Minimizing attosecond CEP jitter by carrier envelope phase tuning

Minimizing the CEP jitter of isolated attosecond pulses (IAP) will be important for future applications. This jitter is experimentally and theoretically investigated and can be minimized when the driving pulse is near its Fourier limit but with slightly negative chirp. Thus, understanding and characterization of the CEP jitter of IAPs is a first step towards exact control of the electric field of IAP pulses

Zeeman-incremented multiple-quantum NMR

A new method for performing multiple-quantum NMR experiments is described. Instead of incrementing the evolution period t1 in the conventional manner, t1 is kept fixed while the magnetic field is increased, successively. The method is illustrated using 19F spins in dipolar coupled 2,2-difluorotetrachloroethane, 1,1,1 -trichlorotrifluoroethane, and hexafluorobenzene, oriented in a nematic liquid crystal. It is demonstrated that Zeeman-incremented multiple-quantum NMR experiments give rise to simplified spectra in the multiple-quantum t1 domain, free from T2 decay. For example, in the case of hexafluorobenzene, just seven equally spaced peaks are observed, corresponding to Δm = ± 0, 1, . . . , 6.<p/

A study of the induced magnetism in the Au spacer layer of Co/Au/CoO exchange-bias trilayers and related systems

We report the first observation of the effects of exchange bias on the nuclear spin polarization and induced magnetic moments at a magnetic/non-magnetic interface, applying low temperature nuclear orientation (LTNO) to Co/Au(x)/CoO trilayer systems. This technique allows us to determine simultaneously the average alignment of the nuclear moments for the two radioactive probe isotopes 198Au and 60Co with respect to an external magnetic field axis. The total average Au γ-ray anisotropy measured was found (i) to decrease with increasing Au thickness, indicating that large hyperfine fields are restricted to the interfacial Au layers and (ii) to be canted away from the applied field axis even when the Co layers are magnetically saturated. This canting was found to originate at the CoO/Au interface as could be shown from comparative measurements on CoO/Au/CoO trilayers containing two AFM CoO/Au interfaces and on a Co/Au/Co trilayer with two FM Co/Au interfaces. In the case of CoO/Au/CoO, the observed canting was found to be dependent on the Au layer thickness

Magnetic anisotropy of Ni modified by extreme lattice expansion

The induced magnetism of isolated (Cd) adatoms, soft-landed onto ultrathin Ni layers grown pseudo-morphologically on Pd(001) ($a_{Pd} = 3.8907$ Å), was studied using the perturbed angular correlation (PAC) technique. The magnitude of the induced magnetic response (magnetic hyperfine field of |5.2| T) was found to be ca. 30% smaller than on bulk Ni ($a_{Ni} = 3.524$ Å) surfaces. This result is compared to ab initio calculations. Additionally, the magnetic anisotropy of the induced response was found to be modified as compared to bulk Ni surfaces and the induced hyperfine field was observed to emerge from the plane at an angle of 50(5)$^{\circ}$ to the surface normal. This canted magnetic anisotropy is attributed to the large lattice expansion of the ultrathin Ni film on Pd(001)

Power scaling of supercontinuum seeded megahertz-repetition rate optical parametric chirped pulse amplifiers

Optical parametric chirped-pulse amplifiers with high average power are possible with novel high-power Yb:YAG amplifiers with kW-level output powers. We demonstrate a compact wavelength-tunable sub-30-fs amplifier with 11.4 W average power with 20.7% pump-to-signal conversion efficiency. For parametric amplification, a beta-barium borate crystal is pumped by a 140 W, 1 ps Yb: YAG InnoSlab amplifier at 3.25 MHz repetition rate. The broadband seed is generated via supercontinuum generation in a YAG crystal

Long-term stabilization of high power optical parametric chirped-pulse amplifiers

The long-term stability of optical parametric chirped-pulse amplifiers is hindered by thermal path length drifts affecting the temporal pump-to-signal overlap. A kilowatt-pumped burst amplifier is presented delivering broadband 1.4 mJ pulses with a spectral bandwidth supporting sub-7 fs pulse duration. Active temporal overlap control can be achieved by feedback of optical timing signals from cross-correlation or spectral measurements. Using a balanced optical cross-correlator, we achieve a pump-to-signal synchronization with a residual jitter of only (46 ± 2)fs rms. Additionally, we propose passive pump-to-signal stabilization with an intrinsic jitter of (7.0 ± 0.5)fs rms using white-light continuum generation

The formation of orbital moments on iron impurities in Ag

Using the high specificity and sensitivity of the in-beam perturbed γ-ray angular distribution method, we have investigated the magnetic behavior of very dilute ${}^{54}$Fe probes in Ag${}_{1-x}$Au${}_x$ alloys. The nuclear damping time and local susceptibility of Fe are found to depend strongly on its local environment, showing inhomogeneous line broadening as well as discrete magnetic responses due to the different configurations of Ag/Au nearest neighbors. The results can be understood with the aid of ab initio calculations of electronic structure, magnetic moments and hyperfine fields. They underline the central importance of orbital magnetism for understanding the experimental results

Thermal properties of borate crystals for high power optical parametric chirped-pulse amplification

The potential of borate crystals, BBO, LBO and BiBO, for high average power scaling of optical parametric chirped-pulse amplifiers is investigated. Up-to-date measurements of the absorption coefficients at 515 nm and the thermal conductivities are presented. The measured absorption coefficients are a factor of 10–100 lower than reported by the literature for BBO and LBO. For BBO, a large variation of the absorption coefficients was found between crystals from different manufacturers. The linear and nonlinear absorption coefficients at 515 nm as well as thermal conductivities were determined for the first time for BiBO. Further, different crystal cooling methods are presented. In addition, the limits to power scaling of OPCPAs are discussed

The formation of orbital moments on iron impurities in Ag1 xAux alloys

Using the high specificity and sensitivity of the in-beam perturbed γ-ray angular distribution method, we have investigated the magnetic behavior of very dilute ${}^{54}$Fe probes in Ag${}_{1-x}$Au${}_x$ alloys. The nuclear damping time and local susceptibility of Fe are found to depend strongly on its local environment, showing inhomogeneous line broadening as well as discrete magnetic responses due to the different configurations of Ag/Au nearest neighbors. The results can be understood with the aid of ab initio calculations of electronic structure, magnetic moments and hyperfine fields. They underline the central importance of orbital magnetism for understanding the experimental results