33 research outputs found
Spatial properties of entangled photon pairs generated in nonlinear layered structures
A spatial quantum model of spontaneous parametric down-conversion in
nonlinear layered structures is developed expanding the interacting vectorial
fields into monochromatic plane waves. A two-photon spectral amplitude
depending on the signal- and idler-field frequencies and propagation directions
is used to derive transverse profiles of the emitted fields as well as their
spatial correlations. Intensity spatial profiles and their spatial correlations
are mainly determined by the positions of transmission peaks formed in these
structures with photonic bands. A method for geometry optimization of the
structures with respect to efficiency of the nonlinear process is suggested.
Several structures composed of GaN/AlN layers are analyzed as typical examples.
They allow the generation of photon pairs correlated in several emission
directions. Photon-pair generation rates increasing better than the second
power of the number of layers can be reached. Also structures efficiently
generated photon pairs showing anti-bunching and anti-coalescence can be
obtained. Three reasons for splitting the correlated area in photonic-band-gap
structures are revealed: zig-zag movement of photons inside the structure,
spatial symmetry and polarization-dependent properties. Also spectral splitting
can be observed in these structures.Comment: 13 pages, 17 figure
Measurement-based tailoring of Anderson localization of partially coherent light
We put forward an experimental configuration to observe transverse Anderson
localization of partially coherent light beams with a tunable degree of
first-order coherence. The scheme makes use of entangled photons propagating in
disordered waveguide arrays, and is based on the unique relationship between
the degree of entanglement of a pair of photons and the coherence properties of
the individual photons constituting the pair. The scheme can be readily
implemented with current waveguide-on-a-chip technology, and surprisingly, the
tunability of the coherence properties of the individual photons is done at the
measurement stage, without resorting changes of the light source itself.Comment: 7 pages, 5 figures, additional correction
Surface spontaneous parametric down-conversion
Surface spontaneous parametric down-conversion is predicted as a consequence
of continuity requirements for electric- and magnetic-field amplitudes at a
discontinuity of chi2 nonlinearity. A generalization of the usual two-photon
spectral amplitude is suggested to describe this effect. Examples of nonlinear
layered structures and periodically-poled nonlinear crystals show that surface
contributions to spontaneous down-conversion can be important.Comment: 4 pages, 3 figure
Proposal for the generation of photon pairs with nonzero orbital angular momentum in a ring fiber
We present a method for the generation of correlated photon pairs in desired
orbital-angular-momentum states using a non-linear silica ring fiber and
spontaneous parametric down-conversion. Photon-pair emission under
quasi-phase-matching conditions with quantum conversion efficiency is found in a 1-m long fiber with a thermally induced
nonlinearity in a ring-shaped core
Emission of photon pairs at discontinuities of nonlinearity in spontaneous parametric down-conversion
In order to fulfil the continuity requirements for electric- and
magnetic-field amplitudes at discontinuities of chi2 nonlinearity additional
photon pairs have to be emitted in the area of discontinuity. Generalized
two-photon spectral amplitudes can be used to describe properties of photon
pairs generated in this process that we call surface spontaneous parametric
down-conversion. The spectral structure of such photon pairs is similar to that
derived for photon pairs generated in the volume. Surface and volume
contributions to spontaneous down-conversion can be comparable as an example of
nonlinear layered structures shows.Comment: 11 pages, 8 figure