arXiv subjects

M. Yamagiwa

Publications and source records attributed to M. Yamagiwa.

5 recordsLinked to original sources

arXiv2008

Photon correlation in GaAs self-assembled quantum dots

We report on photon coincidence measurement in a single GaAs self-assembled quantum dot (QD) using a pulsed excitation light source. At low excitation, when a neutral exciton line was present in the photoluminescence (PL) spectrum, we observed nearly perfect single photon emission from an isolated QD at 670 nm wavelength. For higher excitation, multiple PL lines appeared on the spectra, reflecting the formation of exciton complexes. Cross-correlation functions between these lines showed either bunching or antibunching behavior, depending on whether the relevant emission was from a biexciton cascade or a charged exciton recombination.

cond-mat.other↗

arXiv2007

Tunable high-energy ion source via oblique laser pulse incidence on a double-layer target

The laser-driven acceleration of high quality proton beams from a double-layer target, comprised of a high-Z ion layer and a thin disk of hydrogen, is investigated with three-dimensional particle-in-cell simulations in the case of oblique incidence of a laser pulse. It is shown that the proton beam energy reaches its maximum at a certain incidence angle of the laser pulse, where it can be much greater than the energy at normal incidence. The proton beam propagates at some angle with respect to the target surface normal, as determined by the proton energy and the incidence angle.

physics.plasm-ph↗

arXiv2006

Self-assembly of laterally aligned GaAs quantum dot pairs

We report the fabrication of self-assembled, strain-free GaAs/Al$_{0.27}$Ga$_{0.73}$As quantum dot pairs which are laterally aligned in the growth plane, utilizing the droplet epitaxy technique and the anisotropic surface potentials of the GaAs (100) surface for the migration of Ga adatoms. Photoluminescence spectra from a single quantum dot pair, consisting of a doublet, have been observed. Finite element energy level calculations of a model quantum dot pair are also presented.

cond-mat.mtrl-sci↗

arXiv2005

Laser Ion Acceleration Scaling Laws Seen in Muti-Parametric PIC Simulations

The ion acceleration driven by a laser pulse at intensity $I = 10^{20} - 10^{22} $W/cm$^2\times(μ$m$/λ)^2$ from a double layer target is investigated with multi-parametric Particle-in-Cell (PIC) simulations. For targets with a wide range of thickness $l$ and density $n_e$, at given intensity the highest ion energy gain occurs at certain {\it critical depth} of the target $σ= n_e l$, which is proportional to the square root of intensity. In the case of thin targets and optimal laser pulse duration, the ion maximum energy scales as the square root of the laser pulse power. When the radiation pressure of the laser field becomes dominant, the ion maximum energy becomes proportional to the laser pulse energy.

physics.plasm-ph↗

arXiv2005

Theory of the Laser Wake-Field Accelerator Revisited: Wake Overtaking, Localized Spectrum and Ponderomotive Acceleration

The electron and positron acceleration in the first cycle of a laser-driven wakefield is investigated. Separatrices between different types of the particle motion (confined, reflected by the wakefield or ponderomotive potential and transient) are demonstrated. The ponderomotive acceleration is negligible for electrons but is substantial for positrons. An electron bunch, injected as quasi-monoenergetic, acquires a localized energy spectrum with a cut-off at the maximum energy.

physics.plasm-ph↗