Generation of three-cycle multi-millijoule laser pulses at 318 W average power

The generation of three-cycle multi-millijoule pulses at 318W power is reported by compressing pulses of a Yb-fiber chirped pulse amplifier in a 6 m long stretched flexible hollow fiber. This technique brings high-power lasers to the few-cycle regime. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Carrier-envelope offset stable, coherently combined ytterbium-doped fiber CPA delivering 1 kW of average power

We present a carrier-envelope offset (CEO) stable ytterbium-doped fiber chirped-pulse amplification system employing the technology of coherent beam combining and delivering more than 1 kW of average power at a pulse repetition rate of 80 MHz. The CEO stability of the system is 220 mrad rms, characterized out-of-loop with an f -to-2f interferometer in a frequency offset range of 10 Hz to 20 MHz. The high-power amplification system boosts the average power of the CEO stable oscillator by five orders of magnitude while increasing the phase noise by only 100 mrad. No evidence of CEO noise deterioration due to coherent beam combining is found. Low-frequency CEO fluctuations at the chirped-pulse amplifier are suppressed by a “slow loop” feedback. To the best of our knowledge, this is the first demonstration of a coherently combined laser system delivering an outstanding average power and high CEO stability at the same time. © 2020 Optical Society of Americ

Broadband spectral characterization of the phase shift induced by population inversion in Ti:Sapphire

The spectral phase shift of broadband amplified pulses, induced by population inversion, was measured in Ti:Sapphire at different pump fluence values. The measurement was performed for two orthogonal polarization directions and at two different crystal temperatures of 296 K and 30 K. Zero shifts and sign changes were observed in the spectral phase, which are connected to the gain spectrum of the crystal. The electronic refractive index changes were also numerically calculated by the Kramers-Kronig theory. The results are highly important for achieving sub-10 fs pulse duration and phase stability in the next generation of Ti:Sapphire-based laser systems. © 2019 Optical Society of America

Microwave-assisted Pd-catalyzed C-P or C-C cross couplings on 13α-estrane core

Novel 2- or 4-substituted 13α-estrone derivatives were synthesized via Hirao or Suzuki reaction. Transformations of 2- and/or 4-halogenated derivatives of 13α-estrone and its 3- benzyl or -methyl ether were carried out in a microwave (MW) reactor. Facile and efficient CC or C-P coupling procedures were established using Pd or Ni catalysts. The newly synthesized compounds might have promising antitumoral properties

All-Optical Experimental Control of High-Harmonic Photon Energy

We generate high-order harmonics in gaseous medium with tunable photon energy using time domain interferometry of double pulses in a non-collinear generation geometry. The method is based on the fact that the generated harmonics inherit certain spectral properties of the driving laser. The two temporally delayed ultrashort laser pulses, identical in all parameters, are produced by a custom-made split-and-delay unit utilizing wave front splitting without a significant energy loss. The arrangement is easy to implement in any attosecond pulse generation beamline, and is suitable for the production of an extreme ultraviolet source with simply and quickly variable central photon energy, useful for a broad range of applications.Comment: 6 pages, 5 figures, after peer-revie

Synthesis, Biological Evaluation and Docking Studies of 13-Epimeric 10-fluoro- and 10-Chloroestra-1,4-dien-3-ones as Potential Aromatase Inhibitors

Fluorination of 13-epimeric estrones and their 17-deoxy counterparts was performed with Selectfluor as the reagent. In acetonitrile or trifluoroacetic acid (TFA), 10β-fluoroestra-1,4-dien-3-ones were formed exclusively. Mechanistic investigations suggest that fluorinations occurred via SET in acetonitrile, but another mechanism was operative in TFA. Simultaneous application of N-chlorosuccinimide (NCS) and Selectfluor in TFA led to a 1.3:1 mixture of 10β-fluoroestra-1,4-dien-3-one and 10β-chloroestra-1,4-dien-3-one as the main products. The potential inhibitory action of the 10-fluoro- or 10-chloroestra-1,4-dien-3-one products on human aromatase was investigated via in vitro radiosubstrate incubation. The classical estrane conformation with trans ring anellations and a 13β-methyl group seems to be crucial for the inhibition of the enzyme, while test compounds bearing the 13β-methyl group exclusively displayed potent inhibitory action with submicromolar or micromolar IC50 values. Concerning molecular level explanation of biological activity or inactivity, computational simulations were performed. Docking studies reinforced that besides the well-known Met374 H-bond connection, the stereocenter in the 13 position has an important role in the binding affinity. The configuration inversion at C-13 results in weaker binding of 13α-estrone derivatives to the aromatase enzyme