Influence of PBF-LB Process Atmosphere on the Fatigue Strength of Hot Isostatically Post-Densified Duplex Steel Parts Produced via the Shell Core Approach.

Laser-based additive manufacturing is a great manufacturing technology for producing parts of any geometry. To also increase the strength and reliability of parts produced via powder bed fusion with laser beam (PBF-LB), hot isostatic pressing (HIP) is often used to densify residual porosity or lack-of-fusion defects. When components are post-densified via HIP, they do not require a high density beforehand, only a closed porosity or a dense shell.

Extreme Concentration and Nanoscale Interaction of Light.

Concentrating light strongly calls for appropriate polarization patterns of the focused light beam and for up to a full 4π solid angle geometry. Focusing on the extreme requires efficient coupling to nanostructures of one kind or another via cylindrical vector beams having such patterns, the details of which depend on the geometry and property of the respective nanostructure. Cylindrical vector beams can not only be used to study a nanostructure, but also vice versa.

Single Photons Emitted by Nanocrystals Optically Trapped in a Deep Parabolic Mirror.

We investigate the emission of single photons from CdSe/CdS dots-in-rod which are optically trapped in the focus of a deep parabolic mirror. Thanks to this mirror, we are able to image almost the full 4π emission pattern of nanometer-sized elementary dipoles and verify the alignment of the rods within the optical trap. From the motional dynamics of the emitters in the trap, we infer that the single-photon emission occurs from clusters comprising several emitters.

Shifting the phase of a coherent beam with a ion: influence of the scattering cross section.

We discuss and measure the phase shift imposed onto a radially polarized light beam when focusing it onto an ion. In the derivation of the expected phase shifts, we include the properties of the involved atomic levels. Furthermore, we emphasize the importance of the scattering cross section and its relation to the efficiency for coupling the focused light to an atom.

Light-matter interaction in free space.

We review recent experimental advances in the field of efficient coupling of single atoms and light in free space. Furthermore, a comparison of efficient free space coupling and strong coupling in cavity quantum electrodynamics (QED) is given. Free space coupling does not allow for observing oscillatory exchange between the light field and the atom which is the characteristic feature of strong coupling in cavity QED.

Interferometric null test of a deep parabolic reflector generating a Hertzian dipole field.

We report on interferometric characterization of a deep parabolic mirror with a depth of more than five times its focal length. The interferometer is of Fizeau type; its core consists of the mirror itself, a spherical null element, and a reference flat. Because of the extreme solid angle produced by the paraboloid, the alignment of the setup appears to be very critical and needs auxiliary systems for control.

Planar microelectrode-cavity array for high-resolution and parallel electrical recording of membrane ionic currents.

Increasing the throughput and resolution of electrical recording of currents through ion conducting channels and pores is an important technical challenge both for the functional analysis of ion channel proteins and for the application of nanoscale pores in single molecule analytical tasks. We present a novel design based on sub-picoliter-cavities arrayed in a polymer substrate and endowed with individual planar microelectrodes that allows low-noise and parallel electrical recording from ion channels and pores. Resolution of voltage-dependent current transitions of alamethicin channels as well as polyethylene-glycol-induced blocking events of alpha-hemolysin nanopores on the submillisecond time scale is demonstrated using this device.

High-resolution electrophysiology on a chip: Transient dynamics of alamethicin channel formation.

Microstructured planar substrates have been shown to be suitable for patch clamp recording from both whole cells and isolated patches of membrane, as well as for measurements from planar lipid bilayers. Here, we further explore this technology with respect to high-resolution, low noise single-channel recording. Using solvent-free lipid bilayers from giant unilamellar vesicles obtained by electro-swelling, we recorded channels formed by the peptaibol alamethicin, a well-studied model system for voltage-dependent channels, focusing on the transient dynamics of single-channel formation upon application of a voltage step.

Correlation properties and drift phenomena in the dynamics of vertical-cavity surface-emitting lasers with optical feedback.

We investigate experimentally the polarization dynamics of vertical-cavity surface-emitting lasers with isotropic optical feedback operating in the long-cavity regime. By means of an analysis of the correlation properties in the time domain and in the frequency domain a connection between a drift phenomenon and frequency components that deviate from the harmonics of the external cavity round-trip frequency is revealed. The latter frequency components are shown to result from an interaction of external cavity dynamics and relaxation oscillations.