High repetition rate relativistic laser-solid-plasma interaction platform featuring simultaneous particle and radiation detection.

We report on a uniquely designed high repetition rate relativistic laser-solid-plasma interaction platform, featuring the first simultaneous measurement of emitted high-order harmonics, relativistic electrons, and low divergence proton beams. This versatile setup enables detailed parametric studies of the particle and radiation spatio-spectral beam properties under a wide range of controlled interaction conditions, such as pulse duration and plasma density gradient. Its array of complementary diagnostics unlocks the potential to unravel interdependencies among the observables and should aid in further understanding the complex collective dynamics at play during laser-plasma interactions and in optimizing the secondary beam properties for applications.

Single-stage few-cycle nonlinear compression of milliJoule energy Ti:Sa femtosecond pulses in a multipass cell.

We report on the nonlinear temporal compression of mJ energy pulses from a Ti:Sa chirped pulse amplifier system in a multipass cell filled with argon. The pulses are compressed from 30 fs down to 5.3 fs, corresponding to two optical cycles. The post-compressed beam exhibits excellent spatial quality and homogeneity. These results provide guidelines for optimizing the compressed pulse quality and further scaling of multipass-cell-based post-compression down to the single-cycle regime.

Orbital angular momentum beams generation from 61 channels coherent beam combining femtosecond digital laser.

We report on the use of a 61 beamlets coherent beam combination femtosecond fiber amplifiers as a digital laser source to generate high-power orbital angular momentum beams. Such an approach opens the path for higher-order non-symmetrical user-defined far field distributions.

Coherent beam combining of 61 femtosecond fiber amplifiers.

We report on the coherent beam combining of 61 femtosecond fiber chirped-pulse amplifiers in a tiled-aperture configuration along with an interferometric phase measurement technique. Relying on coherent beam recombination in the far field, this technique appears suitable for the combination of a large number of fiber amplifiers. The 61 output beams are stacked in a hexagonal arrangement and collimated through a high fill factor hexagonal micro-lens array. The residual phase error between two fibers is as low as λ/90 RMS, while a combining efficiency of ∼50% is achieved.

Coherent beam combining of seven fiber chirped-pulse amplifiers using an interferometric phase measurement.

Coherent beam combining in tiled-aperture configuration is demonstrated on seven femtosecond fiber amplifiers using an interferometric phase measurement technique. The residual phase error between two fibers is as low as λ/55 RMS and a combination efficiency of 48% has been achieved. The combined pulses are compressed to 216 fs, delivering 71 W average power at a repetition rate of 55 MHz. Operating the laser system in a nonlinear regime with an estimated B-integral of 5 rad yields a combining efficiency of 45% with the same phase stability. These results pave the way to very large high-power and high energy coherent beam combining systems.

Transient Two-Dimensional Infrared Spectroscopy in a Vibrational Ladder.

We report on transient 2D Fourier transform infrared spectroscopy (2DIR) after vibrational ladder climbing induced in the CO-moiety longitudinal stretch of carboxyhemoglobin. The population distribution, spreading up to seven vibrational levels, results in a nonequilibrium 2DIR spectrum evidencing a large number of peaks that can be easily attributed to individual transitions thanks to the anharmonicity of the vibrational potential. We discuss the physical origin of the observed peaks as well as the qualitative behavior of the subsequent dynamics governed by population relaxation in the vibrational ladder.

Arbitrary-detuning asynchronous optical sampling with amplified laser systems.

We demonstrate that Arbitrary-Detuning ASynchronous OPtical Sampling (AD-ASOPS) makes possible multiscale pump-probe spectroscopy with time delays spanning from picosecond to millisecond. The implementation on pre-existing femtosecond amplifiers seeded by independent free-running oscillators is shown to be straightforward. The accuracy of the method is determined by comparison with spectral interferometry, providing a distribution with a standard deviation ranging from 0.31 to 1.7 ps depending on experimental conditions and on the method used to compute the AD-ASOPS delays.

Ultrafast Dynamics of Carboxy-Hemoglobin: Two-Dimensional Infrared Spectroscopy Experiments and Simulations.

This Letter presents a comparison between experimental and simulated 2D mid-infrared spectra of carboxy-hemoglobin in the spectral region of the carbon monoxide stretching mode. The simulations rely on a fluctuating potential energy surface that includes both the effect of heme and the protein surroundings computed from molecular dynamics simulations. A very good agreement between theory and experiment is obtained with no adjustable parameters. The simulations show that the effect of the distal histidine through the hydrogen bond is strong and is directly responsible for the slow decay of the frequency-frequency correlation function on a 10 ps time scale. This study confirms that fluctuations in carboxy-hemoglobin are more inhomogeneous than those in the more frequently studied carboxy-myoglobin. The comparison between simulations and experiments brings valuable information on the complex relation between protein structure and spectral diffusion.

Femtosecond fiber chirped- and divided-pulse amplification system.

We implement both chirped pulse amplification and divided pulse amplification in the same femtosecond fiber amplifier setup. This scheme allows an equivalent stretched pulse duration of 2.4 ns in a compact tabletop system. The generation of 77 W of compressed average power at 4.8 MHz, together with 320 fs and 430 µJ pulses at a repetition rate of 96 kHz, is demonstrated using a distributed mode-filtering, rod-type, ytterbium-doped fiber. Limitations in the temporal recombining efficiency due to gain saturation inside the fiber amplifier are identified.

Passive coherent beam combining of two femtosecond fiber chirped-pulse amplifiers.

We propose and demonstrate an architecture that achieves passive coherent combination of two femtosecond fiber chirped-pulse amplifiers. The setup consists in the use of a well-balanced amplifying Sagnac interferometer. The experiment shows that the temporal, spectral, and spatial qualities of each beam are retained, with the generation of 250 fs pulses at 35 MHz repetition rate, an uncompressed average power of 10 W, and a combining efficiency of 96%. The behavior of this architecture in the presence of high accumulated nonlinear phase is investigated.