Photon deceleration in plasma wakes generates single-cycle relativistic tunable infrared pulses.

Availability of relativistically intense, single-cycle, tunable infrared sources will open up new areas of relativistic nonlinear optics of plasmas, impulse IR spectroscopy and pump-probe experiments in the molecular fingerprint region. However, generation of such pulses is still a challenge by current methods. Recently, it has been proposed that time dependent refractive index associated with laser-produced nonlinear wakes in a suitably designed plasma density structure rapidly frequency down-converts photons.

High-resolution phase-contrast imaging of biological specimens using a stable betatron X-ray source in the multiple-exposure mode.

Phase-contrast imaging using X-ray sources with high spatial coherence is an emerging tool in biology and material science. Much of this research is being done using large synchrotron facilities or relatively low-flux microfocus X-ray tubes. An alternative high-flux, ultra-short and high-spatial-coherence table-top X-ray source based on betatron motions of electrons in laser wakefield accelerators has the promise to produce high quality images.

Single-shot visualization of evolving laser wakefields using an all-optical streak camera.

We visualize ps-time-scale evolution of an electron density bubble--a wake structure created in atmospheric density plasma by an intense ultrashort laser pulse--from the phase "streak" that the bubble imprints onto a probe pulse that crosses its path obliquely. Phase streaks, recovered in one shot using frequency-domain interferometric techniques, reveal the formation, propagation, and coalescence of the bubble within a 3 mm long ionized helium gas target. 3D particle-in-cell simulations validate the observed density-dependent bubble evolution, and correlate it with the generation of a quasimonoenergetic ∼ 100 MeV electron beam.

Single-shot visualization of evolving, light-speed structures by multiobject-plane phase-contrast imaging.

We demonstrate a single-shot method of visualizing the evolution of light-speed, laser-generated structures as they propagate over hundreds of Rayleigh lengths (typically ≥10 cm) through a tenuous medium. An ultrashort probe pulse crosses the object's path at a small angle (θ<5°) and a specific time delay. Copies of the phase-modulated probe are then relay-imaged to separate detectors from selected object planes along the propagation path.

Tomography of high harmonic generation in a cluster jet.

Tomographic measurement of high harmonic generation in a cluster jet was demonstrated by programming the cluster density distribution with a laser machining technique. The growth of harmonic energy with the propagation of the pump pulse was resolved by scanning the end of the argon cluster distribution in the path of the pump pulse. A downstream shift of the position of rapid growth and a decrease of the slope with increasing backing pressure as results of changes in the phase-matching condition were observed, which explains the presence of an optimal backing pressure.