Writing 3D Waveguides With Femtosecond Pulses in Polymers

We present novel waveguide writing concepts in bulk PMMA. The writing relies on laser induced modification tracks that are completely surrounding a waveguide core. We found the optimal parameters to construct highly reproducible, single-mode waveguides with minimal propagation losses down to 0.6 dB cm -1 . Employing the best geometry, we demonstrate 2D and 3D Y-splitters that are the building blocks for creating complex optical networks such as sensors or lab-on-chip devices in polymer materials

Efficient tunable UV pulse generation from a green pumped fs-OPCPA

High energy tunable ultrafast UV pulses are of great interest for a variety of applications. These pulses are also required for high repetition rate, fully coherent UV seeded free electron lasers [1] . In the absence of proper laser gain materials, optical parametric chirped pulse amplification (OPCPA) is considered as a foremost technique to generate high power tunable ultra-short laser pulses in various spectral ranges [2] . A typical example is the broadband green pumped OPCPA system driven by frequency doubled Ytterbium based chirped pulse laser amplifiers (CPA). The excellent power scalability of the OPCPAs allows generation of multi-millijoule, few femtosecond pulses with hundreds of watts of average power harnessing high energy and repetition rate commercially available CPA pump systems [3] . The absence of proper nonlinear crystals hinders operating OPCPAs directly in the UV spectral range. Therefore, frequency doubling, tippling or quadrupling of conventional OPCPAs are the usual techniques of generating tunable UV pulses. However, these schemes suffer from the strong two-photon absorption, narrow phase matching bandwidth, and non-linear phase transfer to UV range. As a consequence, for ultra-short pulses the maximum conversion efficiency of such schemes is typically limited to below 10%, and usually accompanied by pulse compression complications

7th7^{\text{th}} harmonic generation in gases for coherent 150 nm light production

We investigate the $7^{\text{th}}$ harmonic generation conversion efficiency and pulse energy output of a 1025 nm source in rare gases. The measurements yield $5×10^{−6}$ maximum efficiency, limited by collective effects from a phase-mismatched generation process

FLASH2020+ Pump-Probe Laser Upgrade: Concept and Current Status

Time-resolved experiments are increasingly relevant in modern FEL user facilities. With the FLASH2020+upgrade project, the pump-probe capabilities of the FLASH will be extended. Besides offering fixed wavelengths(1030 nm fundamental and its harmonics), tunable wavelengths are under development: sub-150 fslong tunable mid-infrared (2-5 microns) pulses for the solid-state community and sub-40 fs long tunable UVVIS(200-500 nm) pulses for the general chemistry, atomic molecular and optical physics (AMO) communities.The optical pulses will be fully synchronized with the FEL pulses and are generated with up to a 1 MHz repetitionrate in bursts of 0.6 ms in length at 10 Hz. Since we are limited by our pump-lasers available fixedaverage power, we can also reduce the repetition rate to 200kHz or less for delivering higher energy pulsesfor experiments using small density targets (such as gas phases or clusters).Here, we present our pump-probe laser concept: from the laser front end to the beam delivery to experimentalend-stations and instruments. We would be happy to receive any feedback from the users on their needs sowe can adjust our concept as needed

FLASH FEL pump-probe laser concept based on spectral broadening of high-power Ytterbiumpicosecond systems in multi-pass cells

Within the FLASH2020+ upgrade, the pump-probe laser capabilities of the Free-Electron Laser (FEL)FLASH in Hamburg will be extended. In particular, providing wavelength tunability, shorter pulse durations andreduced arrival time jitter will increase the scientific opportunities and the time resolution for the FEL-opticallaser pump-probe experiments. We present here a novel concept for the pump-probe laser at FLASH, basedon post-compression of a picosecond high-power Ytterbium laser amplifier chain, employing a multi-pass cell.We also show, for the first time, pumping of a mid-IR optical parametric amplifier and difference frequencygeneration stage by high energy post-compressed pulses to obtain multi-μJ, sub-150 fs pulses over the range1.3-16 μm. Additionally, a modular reconfiguration approach for the wavelength conversion schemes close tothe FEL instruments is implemented to enable fast turnover and flexibility from one beamline to the other in theexperimental halls

Pulse post-compression via multi-pass cells for FEL pump-probe experiments at FLASH

The soft x-ray Free-Electron Laser (FEL) FLASH is a unique tool to study ultrafast processes and is mostly used for pump-probe experiments in combination with an optical laser. Within the framework of the FLASH2020+ facility upgrade, the currently operating Ti:Sapphire and OPCPA systems will be largelyreplaced by high-power Yb:YAG lasers combined with nonlinear pulse compression in multi-pass cells (MPCs). This approach offers superior compactness, efficiency and simplicity of the optical laser systems. We here present first example implementations of MPC compression-based pump-probe laser systems. In particular, we investigate pulse stability, temporal contrast and intra-burst pulse dynamics. Our results confirm the applicability of MPC-based pulse compression for pump-probe experiments including promising pulse characteristics for driving secondary frequency conversion stages