44 research outputs found
Thermal Light as a Mixture of Sets of Pulses: the Quasi-1D Example
The relationship between thermal light and coherent pulses is of fundamental
and practical interest. We now know that thermal light cannot be represented as
a statistical mixture of single pulses. In this paper we ask whether or not
thermal light can be represented as a statistical mixture of sets of pulses. We
consider thermal light in a one-dimensional wave-guide, and find a convex
decomposition into products of orthonormal coherent states of localized,
nonmonochromatic modes.Comment: 6 pages and 3 figures, published versio
Teleportation using squeezed single photons
We present an analysis of squeezed single photon states as a resource for
teleportation of coherent state qubits and propose proof-of-principle
experiments for the demonstration of coherent state teleportation and
entanglement swapping. We include an analysis of the squeezed vacuum as a
simpler approximation to small-amplitude cat states. We also investigate the
effects of imperfect sources and inefficient detection on the proposed
experiments.Comment: 9 pages, 12 figures. Submitted to Phys. Rev.
Towards efficient modelling of optical micromanipulation of complex structures
Computational methods for electromagnetic and light scattering can be used
for the calculation of optical forces and torques. Since typical particles that
are optically trapped or manipulated are on the order of the wavelength in
size, approximate methods such as geometric optics or Rayleigh scattering are
inapplicable, and solution or either the Maxwell equations or the vector
Helmholtz equation must be resorted to. Traditionally, such solutions were only
feasible for the simplest geometries; modern computational power enable the
rapid solution of more general--but still simple--geometries such as
axisymmetric, homogeneous, and isotropic scatterers. However, optically-driven
micromachines necessarily require more complex geometries, and their
computational modelling thus remains in the realm of challenging computational
problems. We review our progress towards efficient computational modelling of
optical tweezers and micromanipulation, including the trapping and manipulation
of complex structures such as optical micromachines. In particular, we consider
the exploitation of symmetry in the modelling of such devices.Comment: 5 pages, 4 figure
Modelling optical micro-machines
A strongly focused laser beam can be used to trap, manipulate and exert
torque on a microparticle. The torque is the result of transfer of angular
momentum by scattering of the laser beam. The laser could be used to drive a
rotor, impeller, cog wheel or some other microdevice of a few microns in size,
perhaps fabricated from a birefringent material. We review our methods of
computationally simulating the torque and force imparted by a laser beam. We
introduce a method of hybridizing the T-matrix with the Finite Difference
Frequency Domain (FDFD) method to allow the modelling of materials that are
anisotropic and inhomogeneous, and structures that have complex shapes. The
high degree of symmetry of a microrotor, such as discrete or continuous
rotational symmetry, can be exploited to reduce computational time and memory
requirements by orders of magnitude. This is achieved by performing
calculations for only a given segment or plane that is repeated across the
whole structure. This can be demonstrated by modelling the optical trapping and
rotation of a cube.Comment: 4 pages, 3 figure