Alexandre Trisorio

Generation of 4.3 fs, 1 mJ laser pulses via compression of circularly polarized pulses in a gas-filled hollow-core fiber

We report the generation of 4.3 fs, 1 mJ pulses at 1 kHz using a hollow-core fiber compressor seeded with circularly polarized laser pulses. We observe up to 30% more energy throughput compared to the case of linearly polarized laser input, together with significantly improved output spectral stability. Seeding with circularly polarized pulses proves to be an effective approach for high-energy operation of the hollow-fiber compression technique.

Carrier-envelope phase stabilization and control using a transmission grating compressor and an AOPDF

Carrier-envelope phase (CEP) stabilization of a femtosecond chirped-pulse amplification system featuring a compact transmission grating compressor is demonstrated. The system includes two amplification stages and routinely generates phase-stable (approximately 250 mrad rms) 2 mJ, 25 fs pulses at 1 kHz. Minimizing the optical pathway in the compressor enables phase stabilization without feedback control of the grating separation or beam pointing. We also demonstrate for the first time to the best of our knowledge, out-of-loop control of the CEP using an acousto-optic programmable dispersive filter inside the laser chain.

Superresolved femtosecond laser ablation

The determinist behavior of the femtosecond ablation process allows morphing features well under the diffraction limit by utilizing the thresholding effect, down to the nanometer scale. Because there are a vast range of applications where scaling down the size of the features is a major concern, we investigate the use of superresolving pupil plane filters. As is well known, these filters redistribute the focused optical intensity for a narrower bright spot and, as a trade-off, increase the sidelobes. However, this drawback can be rendered insignificant if all the outer optical power is kept under the determinist threshold value. Two types of pure absorbing binary filter have been tried, giving credence to a size reduction of the ablations in fused silica.

Laser Arrival Time Measurement and Correction for the SwissFEL Lasers

SwissFEL will ultimately produce sub-fs X-ray pulses. Both the photo-injector laser and the pump lasers used for the experimental end stations therefore have tight requirements for relative arrival time to the machine and the X-rays. The gun laser oscillator delivers excellent absolute (including reference jitter) jitter performance at ~25 fs integrated from 10 Hz-10MHz. The Yb:CaF2 regenerative amplifier, with an over 1 km total propagation path, calls for active control of the laser arrival time. This is achieved by balanced cross-correlation against the oscillator pulses and a translation stage before amplification. The experimental laser, based on Ti:sapphire laser technology will use a spectrally resolved cross-correlator to determine relative jitter between the optical reference and the laser, with fs resolution. To be able to perform fs resolution pump-probe measurements the laser has to be timed with the X-rays with <10 fs accuracy. These systems will be integrated into the machine timing and complemented by electron bunch and X-ray timing tools. Here we present the overall concept and the first results obtained on the existing laser systems.

Chirped pulses sum frequency generation for deep - UV picosecond pulse shaping

We show by experiments and simulations that properly chirped laser pulses enable efficient and broadband sum frequency generation in nonlinear crystals. We achieved high energy, picosecond deep-UV pulses with spectral width one order of magnitude greater than the acceptance bandwidth of the nonlinear interaction. The broad spectrum supports shaping of ps flat-top deep-UV pulses with short rise- and fall-time, which are optimal for driving high brightness photocathode electron guns.

Carrier-Envelope Phase control using a transmission grating compressor and an AOPDF

Stabilizing the Carrier-Phase-Envelope (CEP) in grating-based CPA systems is of prime interest since they can produce significantly higher pulse energies than lasers with prism-based compressors. It was recently shown that feedback control of the effective grating separation in either the stretcher or compressor could be used as a method for correcting for the slow phase drift of the amplified pulses [2]. Using small pulse stretching factors has the advantage of keeping minimal optical paths, thereby minimizing the sources of dispersion fluctuations and offering better prospects for long-term CEP stability.

Spatio-Temporal Dynamics in Ultrafast Crossed-Polarized-Wave Generation

We experimentally and numerically investigate the strong effects of dispersive temporal focusing, temporal filtering and spatial self-focusing on the degenerate ?(3)process of crossed-polarized wave generation with sub-30fs pulses.

High-energy few-cycle pulse generation in a filament for relativistic applications at kHz repetition rate

We demonstrate efficient generation of 9.5-fs 1.8 mJ pulses by filamentation. The pulse wave front, the low energy fluctuations and the good temporal contrast make this source suited for relativistic laser-solid experiments at kHz repetition rate.

Organizing and characterizing multiple filaments in space and time

Multiple femtosecond filamentation(MF) are spatially organized by polarization control. Spatio- temporal characterization demonstrates a stable multi-filament pattern and compression to ultrashort pulses in each individual filament.

Generation of high-fidelity sub-10-fs milIijoule pulses through filamentation for relativistic laser-matter experiments at 1 kHz

We report the efficient generation of high-fidelity 1.8-mJ, 9.6-fs pulses at a 1-kHz repetition through filamentation of 3.6-mJ, 42-fs pulses in an argon pressure-gas cell. Pulses emerging from the 65-cm-long filament channel are spectrally broadened and carry an unexpected large negative group delay dispersion of more than −500 fs2. Post-compression down to sub-10-fs duration thus does not require the use of chirped mirrors since the essentially linear negative chirp can be compensated by simple linear propagation through a combination of different glasses. The good shot-to-shot stability, exceptional peak-to-pedestal contrast ratio and good focusability of this source are sufficient to drive relativistic laser-solid target interactions at 1-kHz.