28 research outputs found
On the modelization of optical devices: from dielectric cavities to radiating structures
Premièrement, nous allons explorer la modélisation des cavités diélectriques bidimensionnelles. Plus spécifiquement, nous allons développer différentes méthodes de modélisation valides pour des cavités diélectriques à géométrie et profil d’indice de réfraction arbitraires. Ce degré de liberté supplémentaire pourra être utilisé dans le design de microcavités pour des applications spécifiques. Un formalisme de diffusion permettra de définir les modes caractéristiques de ce type de structure et d’en calculer les résonances. Une analyse numérique des équations résultantes montrera que les méthodes intégrales sont possiblement meilleures que les méthodes différentielles. Deuxièmement, nous discuterons de la modélisation de structures radiatives. Nous utiliserons les méthodes développées dans la section précédente pour modéliser les propriétés lasers des microcavités bidimensionnelles prédites par la théorie SALT. Nous aborderons aussi la modélisation de fibres-antennes RF, plus particulièrement les câbles coaxiaux à perte radiative, dans le but d’intégrer des fonctionnalités radio dans un textile de manière transparente à l’utilisateur.In this essay, we will develop different modelization techniques valid for bidimensional dielectric cavities having arbitrary geometries and refractive index profiles and provide a way to accurately compute the resonances of such structures. The refractive index thus becomes an additional design variable for dielectric cavities. A numerical analysis of of the underlying equations of the theory will reveal that perhaps it is best to forego differential equations in favour of integral ones for the scattering problem. In the second part, we will discuss the modelization of radiating structures. Using the formalism developed in the previous section, we will study the lasing properties of bidimensional cavities using the newly developed self-consistent ab initio laser theory (SALT). We will also touch on the modelization of the class of antenna known as leaky coa
Adding SALT to Coupled Microcavities: the making of active photonic molecule lasers
A large body of work has accumulated over the years in the study of the
optical properties of single and coupled microcavities for a variety of
applications, ranging from filters to sensors and lasers. The focus has been
mostly on the geometry of individual resonators and/or on their combination in
arrangements often referred to as photonic molecules (PMs).
Our primary concern will be the lasing properties of PMs as ideal candidates
for the fabrication of integrated microlasers, photonic molecule lasers.
Whereas most calculations on PM lasers have been based on cold-cavity (passive)
modes, i.e. quasi-bound states, a recently formulated steady-state ab initio
laser theory (SALT) offers the possibility to take into account the spectral
properties of the underlying gain transition, its position and linewidth, as
well as incorporating an arbitrary pump profile. We will combine two
theoretical approaches to characterize the lasing properties of PM lasers: for
two-dimensional systems, the generalized Lorenz-Mie theory will obtain the
resonant modes of the coupled molecules in an active medium described by SALT.
Not only is then the theoretical description more complete, the use of an
active medium provides additional parameters to control, engineer and harness
the lasing properties of PM lasers for ultra-low threshold and directional
single-mode emission.Comment: 16th International Conference on Transparent Optical Networks (2014
Optimization of integrated polarization filters
This study reports on the design of small footprint, integrated polarization
filters based on engineered photonic lattices. Using a rods-in-air lattice as a
basis for a TE filter and a holes-in-slab lattice for the analogous TM filter,
we are able to maximize the degree of polarization of the output beams up to 98
% with a transmission efficiency greater than 75 %. The proposed designs allow
not only for logical polarization filtering, but can also be tailored to output
an arbitrary transverse beam profile. The lattice configurations are found
using a recently proposed parallel tabu search algorithm for combinatorial
optimization problems in integrated photonics
S and Q Matrices Reloaded: applications to open, inhomogeneous, and complex cavities
We present a versatile numerical algorithm for computing resonances of open
dielectric cavities. The emphasis is on the generality of the system's
configuration, i.e. the geometry of the (main) cavity (and possible inclusions)
and the internal and external dielectric media (homogeneous and inhomogeneous).
The method is based on a scattering formalism to obtain the position and width
of the (quasi)-eigenmodes. The core of the method lies in the scattering
S-matrix and its associated delay Q-matrix which contain all the relevant
information of the corresponding scattering experiment. For instance, the
electromagnetic near- and far-fields are readily extracted. The flexibility of
the propagation method is displayed for a selected system.Comment: 15th International Conference on Transparent Optical Networks (2013
Ab initio investigation of lasing thresholds in photonic molecules
We investigate lasing thresholds in a representative photonic molecule
composed of two coupled active cylinders of slightly different radii.
Specifically, we use the recently formulated steady-state ab initio laser
theory (SALT) to assess the effect of the underlying gain transition on lasing
frequencies and thresholds. We find that the order in which modes lase can be
modified by choosing suitable combinations of the gain center frequency and
linewidth, a result that cannot be obtained using the conventional approach of
quasi-bound modes. The impact of the gain transition center on the lasing
frequencies, the frequency pulling effect, is also quantified
Coherent beam shaping using two-dimensional photonic crystals
Optical devices based on photonic crystals such as waveguides, lenses and
beam-shapers, have received considerable theoretical and experimental attention
in recent years. The production of these devices has been facilitated by the
wide availability of silicon-on-insulator fabrication techniques. In this
theoretical work, we show the possibility to design a coherent PhC-based
beam-shaper. The basic photonic geometry used is a 2D square lattice of air
holes in a high-index dielectric core. We formulate the beam shaping problem in
terms of objective functions related to the amplitude and phase profile of the
generated beam. We then use a parallel tabu search algorithm to minimize the
two objectives simultaneously. Our results show that optimization of several
attributes in integrated photonics design is well within reach of current
algorithms.Comment: 15th International Conference on Transparent Optical Networks (2013
Beam shaping using genetically optimized two-dimensional photonic crystals
We propose the use of two-dimensional photonic crystals with engineered
defects for the generation of an arbitrary-profile beam from a focused input
beam. The cylindrical harmonics expansion of complex-source beams is derived
and used to compute the scattered wavefunction of a 2D photonic crystal via the
multiple scattering method. The beam shaping problem is then solved using a
genetic algorithm. We illustrate our procedure by generating different orders
of Hermite-Gauss profiles, while maintaining reasonable losses and tolerance to
variations in the input beam and the slab refractive index