Photonic Crystal Vertical Cavity Lasers

Photonic crystal confinement in vertical cavity surface-emitting lasers (VCSELs) is a robust and reliable technology for achieving operation in the fundamental lateral mode and is potentially applicable to a variety of materials systems and operating wavelengths. We demonstrate photonic crystal VCSELs operating in a single transverse mode with over 30 dB side mode suppression and over 1 mW of output power. These lasers have been subjected to a post-process technique to introduce the etched holes making up the photonic crystals that surround a centralized defect in which lasing occurs. We also show that coupling between adjacent defects in a photonic lattice is possible, further increasing the power available in the devices

HST Observations of SGR 0526-66: New Constraints on Accretion and Magnetar Models

Soft Gamma-ray Repeaters (SGRs) are among the most enigmatic sources known today. Exhibiting huge X- and Gamma-ray bursts and flares, as well as soft quiescent X-ray emission, their energy source remains a mystery. Just as mysterious are the Anomalous X-ray pulsars (AXPs), which share many of the same characteristics. Thanks to recent Chandra observations, SGR 0526-66, the first SGR, now appears to be a transition object bridging the two classes, and therefore observations of it have implications for both SGRs and AXPs. The two most popular current models for their persistent emission are accretion of a fossil disk or decay of an enormous (~10^15 G) magnetic field in a magnetar. We show how deep optical observations of SGR 0526-66, the only SGR with small enough optical extinction for meaningful observations, show no evidence of an optical counterpart. These observation place strong new constraints on both accretion disk and magnetar models, and suggest that the spectral energy distribution may peak in the hard-UV. Almost all accretion disks are excluded by the optical data, and a magnetar would require a ~10^15-10^16 G field.Comment: 23 pages, 5 figures. Accepted by Ap

Liquid Crystal-Solid Interface Structure at the Antiferroelectric-Ferroelectric Phase Transition

Total Internal Reflection (TIR) is used to probe the molecular organization at the surface of a tilted chiral smectic liquid crystal at temperatures in the vicinity of the bulk antiferroelectric-ferroelectric phase transition. Data are interpreted using an exact analytical solution of a real model for ferroelectric order at the surface. In the mixture T3, ferroelectric surface order is expelled with the bulk ferroelectric-antiferroelectric transition. The conditions for ferroelectric order at the surface of an antiferroelectric bulk are presented

Field-induced confinement in (TMTSF)2ClO4 under accurately aligned magnetic fields

We present transport measurements along the least conducting c direction of the organic superconductor (TMTSF)2ClO4, performed under an accurately aligned magnetic field in the low temperature regime. The experimental results reveal a two-dimensional confinement of the carriers in the (a,b) planes which is governed by the magnetic field component along the b' direction. This 2-D confinement is accompanied by a metal-insulator transition for the c axis resistivity. These data are supported by a quantum mechanical calculation of the transverse transport taking into account in self consistent treatment the effect of the field on the interplane Green function and on the intraplane scattering time

Orbital quantization in the high magnetic field state of a charge-density-wave system

A superposition of the Pauli and orbital coupling of a high magnetic field to charge carriers in a charge-density-wave (CDW) system is proposed to give rise to transitions between subphases with quantized values of the CDW wavevector. By contrast to the purely orbital field-induced density-wave effects which require a strongly imperfect nesting of the Fermi surface, the new transitions can occur even if the Fermi surface is well nested at zero field. We suggest that such transitions are observed in the organic metal $\alpha$-(BEDT-TTF)$_2$KHg(SCN)$_4$ under a strongly tilted magnetic field.Comment: 14 pages including 4 figure

Response of Temperate, Subtropical and Tropical Soybean Genotypes to Type-B Overflow Tidal Swamp of Indonesia

Twenty-nine soybean genotypes originating from various countries were evaluated on the tidal swamp of Indonesia to obtain information of agronomic character diversity as the soybean response to the environment and to obtain adaptive genotypes that can be used to develop soybean genotypes for the land. This study was conducted in a complete randomized block design with 3 replications. Diverse genetic backgrounds, countries and climatic regions of the 29 soybean genotypes were responsible for the difference in agronomic responses among the genotypes. All temperate and sub-tropical genotypes were able to produce seeds in the tropical type-B overflow tidal swamp. Adaptability based on seed yield resulted in 1 highly adaptive, 17 adaptive, 5 moderately adaptive and 6 non-adaptive genotypes. Adaptive and highly adaptive genotypes produced 1.56 - 2.58 tons ha-1 of seeds. Karasumame (Naihou), a subtropical genotype, produced the highest seed yield which was 65% higher than Indonesia average soybean productivity and 225% higher than soybean productivity with non-saturated soil culture technology on the tidal swamp. This study concluded that temperate and subtropical genotypes could be used as germplasm sources for soybean development in the tropical type-B overflow tidal swamp in Indonesia