1,051 research outputs found
Ultrafast Optical Signal Processing with Bragg Structures
The phase, amplitude, speed, and polarization, in addition to many other
properties of light, can be modulated by photonic Bragg structures. In
conjunction with nonlinearity and quantum effects, a variety of ensuing micro-
or nano-photonic applications can be realized. This paper reviews various
optical phenomena in several exemplary 1D Bragg gratings. Important examples
are resonantly absorbing photonic structures, chirped Bragg grating, and
cholesteric liquid crystals; their unique operation capabilities and key issues
are considered in detail. These Bragg structures are expected to be used in
wide-spread applications involving light field modulations, especially in the
rapidly advancing field of ultrafast optical signal processing.Comment: To be published in a special issue of journal Applied Sciences, on
the topic of Guided-Wave Optic
Anderson localization of entangled photons in an integrated quantum walk
Waves fail to propagate in random media. First predicted for quantum
particles in the presence of a disordered potential, Anderson localization has
been observed also in classical acoustics, electromagnetism and optics. Here,
for the first time, we report the observation of Anderson localization of pairs
of entangled photons in a two-particle discrete quantum walk affected by
position dependent disorder. A quantum walk on a disordered lattice is realized
by an integrated array of interferometers fabricated in glass by femtosecond
laser writing. A novel technique is used to introduce a controlled phase shift
into each unit mesh of the network. Polarization entanglement is exploited to
simulate the different symmetries of the two-walker system. We are thus able to
experimentally investigate the genuine effect of (bosonic and fermionic)
statistics in the absence of interaction between the particles. We will show
how different types of randomness and the symmetry of the wave-function affect
the localization of the entangled walkers.Comment: 7 pages, 5 figures, revised version published on Nature Photonics 7,
322-328 (2013
Gradient Optics of subwavelength nanofilms
Propagation and tunneling of light through subwavelength photonic barriers,
formed by dielectric layers with continuous spatial variations of dielectric
susceptibility across the film are considered. Effects of giant
heterogeneity-induced non-local dispersion, both normal and anomalous, are
examined by means of a series of exact analytical solutions of Maxwell
equations for gradient media. Generalized Fresnel formulae, visualizing a
profound influence of gradient and curvature of dielectric susceptibility
profiles on reflectance/transmittance of periodical photonic heterostructures
are presented. Depending on the cutoff frequency of the barrier, governed by
technologically managed spatial profile of its refractive index, propagation or
tunneling of light through these barriers are examined. Nonattenuative transfer
of EM energy by evanescent waves, tunneling through dielectric gradient
barriers, characterized by real values of refractive index, decreasing in the
depth of medium, is shown. Scaling of the obtained results for different
spectral ranges of visible, IR and THz waves is illustrated. Potential of
gradient optical structures for design of miniaturized filters, polarizers and
frequency-selective interfaces of subwavelength thickness is considered
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