179 research outputs found
Slow light with flat or offset band edges in multi-mode fiber with two gratings
We consider mode coupling in multimode optical fibers using either two Bragg
gratings or a Bragg grating and a long-period grating. We show that the
magnitude of the band edge curvature can be controlled leading to a flat,
quartic band-edge or to two band edges at distinct, nonequivalent -values,
allowing precise control of slow light propagation.Comment: 6 pages, 3 figure
Coherent perfect absorption and reflection in slow-light waveguides
We identify a family of unusual slow-light modes occurring in lossy
multi-mode grating waveguides, for which either the forward or backward mode
components, or both, become degenerate. In the fully-degenerate case, by
varying the wave amplitudes in a uniform input waveguide, one can modulate
between coherent perfect absorption (zero reflection) and perfect reflection.
The perfectly-absorbed wave has anomalously short absorption length, scaling as
the inverse 1/3 power of the absorptivity
Efficient slow-light coupling in a photonic crystal waveguide without transition region
We consider the coupling into a slow mode that appears near an inflection point in the band structure of a photonic crystal waveguide. Remarkably, the coupling into this slow mode, which has a group index n(g) > 1000, can be essentially perfect without any transition region. We show that this efficient coupling occurs thanks to an evanescent mode in the slow medium, which has appreciable amplitude and helps satisfy the boundary conditions but does not transport any energy. (C) 2008 Optical Society of AmericaPublisher PDFPeer reviewe
Comparison of the sensitivity of air and dielectric modes in photonic crystal slab sensors
Optical cavities provide a route to sensing through the shift of the optical resonant peak. However, effective sensing with optical cavities requires the optimization of the modal quality factor, Q, and the field overlap with the sample, f. For a photonic crystal slab (PCS) this figure of merit, M =fQ, involves two competing effects. The air modes usually have large f but small Q, whereas the dielectric modes have high-Q and small f. We compare the sensitivity of air and dielectric modes for different PCS cavity designs and account for loss associated with absorption by the sensed sample or its host liquid. We find that optimizing Q at the expense f is the most beneficial strategy, and modes deriving from the dielectric bands are thus preferred. ©2009 Optical Society of America
Supermodes of Hexagonal Lattice Waveguide Arrays
We present a semi-analytical formulation for calculating the supermodes and
corresponding Bloch factors of light in hexagonal lattice photonic crystal
waveguide arrays. We then use this formulation to easily calculate dispersion
curves and predict propagation in systems too large to calculate using standard
numerical methods.Comment: Accepted by J. Opt. Soc. Am. B, DocID:160522.
http://www.opticsinfobase.org/abstract.cfm?msid=16052
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