Substrate-emitting ring interband cascade lasers

The authors acknowledge the support by the Austrian Science Fund (FWF) projects P26100-N27 (H2N) and NextLite (F4909-N23), and the State of Bavaria. HD acknowledges financial support through an APART fellowship from the Austrian Academy of Sciences.We demonstrate interband cascade lasers fabricated into ring-shaped cavities with vertical light emission through the substrate at a wavelength of λ ≈ 3.7 µm. The out-coupling mechanism is based on a metallized second-order distributed feedback grating. At room-temperature, a pulsed threshold current-density of 0.75 kA/cm2 and a temperature-tuning rate of 0.3 nm/°C is measured. In contrast to the azimuthal polarization of ring quantum cascade lasers, we observe a radial polarization of the projected nearfield of ring interband cascade lasers. These findings underline the fundamental physical difference between light generation in interband and intersubband cascade lasers, offering new perspectives for device integration.Publisher PDFPeer reviewe

Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm

We present the first results of the Fermilab Muon g-2 Experiment for the positive muon magnetic anomaly $a_\mu \equiv (g_\mu-2)/2$. The anomaly is determined from the precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency $\omega_a$ between the spin-precession and cyclotron frequencies for polarized muons in a magnetic storage ring. The storage ring magnetic field is measured using nuclear magnetic resonance probes calibrated in terms of the equivalent proton spin precession frequency ${\tilde{\omega}'^{}_p}$ in a spherical water sample at 34.7$^{\circ}$C. The ratio $\omega_a / {\tilde{\omega}'^{}_p}$, together with known fundamental constants, determines $a_\mu({\rm FNAL}) = 116\,592\,040(54)\times 10^{-11}$ (0.46\,ppm). The result is 3.3 standard deviations greater than the standard model prediction and is in excellent agreement with the previous Brookhaven National Laboratory (BNL) E821 measurement. After combination with previous measurements of both $\mu^+$ and $\mu^-$, the new experimental average of $a_\mu({\rm Exp}) = 116\,592\,061(41)\times 10^{-11}$ (0.35\,ppm) increases the tension between experiment and theory to 4.2 standard deviationsComment: 10 pages; 4 figure

Pharmacokinetic and behavioral effects of allopregnanolone in healthy women

Rationale  The behavioral effects of allopregnanolone (3α-hydroxy-5α-pregnan-20-one) in women are not known. Objective  Allopregnanolone, a neuroactive steroid secreted by the mammalian ovary, exerts its anesthetic, anxiolytic, and sedative/hypnotic effects through potentiation of GABAA receptors. The purpose of this study was to evaluate the behavioral effects of allopregnanolone in healthy women. Methods  Ten healthy women were given three increasing intravenous doses of allopregnanolone in the follicular phase of the menstrual cycle. Saccadic eye movement parameters and visual analogue scales of sedation were used to evaluate the behavioral response of allopregnanolone. Repeated blood samples for analyses of allopregnanolone were drawn throughout the study day. Results  Exogenously administered allopregnanolone decreases saccadic eye movement parameters and increases subjective ratings of sedation that correlate with increased serum concentrations of this neuroactive steroid. Conclusion  The behavioral effects of allopregnanolone are similar to that of its 5β-stereoisomer, pregnanolone (3α-hydroxy-5β-pregnan-20-one). Apart from fatigue and mild nausea, allopregnanolone given in a cumulative dose of 0.09 mg/kg did not have any adverse effects