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[pt] COLOCANDO INTERAÇÕES OPTOMECÂNICAS EM USO: DO APRISIONAMENTO DE ORGANISMOS AO EMARANHAMENTO DE NANOESFERAS / [en] HARNESSING OPTOMECHANICAL INTERACTIONS: FROM TRAPPING ORGANISMS TO ENTANGLING NANOSPHERESIGOR BRANDAO CAVALCANTI MOREIRA 28 June 2021 (has links)
[pt] Nas últimas décadas, interações entre luz e matéria provaram ser uma
ferramenta versátil para medir e controlar sistemas mecânicos, encontrando
aplicações desde detecção de forças até resfriamento ao estado fundamental
de nanoesferas. Nesta dissertação, nós apresentamos algumas das ferramentas
teóricas necessárias para descrever interferômetros, pinças ópticas e cavidades
ópticas, constituintes fundamentais da caixa de ferramentas optomecânica.
No regime clássico, estudamos o campo eletromagnético circulante em
interferômetros lineares e mostramos como encontrar o campo resultante
transmitido, apresentando exemplos de cavidades ópticas com um número
arbitrário de elementos dispersivos. Nós também estudamos as forças de
pressão de radiação que feixes ópticos podem imprimir em partículas dielétricas
e mostramos como o aprisionamento óptico 3D é possível em focos claros e
escuros. A potencial aplicação para captura de organismos vivos é estudada.
No regime quântico, nós estudamos como o campo ressonante de cavidades
ópticas pode interagir de forma dispersiva com diferentes sistemas
mecânicos, dando origem a uma dinâmica quântica fechada emaranhante. Ao
considerar uma nuvem ultra resfriada de átomos interagindo com dois modos
ópticos, mostramos o surgimento de emaranhamento óptico que evidencia a
natureza não-clássica do conjunto atômico macroscópico. A viabilidade experimental
deste experimento com tecnologia atual é estudada.
Além disso, nós investigamos o cenário em que uma pinça óptica posiciona
uma partícula levitada dentro de uma cavidade óptica de forma que os fótons
da pinça espalhados pela partícula possam sobreviver dentro da cavidade. Já
foi demonstrado que esta interação, chamada de espalhamento coerente, pode
resfriar nanopartículas até números de fônons menores do que um, atingindo
profundamente o regime quântico. Nós mostramos que esta interação também
pode gerar emaranhamento mecânico entre muitas partículas levitadas, mesmo
em um ambiente a temperatura de 300K. Um resumo sobre sistemas de
variáveis contínuas e a caixa de ferramentas numérica customizada usada ao
longo deste trabalho são apresentados. / [en] Over the last decades, light-matter interactions have proven to be a
versatile tool to measure and control mechanical systems, finding application
from force sensing to ground state cooling of nanospheres. In this dissertation,
we present some of the theoretical tools that describe interferometers, optical
tweezers and optical cavities, fundamental constituents of the optomechanical
toolbox. In the classical regime, we study the circulating electromagnetic field
within linear interferometers and show how one can find the resulting transmitted
field, presenting examples of optical cavities with an arbitrary number
of dispersive elements. Moreover, we also study the radiation-pressure forces
that optical beams can imprint on dielectric particles and show how 3D optical
trapping is possible in both bright and dark focuses. Potential application to
trapping of living organisms is studied. In the quantum regime, we study how the resonant field of optical cavities can dispersivelly interact with different mechanical systems, giving rise to an
entangling closed quantum dynamics. When considering an ultracold cloud of
atoms interacting with two optical modes, we show the emergence of optical
entanglement which evidences the nonclassical nature of the macroscopic
atomic ensemble. The experimental feasibility of this experiment with current
technology is studied. Furthermore, we investigate the scenario where a finely tuned optical
tweezer places a trapped particle inside an optical cavity such that the tweezer s
scattered photons can survive inside the cavity. This so-called coherent scattering
interaction has been shown to cool nanoparticles to phonon numbers
lower than one deep into the quantum regime. We show that it also can generate
mechanical entanglement between many levitated particles even in a room
temperature environment. An overview on continuous variable systems and
the custom numerical toolbox used throughout this work are presented.
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Photonic Integration with III-V Semiconductor TechnologiesPaul, Tuhin 13 April 2022 (has links)
This dissertation documents works on two projects, which are broadly related to
photonic integration using III-V semiconductor platform for fiber-based optical
communication. Our principal project aims to demonstrate continuous variable
quantum key distribution (CV-QKD) with InP-based photonic integrated cir cuit at the 1550 nanometer of optical wavelength. CV QKD protocols, in which
the key is encoded in the quadrature variables of light, has generated immense
interest over the years because of its compatibility with the existing telecom
infrastructure. In this thesis, we have proposed a design of a photonic inte grated circuit potentially capable of realizing this protocol with coherent states
of light. From the practical perspective, we have basically designed an optical
transmitter and an optical receiver capable of carrying out coherent communi cation via the optical fiber. Initially, we established a mathematical model of
the transceiver system based on the optical transfer matrix of the foundry spe cific (Fraunhofer Heinrich Hertz Institute-Germany) building blocks. We have
shown that our chip design is versatile in the sense that it can support multiple
modulation schemes. Based on the mathematical model, we estimated the link
budget to assess the feasibility of on-chip implementation of our protocol. Then
we ran a circuit level simulation using the process design kit provided by our
foundry to put our analysis on a better footing. The encouraging result from
this step prompted us to generate the mask layout for our transceiver chips,
which we eventually submitted to the foundry. The other project in the thesis
grew out of a collaboration with one of our industry partners. The goal of the
project is to enhance the performance of a distributed feedback laser emitting
at the 1310 nanometer of optical wavelength by optimizing its design. To that
end, we first derived the expression for transmission and reflection spectrum
for the laser cavity. Those expressions contained parameters which needed to
be obtained from the transverse and the longitudinal mode analysis of the laser.
We performed the transverse mode analysis and the longitudinal mode analysis
with commercially available numerical solvers. Those mode profiles critically
depend on the grating physical parameters. Therefore by tweaking grating dimensions one can control the transmission characteristics of the laser.
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