We present an overview of the cryo-amplifier concept and design utilized in the DiPOLE100 laser system built for use at the HiLASE Center, which has been successfully tested operating at an average power of 1kW. Following this we describe the alterations made to the design in the second generation system being constructed for high energy density (HED) experiments in the HED beamline at the European XFEL. These changes are predominantly geometric in nature, however also include improved mount design and improved control over the temporal shape of the output pulse. Finally, we comment on future plans for development of the DiPOLE laser amplifier architecture.
In this paper, we review the development, at the STFC’s Central Laser Facility (CLF), of high energy, high repetition rate diode-pumped solid-state laser (DPSSL) systems based on cryogenically-cooled multi-slab ceramic Yb:YAG. Up to date, two systems have been completed, namely the DiPOLE prototype and the DiPOLE100 system. The DiPOLE prototype has demonstrated amplification of nanosecond pulses in excess of 10 J at 10 Hz repetition rate with an opticalto- optical efficiency of 22%. The larger scale DiPOLE100 system, designed to deliver 100J temporally-shaped nanosecond pulses at 10 Hz repetition rate, has been developed at the CLF for the HiLASE project in the Czech Republic. Recent experiments conducted on the DiPOLE100 system demonstrated the energy scalability of the DiPOLE concept to the 100 J pulse energy level. Furthermore, second harmonic generation experiments carried out on the DiPOLE prototype confirmed the suitability of DiPOLE-based systems for pumping high repetition rate PW-class laser systems based on Ti:sapphire or optical parametric chirped pulse amplification (OPCPA) technology.
Here we present recent progress from the new CLF
Adaptive Optics program including a new development laboratory
and tests of a high damage threshold dielectric deformable mirror.
The recently refurbished laboratory has versatile optical layout,
multi wavelength, large beam diameter and large propagation
distance (~10 m) for testing deformable mirrors up to 150 mm
diameter, as well as manufacturing capabilities.
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.
We describe two development projects: Astra-Gemini: a Petawatt class system based Ti: Sapphire amplifiers and a
10 PW upgrade for the Vulcan laser. The design concepts, features of the optical design of amplifiers and compressors
are presented. Radial delay compensation techniques used for a 3-x beam expander are discussed.
We report here some observations and preliminary findings from a study focussed on the vacuum-UV (λ, 40-60 nm) radiation emitted during the interaction of 150 ps laser pulses (100-400 mJ) with copper pre-plasmas formed by an electro-optically synchronised (0.1 - 0.8 J, 8 ns) long pulse laser. We have observed significant gains in VUV flux that scale with inter-laser delay. We also report preliminary observations on total X-ray emission from the interaction of a superintense 80 fs, 200 mJ laser pulse at the UK ASTRA laser facility with a similar pre-plasma at irradiances approaching 1019 W/cm2
This paper presents an experimental technique for measurement of the contrast ratio of ultrashort UV pulses. The multiple shot device based on the scheme of difference frequency generation is, to our knowledge, the only cross correlator in the UV so far, which offers a dynamic range of >= 107 and operates with input pulse energies as low as 5 (mu) J. Changing the cross correlator into single shot mode, the temporal shape of the UV pulse can be measured.
An injector-amplifier architecture for XUV lasers has been developed and demonstrated using the Ge XXIII collisional laser. Results are described for injection into single and double plasma amplifiers. Prismatic lens-like and higher order aberrations in the amplifier are considered. Limitations on ultimate brightness are discussed and also scaling to operation at shorter wavelengths. A preliminary study has been made of UV multiphoton ionization using 300 fs pulses at high intensity.
A large aperture KrF laser (SPRITE) based on a 27 cm diameter electron beam pumped amplifier has been developed at the Rutherford Appleton Laboratory and is in operation as a user facility. Recent development of this system has concentrated on the demands of short pulse and high brightness and this has led to two parallel program. One concentrates on efficient multiplexed energy extraction in one or more very low divergence beams using the approach known as 'Raman beam combining'. The second is directed to maximizing the brightness of a single amplified pulse by minimizing the pulse duration and using the technique of chirped pulse amplification (CPA) and recompression.
Results are presented for preliminary investigations into the way optical elements that are exposed to corrosive environments exhibit an increase in transmissive scatter the longer that such exposure exists. Near angle (i.e. < 1 degree(s)) scatter data is presented for fused silica substrates exposed to fluorine atmospheres of differing concentrations. The fluorine reacts with any water vapor present to form hydrofluoric acid which etches materials such as silica. The scatter probe wavelength used was 633 nm and scattering angles from 4 to 15 mR studied. Results are presented in bidirectional transmission distribution function (BTDF) format as well as photographs of the resulting diffraction patterns arising from passing a HeNe laser beam through the bulk of the sample which seem to show a periodic roughness profile. It is suggested that surface cleaning prior to exposure provides seeding sites, or micro scratches, for preferential attack by hydrofluoric acid.
High power krypton fluoride lasers are being developed as an alternative more efficient and
more cost effective technology for the production of ultra high power pulses. Novel laser
architectures are being evolved for this purpose including the use of angular multiplexing
and Raman beam combining. Prototype systems are being developed in several laboratories
worldwide and in particular at the Rutherford Appleton Laboratory where the Sprite laser
installation has been used to demonstrate operation in an angular multiplexed and Raman
beam combined mode for the generation of exceptionally low beam divergence and high
power in short pulses. Details are reported of the work with the Sprite system and of design
extrapolations which are under consideration as the basis of future larger laser facilities,
including the possible European Laser Facility with a performance target in the region of
1 PW peak power and 100 kJ maximum energy.