Jennifer Elle

Shock formation in supersonic cluster jets and its effect on axially modulated laser-produced plasma waveguides

We examine the generation of axially modulated plasmas produced from cluster jets whose supersonic flow is intersected by thin wires. Such plasmas have application to modulated plasma waveguides. By appropriately limiting shock waves from the wires, plasma axial modulation periods can be as small as 70 μm, with plasma structures as narrow as 45 µm. The effect of shocks is eliminated with increased cluster size accompanied by a reduced monomer component of the flow.

Generation of axially modulated plasma waveguides using a spatial light modulator

We demonstrate the generation of axially modulated plasma waveguides using spatially patterned high-energy laser pulses. A spatial light modulator (SLM) imposes transverse phase front modulations on a low-energy (10 mJ) laser pulse which is interferometrically combined with a high-energy (130-450 mJ) pulse, sculpting its intensity profile. This enables dynamic and programmable shaping of the laser profile limited only by the resolution of the SLM and the intensity ratio of the two pulses. The plasma density profile formed by focusing the patterned pulse with an axicon lens is likewise dynamic and programmable. Centimeter-scale, axially modulated plasmas of varying shape and periodicity are demonstrated.

Dependence of single-shot pulse durations on near-infrared filamentation-guided breakdown in air

We present results of an experimental investigation of laser pulsewidth dependence of filamentation-guided high voltage breakdown in air. The experiments are conducted at laser peak power levels of 1 TW and pulse durations of 0.7 to 10 ps with a discharge gap separation of 10 cm. Synchronized electrical and optical diagnostic techniques were used to determine the pulsewidth dependence on the breakdown mechanism, threshold levels, time delays and associated jitter. The results indicate that longer pulses provide greater than 30% reduction in breakdown threshold voltage.

Modulated Plasma Waveguides Generated by Intense Bessel Beams Patterned with a Spatial Light Modulator

Plasma guiding structures are generated with programmable axial density modulations using a Spatial Light Modulator (SLM). A coherent beam-combining scheme enables the sculpting of high power beams with modest energy passing through the SLM.

Electron density measurements of plasma columns for N 2 atmospheric lasing

Line emission of N₂ and time-resolved electron density are measured in a several centimeter long plasma column. Peak density is 6*10¹⁵ cm^-3 and emission from the second positive system of N₂ is observed.

Acceleration of Electrons in Modulated Plasma Channels with Radially Polarized Laser Pulses

Two highly versatile experimental techniques are demonstrated for making preformed plasma waveguides with periodic structure capable of supporting the propagation of ultra‐intense femtosecond laser pulses. These waveguides were made in hydrogen, nitrogen and argon plasmas with a length of 15 mm and modulation period as short as 35 μm. Simulations show that these guides allow direct laser acceleration of electrons, achieving gradients of 80 MV/cm and 10 MV/cm for laser pulse powers of 1.9 TW and 30 GW, respectively. We also demonstrate a technique for making the required radially polarized pulses.