J. L. Collier

The Vulcan 10 PW project

The aim of this project is to establish a 10 PW facility on the Vulcan laser system capable of being focussed to intensities of at least 1023 Wcm−2 and integrate this into a flexible and unique user facility This paper will present progress made in Phase one developing the 10PW Front End as well as the concept for the new Vulcan 10 PW facility. The new facility will be configured in a unique way to maximise the scientific opportunities presented through a combination with the existing capabilities already established on Vulcan. This ground breaking development will open up a range of new scientific opportunities.

High-spatiotemporal-quality petawatt-class laser system

We have developed a femtosecond high-intensity laser system that combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric CPA (OPCPA) techniques and produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. With a cleaned high-energy seeded OPCPA preamplifier as a front end in the system, for the compressed pulse without pumping the final amplifier, we found that the temporal contrast in this system exceeds 10(10) on the subnanosecond time scales, and is near 10(12) on the nanosecond time scale prior to the peak of the main femtosecond pulse. Using diffractive optical elements for beam homogenization of a 100 J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with a near-perfect top-hat-like intensity distribution.

Extreme Light Infrastructure: Architecture and major challenges

Extreme Light Infrastructure (ELI), the first research facility hosting an exawatt class laser will be built with a joint international effort and form an integrated infrastructure comprised at last three branches: Attosecond Science (in Szeged, Hungary) designed to make temporal investigation at the attosecond scale of electron dynamics in atoms, molecules, plasmas and solids. High Field Science will be mainly focused on producing ultra intense and ultra short sources of electons, protons and ions, coherent and high energetic X rays (in Prague, Czech Republic) as well as laserbased nuclear physics (in Magurele, Romania). The location of the fourth pillar devoted to Extreme Field Science, which will explore laser-matter interaction up to the non linear QED limit including the investigation of vacuum structure and pair creation, will be decided after 2012. The research activities will be based on an incremental development of the light sources starting from the current high intensity lasers (APOLLON, GEMINI, Vulcan and PFS) as prototypes to achieve unprecedented peak power performance, from tens of petawatt up to a fraction of exawatt (1018 W). This last step will depend on the laser technology development in the above three sites as well as in current high intensity laser facilities.

Optimised design for a 1 kJ diode-pumped solid-state laser system

A conceptual design for a kJ-class diode-pumped solid-state laser (DPSSL) system based on cryogenic gas-cooled multislab ceramic Yb:YAG amplifier technology has been developed at the STFC as a building block towards a MJ-class source for inertial fusion energy (IFE) projects such as HiPER. In this paper, we present an overview of an amplifier design optimised for efficient generation of 1 kJ nanosecond pulses at 10 Hz repetition rate. In order to confirm the viability of this technology, a prototype version of this amplifier scaled to deliver 10 J at 10 Hz, DiPOLE, is under development at the Central Laser Facility. A progress update on the status of this system is also presented.

Ultrafast science and development at the Artemis facility

The Artemis facility for ultrafast XUV science is constructed around a high average power carrier-envelope phasestabilised system, which is used to generate tuneable pulses across a wavelength range spanning the UV to the far infrared, few-cycle pulses at 800nm and short pulses of XUV radiation produced through high harmonic generation. The XUV pulses can be delivered to interaction stations for materials science and atomic and molecular physics and chemistry through two vacuum beamlines for broadband XUV or narrow-band tuneable XUV pulses. The novel XUV monochromator provides bandwidth selection and tunability while preserving the pulse duration to within 10 fs. Measurements of the XUV pulse duration using an XUV-pump IR-probe technique demonstrate that the XUV pulselength is below 30 fs for a 28 fs drive laser pulse. The materials science station, which contains a hemispherical electron analyser and five-axis manipulator cooled to 14K, is optimised for photoemission experiments with the XUV. The end-station for atomic and molecular physics and chemistry includes a velocity-map imaging detector and molecular beam source for gas-phase experiments. The facility is now fully operational and open to UK and European users for twenty weeks per year. Some of the key new scientific results obtained on the facility include: the extension of HHG imaging spectroscopy to the mid-infrared; a technique for enhancing the conversion efficiency of the XUV by combining two laser fields with non-harmonically related wavelengths; and observation of D3+ photodissociation in intense laser fields.

Design and characterization of the XUV monochromator for ultrashort pulses at the ARTEMIS facility

ARTEMIS, a multi-partner and multidisciplinary project, will be a users-dedicated facility that will provide ultrashort XUV pulses through high harmonic generation in a gas target. This high repetition rate synchronized source will allow new science in research fields spanning from the material science to the molecular physics and chemistry. The XUV radiation is expected to cover the range 10-100 nm with an estimated photons flux up to 1011 photons/s per harmonic. In this work we present the design and characterization of the monochromator that will be used in the beamline for the experiments requiring wavelength and bandwidth selection. The working principle is based on a plane grating operated at grazing incidence in the off-plane mount. This geometry has been selected because of the high diffraction efficiency, expected to be about 30%. To cover the entire spectral range four gratings can be selected which span over different regions and with different spectral resolution. When the appropriate grating is chosen, the wavelength scanning is performed by rotating the grating around an axis passing through the grating center and parallel to the grooves direction. The off-plane mount requires the grating to be used in collimated light, consequently the optical scheme is completed by two toroidal mirrors, the first in front of the source that collimates the XUV radiation before the grating and the second after the grating to focalize the spectrally dispersed photons on the exit slit. Using a single grating, the configuration is not time-delay-compensated, nevertheless the time broadening (depending on the source divergence, the wavelength, and the grating) is less than 50 fs.

DiPOLE100: A 100 J, 10 Hz DPSSL using cryogenic gas cooled Yb:YAG multi slab amplifier technology

In this paper we provide an overview of the design of DiPOLE100, a cryogenic gas-cooled DPSSL system based on Yb:YAG multi-slab amplifier technology, designed to efficiently produce 100 J pulses, between 2 and 10 ns in duration, at up to 10 Hz repetition rate. The current system is being built at the CLF for the HiLASE project and details of the front end, intermediate 10J cryo-amplifier and main 100J cryo-amplifier are presented. To date, temporal and spatial pulse shaping from the front end has been demonstrated, with 10 ns pulses of arbitrary shape (flat-top, linear ramps, and exponentials) produced with energies up to 150 mJ at 10 Hz. The pump diodes and cryogenic gas cooling system for the 10J cryo-amplifier have been fully commissioned and laser amplification testing has begun. The 100J, 940 nm pump sources have met full specification delivering pulses with 250 kW peak power and duration up to 1.2 ms at 10 Hz, corresponding to 3 kW average power each. An intensity modulation across the 78 mm square flat-top profile of < 5 % rms was measured. The 100J gain media slabs have been supplied and their optical characteristics tested. Commissioning of the 100J amplifier will commence shortly.

DiPOLE: a scalable laser architecture for pumping multi-Hz PW systems

DiPOLE is a concept for a large aperture gas-cooled cryogenic multislab DPSSL amplifier based on ceramic Yb:YAG. It is designed to amplify ns-pulses at multi-Hz repetition rates and is scalable up the kJ-level. The concept was first tested on a small scale prototype which has so far produced 7.4 J at 10 Hz, with the aim of reaching 10 J at an optical-to-optical efficiency of 25 %. The design of an additional amplifier stage producing 100 J at 10 Hz is underway. When used to pump short-pulse Ti:S or OPCPA systems, PW peak power levels can be produced at repetition rates and efficiencies that lie orders of magnitude above what is achievable today.

HiPER laser reference design

HiPER (High Power laser Energy Research) is the first European plan for international cooperation in developing inertial fusion energy. ICF activities are ongoing in a number of nations and the first ignition experiments are underway at the National Ignition Facility (NIF) in the USA. Although HiPER is still in the preparatory phase, it is appropriate for Europe to commence planning for future inertial fusion activities that leverage the demonstration of ignition. In this paper we shall detail some of the key points of the laser design. Some of the main topics of the laser architecture are presented and discussed.

Concept for Cryogenic kJ-Class Yb:YAG Amplifier

More and more projects and applications require the development of ns, kJ-class DPSSL systems with multi-Hz repetition rate. We present an amplifier concept based on cryogenically cooled Yb:YAG, promising high optical-to-optical efficiency and high gain.