We present our progress on developing an innovative compact thulium-based fiber CPA emitting at 2 µm central wavelength. The laser parameters comprise >100 µJ pulse energy at an average power of >30W. The system comes in an industrial-grade platform optimized for long-term operation and its optimized packaging is well suited for the integration in laser machines for materials processing. The laser parameters are ideally suited for processing semiconductors, e.g. silicon by microwelding or cutting of filaments.
We introduce a high-harmonic generation (HHG)-based XUV source that offers a broad photon flux range from 40 eV to 150 eV. This source utilizes an industrial-grade TruMicro 2030 laser system with 20-W average power, delivering up to 100 µJ with pulse durations under 400 fs. A post-compression unit is incorporated to reduce the pulses to approximately 40 fs with just a 10% average power loss. The turnkey source achieves a photon flux exceeding 10^10 photons/s around 70 eV.
We have developed an advanced design for a dual-wavelength laser source used in Coherent Anti-Stokes Raman scattering (CARS) microscopy and Stimulated Raman Spectroscopy (SRS) addressing a wider frequency range for bio-imaging, spanning from <630cm^-1 to 2250cm^-1, while maintaining a fast tuning time of a few seconds across the entire range. Furthermore, we have achieved improved tunability of the Stokes and pump power, allowing for versatile applications. The system supports repetition rates of up to 10MHz, and the spectral width of the signals is narrow (<15cm^-1), enabling a wide range of potential uses.
We present our progress on developing an innovative compact thulium-based fiber CPA emitting at 2 µm central wavelength. The laser parameters comprise >100 µJ pulse energy at an average power of >30W. The system comes in an industrial-grade platform optimized for long-term operation and its optimized packaging is well suited for the integration in laser machines for materials processing. The laser parameters are ideally suited for processing semiconductors, e.g. silicon by microwelding or cutting of filaments.
Fiber-based laser sources for Coherent Anti-Stokes Raman scattering (CARS) microscopy and Stimulated Raman Spectroscopy (SRS) have been successfully used for label-free bio-imaging in the past. We present an improved design of a dual-wavelength source for CARS and SRS enabling a wider frequency-range from <630cm^-1 up to 2250cm^-1 while the tuning time remains in the range of a few seconds over the full range. The system is fiber-based and thus resistant to detrimental thermal effects even at output powers in the Watt-range with improved tunability of Stokes and pump power. Repetition rates up to 10MHz are possible and the spectral width of the signals is <15cm^-1 enabling most applications.
We present a HHG-based XUV source providing large photon flux across a wide range between 40 eV and 150 eV. It is driven by an industrial-grade TruMicro 2030 20-W average power laser system delivering up to 100 µJ at <400-fs pulse duration. A post-compression unit is part of the device to shorten the pulses to approx. 40 fs at only 10% average power loss. The turnkey source provides photon flux of >10^10 photons/s near 70 eV.
We present a sub-2-cycle laser system combining high average power, pulse energy and repetition rate with CEP-stable operation. The laser system creates 300 fs pulses with 1.8 mJ pulse energy that are nonlinearly post-compressed down to few optical cycles in two subsequent multipass cells (MPC). A pulse duration of 5.8fs (sub-2-cycle) at a pulse energy of 1.1mJ in combination with 110W average power (100 kHz) is achieved. This corresponds to the shortest pulses and highest compressed average power for few-cycle MPCs. Furthermore, the carrier-to-envelope-phase stability amounts to 300 mrad for frequencies above 2 kHz as measured by stereo—above-threshold-ionization (ATI).
We present an ultrafast high-power coherently combined thulium-based fiber-CPA. The laser system aims to deliver 400 µJ pulse energy at a pulse repetition frequency of 500 kHz. The simultaneous availability of 200 W-class average power and 1 GW-class peak power in the 2 µm wavelength regime will not only be unique in the world of science but also will pave the way to more compact, cost-effective lasers which are ideally suited for high-harmonic generation into the water-window and nonlinear-frequency conversion to the mid-IR and THz spectral range.
We present a CEO-stable 1.1 kW CPA system that is designed to drive a few-cycle-generation stage (<6fs pulse duration) and a subsequent atto-second beamline at the ELI-ALPS facility in Szeged. It currently delivers >300W of average power at 100kHz repetition-rate providing <10fs pulses. The chirped-pulse-amplification system (CPA) demonstrates excellent noise properties with <220mrad of the integrated carrier-envelope-offset (CEO) noise (10Hz to 20MHz) at a pulse repetition rate of 80MHz while the relative-intensity-noise (RIN) stayed <0.3%. This is the first CEO-stable laser system at 1kW level average power.
High harmonic generation at high repetition rate is realized with a high average power 100W, 600kHz fiber laser system. Optimization is done for two different operation regimes. At 69-75eV the source delivers a world-record photon flux of >10^11photons/s/harmonic when using argon gas jets. The use of neon gas allows for operation at significantly shorter wavelength. The important 93eV harmonic can be generated at 5·10^9 photons/s/(1% bandwidth), while even higher values of >10^10 photons/s/(1% bandwidth) are achieved between 115-140eV. The HHG source provides excellent long-term power stability of ~1% RMS for each of the operation regimes.
We present the first high-power coherently combined thulium-doped fiber-CPA. The laser system delivers >228 µJ pulse energy with <120 fs pulse duration at a pulse repetition frequency of 500 kHz. Excellent long-term stability is achieved with an average power fluctuation of <0.5% RMS over >48 hours of operation even at an average-power >120 W. The simultaneous availability of 100 W class average power and 1 GW-class peak power in the 2 µm wavelength regime is not only unique in the world of science but also comes in a fully engineered and commercially available system design optimized for long-term operation..
Fiber-based laser sources for Coherent Anti-Stokes Raman scattering (CARS) microscopy and Stimulated Raman Spectroscopy (SRS) have been successfully used for label-free bio-imaging in the last few years. However, these systems were limited so far to a few experimental setups in university labs. We present the first extremely compact commercially available dual-wavelength source for CARS and SRS. With a foot-print of <30cm x 50cm this alignment-free turn-key system offers tuning over the highly relevant frequency range from <500cm^-1 up to 5000cm^-1 within a few seconds without any detrimental thermal effects. The spectral width of the signals is <10cm^-1 enabling a multitude of applications.
Here we present the latest experimental results of a high-power CEP-stable FCPA system. The 16-channel FCPA runs at 0.3% RMS power stability (>9hours) delivering more than 1kW and 10mJ after the compressor at a pulse duration of 280fs. To generate 6fs pulses, stretched hollow-core fibers are being employed. We present a significant up-scaling of this technique towards an output of 5mJ, 100kHz and 6fs.
The timeframe between the first demonstration of novel laser parameters and the commercial availability of systems delivering those parameters has been shrinking over the recent years. This development makes femtosecond laser systems with unparalleled parameters available to a wide range of applicants. We present the progress in setting up such a FCPA laser system delivering 5mJ pulse energy at 100kHz pulse repetition rate (i.e. 500W of average power) and with pulse durations of 6fs. The system, the so-called HR2 laser, will be implemented at the ELI-ALPS facility in Szeged, Hungary. Furthermore, the laser is optimized to generate output pulses with a stable carrier-envelope-phase (CEP). Since 6fs requires a bandwidth not supplied by Yb-based gain-media, and thus nonlinear compression is necessary, the chirped-pulse-amplification (CPA) system itself must deliver a higher energy to compensate for the losses in these nonlinear-compression-stages. Hence, the CPA is operated at 12mJ and 1.2kW delivering sub 300-fs pulses with an almost diffraction limited beam quality. To achieve such a parameter-set, the output of 16 main-amplifier channels is coherently combined using a polarization-based filled-aperture combining scheme. Maintaining the CEP stability of the oscillator throughout the entire system is another key challenge of the project. We finally discuss further power-scaling approaches and possibilities to reduce system size, complexity and, therewith, cost. By using these revolutionary laser systems, even demanding applications such as laser-based particle acceleration or XUV-generation via high-harmonic generation will be able to perform the important step from the laboratory to real-world applications allowing to access repetition rates orders of magnitude higher than before.
Here, we present a passive 30-m long enhancement cavity that supports a steady-state enhancement of 198, which is the highest enhancement that has ever been reached in such a long cavity. Furthermore, we demonstrate the extraction of a short burst with a total energy of 53.6 μJ employing an acousto-optic modulator (AOM) as a switching device. The cavity was seeded with pulses of 1.49 μJ energy at 10 MHz repetition rate. The individual output coupled pulses showed an energy enhancement of up to 8.5 while the whole burst contained the entire energy of 36 input pulses. In the last section theoretical considerations for the single pulse extraction are presented and briefly discussed.
In this work we present guidelines to increase the transverse mode instability threshold of high power fiber amplifiers and also, for the first time to the best of our knowledge, of fiber oscillators. These guidelines do not involve changes in the composition of the active material (except for its doping concentration), but they can still lead to a significant increase of the transverse mode instability threshold. The dependence of this parameter on the active ion concentration, the core conformation, the pump configuration and the mirror reflectivities in a fiber oscillator will be studied and discussed.
Novel laser applications such as laser-wake-field acceleration of particles require extreme parameters from ultra-short-pulse systems. We propose a concept capable to realize simultaneously multi-TW peak powers and multi-kW average powers by employing spatially and temporally separated amplification of chirped laser pulses delivered by fiber-amplifiers. As a combining element for the temporally 100 ns separated pulses (10 MHz repetition rate) we suggest a non-steady-state enhancement cavity using a fast switching-element to dump out the enhanced pulses at 15 kHz.
There is a great interest in obtaining laser pulses with a high average power as well as high pulse energies. Continuously pulsed systems face many problems to satisfy those requirements, independent on the amplifier concept. While many applications such as electron beam characterization and free-electron-laser seeding need high pulse energies at high repetition rates, they only need those laser pulses for a certain amount of time. Therefore, it is not necessary to run a laser system with continuous pulses at those parameters and a so-called burst mode might be sufficient and even essential in such cases. We report on a CPA-laser system, based on a large pitch fiber as a main-amplifier delivering bursts containing ultra-short, highly-energetic pulses. The burst rate is set to 20Hz, while each burst contains 2000 pulses at a pulse-repetition-rate of 10MHz and with a pulse-duration of 700fs. Hence the duty cycle D is 0.4%. To achieve a homogeneous pulse energy level between 27μJ and 31μJ after the compression, the main amplifier is pumped with a very high power of 1.6kW in a burst-mode (D=10%). By using an acousto-optical modulator (AOM) after the main-amp fiber, the residual output before and after the burst is removed to suppress ASE and any underground-pulses around the amplified burst. The limitations that could be observed during this experiment were mainly due to mode instabilities, which were detectable even on a very short time scale of a few hundred μs using a high speed camera.
The coherent combining of ultrashort pulses is a concept for scaling the pulse energy and average power of laser systems
emitting ultrashort pulses. In this contribution the experimental results of a coherently combined femtosecond fiber CPA
laser system consisting of 2 amplifiers is presented. Combining efficiencies as high as 89% and compressed pulse
energies of up to 3mJ were achieved. Additionally, the system showed excellent long-term stability.
We report on a novel concept to scale the performance of ultra-fast lasers by means of coherent combination. Pulses
from a single mode-locked laser are distributed to a number of spatially separated fiber amplifiers and coherently
combined after amplification. The splitting and combination process is based on the polarization combining technique
using polarization cubes. A Hansch-Couillaud detector measures the polarization state of the combined beam. The error
signal (deviation from linear polarization) is used to stabilize the optical path lengths in the different channels with a
piezo mounted mirror. In a proof-of-principle experiment the combination of two femtosecond fiber-based amplifiers in
a CPA systems is presented. A combining efficiency as high as 97% has been achieved. Additional measurements were
carried out to investigate the stability of the system. The concept offers a unique scaling potential and can be applied to
all ultrafast amplification schemes independent of the architecture of the gain medium.
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