Photothermal effects in ultra-precisely stabilized tunable microcavities

We study the mechanical stability of a tunable high-finesse microcavity under ambient conditions and investigate light-induced effects that can both suppress and excite mechanical fluctuations. As an enabling step, we demonstrate the ultra-precise electronic stabilization of a microcavity. We then show that photothermal mirror expansion can provide high-bandwidth feedback and improve cavity stability by almost two orders of magnitude. At high intracavity power, we observe self-oscillations of mechanical resonances of the cavity. We explain the observations by a dynamic photothermal instability, leading to parametric driving of mechanical motion. For an optimized combination of electronic and photothermal stabilization, we achieve a feedback bandwidth of $500\,$kHz and a noise level of $1.1 \times 10^{-13}\,$m rms

Inducing vortices in a Bose-Einstein condensate using holographically produced light beams

In this paper we demonstrate a technique that can create out-of-equilibrium vortex configurations with almost arbitrary charge and geometry in a Bose-Einstein condensate. We coherently transfer orbital angular momentum from a holographically generated light beam to a Rubidium 87 condensate using a two-photon stimulated Raman process. Using matter wave interferometry, we verify the phase pattern imprinted onto the atomic wave function for a single vortex and a vortex-antivortex pair. In addition to their phase winding, the vortices created with this technique have an associated hyperfine spin texture.Comment: 4 pages, 5 figure

The Calibration Home Base for Imaging Spectrometers

The Calibration Home Base (CHB) is an optical laboratory designed for the calibration of imaging spectrometers for the VNIR/SWIR wavelength range. Radiometric, spectral and geometric calibration as well as the characterization of sensor signal dependency on polarization are realized in a precise and highly automated fashion. This allows to carry out a wide range of time consuming measurements in an ecient way. The implementation of ISO 9001 standards in all procedures ensures a traceable quality of results. Spectral measurements in the wavelength range 380–1000 nm are performed to a wavelength uncertainty of +- 0.1 nm, while an uncertainty of +-0.2 nm is reached in the wavelength range 1000 – 2500 nm. Geometric measurements are performed at increments of 1.7 µrad across track and 7.6 µrad along track. Radiometric measurements reach an absolute uncertainty of +-3% (k=1). Sensor artifacts, such as caused by stray light will be characterizable and correctable in the near future. For now, the CHB is suitable for the characterization of pushbroom sensors, spectrometers and cameras. However, it is planned to extend the CHBs capabilities in the near future such that snapshot hyperspectral imagers can be characterized as well. The calibration services of the CHB are open to third party customers from research institutes as well as industry

Towards 6Li - 40K ground state molecules

The production of a quantum gas with strong long - range dipolar interactions is a major scientific goal in the research field of ultracold gases. In their ro - vibrational ground state Li -K dimers possess a large permanent dipole moment, which could possibly be exploited for the realization of such a quantum gas. A production of these molecules can be achieved by the association of Li and K at a Feshbach resonance, followed by a coherent state transfer. In this thesis, detailed theoretical an experimental preparations to achieve state transfer by means of Stimulated Raman Adiabatic Passage (STIRAP) are described. The theoretical preparations focus on the selection of an electronically excited molecular state that is suitable for STIRAP transfer. In this context, molecular transition dipole moments for both transitions involved in STIRAP transfer are predicted for the first time. This is achieved by the calculation of Franck -Condon factors and a determination of the state in which the 6Li - 40K Feshbach molecules are produced. The calculations show that state transfer by use of a single STIRAP sequence is experimentally very well feasible. Further, the optical wavelengths that are needed to address the selected states are calculated. The high accuracy of the data will allow to carry out the molecular spectroscopy in a fast and efficient manner. Further, only a comparatively narrow wavelength tuneability of the spectroscopy lasers is needed. The most suitable Feshbach resonance for the production of 6Li - 40K molecules at experimentally manageable magnetic field strengths is occurring at 155G. Experimentally, this resonance is investigated by means of cross - dimensional relaxation. The application of the technique at various magnetic field strengths in the vicinity of the 155G Feshbach resonance allows a determination of the resonance position and width with so far unreached precision. This reveals the production of molecules on the atomic side of the resonance, thereby establishing the first observation of a many body effect in the crossover regime of a narrow Feshbach resonance. Further, mass dependent factors, with which the equilibration of an induced anisotropic temperature of the trapped particle samples can be described, are experimentally determined for the first time. The type of resonance as well as the measured molecular lifetimes are found to be very well suited for STIRAP transfer. A Raman laser system is designed based on the transition wavelengths and durations of state transfer which are predicted. As the wavelengths of the Raman lasers differ widely but coherence of the light fields is needed, the technical realization of a laser system is challenging. As a part of the laser system, the construction and characterization of a reference optical resonator are presented. Laser frequency stabilization with a linewidth of approximately 500Hz and an Allan deviation below 10−12 for timespans up to several ten seconds are demonstrated. Further, the stabilization of a frequency comb to this reference laser is demonstrated. For the laser spectroscopy of electronically excited Li -K states an interferometric laser frequency stabilization will be used. The device is a commercial design, for which a calibration procedure that enhances the precision by several orders of magnitude is worked out within this thesis. The calibration scheme includes the precise measurement of the stabilization’s wavelength dependent frequency deviations by means of a frequency comb. By the implementation of several calibration steps a remaining frequency deviation of less than 5.7MHz (rms 1.6MHz) in the whole relevant wavelength range 750 - 795 nm is achieved. Only the exceptional precision of the fully calibrated device permits the usage for the Li -K spectroscopy, while the demonstrated wide tuning capability facilitates the completion of the latter in a fast and convenient manner

Twelve-month follow-up of left atrial appendage occlusion with Amplatzer Amulet

  Background: The Amplatzer Amulet (St. Jude Medical, Minneapolis, MN, USA) is a second gen­eration Amplatzer device for left atrial appendage (LAA) occlusion (LAAO) for stroke prophylaxis in patients with atrial fibrillation. This research sought to assess the clinical performance of the Amplatzer Amulet device and in follow up for 12 months. Methods: In this single-center registry patients with atrial fibrillation and contraindication to oral anticoagulation underwent LAAO with the Amplatzer Amulet device. Follow-up was performed before discharge, by transesophageal echocardiography (TEE) after 6 weeks and telephone interview after 3, 6 and 12 months. Results: Between October 2014 and August 2015 50 patients (76.1 ± 8.3 years; 30 male) were en­rolled. Procedural success was achieved in 49 (98%) patients. Major periprocedural adverse events were observed in 4 (8%) of patients: 1 device embolization, 2 pericardial effusions requiring pericardiocente­sis and 1 prolonged hospital stay due to retropharyngeal hematoma from the TEE probe. Follow-up TEE was available in 38 of 50 patients showing complete LAA sealing in all. 2 device-related thrombi were also documented. At 12-month follow-up 7 patients had died unrelated to the device. Ischemic stroke occurred in 3 patients. According to neurological examination two were classified as microangiopathic and not cardio-embolic. The other one could not be classified. Bleeding complications (5 minor, 3 major) were documented in 8 patients. Conclusions: Although minimizing procedure-related complications remains challenging, LAAO with the Amplatzer Amulet device showed high procedural success and excellent LAA sealing. (Cardiol J 2017; 24, 2: 131–138

Do Acute Coronary Events Affect Lipid Management and Cholesterol Goal Attainment in Germany?

Objective To document utilization of lipid-lowering therapy, attainment of low-density lipoprotein cholesterol target values, and cardiovascular outcomes in patients hospitalized for acute coronary syndrome in Germany. Methods The Dyslipidemia International Study II was a multicenter, observational study of the prevalence of dyslipidemia and lipid target value attainment in patients surviving any acute coronary syndrome event. Among patients on lipid-lowering therapy for ≥3 months, use of lipid-lowering therapy and lipid profiles were assessed at admission and again at 120 ± 15 days after admission (the follow-up time point). Multivariate logistic regression was used to identify variables predictive of low-density lipoprotein cholesterol target value attainment in patients using lipid-lowering therapy. Results A total of 461 patients hospitalized for acute coronary syndrome were identified, 270 (58.6%) of whom were on lipid-lowering therapy at admission. Among patients on lipid-lowering therapy, 90.7% and 85.9% were receiving statin monotherapy at admission and follow-up, respectively. Mean (SD) lowdensity lipoprotein cholesterol levels in patients on lipid-lowering therapy were 101 (40) mg/dl and 95 (30) mg/dl at admission and follow-up, respectively. In patients with data at both admission and followup (n= 61), low-density lipoprotein cholesterol target value attainment rates were the same (19.7%) at both time points. Smoking was associated with a 77% lower likelihood of attaining the low-density lipoprotein cholesterol target value. Conclusion Hospitalization for an acute event does not greatly alter lipid management in acute coronary syndrome patients in Germany. Both lipid-lowering therapy doses and rates of low-density lipoprotein cholesterol target value attainment remained essentially the same several months after the event