dimensional Ar atoms by linearly polarized few-cycle pulses. The resulting two-electron momentum distributions exhibit a strong dependence on the pulse's carrier-envelope phase (CEP). The calculated Ar2+ ion momentum distributions parallel to the laser polarization direction are in good agreement with the experimental measurements of Liu et al (2004 Phys. Rev. Lett. 93 263001). The ratio of the total double ionization yields from the first and third quadrants as a function of the CEP is similar to the ratio of the total single ionization yields from the left and right sides. The influence of electron–electron Coulomb repulsion on double ionization is also investigated by comparing a short-range interaction with the infinite-range interaction. Our theoretical simulations provide a prediction for determining the CEP value of few-cycle pulses by comparing with the experimental measurements.

Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions: roles of frequency, intensity and an additional IR pulse

The effects of the carrier-envelope phase (CEP) of a few-cycle attosecond pulse on ionized electron momentum and energy spectra are analyzed, both with and without an additional few-cycle IR pulse. In the absence of an IR pulse, the CEP-induced asymmetries in the ionized electron momentum distributions are shown to vary as the 3/2 power of the attosecond pulse intensity. These asymmetries are also found to satisfy an approximate scaling law involving the frequency and intensity of the attosecond pulse. In the presence of even a very weak IR pulse (having an intensity of the order of 1011–1012 W cm−2), the attosecond pulse CEP-induced asymmetries in the ionized electron momentum distributions are found to be significantly augmented. In addition, for higher IR laser intensities, we observe for low electron energies peaks separated by the IR photon energy in one electron momentum direction along the laser polarization axis; in the opposite direction, we find structured peaks that are spaced by twice the IR photon energy. Possible physical mechanisms for such asymmetric, low-energy structures in the ionized electron momentum distribution are proposed. Our results are based on single-active-electron solutions of the three-dimensional, time-dependent Schrödinger equation including atomic potentials appropriate for the H and He atoms.

Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions

We analyze carrier-envelope phase (CEP) effects on electron wave-packet momentum and energy spectra produced by one or two few-cycle attosecond xuv pulses. The few-cycle attosecond pulses are assumed to have arbitrary phases. We predict CEP effects on ionized electron wave-packet momentum distributions produced by attosecond pulses having durations comparable to those obtained by Sansone et al. [Science 314, 443 (2006)]. The onset of significant CEP effects is predicted to occur for attosecond pulse field strengths close to those possible with current experimental capabilities. Our results are based on single-active-electron solutions of the three-dimensional, time-dependent Schr\odinger equation including atomic potentials appropriate for the H and He atoms.

All-optical stabilization of carrier-envelope phase by use of difference frequency generation with seeded amplification of colored conical emission

We stabilized the carrier-envelope phase of pulses emitted by a femtosecond regenerative amplifier through difference frequency generation between pump and seeded amplification of colored conical emission. Seeded amplification of colored conical emission was induced by modulational instability in the second harmonic generation with a supercontinuum injected and amplified. As a consequence, it inherited the origin phase of the pump pulse. After difference frequency with the pump pulses, the generated tunable idler pulses were carrier-envelope phase stabilized, which was verified with a simple and robust spectral interference setup.

Observation of carrier-envelope phase phenomena in the multi-optical-cycle regime.

So far the role of the carrier-envelope phase of a light pulse has been clearly experimentally evidenced only in the sub-6-fs temporal regime. Here we show, both experimentally and theoretically, the influence of the carrier-envelope phase of a multi-optical-cycle light pulse on high-order harmonic generation. For the first time, we demonstrate that the short and long electron quantum paths contributing to harmonic generation are influenced in a different way by the pulse carrier-envelope phase.