Influence of carrier-carrier and carrier-phonon correlations on optical absorption and gain in quantum-dot systems

A microscopic theory is used to study the optical properties of semiconductor quantum dots. The dephasing of a coherent excitation and line-shifts of the interband transitions due to carrier-carrier Coulomb interaction and carrier-phonon interaction are determined from a quantum kinetic treatment of correlation processes. We investigate the density dependence of both mechanisms and clarify the importance of various dephasing channels involving the localized and delocalized states of the system.Comment: 12 pages, 10 figure

In situ compression tests on micron-sized silicon pillars by Raman microscopy—Stress measurements and deformation analysis

Mechanical properties of silicon are of high interest to the microelectromechanical systems community as it is the most frequently used structural material. Compression tests on 8 μm diameter silicon pillars were performed under a micro-Raman setup. The uniaxial stress in the micropillars was derived from a load cell mounted on a microindenter and from the Raman peak shift. Stress measurements from the load cell and from the micro-Raman spectrum are in excellent agreement. The average compressive failure strength measured in the middle of the micropillars is 5.1 GPa. Transmission electron microscopy investigation of compressed micropillars showed cracks at the pillar surface or in the core. A correlation between crack formation and dislocation activity was observed. The authors strongly believe that the combination of nanoindentation and micro-Raman spectroscopy allowed detection of cracks prior to failure of the micropillar, which also allowed an estimation of the in-plane stress in the vicinity of the crack ti

Linear optics implementation of general two-photon projective measurement

We will present a method of implementation of general projective measurement of two-photon polarization state with the use of linear optics elements only. The scheme presented succeeds with a probability of at least 1/16. For some specific measurements, (e.g. parity measurement) this probability reaches 1/4.Comment: 8 page

Non-resonant dot-cavity coupling and its applications in resonant quantum dot spectroscopy

We present experimental investigations on the non-resonant dot-cavity coupling of a single quantum dot inside a micro-pillar where the dot has been resonantly excited in the s-shell, thereby avoiding the generation of additional charges in the QD and its surrounding. As a direct proof of the pure single dot-cavity system, strong photon anti-bunching is consistently observed in the autocorrelation functions of the QD and the mode emission, as well as in the cross-correlation function between the dot and mode signals. Strong Stokes and anti-Stokes-like emission is observed for energetic QD-mode detunings of up to ~100 times the QD linewidth. Furthermore, we demonstrate that non-resonant dot-cavity coupling can be utilized to directly monitor and study relevant QD s-shell properties like fine-structure splittings, emission saturation and power broadening, as well as photon statistics with negligible background contributions. Our results open a new perspective on the understanding and implementation of dot-cavity systems for single-photon sources, single and multiple quantum dot lasers, semiconductor cavity quantum electrodynamics, and their implementation, e.g. in quantum information technology.Comment: 17 pages, 4 figure

The effect of δ-hydride on the micromechanical deformation of Zircaloy-4 studied by in situ high angular resolution electron backscatter diffraction

Zircaloy-4(Zr-1.5%Sn-0.2%Fe-0.1%Cr wt%)is usedas nuclear fuel cladding materials and hydride embrittlementis amajor failure mechanism. To explore the effect of δ-hydrideon plastic deformation and performance of Zircaloy-4, in situhigh angular resolution electron backscatter diffraction(HR-EBSD)was used to quantify stress andgeometrically necessarydislocation(GND)density during bending tests of hydride-free and hydride-containingsingle crystalZircaloy-4 microcantilevers. Results suggest that while the stress applied was accommodated by plastic slip in the hydride-free cantilever,the hydride-containing cantilever showedprecipitation-induced GND pile-up at hydride-matrix interfacepre-deformation, andconsiderable locally-increasing GNDdensity under tensile stressupon plastic deformation

A simple method for measuring plasma power in rf-GDOES instruments

A method for determining plasma power in rf-GDOES is presented. It is based on an effective resistance located in the inductive coil of the impedance matching. The amount of electrical power consumed in the matching system depends on the capacitive current flowing through the matching system, which depends on the applied voltage, the stray capacity, and the frequency. This correction method is experimentally evaluated and compared with the integral plasma power calculatio