Advancing ultrafast high-repetition-rate lasers to shortest pulse durations comprising only a few... more Advancing ultrafast high-repetition-rate lasers to shortest pulse durations comprising only a few optical cycles while pushing their energy into the multi-millijoule regime opens a route towards terawatt-class peak powers at unprecedented average power. We explore this route via efficient post-compression of high-energy 1.2 ps pulses from an Ytterbium InnoSlab laser to 9.6 fs duration using gas-filled multi-pass cells (MPCs) at a repetition rate of 1 kHz. Employing dual-stage compression with a second MPC stage supporting a close-to-octave-spanning bandwidth enabled by dispersion-matched dielectric mirrors, a record compression factor of 125 is reached at 70% overall efficiency, delivering 6.7 mJ pulses with a peak power of about 0.3 TW. Moreover, we show that post-compression can improve the temporal contrast at picosecond delay by at least one order of magnitude. Our results demonstrate efficient conversion of multi-millijoule picosecond lasers to high-peak-power few-cycle sources, opening up new parameter regimes for laser plasma physics, high energy physics, biomedicine and attosecond science.
We investigate compression of ultrashort laser pulses by nonlinear propagation in gas-filled plan... more We investigate compression of ultrashort laser pulses by nonlinear propagation in gas-filled planar hollow waveguides, using (3+1)dimensional numerical simulations. In this geometry, the laser beam is guided with a fixed size in one transverse dimension, generating significant spectral broadening, while it propagates freely in the other, allowing for energy up-scalability. In this respect the concept outperforms compression techniques based on hollow core fibers or filamentation. Small-scale selffocusing is a crucial consideration, which introduces mode deterioration and finally break-up in multiple filaments. The simulation results, which match well with initial experiments, provide important guidelines for scaling the few-cycle pulse generation to higher energies. Pulse compression down to few-cycle duration with energies up to 100 mJ levels should be possible.
Abstract (35 Word Limit) We investigate nonlinear propagation dynamics of ultrashort pulses using... more Abstract (35 Word Limit) We investigate nonlinear propagation dynamics of ultrashort pulses using their spectrograms; and developed a FROG setup, capable of measuring pulse durations down to single optical cycles. We also demonstrate relativistic intensities with table-top laser source.
Efficient, diode-pumped high energy femtosecond laser systems around 1 μm based on Yb-gain media ... more Efficient, diode-pumped high energy femtosecond laser systems around 1 μm based on Yb-gain media are readily commercially available. However, owing to the gain bandwidth limitations, the pulses generated in such lasers are substantially longer than the ones generated in Ti:Sapphire systems. A simple, energy-scalable pulse self-compression scheme for the pulses around 1 μm thus would be of great interest for many applications, including time-resolved pump-probe spectroscopy, high-harmonics generation, etc. The self-phase modulation during nonlinear propagation in filaments in gasses is often employed for pulse self-compression [1,2]. Such schemes typically require rather bulky setups and careful control of group velocity dispersion. Some years ago it has been shown theoretically that Raman-active molecules in gaseous form could be used for mid-infrared pulse compression [3].
We experimentally demonstrate that high energy ultrashort pulses can be compressed through self-p... more We experimentally demonstrate that high energy ultrashort pulses can be compressed through self-phase-modulation in hollow planar waveguides. The beam is guided in one transverse dimension and propagates free in other, allowing scalability to higher energies.
When an intense, few-cycle light pulse impinges on a dielectric or semiconductor material, the el... more When an intense, few-cycle light pulse impinges on a dielectric or semiconductor material, the electric field will interact nonlinearly with the solid, driving a coherent current. An asymmetry of the ultrashort, carrier-envelope-phase-stable waveform results in a net transfer of charge, which can be measured by macroscopic electric contact leads. This effect has been pioneered with extremely short, single-cycle laser pulses at low repetition rate, thus limiting the applicability of its potential for ultrafast electronics. We investigate lightwave-driven currents in gallium nitride using few-cycle laser pulses of nearly twice the duration and at a repetition rate two orders of magnitude higher than in previous work. We successfully simulate our experimental data with a theoretical model based on interfering multiphoton transitions, using the exact laser pulse shape retrieved from dispersion-scan measurements. Substantially increasing the repetition rate and relaxing the constraint on the pulse duration marks an important step forward towards applications of lightwave-driven electronics.
The precise characterization of femtosecond laser pulses is as challenging as their generation an... more The precise characterization of femtosecond laser pulses is as challenging as their generation and a topic of intense research. Dispersion-scan (d-scan) [1] is a recently established technique where the spectrum of a nonlinear signal, e.g., second-harmonic generation (SHG), is measured as a function of dispersion applied to the pulse. The spectral phase of the pulse can then be retrieved from the resulting 2D trace using an iterative algorithm. An important implementation of d-scan, based on a chirped mirror and wedge compressor, involves progressively moving one of the wedges around the maximum compression point and acquiring the resulting SHG spectrum for each insertion with a standard spectrometer. This robust and fully inline approach, which does not require any beamsplitting or temporal delays, has enabled the simultaneous compression and measurement of pulses down to single-cycle durations [2-4], but its scanning nature precludes single-shot operation. A single-shot d-scan variant that explores the spatially dependent dispersion of a glass prism was successfully demonstrated with 3.2 fs pulses [5], but the relatively small amount of dispersion that can be introduced by a single prism limits its use to few-cycle pulses.
We present different approaches for high repetition rate, few-cycle pulse generation with μJ-leve... more We present different approaches for high repetition rate, few-cycle pulse generation with μJ-level energy from compact OPCPA systems. The sources are based on octave spanning Ti:Sa oscillators with all-optical synchronization to state-of-the-art Ytterbium based amplifiers.
We present a compact and ultra-stable few-cycle OPCPA system. In two non-collinear parametric amp... more We present a compact and ultra-stable few-cycle OPCPA system. In two non-collinear parametric amplification stages pulse energies up to 17 µJ at 200 kHz repetition rate are obtained. Recompression of the broadband pulses down to 6.3 fs is performed with chirped mirrors leading to peak powers above 800 MW. The parametric amplification processes were studied in detail employing (2 + 1) dimensional numerical simulations and compared to experimental observations in terms of spectral shapes, pulse energy, spatial effects as well as delay dependent nonlinear mixing products. This gives new insights into the parametric process and design guidelines for high repetition rate OPCPA systems.
We study the spectral phase introduced by parametric amplification and how high extraction effici... more We study the spectral phase introduced by parametric amplification and how high extraction efficiency of energy leads to deterioration of the phase. Avoiding this regime, and using a pulse shaper, we achieve high-contrast ultrashort pulses.
We present a simple method for choosing an efficient high-order harmonic generation (HHG) gas tar... more We present a simple method for choosing an efficient high-order harmonic generation (HHG) gas target, given the driving laser characteristics. The predictions are validated by simulations based on solving the time-dependent Schrödinger and propagation equations.
A grating compressor is characterized using the dispersion scan technique and a reference piece o... more A grating compressor is characterized using the dispersion scan technique and a reference piece of glass. The procedure yields both the spectral phase of the ultrashort pulses and the dispersion of the compressor itself.
Advancing ultrafast high-repetition-rate lasers to shortest pulse durations comprising only a few... more Advancing ultrafast high-repetition-rate lasers to shortest pulse durations comprising only a few optical cycles while pushing their energy into the multi-millijoule regime opens a route towards terawatt-class peak powers at unprecedented average power. We explore this route via efficient post-compression of high-energy 1.2 ps pulses from an Ytterbium InnoSlab laser to 9.6 fs duration using gas-filled multi-pass cells (MPCs) at a repetition rate of 1 kHz. Employing dual-stage compression with a second MPC stage supporting a close-to-octave-spanning bandwidth enabled by dispersion-matched dielectric mirrors, a record compression factor of 125 is reached at 70% overall efficiency, delivering 6.7 mJ pulses with a peak power of about 0.3 TW. Moreover, we show that post-compression can improve the temporal contrast at picosecond delay by at least one order of magnitude. Our results demonstrate efficient conversion of multi-millijoule picosecond lasers to high-peak-power few-cycle sources, opening up new parameter regimes for laser plasma physics, high energy physics, biomedicine and attosecond science.
We investigate compression of ultrashort laser pulses by nonlinear propagation in gas-filled plan... more We investigate compression of ultrashort laser pulses by nonlinear propagation in gas-filled planar hollow waveguides, using (3+1)dimensional numerical simulations. In this geometry, the laser beam is guided with a fixed size in one transverse dimension, generating significant spectral broadening, while it propagates freely in the other, allowing for energy up-scalability. In this respect the concept outperforms compression techniques based on hollow core fibers or filamentation. Small-scale selffocusing is a crucial consideration, which introduces mode deterioration and finally break-up in multiple filaments. The simulation results, which match well with initial experiments, provide important guidelines for scaling the few-cycle pulse generation to higher energies. Pulse compression down to few-cycle duration with energies up to 100 mJ levels should be possible.
Abstract (35 Word Limit) We investigate nonlinear propagation dynamics of ultrashort pulses using... more Abstract (35 Word Limit) We investigate nonlinear propagation dynamics of ultrashort pulses using their spectrograms; and developed a FROG setup, capable of measuring pulse durations down to single optical cycles. We also demonstrate relativistic intensities with table-top laser source.
Efficient, diode-pumped high energy femtosecond laser systems around 1 μm based on Yb-gain media ... more Efficient, diode-pumped high energy femtosecond laser systems around 1 μm based on Yb-gain media are readily commercially available. However, owing to the gain bandwidth limitations, the pulses generated in such lasers are substantially longer than the ones generated in Ti:Sapphire systems. A simple, energy-scalable pulse self-compression scheme for the pulses around 1 μm thus would be of great interest for many applications, including time-resolved pump-probe spectroscopy, high-harmonics generation, etc. The self-phase modulation during nonlinear propagation in filaments in gasses is often employed for pulse self-compression [1,2]. Such schemes typically require rather bulky setups and careful control of group velocity dispersion. Some years ago it has been shown theoretically that Raman-active molecules in gaseous form could be used for mid-infrared pulse compression [3].
We experimentally demonstrate that high energy ultrashort pulses can be compressed through self-p... more We experimentally demonstrate that high energy ultrashort pulses can be compressed through self-phase-modulation in hollow planar waveguides. The beam is guided in one transverse dimension and propagates free in other, allowing scalability to higher energies.
When an intense, few-cycle light pulse impinges on a dielectric or semiconductor material, the el... more When an intense, few-cycle light pulse impinges on a dielectric or semiconductor material, the electric field will interact nonlinearly with the solid, driving a coherent current. An asymmetry of the ultrashort, carrier-envelope-phase-stable waveform results in a net transfer of charge, which can be measured by macroscopic electric contact leads. This effect has been pioneered with extremely short, single-cycle laser pulses at low repetition rate, thus limiting the applicability of its potential for ultrafast electronics. We investigate lightwave-driven currents in gallium nitride using few-cycle laser pulses of nearly twice the duration and at a repetition rate two orders of magnitude higher than in previous work. We successfully simulate our experimental data with a theoretical model based on interfering multiphoton transitions, using the exact laser pulse shape retrieved from dispersion-scan measurements. Substantially increasing the repetition rate and relaxing the constraint on the pulse duration marks an important step forward towards applications of lightwave-driven electronics.
The precise characterization of femtosecond laser pulses is as challenging as their generation an... more The precise characterization of femtosecond laser pulses is as challenging as their generation and a topic of intense research. Dispersion-scan (d-scan) [1] is a recently established technique where the spectrum of a nonlinear signal, e.g., second-harmonic generation (SHG), is measured as a function of dispersion applied to the pulse. The spectral phase of the pulse can then be retrieved from the resulting 2D trace using an iterative algorithm. An important implementation of d-scan, based on a chirped mirror and wedge compressor, involves progressively moving one of the wedges around the maximum compression point and acquiring the resulting SHG spectrum for each insertion with a standard spectrometer. This robust and fully inline approach, which does not require any beamsplitting or temporal delays, has enabled the simultaneous compression and measurement of pulses down to single-cycle durations [2-4], but its scanning nature precludes single-shot operation. A single-shot d-scan variant that explores the spatially dependent dispersion of a glass prism was successfully demonstrated with 3.2 fs pulses [5], but the relatively small amount of dispersion that can be introduced by a single prism limits its use to few-cycle pulses.
We present different approaches for high repetition rate, few-cycle pulse generation with μJ-leve... more We present different approaches for high repetition rate, few-cycle pulse generation with μJ-level energy from compact OPCPA systems. The sources are based on octave spanning Ti:Sa oscillators with all-optical synchronization to state-of-the-art Ytterbium based amplifiers.
We present a compact and ultra-stable few-cycle OPCPA system. In two non-collinear parametric amp... more We present a compact and ultra-stable few-cycle OPCPA system. In two non-collinear parametric amplification stages pulse energies up to 17 µJ at 200 kHz repetition rate are obtained. Recompression of the broadband pulses down to 6.3 fs is performed with chirped mirrors leading to peak powers above 800 MW. The parametric amplification processes were studied in detail employing (2 + 1) dimensional numerical simulations and compared to experimental observations in terms of spectral shapes, pulse energy, spatial effects as well as delay dependent nonlinear mixing products. This gives new insights into the parametric process and design guidelines for high repetition rate OPCPA systems.
We study the spectral phase introduced by parametric amplification and how high extraction effici... more We study the spectral phase introduced by parametric amplification and how high extraction efficiency of energy leads to deterioration of the phase. Avoiding this regime, and using a pulse shaper, we achieve high-contrast ultrashort pulses.
We present a simple method for choosing an efficient high-order harmonic generation (HHG) gas tar... more We present a simple method for choosing an efficient high-order harmonic generation (HHG) gas target, given the driving laser characteristics. The predictions are validated by simulations based on solving the time-dependent Schrödinger and propagation equations.
A grating compressor is characterized using the dispersion scan technique and a reference piece o... more A grating compressor is characterized using the dispersion scan technique and a reference piece of glass. The procedure yields both the spectral phase of the ultrashort pulses and the dispersion of the compressor itself.
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