arXiv subjects

F. Richter

Publications and source records attributed to F. Richter.

4 recordsLinked to original sources

arXiv2025

A phase-modulation interferometer for intense, ultrashort, near infrared laser pulses

The investigation of coherent phenomena in strong-field processes requires interferometric measurement schemes with high selectivity to disentangle the complex nonlinear response of the system. Interferometers combining acousto-optical phase modulation with lock-in detection feature excellent dynamic range and highly selective detection, thus providing a promising solution. However, acousto-optical modulators (AOMs) cause several issues when operated with intense, ultrashort, near infrared (NIR) laser pulses. The AOMs introduce temporal and angular dispersion, self-phase modulation and reduced acousto-optic efficiency at NIR wavelengths. Here, we present an acousto-optical phase modulation interferometer design that solves these issues. The presented solutions pave the way for the investigation of strong-field processes with phasemodulated interferometry and are also useful to improve the performance of phase-modulation interferometers in other applications.

physics.optics↗

arXiv2019

A parylene coating system specifically designed for producing ultra-thin films for nanoscale device applications

We report on a parylene chemical vapor deposition system custom designed for producing ultra-thin parylene films (5-100 nm thickness) for use as an electrical insulator in nanoscale electronic devices, including as the gate insulator in transistors. The system features a small deposition chamber that can be isolated and purged for process termination, a quartz crystal microbalance for monitoring deposition, and a rotating angled stage to increase coating conformity. The system was mostly built from off-the-shelf vacuum fittings allowing for easy modification and reduced cost compared to commercial parylene coating systems. The production of ultra-thin parylene films for device applications is a niche not well catered to by commercial coating systems, which are typically designed to give thicker coatings (microns) with high uniformity over much larger areas. An added advantage of our design for nanoscale device applications is that the small deposition chamber is readily removable for transfer to a glovebox to enable parylene deposition onto pristine surfaces prepared in oxygen/water-free environments with minimal contamination.

cond-mat.mes-hall↗

arXiv2009

Green function approach to scattering of nonclassical light by bounded media

We show that using the properties of the photon Green's function one can successfully describe the propagation of arbitrary nonclassical optical radiation through structured materials. In contrast to the similar input-output approach, our method is not restricted neither to the spatial homogeneous matter nor to the specific direction of light beam incidence or outcoupling. Several quantum states of light are addressed in detail, such as Fock, Glauber, and different squeezed light states, and their Green functions are given. Furthermore, it is demonstrated how scattering of light at a slab can be described with Poynting's energy flow vector, and how experimental setups can be modeled.

physics.optics↗

arXiv1998

Sterols sense swelling in lipid bilayers

In the mimetic membrane system of phosphatidylcholine bilayers, thickening (pre-critical behavior, anomalous swelling) of the bilayers is observed, in the vicinity of the main transition, which is non-linear with temperature. The sterols cholesterol and androsten are used as sensors in a time-resolved simultaneous small- and wide angle x-ray diffraction study to investigate the cause of the thickening. We observe precritical behavior in the pure lipid system, as well as with sterol concentrations less than 15%. To describe the precritical behavior we introduce a theory of precritical phenomena.The good temperature resolution of the data shows that a theory of the influence of fluctuations needs modification. The main cause of the critical behavior appears to be a changing hydration of the bilayer.

cond-mat.soft↗