13 research outputs found
Atomic selfordering in a ring cavity with counterpropagating pump
The collective dynamics of mobile scatterers and light in optical resonators
generates complex behaviour. For strong transverse illumination a phase
transition from homogeneous to crystalline particle order appears. In contrast,
a gas inside a single-side pumped ring cavity exhibits an instability towards
bunching and collective acceleration called collective atomic recoil lasing
(CARL). We demonstrate that by driving two orthogonally polarized counter
propagating modes of a ring resonator one realises both cases within one
system. The corresponding phase diagram depending on the two pump intensities
exhibits regions in which either a generalized form of self-ordering towards a
travelling density wave with constant centre of mass velocity or a CARL
instability is formed. Controlling the cavity driving then allows to accelerate
or slow down and trap a sufficiently dense beam of linearly polarizable
particles.Comment: 5 page
Analytic elastic constants in molecular calculations: Finite strain, non-affine displacements, and many-body interatomic potentials
Elastic constants are among the most fundamental and important properties of
solid materials, which is why they are routinely characterized in both
experiments and simulations. While conceptually simple, the treatment of
elastic constants is complicated by two factors not yet having been
concurrently discussed: finite-strain and non-affine, internal displacements.
Here, we revisit the theory behind zero-temperature, finite-strain elastic
constants and extend it to explicitly consider non-affine displacements. We
further present analytical expressions for second-order derivatives of the
potential energy for two-body and generic many-body interatomic potentials,
such as cluster and empirical bond-order potentials. Specifically, we revisit
the elastic constants of silicon, silicon carbide and silicon dioxide under
hydrostatic compression and dilatation. Based on existing and new results, we
outline the effect of multiaxial stress states as opposed to volumetric
deformation on the limits of stability of their crystalline lattices.Comment: 22 pages, 7 figure
Coherent subcarrier-WDM-PON system with SSB modulation and wavelength reuse
We propose a Subcarrier-WDM-PON system suitable for up to 320 users, using SSB modulation and wavelength reuse for colorless ONUs. The experimental results have shown the feasibility of such a concept
Das Blickverhalten der Kunden als Grundlage für die Warenplatzierung im Lebensmitteleinzelhandel
Self-ordering and collective dynamics of transversely illuminated point-scatterers in a 1D trap
A Vlasov approach to bunching and selfordering of particles in optical resonators
We develop a Vlasov type continuum density description for the coupled nonlinear dynamics of polarizable particles moving in the light field of a high Q optical resonator. The intracavity light field, which exerts optical forces on the particles, depends itself on the dynamics of the particle density, which constitutes a time dependent refractive index. This induces mode frequency shifts, losses and coupling. For typical geometries we find solid analytic criteria for the stability of an initial homogeneous particle density for a wide class of initial velocity distributions including thermal distributions. These agree with previously found bunching and self-ordering instabilities but are extended to a wider range of parameters and initial conditions. Using a linear perturbation expansion we calculate the growth exponents of small density perturbations in the parameter region beyond this instability threshold. Numerical solutions of the full equations as well as simulations of the underlying many particle trajectories confirm these results. In addition the equations allow to extract analytical scaling laws to extrapolate cavity cooling and selfordering dynamics to higher particle numbers