15,976 research outputs found
Single-mode propagation of light in one-dimensional all-dielectric light-guiding systems
Numerical results are presented for single-mode guidance, which is based on
photonic band gap (PBG) effect, in one-dimensional planar all-dielectric
light-guiding systems. In such systems there may be two kinds of light-speed
point (the intersection of a mode-dispersion curve and the light line of
guiding region ambient medium): one is the intrinsic light-speed point that is
independent of the guiding region width, and the other is the movable
light-speed point that varies with the guiding region width. It is found that
the intrinsic light-speed point plays an important role to form the single-mode
regime by destroying the coexistence of the lowest guided TM and TE modes that
are born with a degeneration point. A sufficient and necessary condition for
intrinsic light-speed points is given. The transverse resonance condition is
derived in the Maxwell optics frame, and it is shown that there is a
significant revision to the traditional one in the ray optics model. A
mode-lost phenomenon is exposed and this phenomenon suggests a way of how to
identify PBG-guided fundamental modes. Quasi-cutoff-free index-guided modes in
the PBG guiding structures, which appear when the higher-index layers are
adjacent to the guiding region and the guiding region width is small, are
exposed and analyzed as well.Comment: 13 pages, 8 figures, 32 reference
Properties and numerical solutions of dispersion curves in general isotropic waveguides
In this paper, some properties of dispersion curves in general isotropic piecewise homogeneous waveguides are rigorously derived. These properties are leveraged in a numerical implementation capable of determining the dispersion curves of such waveguides with cross-section materials that can be highly conductive (such as copper). In a numerical example, the influence of a lossy shielding conductor on the complex modes of a shielded dielectric image guide is investigated for the first time
Towards all-dielectric metamaterials and nanophotonics
We review a new, rapidly developing field of all-dielectric nanophotonics
which allows to control both magnetic and electric response of structured
matter by engineering the Mie resonances in high-index dielectric
nanoparticles. We discuss optical properties of such dielectric nanoparticles,
methods of their fabrication, and also recent advances in all-dielectric
metadevices including couple-resonator dielectric waveguides, nanoantennas, and
metasurfaces
Analytical approach to dielectric optical bent slab waveguides
A rigorous classical analytic frequency domain model of con?ned optical wave propagation along 2D bent slab waveguides and curved dielectric interfaces is investigated, based on a piecewise ansatz for bend mode profiles in terms of Bessel and Hankel functions. This approach provides a clear picture of the behaviour of bend modes, concerning their decay for large radial arguments or effects of varying bend radius. Fast and accurate routines are required to evaluate Bessel functions with large complex orders and large arguments. Our implementation enabled detailed studies of bent waveguide properties, including higher order bend modes and whispering gallery modes, their interference patterns, and issues related to bend mode normalization and orthogonality properties
Design of mid-IR and THz quantum cascade laser cavities with complete TM photonic bandgap
We present the design of mid-infrared and THz quantum cascade laser cavities
formed from planar photonic crystals with a complete in-plane photonic bandgap.
The design is based on a honeycomb lattice, and achieves a full in-plane
photonic gap for transverse-magnetic polarized light while preserving a
connected pattern for efficient electrical injection. Candidate defects modes
for lasing are identified. This lattice is then used as a model system to
demonstrate a novel effect: under certain conditions - that are typically
satisfied in the THz range - a complete photonic gap can be obtained by the
sole patterning of the top metal contact. This possibility greatly reduces the
required fabrication complexity and avoids potential damage of the
semiconductor active region.Comment: 14 pages, 14 figure
Dielectric multilayer waveguides for TE and TM mode matching
We analyse theoretically for the first time to our knowledge the perfect
phase matching of guided TE and TM modes with a multilayer waveguide composed
of linear isotropic dielectric materials. Alongside strict investigation into
dispersion relations for multilayer systems, we give an explicit qualitative
explanation for the phenomenon of mode matching on the basis of the standard
one-dimensional homogenization technique, and discuss the minimum number of
layers and the refractive index profile for the proposed device scheme. Direct
applications of the scheme include polarization-insensitive, intermodal
dispersion-free planar propagation, efficient fibre-to-planar waveguide
coupling and, potentially, mode filtering. As a self-sufficient result, we
present compact analytical expressions for the mode dispersion in a finite,
N-period, three-layer dielectric superlattice.Comment: 13 pages with figure
Modal Analysis and Coupling in Metal-Insulator-Metal Waveguides
This paper shows how to analyze plasmonic metal-insulator-metal waveguides
using the full modal structure of these guides. The analysis applies to all
frequencies, particularly including the near infrared and visible spectrum, and
to a wide range of sizes, including nanometallic structures. We use the
approach here specifically to analyze waveguide junctions. We show that the
full modal structure of the metal-insulator-metal (MIM) waveguides--which
consists of real and complex discrete eigenvalue spectra, as well as the
continuous spectrum--forms a complete basis set. We provide the derivation of
these modes using the techniques developed for Sturm-Liouville and generalized
eigenvalue equations. We demonstrate the need to include all parts of the
spectrum to have a complete set of basis vectors to describe scattering within
MIM waveguides with the mode-matching technique. We numerically compare the
mode-matching formulation with finite-difference frequency-domain analysis and
find very good agreement between the two for modal scattering at symmetric MIM
waveguide junctions. We touch upon the similarities between the underlying
mathematical structure of the MIM waveguide and the PT symmetric quantum
mechanical pseudo-Hermitian Hamiltonians. The rich set of modes that the MIM
waveguide supports forms a canonical example against which other more
complicated geometries can be compared. Our work here encompasses the microwave
results, but extends also to waveguides with real metals even at infrared and
optical frequencies.Comment: 17 pages, 13 figures, 2 tables, references expanded, typos fixed,
figures slightly modifie
Chains of coupled square dielectric optical microcavities
Chains of coupled square dielectric cavities are investigated in a 2-D setting, by means of a quasi-analytical eigenmode expansion method. Resonant transfer of optical power can be achieved along quite arbitrary, moderately long rectangular paths (up to 9 coupled cavities are considered), even with individual standing-wave resonators of limited quality. We introduce an ab-initio coupled mode model, based on a simple superposition of slab mode profiles as a template for the field of individual cavities. Although no loss mechanisms are built in, the model can still help to interprete the results of the former numerical experiments
Axially open nonradiative structures: an example of single-mode resonator based on the sample holder
The concept of nonradiative dielectric resonator is generalized in order to
include axially open configurations having rotational invariance. The resulting
additional nonradiative conditions are established for the different resonance
modes on the basis of their azimuthal modal index. An approximate chart of the
allowed dielectric and geometrical parameters for the TE011 mode is given. A
practical realization of the proposed device based on commercial fused quartz
tubes is demonstrated at millimeter wavelengths, together with simple
excitation and tuning mechanisms. The observed resonances are characterized in
their basic parameters, as well as in the field distribution by means of a
finite element method. The predictions of the theoretical analysis are well
confirmed, both in the general behaviour and in the expected quality factors.
The resulting device, in which the sample holder acts itself as single-mode
resonating element, combines an extreme ease of realization with
state-of-the-art performances. The general benefits of the proposed open
single-mode resonators are finally discussed.Comment: 18 pages, 10 figure
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