Single thin-plate compression of multi-TW laser pulses to 3.9 fs.

Post-compression of 12-fs laser pulses with multi-TW peak power from an optical parametric chirped pulse amplification (OPCPA) system was performed by using a single thin fused silica plate in a vacuum. By optimizing the input pulses in both spatial and temporal domains, after compression with customized chirped mirrors, we achieved pulses as short as 3.87 fs, in combination with 12-mJ energy. The spatio-spectral quality of the post-compressed pulses was thoroughly analyzed. The generated 1.4-cycle pulses pave the way for next generation attosecond and particle acceleration experiments.

The petawatt laser of ELI ALPS: reaching the 700 TW level at 10†Hz repetition rate.

Performance of the novel high repetition rate HF-PW laser system of ELI ALPS is presented in its first operation phase at 400 TW and 700 TW levels. Long-term operation was tested at 2.5 and 10 Hz repetition rates, where an exceptional 0.66% and 1.08% shot-to-shot energy stability was demonstrated, respectively. Thorough spatio-spectral and temporal measurements confirmed high quality output pulses with a Strehl ratio of >0.9 after compression at both repetition rates. Amplified pulses with an unprecedentedly high 240 W average power were reached for the first time from a PW-class amplifier chain by using novel pseudo-active mirror disk amplification-based pump lasers.

Sub-7 fs radially-polarized pulses by post-compression in thin fused silica plates.

We experimentally demonstrate the post-compression of radially polarized 25 fs pulses at 800 nm central wavelength in a multiple thin plate arrangement for the first time, to the best of our knowledge. Sub-7 fs pulses with 90 µJ energy were obtained after dispersion compensation, corresponding to a compression factor of more than 3.5. Preservation of radial polarization state was confirmed by polarized intensity distribution measurements. Linear projections of the radially polarized pulses were also fully characterized in the temporal domain.

Relativistic near-single-cycle optical vortex pulses from noble gas-filled multipass cells.

We propose to obtain relativistic near-single-cycle optical vortices carrying orbital angular momentum through the post-compression of Laguerre-Gaussian pulses in gas-filled multipass cells. Our simulations revealed that 30 fs optical vortex pulses centered around 800 nm with a pulse energy of millijoule level can be compressed to near-single-cycle duration with topological charges from 1 to 20 within an argon-filled cell with five passes. The spectral broadening preserves the topological charge of the input beam; the spatio-spectral couplings are also discussed. The energy of the vortex pulses could be scaled up by increasing the dimensions of the cell. The relativistic near-single-cycle vortices are of great interest for the generation of ultrashort helical electron bunches based on hybrid electron acceleration in underdense plasmas and on isolated relativistic extreme ultraviolet optical vortices from high-order harmonic generation in solid foils.

Broadband spectral characterization of the phase shift induced by population inversion in Ti:Sapphire.

The spectral phase shift of broadband amplified pulses, induced by population inversion, was measured in Ti:Sapphire at different pump fluence values. The measurement was performed for two orthogonal polarization directions and at two different crystal temperatures of 296 K and 30 K. Zero shifts and sign changes were observed in the spectral phase, which are connected to the gain spectrum of the crystal. The electronic refractive index changes were also numerically calculated by the Kramers-Kronig theory. The results are highly important for achieving sub-10 fs pulse duration and phase stability in the next generation of Ti:Sapphire-based laser systems.

Design of a thin disk amplifier with extraction during pumping for high peak and average power Ti:Sa systems (EDP-TD).

Combination of the scheme of extraction during pumping (EDP) and the Thin Disk (TD) technology is presented to overcome the limitations associated with thermal cooling of crystal and transverse amplified spontaneous emission in high average power laser systems based on Ti:Sa amplifiers. The optimized design of high repetition rate 1-10 PW Ti:Sapphire EDP-TD power amplifiers are discussed, including their thermal dynamic behavior.