Local optical field variation in the neighborhood of a semiconductor micrograting

The local optical field of a semiconductor micrograting (GaAs, 10x10 micro m) is recorded in the middle field region using an optical scanning probe in collection mode at constant height. The recorded image shows the micro-grating with high contrast and a displaced diffraction image. The finite penetration depth of the light leads to a reduced edge resolution in the direction to the illuminating beam direction while the edge contrast in perpendicular direction remains high (~100nm). We use the discrete dipole model to calculate the local optical field to show how the displacement of the diffraction image increases with increasing distance from the surface.Comment: 12 pages, 3 figure

Synthesis of novel poly(dG)-poly(dG)-poly(dC) triplex structure by Klenow exo− fragment of DNA polymerase I

The extension of the G-strand of long (700 bp) poly(dG)-poly(dC) by the Klenow exo− fragment of DNA polymerase I yields a complete triplex structure of the H-DNA type. High-performance liquid chromatography analysis demonstrates that the length of the G-strand is doubled during the polymerase synthesis. Fluorescence resonance energy transfer analysis shows that the 5′ ends of the G- and the C-strands, labeled with fluorescein and TAMRA, respectively, are positioned close to each other in the product of the synthesis. Atomic force microscopy morphology imaging shows that the synthesized structures lack single-stranded fragments and have approximately the same length as the parent 700 bp poly(dG)-poly(dC). CD spectrum of the polymer has a large negative peak at 278 nm, which is characteristic of the poly(dG)-poly(dG)-poly(dC) triplex. The polymer is resistant to DNase and interacts much more weakly with ethidium bromide as compared with the double-stranded DN

Synthesis of novel poly(dG)–poly(dG)–poly(dC) triplex structure by Klenow exo(−) fragment of DNA polymerase I

The extension of the G-strand of long (700 bp) poly(dG)–poly(dC) by the Klenow exo(−) fragment of DNA polymerase I yields a complete triplex structure of the H-DNA type. High-performance liquid chromatography analysis demonstrates that the length of the G-strand is doubled during the polymerase synthesis. Fluorescence resonance energy transfer analysis shows that the 5′ ends of the G- and the C-strands, labeled with fluorescein and TAMRA, respectively, are positioned close to each other in the product of the synthesis. Atomic force microscopy morphology imaging shows that the synthesized structures lack single-stranded fragments and have approximately the same length as the parent 700 bp poly(dG)–poly(dC). CD spectrum of the polymer has a large negative peak at 278 nm, which is characteristic of the poly(dG)–poly(dG)–poly(dC) triplex. The polymer is resistant to DNase and interacts much more weakly with ethidium bromide as compared with the double-stranded DNA

Exciton-photon complexes and dynamics in the concurrent strong-weak coupling regime of singular site-controlled cavity quantum electrodynamics

We investigate the exciton complexes photoluminescence, dynamics and photon statistics in the concurrent strong weak coupling regime in our unique site controlled singular inverted pyramidal InGaAs/GaAs quantum dots photonic crystal cavities platform. Different from a clear boundary between strong and weak QD cavity coupling, we demonstrate the strong and weak coupling can coexist dynamically, as a form of intermediate regime mediated by phonon scattering. The detuning dependent microphotoluminescence spectrum reveals concurrence of exciton cavity polariton mode avoided crossing, as a signature of Rabi doublet of the strong coupled system, the blue shifting of coupled exciton cavity mode energy near zero detuning ascribed to the formation of collective states mediated by phonon assisted coupling, and their partial out of synchronization linewidth narrowing linked to their mixed behavior. By detailing the optical features of strongly confined exciton-photon complexes and the quantum statistics of coupled cavity photons, we reveal the dynamics and antibunching/bunching photon statistical signatures of the concurrent strong weak intermediate coupled system at near zero-detuning. This study suggests our device has potential for new and subtle cavity quantum electrodynamical phenomena, cavity enhanced indistinguishable single photon generation, and cluster state generation via the exciton-photon complexes for quantum networks

Site-controlled quantum dots coupled to photonic crystal waveguides

We demonstrate selective optical coupling of multiple, site controlled semiconductor quantum dots (QDs) to photonic crystal waveguide structures. The impact of the exact position and emission spectrum of the QDs on the coupling efficiency is elucidated. The influence of optical disorder and end-reflections on photon transport in these systems are discussed

Large mode splitting and lasing in optimally coupled photonic-crystal microcavities

Coupling of L-type photonic-crystal (PhC) cavities in a geometry that follows inherent cavity field distribution is exploited for demonstrating large mode splitting of up to similar to 10-20 nm (similar to 15-30 meV) near 1 mu m wavelength. This is much larger than the disorder-induced cavity detuning for conventional PhC technology, which ensures reproducible coupling. Furthermore, a microlaser based on such optimally coupled PhC cavities and incorporating quantum wire gain medium is demonstrated, with potential applications in fast switching and modulation. (C)2011 Optical Society of Americ

Effects of surface plasmon polariton-mediated interactions on second harmonic generation from assemblies of pyramidal metallic nano-cavities

We use polarization-resolved two-photon microscopy to investigate second harmonic generation (SHG) from individual assemblies of site-controlled nano-pyramidal recess templates covered with silver films. We demonstrate the effect of the surface plasmon polaritons (SPPs) at fundamental and second-harmonic frequencies on the effective second order susceptibility tensor as a function of pyramid arrangement and inter-pyramid distance. These results open new perspectives for the application of SHG microscopy as a sensitive probe of coherently excited SPPs, as well as for the design of new plasmonic nanostructure assemblies with tailored nonlinear optical properties. (C)2014 Optical Society of Americ

Non-centrosymmetric plasmonic crystals for second-harmonic generation with controlled anisotropy and enhancement

Rectangular arrays of pyramidal recesses coated by silver film are investigated by means of polarization-resolved nonlinear microscopy at 900 nm fundamental wavelength, demonstrating strong dependence of the dipole-allowed SHG upon the lattice parameters. The plasmonic band gap causes nearly complete SHG suppression in arrays of 650 nm periodicity, whereas a sharp resonance at 550 nm periodicity is observed due to excitation of band edge Bloch states at fundamental frequency, accompanied by symmetry-constrained interactions with similar modes at the second-harmonic frequency. Additionally, coupling with modes at the bottom side of the silver film may lead to extraordinary optical transmission, opening a channel for SHG from the highly nonlinear GaAs substrate. Changing the lattice geometry enables SHG intensity modulation over three orders of magnitude, while the effective nonlinear anisotropy can be continuously switched between the two lattice directions, reaching values as high as +/- 0.96

High-quality 1.3 lm-wavelength GaInAsN/GaAs quantum wells grown by metalorganic vapor phase epitaxy on vicinal substrates

We investigated the composition and optical properties of GaInAsN/GaAs single quantum wells (QWs) grown on vicinal-(001) GaAs substrates using metallorganic vapor phase epitaxy with modulated nitrogen-precursor flux. A significant enhancement in N incorporation and photoluminescence efficiency is achieved with such optimized QW structures. Possible mechanisms of the observed increase in N uptake and reduction in defect density, related to the substrate vicinality, are discussed