F. Salin

Aberration-free stretcher design for ultrashort-pulse amplification

A novel aberration-free pulse stretcher design is presented. This system permits the stretching of a 30-fs pulse to 300 ps and recompression to a duration of 33 fs, limited by the spectral clipping.

Gain-narrowing and gain-shifting of ultra-short pulses in Ti: sapphire amplifiers

Abstract We have developed a simple model for chirped-pulse titanium: sapphire amplification that includes gain narrowing and gain shifting effects. We analyse the spectral limitation in ultra-short pulse amplification and compare two different kinds of pre-amplifiers: multi-pass and regenerative amplifiers. We compare the model to multi-pass Ti: sapphire amplifier measurements using different input bandwidths.

Changes in the geometry during the laser-induced multiple ionization and fragmentation

The average nuclear geometry of molecules during the laser-induced multielectronic ionization and multifragmentation is probed by Coulomb explosion into multicharged atomic fragments. An evolution from the initial bent structure to a linear configuration is observed as the number of removed electrons increases from 3 to 11 in the laser intensity range. This observation shows that the multiple ionization does not follow a simple sequential pattern from the less bound to the more tightly bound electrons of the molecule.

Toward a terawatt-kilohertz repetition-rate laser

We present the different problems related to the amplification of ultrashort pulses at high repetition rate. Phase distortion, gain narrowing and thermal effects are studied in detail. We demonstrate, for the first time, that thermal effects in ultrashort pulse amplifiers can be harnessed and positively exploited in the laser design resulting in the production of diffraction limited beams. We demonstrate that peak powers at the terawatt-level amplification at a kilohertz repetition rate is readily conceivable.

Multi-pass amplification of sub-50 fs pulses up to the 4 TW level

Abstract We describe the design and operation of a 2-stage multi-pass Ti:sapphire amplifier laser system, which is optimised for a broad transmission bandwidth and incorporates a novel reflective spherical mirror pulse-stretcher. Output energies of 180 mJ after compression, and amplified bandwidths up to 30 nm are observed.

Parametric amplification and self-compression of ultrashort tunable pulses

Using a 40-fs Ti:sapphire pump laser, we produced 20-fs infrared pulses in a /spl beta/-barium borate (BaB/sub 2/O/sub 4/) optical parametric amplifier without any external dispersion compensation. These results are in good agreement with a novel semi-analytical computer simulation. We also demonstrate that cascading of second-order nonlinear effects yields simultaneous production of ultrashort visible pulses from a near-infrared (NIR) pump.

Solitonlike pulse shortening in a femtosecond parametric amplifier

Some parametric designs have been shown to exhibit a broad amplification bandwidth and allow for ultrashort tunable pulse generation and amplification. Even pulse shortening can be obtained when benefiting from external recompression. We report on computer simulations and experimental evidence of solitonlike parametric self-compression in the femtosecond domain.

Characterization of a femtosecond kHz amplifier chain by spectral shearing interferometry

In a chirped-pulse amplification laser chain, as the spectral phase added by the stretcher and the group-velocity dispersion in all the materials is imperfectly compensated by the compressor, the output pulse is distorted by the residual phase, and its duration and contrast are not optimal. There is thus a need for an efficient characterization of the pulses in order to optimize the system or control a programmable spectral phase modulator. Spectral shearing interferometry is demonstrated as a powerful technique for measuring the amplitude and phase of ultrashort optical pulses. Its implementation is simple, and the phase retrieval from the data is straightforward.

Kilohertz Thermal Eigenmode Multipass Amplifier For High-average-power Chirpedpulse Amplification

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Amplification of femtosecond pulses up to 29 TW at 10 Hz in Ti:sapphire

We demonstrate a femtosecond laser chain that generates 20 TW at 10 Hz in less than 50 fs with focused intensities higher than 3 X 1019 W/cm2. This system is optimized for a broad transmission bandwidth and includes an aberration-free stretcher compressor.