Vertically emitting annular Bragg lasers using polymer epitaxial transfer

Fabrication of a planar semiconductor microcavity, composed of cylindrical Bragg reflectors surrounding a radial defect, is demonstrated. A versatile polymer bonding process is used to transfer active InGaAsP resonators to a low-index transfer substrate. Vertical emission of in-plane modes lasing at telecom wavelengths is observed under pulsed optical excitation with a submilliwatt threshold

Assessment of lithographic process variation effects in InGaAsP annular Bragg resonator lasers

Optical microresonators based on an annular geometry of radial Bragg reflectors have been designed and fabricated by electron-beam lithography, reactive ion etching, and an epitaxial transfer process. Unlike conventional ring resonators that are based on total internal reflection of light, the annular structure described here is designed to support optical modes with very small azimuthal propagation coefficient and correspondingly large free spectral range. The effect of lithographic process variation upon device performance is studied. Laser emission wavelength and threshold optical pump power are found to vary between similar devices given different electron doses during electron-beam lithography. As the resonance wavelength and quality factor of these resonators are very sensitive to environmental changes, these resonators make ideal active light sources that can be integrated into large arrays for gas and liquid sensing applications and are easily interrogated

Probing the braneworld hypothesis with a neutron-shining-through-a-wall experiment

The possibility for our visible world to be a 3-brane embedded in a multidimensional bulk is at the heart of many theoretical edifices in high-energy physics. Probing the braneworld hypothesis is thus a major experimental challenge. Following recent theoretical works showing that matter swapping between braneworlds can occur, we propose a neutron-shining-through-a-wall experiment. We first show that an intense neutron source such as a nuclear reactor core can induce a hidden neutron flux in an adjacent hidden braneworld. We then describe how a low-background detector can detect neutrons arising from the hidden world and quantify the expected sensitivity to the swapping probability. As a proof of concept, a constraint is derived from previous experiments.Comment: 12 pages, 4 figures, final version published in Physical Review

Guiding the synthesis of pentazole derivatives and their mono- and di-oxides with quantum modeling

International audienceThere is high prospect that derivatives of pentazole can lead to high energy density materials. However these molecules are potentially hazardous because of their high formation enthalpies and weak N-N bonds. In order to devise efficient protocols, possible schemes for the synthesis of nitro and azido derivatives of pentazole, and their mono- and di-oxides, have been explored using quantum chemical methods. Reaction pathways have been investigated in detail, with particular emphasis on locating transition states and on obtaining a reliable treatment of solvent effects. Oxidation by ozone is found to be a favorable process, leading to some regioselectivity in favor of b-mono-oxides. Nitration by NO2+BF4- is also predicted to be favorable. In contrast the electrochemical azidation of N5- and its oxidized derivatives is found to be energetically inaccessible. Combination of the individual addition and oxidation steps leads to recommendations for future synthetic work. Finally the kinetic stability of products with respect to N2 and N2O elimination is assessed

P6_4 Tee Off Into Space

Our aim in this paper was explore the possibility of hitting a gold ball into orbit around various objects inthe solar system by using the orbital velocity equation. We found this to be possible around four moons,four dwarf planet candidates and a trojan of Jupiter with masses greater than 10^18kg

P6_5 Matrioshka Brain

The Matrioshka brain is a hypothetical structure originally proposed by Robert Bradbury in 1999[1]. It consists of layers of Dyson spheres around a star, generating energy through solar panels, to power a supercomputer. In this paper we look at the amount of energy and thus computational power that could be obtained from a Matrioshka brain at our current level of technology and then go on to discuss how it would not be feasible to build said structure

Lasing from a circular Bragg nanocavity with an ultra-small modal volume

We demonstrate single-mode lasing at telecommunication wavelengths from a circular nanocavity employing a radial Bragg reflector. Ultra-small modal volume and Sub milliwatt pump threshold level are observed for lasers with InGaAsP quantum well active membrane. The electromagnetic field is shown to be tightly confined within the 300nm central pillar of the cavity. The quality factors of the resonator modal fields are estimated to be on the order of a few thousands.Comment: 3 pages, 4 figures Submitted to AP

Search for passing-through-walls neutrons constrains hidden braneworlds

In many theoretical frameworks our visible world is a $3$-brane, embedded in a multidimensional bulk, possibly coexisting with hidden braneworlds. Some works have also shown that matter swapping between braneworlds can occur. Here we report the results of an experiment - at the Institut Laue-Langevin (Grenoble, France) - designed to detect thermal neutron swapping to and from another braneworld, thus constraining the probability $p^2$ of such an event. The limit, $p<4.6\times 10^{-10}$ at $95 \%$ C.L., is $4$ orders of magnitude better than the previous bound based on the disappearance of stored ultracold neutrons. In the simplest braneworld scenario, for two parallel Planck-scale branes separated by a distance $d$, we conclude that $d>87$ in Planck length units.Comment: 5 pages, 3 figures. Published in Physics Letters