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Results for “Carrier-envelope-phase”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Carrier-envelope-phase characterization of ultrafast mid-infrared laser pulses through harmonic generation and interference in argon

The propagation of an intense, femtosecond, mid-infrared laser pulse in a gaseous medium results in the efficient generation of spectrally overlapping low-order harmonics, whose optical carrier phases are linked to the carrier-envelope phase (CEP) of the mid-infrared driver pulse. Random peak-power fluctuations of the driver pulses, converted to the fluctuations of the nonlinear phases, acquired by the pulses on propagation, cause this phase correlation to smear out. We show that this seemingly irreversible loss of phase can be recovered, and that the complete information needed for the phase correction is contained in the harmonic spectra itself. The optical phases of the intense driver pulse and its harmonics, as fragile as they appear to be against even weak disturbances, evolve deterministically during highly nonlinear propagation through the extended ionization region.

nonlinear optics↗
DOE OSTI2023

Polarization and phase control of electron injection and acceleration in the plasma by a self-steepening laser pulse

Abstract We describe an interplay between two injection mechanism of background electrons into an evolving plasma bubble behind an intense laser pulse: one due to the overall bubble expansion, and another due to its periodic undulation. The two mechanisms occur simultaneously when an intense laser pulse propagating inside a plasma forms a shock-like steepened front. Periodic undulations of the plasma bubble along the laser propagation path can either inhibit or conspire with electron injection due to bubble expansion. We show that carrier-envelope-phase (CEP) controlled plasma bubble undulation induced by the self-steepening laser pulse produces a unique electron injector—expanding phase-controlled undulating bubble (EPUB). The longitudinal structure of the electron bunch injected by the EPUB can be controlled by laser polarization and power, resulting in high-charge (multiple nano-Coulombs) high-current (tens of kilo-amperes) electron beams with ultra-short (femtosecond-scale) temporal structure. Generation of high-energy betatron radiation with polarization- and CEP-controlled energy spectrum and angular distribution is analyzed as a promising application of EPUB-produced beams.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

The effects of laser polarization and wavelength on injection dynamics of a laser wakefield accelerator

Here, we investigate the effects of laser polarization and wavelength on electron injection dynamics in a laser wakefield accelerator. During the ionization process, electrons gain residual momentum and kinetic energy via above threshold ionization, which has a strong dependence on laser polarization. A circularly polarized laser pulse results in a much higher residual momentum and kinetic energy gain for the ionized electrons compared with the linearly polarized case. This residual momentum results in particle injection because of the sensitivity of particle trapping to the initial conditions and enhanced the total injected beam charge in both experiments and particle-in-cell simulations. Due to the strong correlation of above threshold ionization with laser wavelength, in this work we extended the investigation to long wavelength (up to 20 μm) drive pulses using particle-in-cell simulations. Owing to the gain in kinetic energy, it may be expected that the charge trapped would consistently increase for circular polarization with increasing laser wavelength, but this was not observed. Instead, there are oscillations with wavelength in the relative trapped charge between linear and circular polarization cases, which arise because of ionization and heating effects on the plasma. Our studies highlight the complex interplay between several different physical effects, including injection regimes—above threshold ionization assisted injection, wave-breaking injection by carrier-envelope-phase effects and ionization injection—ionization gradient induced laser pulse evolution, and thermal modifications to the wake structure that need considering when extrapolating laser wakefield acceleration to different wavelength regimes.

Ma, Y. (ORCID:0000000239194856)↗
DOE OSTI2021

Generation of isolated soft x-ray attosecond pulses with mid-infrared driving lasers via transient phase-matching gating

Abstract Isolated attosecond pulses (IAPs) in the soft x-ray (SXR) region are highly desirable for attosecond time-resolved experiments. Here we identify a transient phase matching gating method for the generation of such IAPs with mid-infrared (MIR) lasers. This gating method works when a loosely focused, long-duration MIR Gaussian driving beam is slightly reshaped during its propagation in the gas medium under the ‘critical’ ionization condition. Quantitatively, the calculated coherence length of high harmonic is used to analyze the mechanism of the gating method, by using one-dimensional plane-wave beams and by comparing 2000 nm and 800 nm lasers. The robustness of the generation method is checked by varying laser’s carrier-envelope-phase and gas pressure. This gating method provides with an alternative route to efficiently produce tabletop ultrashort attosecond SXR light sources with the emerging MIR lasers.

Physics↗
DOE OSTI2024

Propagation effects in polarization-gated attosecond soft-X-ray pulse generation

Accurate estimation of the duration of soft-x-ray pulses from high-harmonic generation (HHG) remains challenging given their higher photon energies and broad spectral bandwidth. The carrier-envelope-phase (CEP) dependence of generated soft-x-ray spectra is indicative of attosecond pulse generation, but advanced simulations are needed to infer the pulse duration from such data. Here, we employ macroscopic propagation simulations to reproduce experimental polarization-gated CEP-dependent soft-x-ray spectra. The simulations indicate chirped pulses, which we theoretically find to be compressible in hydrogen plasmas, suggesting this as a viable compression scheme for broadband soft-x-rays from HHG.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Multi-millijoule hollow-core fiber compression of short-wave infrared pulses to a single cycle

Approaches for efficient pulse compression can enable dramatic increases in the available peak power, as well as enable the generation of isolated attosecond X-ray pulses. Achieving high compression ratios for longer wavelength drivers has, however, been challenging. We present the compression of few-cycle 2.1 µm central wavelength short-wave infrared laser pulses to 6.9 fs with 2.35 mJ pulse energy at a 10 kHz repetition rate. Electric field resolved measurements reveal a single cycle light field oscillation. With a carrier-envelope-phase stability of 131 mrad and average power fluctuations below 1 %, the system constitutes an excellent light source for strong-field experiments and attosecond physics.

Blöchl, Johannes [Ludwig Maximilian Univ. of Munic↗
DOE OSTI2025

Ionization effects in single-shot carrier-envelope phase detection with gas-gap devices

The carrier-envelope phase (CEP) is a key parameter for attosecond waveform control of ultrashort laser pulses. For laser systems with high repetition rates, however, single-shot CEP detection is still challenging. Building on recent findings on phase detection with electric current generation in gases, we show that with an optimized detection method, a long-term stable single-shot phase detection is feasible. We investigate the achievable performance depending on various parameters such as pulse duration, gas pressure, or incident intensity. The latter exhibits a regime where the saturation of the ionization process boosts the phase sensitivity of the signal, which is elucidated by numerical calculations.

47 OTHER INSTRUMENTATION↗