I.N. Ross

The prospects for ultrashort pulse duration and ultrahigh intensity using optical parametric chirped pulse amplifiers

Abstract The properties of optical parametric amplifiers are presented to show that, in addition to their use in providing tuneable pulses, they can form the critical component in systems generating shorter pulse duration with higher power and intensity than is possible with existing systems. Practical designs are evaluated leading to anticipated powers exceeding 10 PW and focused intensities greater than 10 23 W cm −2 .

Generation of terawatt pulses by use of optical parametric chirped pulse amplification

Optical parametric chirped pulse amplifiers offer exciting prospects for generating new extremes in power, intensity, and pulse duration. An experiment is described that was used to investigate the operation of this scheme up to energies approaching a joule, as a step toward its implementation at the petawatt level. The results demonstrate an energy gain of 10(10) with an energy extraction efficiency of 20% and close to diffraction-limited performance. Some spectral narrowing during amplification was shown to be compatible with the time-varying profile of the pump beam and consistent with the measured recompressed pulse durations of 260 and 300 fs before and after amplification, respectively.

35 J broadband femtosecond optical parametric chirped pulse amplification system

We report on what is believed to be the first large-aperture and high-energy optical parametric chirped pulse amplification system. The system, based on a three-stage amplifier, shows 25% pump-to-signal conversion efficiency and amplification of the full 70 nm width of the seed spectrum. Pulse compression to 84 fs achieved after amplification indicates a potential of 300 TW pulse power for 35 J amplified pulse energy.

High energy amplification of picosecond pulses at 248 nm

Abstract Experiments to amplify picosecond pulses in a large aperture e-beam-pumped KrF amplifier have demonstrated energies of up to 2.5 J in a pulse of ≈ 3.5 ps duration corresponding to a peak power of 0.7 TW. Background amplified spontaneous emission levels were typically 50 mJ in a 20 ns pulse and were strongly dependent on gain staging. Measurements of the saturation fluence and the gain recovery time of the e-beam-pumped gain medium yielded values of 2.0±0.4 mJ cm-2 and ≈ 3 ns respectively.

High contrast multi-terawatt pulse generation using chirped pulse amplification on the VULCAN laser facility

High power (8 TW), ultra-short (2.4 ps), pulses have been generated using chirped pulse amplification techniques on the VULCAN Nd: glass laser. A novel oscillator was developed as a driver producing ≈ ps pulses at 105 nm. The oscillator output was stretched prior to amplification and compressed at an aperture of 150 mm. The contrast ratio obtained was ≈ 106, which is suitable for laser plasma interaction studies.

Binary-phase zone plate arrays for the generation of uniform focal profiles

The generation of uniform focal intensity profiles is important for a number of applications, including laser-plasma interaction experiments. We report on a focusing system that uses a novel binary-phase optic capable of producing efficient two-dimensional uniform top-hat intensity optical and x-ray profiles.

Broadband sum-frequency generation by chirp-assisted group-velocity matching

In dispersive media the bandwidths of generated sum- or difference-frequency pulses can be greatly enlarged by use of previously chirped generating waves. It is shown that this technique is even more advantageous for shorter pulses and at a higher dispersion regime of the crystal. Experimental examples are also discussed.

Binary phase zone-plate arrays for laser-beam spatial-intensity distribution conversion

We report on the theory and development of a diffractive element composed of a binary phase zone-plate array. This component conditions the intensity distribution in the focal plane of a conventional refractive lens to generate efficiently (82%) a flattop intensity envelope on target. Analysis of the design indicates that manufacturing tolerances are not critical. Experimental performances on target from x-ray emission and shock-breakout measurements are also presented.

Optical parametric chirped-pulse amplification source suitable for seeding high-energy systems.

A short-pulse source based on optical parametric chirped-pulse amplification (OPCPA) technology has been developed with properties that make it a suitable seed for a high-energy OPCPA system. This source generated a diffraction-limited pulse at 910 nm with a full bandwidth of > 165 nm and a spectrum having a transform-limited pulse duration of less than 15 fs. The technique has potential for generating bandwidths > 200 nm and pulse durations < 10 fs.

Well characterized 1019W cm2 operation of VULCAN—an ultra-high power Nd:glass laser

Abstract Peak intensities of 1019 W cm2 have been reliably obtained from a high power Nd:glass laser using chirped pulse amplification. An Additive Pulse Modelocked oscillator incorporating diode pumped Nd:LMA was used to generate the sub-picosecond pulse. The focal spot intensity distribution has been characterized in detail showing a three times diffraction limited beam.