Multipass spectral broadening of 18 mJ pulses compressible from 1.3 ps to 41 fs.

Nonlinear compression of laser pulses with tens of millijoule energy in a gas-filled multipass cell is a promising approach to realize a new generation of high average power femtosecond sources. For the first time, to the best of our knowledge, we demonstrate nonlinear broadening of pulses with about 18 mJ of energy at a 5 kHz repetition rate in an argon-filled Herriott cell and show compressibility from 1.3 ps to 41 fs. In addition to the large compression factor, the output beam has an outstanding quality and excellent spectral homogeneity. Furthermore, we discuss prospects to scale the energy to the 100 mJ level in the near future.

Nonlinear pulse compression in a gas-filled multipass cell.

We present an efficient method for compressing sub-picosecond pulses at 200 W average power with 2 mJ pulse energy in a multipass cell filled with different gases. We demonstrate spectral broadening by more than a factor of five using neon, argon, and nitrogen as nonlinear media. The 210 fs input pulses are compressed down to 37 fs and 35 GW peak power with a beam quality factor of 1.3×1.5 at a power throughput of >93%. This concept represents an excellent alternative to hollow-core fiber-based compression schemes and optical parametric amplifiers (OPAs).

1 kW, 200 mJ picosecond thin-disk laser system.

We report on a laser system based on thin-disk technology and chirped pulse amplification, providing output pulse energies of 200 mJ at a 5 kHz repetition rate. The amplifier contains a ring-type cavity and two thin Yb:YAG disks, each pumped by diode laser systems providing up to 3.5 kW power at a 969 nm wavelength. The average output power of more than 1 kW is delivered in an excellent output beam characterized by M2=1.1. The output pulses are compressed to 1.1 ps at full power with a pair of dielectric gratings.

Direct regenerative amplification of femtosecond pulses to the multimillijoule level.

We present a compact femtosecond nonlinear Yb:YAG thin-disk regenerative amplifier delivering pulses carried at a wavelength of 1030 nm with an average power of >200 W at a repetition rate of 100 kHz and an energy noise value of 0.46% (rms) in a beam with a propagation factor of M2<1.4. The amplifier is seeded with bandwidth-limited subpicosecond pulses without temporal stretching. We give estimates for the nonlinear parameters influencing the system and show that chirped mirrors compress the 2 mJ pulses to a near-bandwidth-limited duration of 210 fs.

Carrier-envelope-phase-stable, 1.2 mJ, 1.5 cycle laser pulses at 2.1 µm.

We produce 1.5 cycle (10.5 fs), 1.2 mJ, 3 kHz carrier-envelope-phase-stable pulses at 2.1 µm carrier wavelength, from a three-stage optical parametric chirped-pulse amplifier system, pumped by an optically synchronized 1.6 ps Yb:YAG thin disk laser. A chirped periodically poled lithium niobate crystal is used to generate the ultrabroad spectrum needed for a 1.5 cycle pulse through difference frequency mixing of spectrally broadened pulse from a Ti:sapphire amplifier. It will be an ideal tool for producing isolated attosecond pulses with high photon energies.

Active stabilization for optically synchronized optical parametric chirped pulse amplification.

The development of new high power laser sources tends toward optical parametric chirped pulse amplification (OPCPA) in recent years. One of the difficulties in OPCPA is the the temporal overlap between pump and seed pulses. In this work we characterize our timing jitter on a single-shot basis using spectrally resolved cross-correlation in combination with a position sensitive detector. A commercial beam stabilization is adapted to actively enhance temporal overlap. This delay-stabilizer reduces the RMS jitter from σ = 127 fs down to σ = 24 fs. The enhanced temporal overlap is demonstrated in our frontend and we propose the scheme to be applicable in many optically synchronized high-repetition-rate OPCPA systems.