Spin rings in bi-stable planar semiconductor microcavities

A unique feature of exciton-polaritons, inherited from their mixed light-matter origin, is the strongly spin-dependent polariton-polariton interaction, which has been predicted to result in the formation of spin rings in real space [Shelykh et al., Phys. Rev. Lett. 100, 116401 (2008)]. Here we experimentally demonstrate the spin bi-stability of exciton-polaritons in an InGaAs-based semiconductor microcavity under resonant optical pumping. We observe the formation of spin rings whose size can be finely controlled in a spatial scale down to the micrometer range, much smaller than the spot size. We additionally evaluate the sign and magnitude of the antiparallel polariton spin interaction constant.Comment: 5 pages, 4 figure

Simultaneous Measurement of Strain and Temperature Using a Single Emission Line

In this study, we present and demonstrate a novel sensor system for simultaneous measurement of strain and temperature through a unique combination of a long period grating and a fiber laser based on a fiber Bragg grating. In order to achieve this, a new erbium-doped fiber laser structure is created, showing an optical signal-to-noise ratio of 55 dB and a peak power measured on the optical spectrum analyzer between -5 and 0 dBm. The strain and the temperature information can be obtained by using a unique emission line through monitoring both the fiber laser wavelength shift and the change of the power level, both of which showing a clear linear behavior

Acceptability of intrapartum ultrasound by mothers in an African population

Intrapartum ultrasound is gaining high acceptance by many women as another method for assessing labour progression. Despite growing evidence of the effectiveness of ultrasound in labour, the acceptance of intrapartum ultrasound has not been previously investigated in black Africans. This study aimed to determine women’s acceptance of intrapartum ultrasound and their preference for transperineal ultrasound or digital vaginal examination (digital VE) in Ghana. An analytical cross-sectional study was conducted among mothers who had had both digital VE and transperineal ultrasound during labour in a tertiary hospital. Information about their sociodemographic characteristics, experience with, and preference for ultrasound or digital VE in labour using a pretested structured questionnaire was obtained. Their experiences were categorised as ‘tolerable, ‘quite uncomfortable’ or ‘very uncomfortable’. Categorical variables were compared using Fisher’s exact test. A p value < 0.05 was considered statistically significant. Altogether, 196 women were recruited into the study. The mean age of the women was 26.7 years (standard deviation, 4.6 years). Nearly half (47%) of the women had never delivered before. Significantly more women considered transperineal ultrasound to be more tolerable than digital VE (66% vs. 40%; p < 0.001). Almost all the women (97.5%) described their experience with transperineal ultrasound to be better than digital VE, and would choose transperineal ultrasound over digital VE in the future (98.5% vs. 1.5%; p < 0.001). The findings of this study are comparable to those of other related studies reported recently. This research confirms high acceptance of ultrasound in labour by mothers from different countries and across continents, implying that cultural differences do not influence women’s responses to and interest in intrapartum ultrasound. Most women found ultrasound in labour to be more tolerable than digital VE. Whenever possible, transperineal ultrasound should be provided as an alternative to digital VE during labour.N/

Data Report: Pump Sampling and Sediment Analysis in Support of the Sensor Insertion System Duck, N.C. April and October, 1997

The objectives of this study were to (i) construct a pumping system, (ii) operate the system and collect samples of suspended sediment across the width of the surf zone during two major field experiments planned for the SIS in 1997, and (iii) analyze the resulting samples for sand concentration, sand size distribution, total percent sand, total percent mud, and organic content. The purpose was to provide a high quality data set of pump samples with which to later test the sensitivity of indirect measurements of suspended sand concentration to the presence of suspended mud. The response of OBSs is known to be particularly sensitive to the presence of suspended mud ( turbidity ) due to the inverse response of OBS output to grain size. Without better constraints on the proper interpretation of OBS time series, the overall conclusions with regards to net along-shelf transport of sand during storms may be in doubt (see following section)

Engineering spin-orbit coupling for photons and polaritons in microstructures

One of the most fundamental properties of electromagnetism and special relativity is the coupling between the spin of an electron and its orbital motion. This is at the origin of the fine structure in atoms, the spin Hall effect in semiconductors, and underlies many intriguing properties of topological insulators, in particular their chiral edge states. Configurations where neutral particles experience an effective spin-orbit coupling have been recently proposed and realized using ultracold atoms and photons. Here we use coupled micropillars etched out of a semiconductor microcavity to engineer a spin-orbit Hamiltonian for photons and polaritons in a microstructure. The coupling between the spin and orbital momentum arises from the polarisation dependent confinement and tunnelling of photons between micropillars arranged in the form of a hexagonal photonic molecule. Dramatic consequences of the spin-orbit coupling are experimentally observed in these structures in the wavefunction of polariton condensates, whose helical shape is directly visible in the spatially resolved polarisation patterns of the emitted light. The strong optical nonlinearity of polariton systems suggests exciting perspectives for using quantum fluids of polaritons11 for quantum simulation of the interplay between interactions and spin-orbit coupling.Comment: main text: pages 1-11 (4 figures); supplementary material: pages 12-28 (9 figures