Direct amplification of femtosecond optical vortices in a single-crystal fiber

Spatially twisted light with femtosecond temporal structure is of particular interest in strong-field physics and light–matter interactions.However,present femtosecond vortex sources exhibit limited power handling capabilities,and their amplification remains an ongoing challenge particularly for high-order orbital angular momentum(OAM)states due to several inherent technical difficulties.Here,we exploit a straightforward approach to directly amplify a femtosecond optical vortex(FOV,OAM=-8?)by using a two-stage single-crystal fiber(SCF)amplifier system without pulse stretching and compression in the time domain,delivering 23-W,163-fs pulses at a repetition rate of1 MHz.The spatial and temporal features are well-conserved during the amplification,as well as the high modal purity(>96%).The results indicate that the multi-stage SCF amplifier system is particularly suited for direct amplification of high-order FOVs.The generated high-power femtosecond OAM laser beams are expected to help reveal complex physical phenomena in light–matter interactions and pave the way for practical applications in attoscience,laser plasma acceleration,and high-dimension micromachining.

The dehydration dynamics of a model cell membrane induced by cholesterol analogue 6-ketocholestanol investigated using sum frequency generation vibrational spectroscopy

Dehydration of a surface is the first step for the interaction between biomolecules and the surface. In this study, we systematically investigated the influence of cholesterol analog 6-ketocholestanol(6-KC) on the dehydration of model cell membrane, using sum frequency generation vibrational spectroscopy. In pure DI water environment, two separate dehydration dynamic components were observed in neutrally charged and isotopically labeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine(DMPC) and positively charged 1,2-dimyristoyl-sn-glycero-3-ethylphosphocholine(chloride salt)(DMEPC) bilayer: a large-amplitude fast component and a small-amplitude slow component, which originated from the water molecules with a weak and a strong water-membrane bound strengths, respectively. Dehydration of a negatively charged mixed DMPC/DMPG bilayer lead to the membrane-bound water being reorganized to ordered structures quickly. It is evident that the water-membrane bound strengths depend largely on the charge status of the lipid and has an order of neutrally charged membrane<<positively charged membrane<<negatively charged membrane. In an ionic environment, KCl solution can not only dehydrate DMPC bilayer, but also prevent the 6-KC from further dehydrating this model cell membrane. We observed that the dehydration dynamics behavior of DMPC bilayer in the presence of the chaotropic anions is similar to that of the negatively charged DMPG bilayer because of the penetration of chaotropic anions into the DMPC bilayer. The degree of dehydration difficulty in kosmotropic anions follows a Hofmeister series and linearly correlates with the hydration Gibbs free energy of the anions. Our results provide a molecular basis for the interpretation of the Hofmeister effect of kosmotropic anions on ion transport proteins.

Role of localized phonon vibration in luminescence performance of Pr doped Ba(Mg_(0.28)Zr_(0.16)Ta_(0.56))O_(3)transparent ceramics

Oxygen-assisted high temperature solid-state reaction approach was employed for the fabrication of Pr activated Ba(Mg_(0.28)Zr_(0.16)Ta_(0.56))O_(3)transparent ceramic phosphor.Retiveld refinement of X-ray diffraction pattern was carried out to reveal the lattice parameters and crystal structural information.Under the blue-light excitation ofλ=473 nm,the phosphor exhibits a sharp intense red emission centered at645 nm,accompanied by several other weak peaks.PL evolution with temperature shows a significant luminescence quenching behavior,and the underlying multi-phonon interaction with optical center is revealed by proposing an unprecedent theoretical calculation work.Such a phonon effect is further confirmed from the red-shift of peak position with temperature,and the involved phonon energy of50.7 meV is determined from Raman scattering measurement.More interestingly,the fitted results of transient-state PL spectra show a fluctuation of luminescence lifetime at various temperatures,further indicating a significant effect of phonon vibration in the system.