560 TW peak power has been achieved experimentally using a Cr:forsterite master oscillator at 1250 nm, a stretcher, three optical parametrical amplifiers based on KD*P crystals providing 38 J energy in the chirped pulse at 910 nm central wavelength, and a vacuum compressor providing 43 fs pulse duration. To our knowledge, it is a world-record OPCPA system and one of the five most powerful laser systems currently available.

https://iopscience.iop.org/article/10.1002/lapl.200710008/pdf

Compact 0.56 Petawatt laser system based on optical parametric chirped pulse amplification in KD*P crystals

This article demonstrates a new compression scheme that has the potential to compress a high energy pulse as high as a few hundred Joules in a pulse as short as one optical cycle at 0.8 μm producing a true ultra-relativistic λ3 pulse. This pulse would have a focused intensity of 1024 W/cm2 or a0 of 1000. On interaction with a solid target, this pulse could form an efficient, 10%, relativistic mirror that could further compress the pulse to the atto-zeptosecond regime, with an upshifted wavelength of 1–10 keV. This technique could be a watershed enabling the compression of petawatt pulses into the exawatt and zeptosecond regime possible.

Single cycle thin film compressor opening the door to Zeptosecond-Exawatt physics

Two methods of compensation of thermal lensing in high-power terbium gallium garnet (TGG) Faraday isolators have been investigated in detail: compensation by means of an ordinary negative lens and compensation using FK51 Schott glass possessing a negative dn/dT. Key thermooptic constants for TGG crystals and FK51 glass were measured. We find that the contribution of the photoelastic effect to the total thermal lens cannot be neglected for either TGG or FK51. We define a figure of merit for compensating glass and show that for FK51, an ordinary negative lens with an optimal focus is more efficient, but requires physical repositioning of the lens for different laser powers. In contrast, the use of FK51 as a compensating element is passive and works at any laser power, but is less effective than simple telescopic compensation. The efficiency of adaptive compensation can be considerably enhanced by using a compensating glass with figure of merit more than 50, a crystal with natural birefringence or gel.

/pdf/compensation-of-thermally-induced-modal-distortions-in-vmiv4fxqjm.pdf

Compensation of thermally induced modal distortions in Faraday isolators

We report on the magneto-optical (MO) properties of heavily Tb3+-doped GeO2-B2O3-Al2O3-Ga2O3 glasses towards fiber-integrated paramagnetic MO devices. For a Tb3+ ion concentration of up to 9.7 × 1021 cm−3, the reported glass exhibits an absolute negative Faraday rotation of ~120 rad/T/m at 632.8 nm. The optimum spectral ratio between Verdet constant and light transmittance over the spectral window of 400–1500 nm is found for a Tb3+ concentration of ~6.5 × 1021 cm−3. For this glass, the crystallization stability, expressed as the difference between glass transition temperature and onset temperature of melt crystallization exceeds 100 K, which is a prerequisite for fiber drawing. In addition, a high activation energy of crystallization is achieved at this composition. Optical absorption occurs in the NUV and blue spectral region, accompanied by Tb3+ photoluminescence. In the heavily doped materials, a UV/blue-to-green photo-conversion gain of ~43% is achieved. The lifetime of photoluminescence is ~2.2 ms at a stimulated emission cross-section σem of ~1.1 × 10−21 cm2 for ~ 5.0 × 1021 cm−3 Tb3+. This results in an optical gain parameter σem*τ of ~2.5 × 10−24 cm2s, what could be of interest for implementation of a Tb3+ fiber laser.

Faraday rotation and photoluminescence in heavily Tb 3+ -doped GeO 2 -B 2 O 3 -Al 2 O 3 -Ga 2 O 3 glasses for fiber-integrated magneto-optics

This report presents the conceptual design of a new European research infrastructure EuPRAXIA. The concept has been established over the last four years in a unique collaboration of 41 laboratories within a Horizon 2020 design study funded by the European Union. EuPRAXIA is the first European project that develops a dedicated particle accelerator research infrastructure based on novel plasma acceleration concepts and laser technology. It focuses on the development of electron accelerators and underlying technologies, their user communities, and the exploitation of existing accelerator infrastructures in Europe. EuPRAXIA has involved, amongst others, the international laser community and industry to build links and bridges with accelerator science — through realising synergies, identifying disruptive ideas, innovating, and fostering knowledge exchange. The Eu-PRAXIA project aims at the construction of an innovative electron accelerator using laser- and electron-beam-driven plasma wakefield acceleration that offers a significant reduction in size and possible savings in cost over current state-of-the-art radiofrequency-based accelerators. The foreseen electron energy range of one to five gigaelectronvolts (GeV) and its performance goals will enable versatile applications in various domains, e.g. as a compact free-electron laser (FEL), compact sources for medical imaging and positron generation, table-top test beams for particle detectors, as well as deeply penetrating X-ray and gamma-ray sources for material testing. EuPRAXIA is designed to be the required stepping stone to possible future plasma-based facilities, such as linear colliders at the high-energy physics (HEP) energy frontier. Consistent with a high-confidence approach, the project includes measures to retire risk by establishing scaled technology demonstrators. This report includes preliminary models for project implementation, cost and schedule that would allow operation of the full Eu-PRAXIA facility within 8—10 years.

EuPRAXIA Conceptual Design Report

Experimental results of measurements for Russian magneto-optical glasses MOG101, MOG105, MOG04, and MOG10 are presented, including the coefficient of electronic nonlinearity, energy of thermal defocusing, and power resistance. For comparison, the same parameters are shown for the optical glass K8 (an analog of the well-known BK7 glass), the fused silica QU-1, and the laser phosphate glass GLS-22P. The obtained data allow consumers to choose the proper magneto-optical materials for the device operation mode.

Comparative characteristics of magneto-optical materials

A five-stage neodymium phosphate glass amplifier producing 1–1.5-ns radiation pulses of energy up to 110 J is described. The use of a multistage spatial filter based on an aperture line provides efficient extraction of the stored energy. The exit aperture filling factor is 0.65 and the output radiation divergence is equal to three times the diffraction-limited divergence. The energy efficiency of radiation conversion to the second harmonic is 60%. The amplifier is intended for pumping a chirped-pulse optical parametric amplifier.

http://iopscience.iop.org/article/10.1070/QE2005v035n04ABEH003419/pdf

Compact neodymium phosphate glass laser emitting 100-J, 100-GW pulses for pumping a parametric amplifier of chirped pulses

We describe spatial filters used in a Nd:glass laser with an output pulse energy up to 300 J and a pulse duration of 1 ns. This laser is designed for pumping of a chirped-pulse optical parametric amplifier. We present data required to choose the shape and diameter of a spatial filter lens, taking into account aberrations caused by spherical surfaces. Calculation of the optimal pinhole diameter is presented. Design features of the spatial filters and the procedure of their alignment are discussed in detail.

Spatial filters for high-peak-power multistage laser amplifiers

Small-scale self-focusing is the main cause of power limitation in nanosecond Nd:glass lasers We report pioneer observation in experiment of laser beam noise amplification for B -integral (nonlinear phase) order of unity, ie, without destruction of nonlinear medium Analytical dependences of noise amplification coefficient on the B-integral have been obtained for one nonlinear medium as well as for two nonlinear media separated by an air gap with image relay A simple analytical dependence has been found for an optimal distance between two nonlinear media for which the maximum allowable value of B -integral increases from 27 to 43 The maximum attainable energy in neodymium-phosphate glass lasers with rod amplifiers 10 cm in diameter is 400 J with a pulse duration of 1 ns

A. K. Potemkin

Papers

Comparative characteristics of magneto-optical materials

Compact neodymium phosphate glass laser emitting 100-J, 100-GW pulses for pumping a parametric amplifier of chirped pulses

Spatial filters for high-peak-power multistage laser amplifiers

Compact 300-J/300-GW Frequency-Doubled Neodymium Glass Laser—Part I: Limiting Power by Self-Focusing

Shaping Triangular Picosecond Laser Pulses for Electron Photoinjectors