Generation of one-cycle laser pulses by use of high-amplitude plasma waves

Laser Wakefield Driven Generation of Isolated Carrier-Envelope-Phase Tunable Intense Subcycle Pulses

Sources of intense, ultrashort electromagnetic pulses enable applications such as attosecond pulse generation, control of electron motion in solids, and the observation of reaction dynamics at the electronic level. For such applications, both high intensity and carrier-envelope-phase (CEP) tunability are beneficial, yet hard to obtain with current methods. In this Letter, we present a new scheme for generation of isolated CEP tunable intense subcycle pulses with central frequencies that range from the midinfrared to the ultraviolet. It utilizes an intense laser pulse that drives a wake in a plasma, copropagating with a long-wavelength seed pulse. The moving electron density spike of the wake amplifies the seed and forms a subcycle pulse. Controlling the CEP of the seed pulse or the delay between driver and seed leads to CEP tunability, while frequency tunability can be achieved by adjusting the laser and plasma parameters. Our 2D and 3D particle-in-cell simulations predict laser-to-subcycle-pulse conversion efficiencies up to 1%, resulting in relativistically intense subcycle pulses.

Interaction of electromagnetic waves with caustics in plasma flows

An electromagnetic wave (EMW) interacting with the moving singularity of the charged particle flux undergoes the reflection and absorption as well as frequency change due to Doppler effect and nonlinearity. The singularity corresponding to a caustic in plasma flow with inhomogeneous velocity can arise during the breaking of the finite amplitude Langmuir waves due to nonlinear effects. A systematic analysis of the wave-breaking regimes and caustics formation is presented and the EMW reflection coefficients are calculated.

Powerful terahertz emission from laser wakefields in inhomogeneous magnetized plasmas

Powerful coherent terahertz (THz) pulses with a broad spectrum (0.1-3 THz) can be produced from a laser-driven wakefield through linear mode conversion in inhomogeneous magnetized plasmas with the maximum plasma density of 10(17) cm(-3). This occurs when a laser pulse, with an optimized duration about 300 fs, is incident either normally or obliquely to the density gradient of inhomogeneous magnetized plasmas. The external dc magnetic field has a magnitude of a few tesla. By changing the strength and direction of the magnetic field, one can enhance or suppress the THz emission. The maximum energy conversion efficiency in the magnetized plasmas can be double that in the unmagnetized plasmas. Such wakefield emission can be a powerful THz source at the MW level and capable of affording field strength of a few MV/cm, suitable for THz nonlinear physics. Because these THz emissions are always with a positive chirp, with a proper dispersion compression, single-cycle THz pulses can be generated with higher peak powers and field strengths.

Emission of electromagnetic pulses from laser wakefields through linear mode conversion

Powerful coherent emission around the plasma oscillation frequency can be produced from a laser wakefield through linear mode conversion. This occurs when the laser pulse is incident obliquely to the density gradient of inhomogeneous plasmas. The emission spectrum and conversion efficiency are obtained analytically, which are in agreement with particle-in-cell simulations. The emission can be tuned to be a radiation source in the terahertz region and with field strengths as large as a few GV/m, suitable for high-field applications. The emission also provides a simple way to measure the wakefield produced for particle acceleration.

Light intensification towards the Schwinger limit

A method to generate ultrahigh intense electromagnetic fields is suggested, based on the laser pulse compression, carrier frequency upshift, and focusing by a counterpropagating breaking plasma wave, relativistic flying parabolic mirror. This method allows us to achieve the quantum electrodynamics critical field (Schwinger limit) with present-day laser systems.