Dimitrios Papadopoulos

Broadband high-energy diode-pumped Yb:KYW multipass amplifier

We report a diode-pumped Yb:KYW amplifier delivering up to 27 mJ pulses at a repetition rate of 100 Hz and a spectral bandwidth of 5.5 nm, centered at around 1030 nm. The system is based on a double-head multipass amplifier configuration where the pump thermal load is distributed over two relatively thin laser crystals, which permits a sufficiently large number of passes with minimal passive losses, thus maximizing the energy extraction efficiency. The amplified pulse bandwidth theoretically supports 340 fs pulses, and as a demonstration, a small fraction of the amplified pulses has been compressed to 560 fs.

Temporal cleaning of a high-energy fiber-based ultrafast laser using cross-polarized wave generation

We report the use of cross-polarized wave generation to perform both pulse shortening and temporal cleaning of a high-energy ytterbium-doped fiber-based femtosecond laser system. The nonlinear processes allow both a highly efficient nonlinear conversion of 20% and a large compression ratio of 3.5, with inherently improved coherent and incoherent contrasts. This results in the generation of 37 μJ, 115 fs pulses at a repetition rate of 100 kHz with high temporal quality.

Analysis of Limitations in Divided-Pulse Nonlinear Compression and Amplification

We analyze quantitatively physical effects that limit the coherent combining efficiency in highly nonlinear divided-pulse fiber-based setups such as parabolic amplifiers or nonlinear temporal compression experiment. The impact of differential dispersion and non-equal replicas power is assessed using numerical simulations and compared with experimental demonstrations. We also point out optimization strategies to minimize the impact of these effects on the performance of ultrafast fiber sources.

Polarization and Crystal-Orientation Dependency of Thermal Effects in Cryogenically Cooled Yb:CaF 2

We study beam polarization and crystallographic-orientation dependency of thermal effects in Yb:CaF2 crystals at LN2 temperature. AtypicalSignificant anisotropy for a cubic crystal is demonstrated resulting in polarization-dependent thermal-astigmatism or asymmetric depolarization pattern.

Passive coherent combining of CEP-stable few-cycles pulses from a temporally divided hollow fiber compressor

We demonstrate a robust passive coherent combining technique for post-compression of mJ energy CEP-stable laser pulses down to few-cycle duration in a gas-filled hollow-fiber. High combining efficiency is achieved using carefully oriented calcite plates.

Yb-doped-based High Energy and Broadband Multipass Amplifiers at 100 Hz

A 27mJ diode pumped multipass Yb:KYW amplifier at 100Hz with 5.5nm bandwidth at 1030nm is presented. First results on the subsequent Yb:CaF2 power amplifier stage are also presented resulting 51mJ at 20Hz.

Cross-polarized Wave Generation for Temporal Compression and Cleaning of a High Energy Fiber Chirped Pulse Amplifier

Cross-polarized wave generation is used to perform both pulse shortening and temporal cleaning of a high-energy ytterbium-doped fiber-based femtosecond laser system. This results in the generation of high temporal quality 37 µJ, 115 fs pulses.

2 GW peak power ultrafast fiber system using passive coherent beam combining

Using passive coherent beam combining of two ultrafast fiber amplifiers, we demonstrate the generation of high temporal quality 300 fs 650 µJ pulses at 92 kHz repetition rate, corresponding to 60 W average power.