From Strong to Weak Coupling Regime in a Single GaN Microwire up to Room Temperature

Large bandgap semiconductor microwires constitute a very advantageous alternative to planar microcavities in the context of room temperature strong coupling regime between exciton and light. In this work we demonstrate that in a GaN microwire, the strong coupling regime is achieved up to room temperature with a large Rabi splitting of 125 meV never achieved before in a Nitride-based photonic nanostructure. The demonstration relies on a method which doesn't require any knowledge \'a priori on the photonic eigenmodes energy in the microwire, i.e. the details of the microwire cross-section shape. Moreover, using a heavily doped segment within the same microwire, we confirm experimentally that free excitons provide the oscillator strength for this strong coupling regime. The measured Rabi splitting to linewidth ratio of 15 matches state of the art planar Nitride-based microcavities, in spite of a much simpler design and a less demanding fabrication process. These results show that GaN microwires constitute a simpler and promising system to achieve electrically pumped lasing in the strong coupling regime.Comment: 14 pages, 4 figure

Valence band offset of the ZnO/AlN heterojunction determined by X-ray photoemission spectroscopy

The valence band offset of ZnO/AlN heterojunctions is determined by high resolution x-ray photoemission spectroscopy. The valence band of ZnO is found to be 0.43±0.17 eV below that of AlN. Together with the resulting conduction band offset of 3.29±0.20 eV, this indicates that a type-II (staggered) band line up exists at the ZnO/AlN heterojunction. Using the III-nitride band offsets and the transitivity rule, the valence band offsets for ZnO/GaN and ZnO/InN heterojunctions are derived as 1.37 and 1.95 eV, respectively, significantly higher than the previously determined values

Global seismic energy scaling relationships based on the type of faulting

We derived scaling relationships for different seismic energy metrics for earthquakes around the globe with MW &gt; 6.0 from 1990 to 2022. The seismic energy estimations were derived with two methodologies, the first based on the velocity flux integration and the second based on finite-fault models. In the first case, we analyzed 3331 reported seismic energies derived by integrating far-field waveforms. In the latter methodology, we used the total moment rate functions and the approximation of the overdamped dynamics to quantify seismic energy from 231 finite-fault models (Emrt and EO, EU, respectively). Both methodologies provide compatible energy estimates. The radiated seismic energies estimated from the slip models and integration of velocity records are also compared for different types of focal mechanisms (R, reverse; R-SS, reverse–strike-slip; SS, strike-slip; SS-R, strike-slip–reverse; SS-N, strike-slip–normal; N, normal; and N-SS, normal–strike-slip), and then used to derive converting scaling relations among the different energy types. Additionally, the behavior of radiated seismic energy (ER), energy-to-moment ratio (ER/M0), and apparent stress (τα) for different rupture types at a global scale is examined by considering depth variations in mechanical properties, such as seismic velocities, rock densities, and rigidities. For this purpose, we used a 1-D global velocity model. The ER/M0 ratio is, based on statistical t tests, largest for strike-slip earthquakes, followed by normal-faulting events, with the lowest values for reverse earthquakes for hypocentral depths &lt; 90 km. Not enough data are available for statistical tests at deeper intervals except for the 90 to 120 km range, where we can satisfactorily conclude that ER/M0 for R-SS and SS-R types is larger than for N-type faulting, which also conforms to the previous assumption. In agreement with previous studies, our results exhibit a robust variation in τα with the focal mechanism. Regarding the behavior of τα with depth, our results agree with the existence of a bimodal distribution with two depth intervals where the apparent stress is maximum for normal-faulting earthquakes. At depths in the range of 180–240 km, τα for reverse earthquakes is higher than for normal-faulting events. We find the trend EU &gt; Emrt &gt; EO for all mechanism types based on statistical t tests. Finite-fault energy estimations also support focal mechanism dependence of apparent stress but only for shallow earthquakes (Z &lt; 30 km). The slip distribution population used was too small to conclude that finite-fault energy estimations support the dependence of average apparent stress on rupture type at different depth intervals.</p

Analysis of the ULF electromagnetic emission related to seismic activity, Teoloyucan geomagnetic station, 1998-2001

Results of ULF geomagnetic measurements at station Teoloyucan (Central Mexico, 99.11'35.735''W, 19.44'45.100''N, 2280m height) in relation to seismic activity in the period 1998-2001 and their analysis are presented. Variations of spectral densities for horizontal and vertical components, polarization densities and spectrograms of magnetic field, their derivatives are analyzed as a part of traditional analysis in this study. Values of spectral density were calculated for 6 fixed frequencies <i>f</i>=1, 3, 10, 30, 100 and 300mHz. Fractal characteristics of spectra were analyzed in the conception of SOC (Self-Organized Criticality). 2 nighttime intervals, 0-3 and 3-6h by local time have been used to decrease the noise interference in row data. In order to exclude the intervals with a high geomagnetic activity from analysis we referred to <i>Ap</i> indices, calculated for corresponding time intervals. The contribution of seismic events to geomagnetic emission was estimated by seismic index <i>k_s</i>=10^{0.75<i>Ms</i>}/10<i>D</i>, where <i>Ms</i> is the amplitude of the earthquake and <i>D</i> is the distance from its epicenter to the station

Lifting the Dusty Veil II: A Large-Scale Study of the Galactic Infrared Extinction Law

We combine near-infrared (2MASS) and mid-infrared (Spitzer-IRAC) photometry to characterize the IR extinction law (1.2-8 microns) over nearly 150 degrees of contiguous Milky Way midplane longitude. The relative extinctions in 5 passbands across these wavelength and longitude ranges are derived by calculating color excess ratios for G and K giant red clump stars in contiguous midplane regions and deriving the wavelength dependence of extinction in each one. Strong, monotonic variations in the extinction law shape are found as a function of angle from the Galactic center, symmetric on either side of it. These longitudinal variations persist even when dense interstellar regions, known a priori to have a shallower extinction curve, are removed. The increasingly steep extinction curves towards the outer Galaxy indicate a steady decrease in the absolute-to-selective extinction ratio (R_V) and in the mean dust grain size at greater Galactocentric angles. We note an increasing strength of the 8 micron extinction inflection at high Galactocentric angles and, using theoretical dust models, show that this behavior is consistent with the trend in R_V. Along several lines of sight where the solution is most feasible, A_lambda/A_Ks as a function of Galactic radius is estimated and shown to have a Galactic radial dependence. Our analyses suggest that the observed relationship between extinction curve shape and Galactic longitude is due to an intrinsic dependence of the extinction law on Galactocentric radius.Comment: Accepted to Ap

On the behavior of site effects in central Mexico (the Mexican volcanic belt &ndash; MVB), based on records of shallow earthquakes that occurred in the zone between 1998 and 2011

The Mexican volcanic belt (MVB) is a seismogenic zone that transects the central part of Mexico with an east–west orientation. The seismic risk and hazard of this seismogenic zone has not been studied in detail due to the scarcity of instrumental data as well as because seismicity in the continental regime of central Mexico is not too frequent. However, it is known that there are precedents of large earthquakes (<i>M</i>_w > 6.0) that have taken place in this zone. The valley of Mexico City (VM) is the sole zone, within the MVB, that has been studied in detail. Studies have mainly focused on the ground amplification during large events such as the 1985 subduction earthquake that occurred off coast of Michoacán. The purpose of this article is to analyze the behavior of site effects in the MVB zone based on records of shallow earthquakes (data not reported before) that occurred in the zone between 1998 and 2011. We present a general overview of site effects in the MVB, a classification of the stations in order to reduce the uncertainty in the data when obtaining attenuation parameters in future works, as well as some comparisons between the information presented here and that presented in previous studies. <br><br> A regional evaluation of site effects and Fourier acceleration spectrum (FAS) shape was estimated based on 80 records of 22 shallow earthquakes within the MVB zone. Data of 25 stations were analyzed. Site effects were estimated by using the horizontal-to-vertical spectral ratio (HVSR) methodology. The results show that seismic waves are less amplified in the northeast sites of the MVB with respect to the rest of the zone and that it is possible to classify two groups of stations: (1) stations with negligible site amplification (NSA) and (2) stations with significant site amplification (SSA). Most of the sites in the first group showed small (<3) amplifications while the second group showed amplifications ranging from 4 to 6.5 at frequencies of about 0.35, 0.75, 15 and 23 Hz. With these groups of stations, average levels of amplification were contrasted for the first time with those caused by the subduction zone earthquakes. With respect to the FAS shapes, most of them showed similarities at similar epicentral distances. Finally, some variations of site effects were found when compared to those obtained in previous studies on different seismicity regions. These variations were attributed to the location of the source. <br><br> These aspects help to advance the understanding about the amplification behavior and of the expected seismic risk on central Mexico due to large earthquakes within the MVB seismogenic zone

Filtered screens and augmented Teichm\"uller space

We study a new bordification of the decorated Teichm\"uller space for a multiply punctured surface F by a space of filtered screens on the surface that arises from a natural elaboration of earlier work of McShane-Penner. We identify necessary and sufficient conditions for paths in this space of filtered screens to yield short curves having vanishing length in the underlying surface F. As a result, an appropriate quotient of this space of filtered screens on F yields a decorated augmented Teichm\"uller space which is shown to admit a CW decomposition that naturally projects to the augmented Teichm\"uller space by forgetting decorations and whose strata are indexed by a new object termed partially oriented stratum graphs.Comment: Final version to appear in Geometriae Dedicat