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Weit uber werbende Auftritte hinaus ist die Grundung einer Privatklinik eine interessante Moglichkeit, neue Betatigungsfelder zu erschliesen. Hierbei sind weitreichende Gestaltungsoptionen hinsichtlich der Rechtsform und des Grunderkreises moglich. So kann etwa die zulassige Einbindung von Investoren neue Chancen bieten. Auch im Hinblick auf die Frage der Liquidation der durchgefuhrten Behandlungen eroffnen sich neue Wege. Die Abrechnung von zuvor mit der Privatklinik vereinbarten Pauschalhonoraren ist unter Beachtung gewisser Voraussetzungen nach vorliegender Auffassung moglich. Eine Bindung an die Gebuhrenordnung fur Arzte (GOA) in diesem Fall also nicht zwingend. So ermoglichen die Grundung und der Betrieb einer Privatklinik auf verschiedenen Ebenen neue und interessante Handlungsoptionen.

The offset frequency from a 1-GHz optical frequency comb has been stabilized using

Ultralow phase-noise mode-locked lasers are crucial for real-world applications. We present two accomplishments: (1) short-term FF CEP stabilization of a SESAM mode-locked Er:Yb:glass laser at 1.55 um with timing jitter below 3 as (1-3 MHz) and (2) a hybrid solution adding a FB technique addressing slowly varying sources of interference to the FF system that demonstrates 75 hours of stabilization with a minimally detrimental effect amounting to a timing jitter of 11 as.

OSA continuum 4(6), 1889 - 1896 (2021). doi:10.1364/OSAC.424340, We present a comparison of two low-noise carrier-envelope offset (CEO) frequency stabilization methods studied using an ytterbium (Yb) fiber laser oscillator based on a nonlinear amplifying loop mirror. We first investigate the phase locking performance achieved with cross-gain modulation (XGM) via injection of an auxiliary low-power continuous-wave (CW) laser into the fiber gain medium. Amplification of the injected CW laser light cross-modulates the gain of the oscillator, resulting in an intra-cavity power modulation, thus providing control of the CEO frequency. The XGM method is then compared with the conventional pump-current modulation scheme. Both stabilization methods provide similar locking performances with sub-200-mrad of integrated residual carrier-envelope-phase (CEP) noise (10 Hz to 1 MHz), suitable for high-resolution comb spectroscopy applications., Published by OSA, Washington, DC

We develop an Arrival Time Monitor (ATM) achieving high sensitivity for soft X-ray pulses in low-fluence conditions. The ATM cross-correlates ultrashort X-ray with 800nm laser pulses using a new multi-layer target designed and grown in-house to achieve optimal sensitivity.

A major design goal for femtosecond fiber lasers is to increase the output power but not at the cost of increasing the noise level or narrowing the bandwidth. Here, we perform a computational study to optimize the cavity design of a femtosecond fiber laser that is passively modelocked with a semiconductor saturable absorbing mirror (SESAM). We use dynamical methods that are more than a thousand times faster than standard evolutionary methods. We show that we can obtain higher pulse energies and hence higher output powers by simultaneously increasing the output coupling ratio, the gain, and the anomalous group delay dispersion. We can obtain output pulses that are from 5 to 15 times the energy of the pulse in the current experimental design with no penalty in the noise level or bandwidth.

We present carrier-envelope phase stabilization of an Er:Yb:glass laser at 1.55 pm via the feed-forward method with 2.9 as (1 Hz - 3 MHz) timing jitter and continuous stabilization over 24 hours.

We present the new drive laser system for the photo-injector of the LCLS-II XFEL at SLAC, including the first commissioning results and challenges encountered due to high power, high repetition rate ultraviolet laser operation.

We present a flexible figure-9 Yb: fiber-laser and investigate the impact of intra-cavity group delay dispersion on amplitude/phase noise. We show that the free-running carrier-envelope-offset frequency short-term linewidth can range from several MHz to

We demonstrate the first frequency comb laser absorption spectroscopy in an industrial environment. Recent advancements in robust frequency comb design enabled installation of the sensor in an operating power plant, where we simultaneously measured temperature, H 2 O and CO 2 concentration in the exhaust of a 16 MW stationary gas turbine. The frequency comb laser spectrometer probed 16,000 individual wavelengths of light spaced by 0.007 cm −1 (0.0014 nm) near 1440 nm, spanning 279 absorption features of H 2 O and 43 features of CO 2 . Fits to the measured absorption spectra yield simultaneous temperature, H 2 O and CO 2 concentrations with between 10 and 60 second time resolution. Measurements over a 5 hour period tracked variations in the exhaust consistent with various changes to the gas turbine operation. Much larger wavelength ranges (200+ nm) and different time resolutions are possible depending on the desired precision by changing various settings on the same spectrometer. Overall, this work demonstrates the potential for frequency comb laser absorption spectroscopy in industrial combustion environments.

Dual-comb spectroscopy systems based on two pulse trains emitted from a single laser cavity benefit from passive mutual coherence between the two pulse trains, which leads to common-mode noise cancellation in the down converted radio-frequency (RF)-comb [1]. Due to their robustness, single cavity dual-color/dual-comb fiber lasers are promising candidates for such spectroscopy systems [2,3]. Here, we present a novel method to generate two pulse trains out of a single fiber laser cavity based on mechanical spectral filtering, which offers two key features: dynamical adjustment of the spectral separation between the two pulse trains and tuning of the difference in repetition rates. After demonstrating the concept in a 23-MHz nonlinear polarization evolution (NPE) mode-locked ytterbium (Yb) laser [4], we have now for the first time implemented this concept in a nonlinear amplified loop mirror (NALM) mode-locked all-polarization maintaining (PM) Yb:fiber laser operating at a repetition rate of 77 MHz, thus improving both the stability as well as the non-aliasing dual-comb bandwidth. The laser contains a free-space arm with a transmission grating compressor, in which the spectral components of the intra-cavity light are spatially dispersed (Fig.1(a)). By introducing a small beam block into the grating compressor, we split the spectrum into two separate regions. We show that these two spectral regions can be independently mode-locked, thus creating two pulse trains with slightly different repetition rates (Fig.1(b-d)). Due to the spatial distribution of the spectral components, we can vary the width of the spectral cut between the two spectra by rotating the beam block (Fig. 1(b), blue curves). Furthermore, adjusting the grating spacing (and thus the amount of dispersion) allows us to tune the difference in the repetition rate Δf rep from 1–6 kHz (Fig. 1(e)). After spectral separation at the cavity output, the pulse centered around 1030 nm is amplified and broadened in a nonlinear fiber to create a spectral overlap with the 1060 nm-pulse (Fig. 1(f)). The overlapping spectrum is bandpass-filtered around 1055 nm and sent onto a photodiode (PD). An oscilloscope trace of the PD output shows interferograms (Fig. 1(f), inset) occurring with a periodicity of 1/Δf rep , which correspond to the Fourier-transform of the down-converted RF comb that is generated by the beating of both optical combs.

We demonstrate the generation of a tunable single-cavity dual-comb out of an all-polarization-maintaining ytterbium fiber laser via spectral subdivision. The feasibility of spectroscopy measurements is demonstrated by measuring the transmission of a 5-mm thick etalon.

Few-cycle pulsed laser technology highlights the need for control and stabilization of the carrier-envelope phase (CEP) for applications requiring shot-to-shot timing and phase consistency. This general requirement has been achieved successfully in a number of free space and fiber lasers via feedback and feed-forward methods. Expanding upon existing results, we demonstrate CEP stabilization through the feed-forward method applied to a SESAM mode-locked Er:Yb:glass laser at 1.55 um with a measured ultralow timing jitter of 2.9 as (1 Hz - 3 MHz) and long-term stabilization over a duration of eight hours. Single-digit attosecond stabilization at telecom wavelengths opens a new direction in applications requiring ultra-stable frequency and time precision such as high-resolution spectroscopy and fiber timing networks., Comment: 4 pages, 4 figures, submitted to Optics Letters

Optical frequency combs have revolutionized optical frequency metrology and are being actively investigated in a number of applications outside of pure optical frequency metrology. For reasons of cost, robustness, performance, and flexibility, the erbium fiber laser frequency comb has emerged as the most commonly used frequency comb system and many different designs of erbium fiber frequency combs have been demonstrated. We review the different approaches taken in the design of erbium fiber frequency combs, including the major building blocks of the underlying mode-locked laser, amplifier, supercontinuum generation and actuators for stabilization of the frequency comb.

We design and realize an arrival time diagnostic for ultrashort X-ray pulses achieving unprecedented high sensitivity in the soft X-ray regime via cross-correlation with a ≈1550 nm optical laser. An interferometric detection scheme is combined with a multi-layer sample design to greatly improve the sensitivity of the measurement. We achieve up to 275% of relative signal change when exposed to 1.6 mJ/cm2 of soft X-rays at 530 eV, more than a hundred-fold improvement in sensitivity as compared to previously reported techniques. The resolution of the arrival time measurement is estimated to around 2.8 fs (rms). The demonstrated X-ray arrival time monitor paves the way for sub-10 fs-level timing jitter at high repetition rate X-ray facilities.

Using an optical frequency comb to directly convert a frequency reference to a useable time output will enable tight synchronization of tomorrow's optical-clock networks. Previous frequency-comb systems experienced cycle slips too often to provide true optical timescales. This study combines innovative fiber-comb designs, digital phase locking, and precise phase-determination methods to demonstrate optical clockwork with no phase slips for over a $m\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}h$. Fault-free timekeeping at the femtosecond level over months is a vital step in supplanting the current microwave time standard with an optical standard, and could improve $e.g.$ gravitational geodesy and GPS technology.

With the progress in the development of optical frequency standards grows the demand for the dissemination of stable optical frequencies. To date, optical fiber links constitute the most promising medium to bridge large geographical distances while still maintaining a high degree of frequency stability and accuracy. We investigated the transfer of an optical frequency along different fiber links during the past years and achieved a fractional instability and uncertainty at a level lower than 10 − 19 using fiber links with lengths of up to almost 2000 km. We give an overview of different techniques and methods that can be used in combination with optical fiber links to achieve a stable frequency transfer. The results of different fiber links are summarized and an outlook of future links is given.

We utilize silicon-nitride waveguides to self-reference a telecom-wavelength fiber frequency comb through supercontinuum generation, using 11.3 mW of optical power incident on the chip. This is approximately ten times lower than conventional approaches using nonlinear fibers and is enabled by low-loss (

The power efficiency of femtosecond fiber lasers with semiconductor saturable absorbers is limited by the wake instability. We computationally optimize the output power and efficiency by increasing the output coupling ratio and gain fiber length.

Optics express 27(20), 28062 - (2019). doi:10.1364/OE.27.028062, We demonstrate dual-comb generation from an all-polarization-maintaining dual-color ytterbium (Yb) fiber laser. Two pulse trains with center wavelengths at 1030 nm and 1060 nm respectively are generated within the same laser cavity with a repetition rate around 77 MHz. Dual-color operation is induced using a tunable mechanical spectral filter, which cuts the gain spectrum into two spectral regions that can be independently mode-locked. Spectral overlap of the two pulse trains is achieved outside the laser cavity by amplifying the 1030-nm pulses and broadening them in a nonlinear fiber. Spatially overlapping the two arms on a simple photodiode then generates a down-converted radio frequency comb. The difference in repetition rates between the two pulse trains and hence the line spacing of the down-converted comb can easily be tuned in this setup. This feature allows for a flexible adjustment of the tradeoff between non-aliasing bandwidth vs. measurement time in spectroscopy applications. Furthermore, we show that by fine-tuning the center-wavelengths of the two pulse trains, we are able to shift the down-converted frequency comb along the radio-frequency axis. The usability of this dual-comb setup is demonstrated by measuring the transmission of two different etalons while the laser is completely free-running, Published by Soc., Washington, DC

We demonstrate frequency comb based, robust, long-term conversion of optical frequency standards to an optical timescale that outputs a 1 pulse per second (PPS) optical time signal at a defined reference plane. This level of robustness is essential for time standards based on optical clocks.

We computationally study wake modes in a fiber comb laser with a slow saturable absorber. We show that these modes will lead to the experimentally-observed sidebands, and we predict the laser's stable operating regime.

We develop a system to convert the high frequency accuracy of optical clocks to an optical timescale that outputs a 1 pulse per second (PPS) optical time signal at a defined reference plane.

Zusammenfassung Marie-Christin Lux und Philipp Schulte »De l’État-Nation à l’Europe. Histoire du ministère de la Défense et des armées en France et en Allemagne aux XIXe et XXe siècles«. Tagung des Deutschen Historischen Instituts Paris (DHIP), des Militärgeschichtlichen Forschungsamtes (MGFA) und des Institut de Recherche Stratégique de l’École Militaire (IRSEM), 20. Juni 2011 in Paris Sven Petersen und Stefan Droste »Militärische Wissenskulturen in der Frühen Neuzeit«. 9. Jahrestagung des Arbeitskreises Militär und Gesellschaft in der Frühen Neuzeit vom 1. bis 3. Dezember 2011 in Göttingen Florian Reichenberger »Guerres futures, guerres imaginées: vers une histoire culturelle de l’avant-1914. Colloque international co-organisé par le Centre International de Recherche de l’Historial de la Grande Guerre et l’Institut historique allemand«, 9. November 2011, Péronne und 10. November 2011, Paris Antje Dierking »Für Frieden und Freiheit oder Shareholder Value und Auslastungsquote? Rüstung in Europa und Nordamerika nach dem Zweiten Weltkrieg«. Workshop des Militärgeschichtlichen Forschungsamtes, 8. bis 9. November 2011 in Potsdam Janine Doerry »Captivité de guerre au XXième siècle. Des archives, des histoires, des mémoires«. Internationale Tagung des Institut historique du temps présent (IHTP), des Centre national de la recherche scientifique (CNRS), des Institut de Recherche Stratégique de l’École Militaire (IRSEM) und der London School of Economics and Political Science (LSE), 17. bis 18. November 2011 in Paris Flavio Eichmann »Freibeuter der Moderne - Politisch-militärische Akteure an den Rändern von Souveränität und Legitimität«. Kolloquium zum 60. Geburtstag von Prof. Dr. Stig Förster, 20. bis 21. Oktober 2011 in Bern Stefan M. Brenner Die Achillesferse der NATO: Die Nordatlantische Allianz und der griechisch-türkische Binnenkonflikt 1952–1989. Ein Überblick zum Stand der Forschung