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High-order harmonic generation of pulses with multiple timescales: selection rules, carrier envelope phase and cutoff energy
摘要： High harmonic generation (HHG) is sensitive to the carrier envelope phase (CEP) of its driving laser field if it is a sufficiently short pulse (several-cycle pulse). Here we show that strong CEP effects can also be found in HHG from long duration multi-cycle pulses (up to 200 fs at 800 nm central wavelength). We find that HHG from multi-cycle pulses may be CEP dependent when the driving pulse exhibits two distinct timescales (multi-timescale pulse): (i) a short timescale associated with the average frequency, and (ii) a long timescale associated with the pulse’s temporal periodicity. The interplay of these timescales results in significant changes to both the cutoff frequency, and the appearance of symmetry allowed harmonics in the spectrum as function of CEP, similar to HHG from several-cycle pulses. We relate this effect to the multi-timescale intensity variations in the driving pulse, and construct an analytical condition to access the phenomenon. Lastly, we numerically demonstrate reconstruction of the CEP through HHG from long duration multi-timescale pulses. Our work may be useful in several areas of strong-field physics and attosecond science, for example, allowing spectroscopy of multi-timescale processes (e.g. HHG from vibrationally active media), and paving the way towards CEP characterisation using long pulses.
关键词： carrier-envelope phase,dynamical symmetry,High harmonic generation
更新于2025-09-23 15:23:52
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Toward the laser control of electronic decoherence
摘要： Controlling electronic decoherence in molecules is an outstanding challenge in chemistry. Recent advances in the theory of electronic decoherence [B. Gu and I. Franco, J. Phys. Chem. Lett. 9, 773 (2018)] have demonstrated that it is possible to manipulate the rate of electronic coherence loss via control of the relative phase in the initial electronic superposition state. This control emerges when there are both relaxation and pure-dephasing channels for decoherence and applies to initially separable electron–nuclear states. In this paper, we demonstrate that (1) such an initial superposition state and the subsequent quantum control of electronic decoherence can be created via weak-field one-photon photoexcitation with few-cycle laser pulses of definite carrier envelope phase (CEP), provided the system is initially prepared in a separable electron–nuclear state. However, we also demonstrate that (2) when stationary molecular states (which are generally not separable) are considered, such one-photon laser control disappears. Remarkably, this happens even in situations in which the initially factorizable state is an excellent approximation to the stationary state with fidelity above 98.5%. The laser control that emerges for initially separable states is shown to arise because these states are superpositions of molecular eigenstates that open up CEP-controllable interference routes at the one-photon limit. Using these insights, we demonstrate that (3) the laser control of electronic decoherence from stationary states can be recovered by using a two-pulse control scheme, with the first pulse creating a vibronic superposition state and the second one inducing interference. This contribution advances a viable scheme for the laser control of electronic decoherence and exposes a surprising artifact that is introduced by widely used initially factorizable system-bath states in the field of open quantum systems.
关键词： electronic decoherence,few-cycle laser pulses,laser control,carrier envelope phase,vibronic superposition state,quantum control
更新于2025-09-23 15:21:01
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[OSA CLEO: Science and Innovations - San Jose, California (2014..-..)] CLEO: 2014 - Arbitrary Carrier-Envelope Phase Control in a 10 kHz, mJ-Class Amplifier
摘要： The carrier-envelope phase of every single shot emitted by a 10 kHz, mJ-class amplifier is measured with a fast spectrometer. A novel high-speed actuator allows arbitrary phase control, with closed-loop integrated phase noise on seed oscillator level (98 mrad, 5.10^5 shots, 50 s).
关键词： Laser amplifiers,Carrier-envelope phase,Ultrafast lasers,Phase control,Amplifier
更新于2025-09-19 17:15:36
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Terahertz Wave Generation Using Single or Few-cycle Laser Pulses in a Gaseous Medium
摘要： We perform theoretical calculations to demonstrate that single or few-cycle laser pulses (at the wavelength of 800 nm) can generate an intense terahertz emission by a directional current. Terahertz (THz) radiation exhibits a strong dependence on the carrier-envelope phase (CEP) of the driving laser pulse as the duration decreases. The strength of the THz radiation is pronounced at the CEP of 90 deg. The design of an experimental setup to demonstrate THz wave generation using single or few-cycle laser pulses in a gaseous medium is also demonstrated.
关键词： directional current,single or few-cycle laser pulses,Terahertz wave generation,carrier-envelope phase (CEP)
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Influence of the Doppler Effect on the Carrier-Envelope Phase
摘要： Carrier-envelope phase (CEP) stabilization plays an important role in the field of attosecond pulse generation and high-field physics [1]. Low-jitter CEP stabilization of ultrashort pulses typically relies on active stabilization schemes, either employing feedback or feed-forward control. However, both established methods come with a detrimental side effect. Feedback control directly modulates pump power or intracavity loss, which causes unwanted power fluctuations of the laser output. While feed-forward control does not corrupt the output stability, it nevertheless induces beam pointing variations in the acousto-optic frequency shifter employed. Here we demonstrate a novel method for modulating the CEP of a laser oscillator, which is based on the Doppler effect and displays neither of the above-mentioned side-effects.
关键词： Doppler effect,CEP stabilization,ultrashort pulses,carrier-envelope phase,laser oscillator
更新于2025-09-16 10:30:52
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Carrier-envelope-phase–controlled molecular dissociation by ultrashort chirped laser pulses
摘要： We demonstrate and characterize that a carrier-envelope-offset-phase (CEP)–controlled ultrashort chirped ?eld is an ef?cient and robust mechanism to modify the dissociation dynamics of molecular hydrogen. Different dissociation pathways are collectively induced and their interference contributes to the kinetic-energy release spectra. Chirping is able to ef?ciently manipulate the interferences of different dissociation pathways. We demonstrate a linear relationship between chirp and CEP dependent dissociation as well as directional electron localization.
关键词： electron localization,molecular dissociation,carrier-envelope-phase,kinetic-energy release spectra,ultrashort chirped laser pulses
更新于2025-09-11 14:15:04
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Carrier-envelope-phase dependence of harmonics induced by a few-cycle vortex laser
摘要： When a few-cycle vortex laser interacted with an inversion-symmetric atomic-like system, beyond the usual odd-order harmonics, some additional components also occur. The detailed numerical investigation on their transverse field distributions discloses that they depend sensitively on the carrier-envelope-phase (CEP) and the rotation period of the transverse distribution is 2π. This could be used to directly determine the CEP value of an incident pulse, unique without falling back on specific polar molecules or static electric fields.
关键词： propagation effects,carrier-envelope-phase,topological charge number,vortex laser,transverse field distribution
更新于2025-09-11 14:15:04
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Three-dimensional carrier-envelope-phase map of focused few-cycle pulsed Gaussian beams
摘要： We derive an analytical expression that describes the complete three-dimensional carrier-envelope-phase (CEP) distribution in the focal volume of ultrashort pulsed Gaussian beams focused by spherical mirrors or lenses. The focal CEP map depends on the so-called factor g specifying the frequency dependence of the beam width of the source few-cycle pulse, on its chirp, and on the small chromatic aberration introduced by a lens without appreciably distorting or broadening the few-cycle pulse. We show how to tailor the CEP map of mirror-focused and lens-focused few-cycle pulses in order to produce negligible transversal and axial CEP variations in specific regions of the focal volume for phase-sensitive interactions of light with matter taking place in a volume or on a surface. We propose a quasiachromatic doublet lens that can implement in practice these tailored CEP distributions.
关键词： CEP map,carrier-envelope-phase,few-cycle pulses,chromatic aberration,Gaussian beams
更新于2025-09-09 09:28:46