Ultracold atom interferometry in space.

Bose-Einstein condensates (BECs) in free fall constitute a promising source for space-borne interferometry. Indeed, BECs enjoy a slowly expanding wave function, display a large spatial coherence and can be engineered and probed by optical techniques. Here we explore matter-wave fringes of multiple spinor components of a BEC released in free fall employing light-pulses to drive Bragg processes and induce phase imprinting on a sounding rocket. The prevailing microgravity played a crucial role in the observation of these interferences which not only reveal the spatial coherence of the condensates but also allow us to measure differential forces. Our work marks the beginning of matter-wave interferometry in space with future applications in fundamental physics, navigation and earth observation.

Compact and robust diode laser system technology for dual-species ultracold atom experiments with rubidium and potassium in microgravity.

We present a compact and robust distributed-feedback diode laser system architecture for ultracold atom experiments with K41 and Rb87 in a mobile setup operating at the ZARM drop tower in Bremen. Our system withstands DC accelerations of up to 43 g in operation with only minor adjustments over several drop campaigns. Micro-integrated master-oscillator-power-amplifier modules in conjunction with miniaturized, free-space opto-mechanics are integrated on a platform with a volume of 43 L. With compact control and driver electronics, this laser system features output power and spectral characteristics suitable for 2D+ and 3D magneto-optical trapping operation, atomic state preparation, Bragg-diffraction-based atom interferometry, and detection.

Space-borne Bose-Einstein condensation for precision interferometry.

Owing to the low-gravity conditions in space, space-borne laboratories enable experiments with extended free-fall times. Because Bose-Einstein condensates have an extremely low expansion energy, space-borne atom interferometers based on Bose-Einstein condensation have the potential to have much greater sensitivity to inertial forces than do similar ground-based interferometers. On 23 January 2017, as part of the sounding-rocket mission MAIUS-1, we created Bose-Einstein condensates in space and conducted 110 experiments central to matter-wave interferometry, including laser cooling and trapping of atoms in the presence of the large accelerations experienced during launch. Here we report on experiments conducted during the six minutes of in-space flight in which we studied the phase transition from a thermal ensemble to a Bose-Einstein condensate and the collective dynamics of the resulting condensate. Our results provide insights into conducting cold-atom experiments in space, such as precision interferometry, and pave the way to miniaturizing cold-atom and photon-based quantum information concepts for satellite-based implementation. In addition, space-borne Bose-Einstein condensation opens up the possibility of quantum gas experiments in low-gravity conditions1,2.

Comparison of symmetric and asymmetric double quantum well extended-cavity diode lasers for broadband passive mode-locking at 780 nm.

We present a compact, mode-locked diode laser system designed to emit a frequency comb in the wavelength range around 780 nm. We compare the mode-locking performance of symmetric and asymmetric double quantum well ridge-waveguide diode laser chips in an extended-cavity diode laser configuration. By reverse biasing a short section of the diode laser chip, passive mode-locking at 3.4 GHz is achieved. Employing an asymmetric double quantum well allows for generation of a mode-locked optical spectrum spanning more than 15 nm (full width at -20 dB) while the symmetric double quantum well device only provides a bandwidth of ∼2.7 nm (full width at -20 dB). Analysis of the RF noise characteristics of the pulse repetition rate shows an RF linewidth of about 7 kHz (full width at half-maximum) and of at most 530 Hz (full width at half-maximum) for the asymmetric and symmetric double quantum well devices, respectively. Investigation of the frequency noise power spectral density at the pulse repetition rate shows a white noise floor of approximately 2100 Hz2/Hz and of at most 170 Hz2/Hz for the diode laser employing the asymmetric and symmetric double quantum well structures, respectively. The pulse width is less than 10 ps for both devices.

Method for in-depth characterization of electro-optic phase modulators.

A flexible method to measure the modulation efficiency and residual amplitude modulation, including non-linearities, of phase modulators is presented. The method is based on demodulation of the modulated optical field in the optical domain by means of a heterodyne interferometer and subsequent analysis of the I&Q quadrature components of the corresponding RF beat note signal. As an example, we determine the phase modulation efficiency and residual amplitude modulation for both the TE and TM modes of a GaAs chip-based phase modulator at the wavelength of 1064 nm. From the results of these measurements, we estimate the linear and quadratic electro-optic coefficients for a P-p-n-N GaAs/AlGaAs double heterostructure.

High-power, micro-integrated diode laser modules at 767 and 780 nm for portable quantum gas experiments.

We present micro-integrated diode laser modules operating at wavelengths of 767 and 780 nm for cold quantum gas experiments on potassium and rubidium. The master-oscillator-power-amplifier concept provides both narrow linewidth emission and high optical output power. With a linewidth (10 µs) below 1 MHz and an output power of up to 3 W, these modules are specifically suited for quantum optics experiments and feature the robustness required for operation at a drop tower or on-board a sounding rocket. This technology development hence paves the way toward precision quantum optics experiments in space.

Ultra-narrow linewidth DFB-laser with optical feedback from a monolithic confocal Fabry-Perot cavity.

We present a compact, ultra-narrow-linewidth semiconductor laser based on a 780 nm distributed feedback diode laser optically self-locked to a mode of an external monolithic confocal Fabry-Perot resonator. We characterize spectral properties of the laser by measuring its frequency noise power spectral density. The white frequency noise levels at 5 Hz(2)/Hz above a Fourier frequency as small as 20 kHz. This noise level is more than five orders of magnitude smaller than the noise level of the same solitary diode laser without resonant optical feedback, and it is three orders of magnitude smaller than the noise level of a narrow linewidth, grating-based, extended-cavity diode laser. The corresponding Lorentzian linewidth of the laser with resonant optical feedback is 15.7 Hz at an output power exceeding 50 mW.

Accurate frequency noise measurement of free-running lasers.

We present a simple method to accurately measure the frequency noise power spectrum of lasers. It relies on creating the beat note between two lasers, capturing the corresponding signal in the time domain, and appropriately postprocessing the data to derive the frequency noise power spectrum. In contrast to methods already established, it does not require stabilization of the laser to an optical reference, i.e., a second laser, to an optical cavity or to an atomic transition. It further omits a frequency discriminator and hence avoids bandwidth limitation and nonlinearity effects common to high-resolution frequency discriminators.

Micro-integrated extended cavity diode lasers for precision potassium spectroscopy in space.

We present a micro-integrated, extended cavity diode laser module for space-based experiments on potassium Bose-Einstein condensates and atom interferometry. The module emits at the wavelength of the potassium D2-line at 766.7 nm and provides 27.5 GHz of continuous tunability. It features sub-100 kHz short term (100 µs) emission linewidth. To qualify the extended cavity diode laser module for quantum optics experiments in space, vibration tests (8.1 g(RMS) and 21.4 g(RMS)) and mechanical shock tests (1500 g) were carried out. No degradation of the electro-optical performance was observed.

A web-based system for clinical decision support and knowledge maintenance for deterioration monitoring of hemato-oncological patients.

We introduce a web-based clinical decision support system (CDSS) and knowledge maintenance based on rules and a set covering method focusing on the problem of detecting serious comorbidities in hemato-oncological patients who are at high risk of developing serious infections and life threatening complications. We experienced that diagnostic problems which are characterized by fuzzy, uncertain knowledge and overlapping signs, still reveal some kind of patterns that can be transferred into a computer-based decision model. We applied a multi-stage evaluation process to assess the system's diagnostic performance. Depending on how system behavior was compared to presumably correct judgment of a case the correctness rate for closed cases with all data available varied between 58% and 71%, the overall rate after critical review was 84%. However, the real time behavior of our approach which data becoming available as time passes still has to be evaluated and observational studies need to be conducted.

Micro-integrated 1 Watt semiconductor laser system with a linewidth of 3.6 kHz.

We demonstrate a compact, narrow-linewidth, high-power, micro-integrated semiconductor-based master oscillator power amplifier laser module which is implemented on a footprint of 50 x 10 mm(2). A micro-isolator between the oscillator and the amplifier suppresses optical feedback. The oscillator is a distributed Bragg reflector laser optimized for narrow-linewidth operation and the amplifier consists of a ridge waveguide entry and a tapered amplifier section. The module features stable single-mode operation with a FWHM linewidth of only 100 kHz and an intrinsic linewidth as small as 3.6 kHz for an output power beyond 1 W.

Shift of the f/t-PSA quotient in relation to renal insufficiency: consequences for the early detection of prostate carcinoma in patients with terminal renal failure.

BACKGROUND: Whether the quotient of free to total PSA (f/t-PSA) can be used to increase the specificity in the early detection of prostate carcinoma is a matter of discussion in cases of renal failure. We therefore compared f/t-PSA values of patients with kidney failure and patients after successful kidney transplantation. PATIENTS AND METHODS: The serum levels of total PSA (t-PSA) and free PSA (f-PSA) were determined in 57 patients. For those where t-PSA was between 2 and 10 ng/ml the f/t-PSA quotient was calculated. Out of the 57 patients, 32 suffered from renal failure (15 cases with prostate carcinoma, 17 with benign prostate disorder), the other 25 had successfully undergone kidney transplantation with a working transplant (10 with prostate carcinoma, 15 with benign prostate disorder). RESULTS: There were no statistically significant differences between the t-PSA levels of the various groups of patients. The f/t-PSA quotients, however, were consistently higher for the patients with kidney failure than for those with a kidney transplant or with a normal kidney function. There were no differences in the f/t-PSA quotients between transplant recipients and men with normal kidney function. CONCLUSION: For the use of the f/t-PSA quotient as a tool to support the decision for or against a prostate biopsy, it should be borne in mind that the cut-off criteria determined for men with a normal kidney function cannot be applied to patients who suffer from kidney failure. The f/t-PSA quotient of patients with terminal renal failure is often shifted towards higher values. On the other hand, there is no statistically significant difference between the f/t-PSA quotients of kidney transplant recipients and patients with normal kidney function, therefore the same diagnostic criteria apply in this case.