10,167 research outputs found
Low-threshold bistability of slow light in photonic-crystal waveguides
We analyze the resonant transmission of light through a
photonic-crystal waveguide side coupled to a Kerr nonlinear cavity, and
demonstrate how to design the structure geometry for achieving bistability
and all-optical switching at ultralow powers in the slow-light regime. We
show that the resonance quality factor in such structures scales inversely
proportional to the group velocity of light at the resonant frequency
and thus grows indefinitely in the slow-light regime. Accordingly, the
power threshold required for all-optical switching in such structures scales
as a square of the group velocity, rapidly vanishing in the slow-light regime
Low-threshold bistability of slow light in photonic-crystal waveguides
We analyze the resonant transmission of light through a photonic-crystal
waveguide side coupled to a Kerr nonlinear cavity, and demonstrate how to
design the structure geometry for achieving bistability and all-optical
switching at ultra-low powers in the slow-light regime. We show that the
resonance quality factor in such structures scales inversely proportional to
the group velocity of light at the resonant frequency and thus grows
indefinitely in the slow-light regime. Accordingly, the power threshold
required for all-optical switching in such structures scales as a square of the
group velocity, rapidly vanishing in the slow-light regime.Comment: LaTeX, 6 pages, 4 figure
Observations of time delayed all-optical routing in a slow light regime
We report an observation of a delayed all-optical routing/switching
phenomenon based on ultraslow group velocity of light via nondegenerate
four-wave mixing processes in a defected solid medium. Unlike previous
demonstrations of enhanced four-wave mixing processes using the slow light
effects, the present observation demonstrates a direct retrieval of the
resonant Raman-pulse excited spin coherence into photon coherence through
coherence conversion processes.Comment: 5 pages with 3 figures include
Interplay between disorder and local field effects in photonic crystal waveguides
We introduce a theory to describe disorder-induced scattering in photonic
crystal waveguides, specifically addressing the influence of local field
effects and scattering within high-index-contrast perturbations. Local field
effects are shown to increase the predicted disorder-induced scattering loss
and result in significant resonance shifts of the waveguide mode. We
demonstrate that two types of frequency shifts can be expected, a mean
frequency shift and a RMS frequency shift, both acting in concert to blueshift
and broaden the nominal band structure. For a representative waveguide, we
predict substantial meV frequency shifts and band structure broadening for a
telecommunications operating frequency, even for state of the art fabrication.
The disorder-induced broadening is found to increase as the propagation
frequency approaches the slow light regime (mode edge) due to restructuring of
the electric field distribution. These findings have a dramatic impact on
high-index-contrast nanoscale waveguides, and, for photonic crystal waveguides,
suggest that the nominal slow-light mode edge may not even exist. Furthermore,
our results shed new light on why it has hitherto been impossible to observe
the very slow light regime for photonic crystal waveguides.Comment: 4 page lette
Transmission of pillar-based photonic crystal waveguides in InP technology
Waveguides based on line defects in pillar photonic crystals have been fabricated in InP/InGaAsP/InP technology. Transmission measurements of different line defects are reported. The results can be explained by comparison with two-dimensional band diagram simulations. The losses increase substantially at mode crossings and in the slow light regime. The agreement with the band diagrams implies a good control on the dimensions of the fabricated features, which is an important step in the actual application of these devices in photonic integrated circuit
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Enhanced forward stimulated Brillouin scattering in silicon photonic slot waveguide Bragg grating
We study the forward stimulated Brillouin scattering process in a suspended silicon slot waveguide Bragg grating. Full-vectorial formalism is applied to analyze the interplay of electrostriction and radiation pressure. We show that radiation pressure is the dominant factor in the proposed waveguide. The Brillouin gain strongly depends on the structural parameters and the maximum value in the order of 106 W−1 m−1 is obtained in the slow light regime, which is more than two orders larger than that of the stand-alone strip and slot waveguides
Transmission of Slow Light through Photonic Crystal Waveguide Bends
The spectral dependence of a bending loss of cascaded 60-degree bends in
photonic crystal (PhC) waveguides is explored in a slab-type
silicon-on-insulator system. Ultra-low bending loss of (0.05+/-0.03)dB/bend is
measured at wavelengths corresponding to the nearly dispersionless transmission
regime. In contrast, the PhC bend is found to become completely opaque for
wavelengths range corresponding to the slow light regime. A general strategy is
presented and experimentally verified to optimize the bend design for improved
slow light transmission.Comment: 4 pages, 3 figures; submitted to Optics Letter
Theory of diffusive light scattering cancellation cloaking
We report on a new concept of cloaking objects in diffusive light regime
using the paradigm of the scattering cancellation and mantle cloaking
techniques. We show numerically that an object can be made completely invisible
to diffusive photon density waves, by tailoring the diffusivity constant of the
spherical shell enclosing the object. This means that photons' flow outside the
object and the cloak made of these spherical shells behaves as if the object
were not present. Diffusive light invisibility may open new vistas in hiding
hot spots in infrared thermography or tissue imaging.Comment: 16 pages, 5 figure
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