Soliton dynamics in liquid-core optical fibers

Solitonen sind selbsterhaltende Wellenmuster, die in vielen dynamischen Systemen in der Natur auftreten. In der Optik ermöglichen die reichhaltigen Dynamiken von nicht- verbreiternden zeitlichen Solitonen die Generation von Superkontinuumsspektren über weite Wellenlängenbereiche. Diese Dissertation untersucht Solitondynamiken in Flüssigkernfasern theoretisch und experimentell. Einem streng empirischen Ansatz folgend werden hybride soliton-ähnliche Zustände als mögliche Lösung dieser Systeme vorgeschlagen. Wichtige Kenngrößen, wie optische Phasenbeziehungen und eine modifizierte Solitonzahl, werden als Werkzeuge zur Klassifizierung nichtinstantaner, nichtlinearer Systeme hinsichtlich ihrer Fähigkeiten zur Beherbergung von Hybrid-Solitonen gefunden und bestätigt. In dieser Arbeit werden außerdem realistische Materialmodelle erarbeitet, die die Identifizierung von Soliton-Regimen in einfach herstellbaren Flüssigkern-Fasern mit Stufenindex Design ermöglichen. Schließlich wird gezeigt, dass hybride solitonähnliche Zustände in simulierten Superkontinuumspektren für diese experimentell adressierbaren Faser- und Laserparameter auftreten. Daraufhin wird die Soliton-gestützte Superkontinuumserzeugung experimentell in Flüssigkernfasern unter Verwendung von modernsten Thuliumfaserlasern demonstriert. Im Zusammenhang mit numerischen Simulationen wird hervorgehoben, dass das ungewöhnliche Verbreitungs- und Kohärenzverhalten der gemessenen Spektren von dominanten, nichtinstantanen, nichtlinearen Effekten in Flüssigkeiten herrührt und somit die ersten positiven Hinweise für die Hypothese neuartiger Hybrid-Soliton-Dynamiken liefert. Die Studie schließt mit der experimentellen Demonstration der externen Soliton-Kontrolle über Temperatur, statischen Druck und flüssige Zusammensetzung. Dabei werden Flüssigkernfasern als dynamische Plattform für breitbandige und abstimmbare nichtlineare Lichterzeugung mit einem weitreichenden, wissenschaftlichenPotenzial hervorgehoben

Axial dispersion-managed liquid-core fibers: A platform for tailored higher-order mode supercontinuum generation

Soliton-based supercontinuum generation is a powerful approach for generating light with the desired properties, although limited dispersion tuning capabilities remain a key challenge. Here, we introduce liquid-core fibers (LCFs) with longitudinally controlled dispersion of a higher-order mode, achieved by axial modulation of the liquid core diameter. This approach provides a versatile photonic platform with unique dispersion control capabilities that are particularly relevant to ultrafast, non-linear frequency conversion. Our tuning concept uses LCFs with anomalous dispersion at telecommunication wavelengths (TE01-mode) and relies on the strong dependence of dispersion on the core diameter. Non-monotonic, complex dispersion profiles feature multiple dispersive waves formation when launching ultrashort pulses. For example, this effect has been used to fill spectral gaps in fibers with linearly decreasing core diameter in order to spectrally smooth the output spectra. Our results highlight the potential of LCFs for controlling dispersion, particularly along the fiber axis, thus yielding novel dispersion landscapes that can reveal unexplored nonlinear dynamics and generate tailored broadband spectra

Hybrid soliton dynamics in liquid-core fibres

The discovery of optical solitons being understood as temporally and spectrally stationary optical states has enabled numerous innovations among which, most notably, supercontinuum light sources have become widely used in both fundamental and applied sciences. Here, we report on experimental evidence for dynamics of hybrid solitons—a new type of solitary wave, which emerges as a result of a strong non-instantaneous nonlinear response in CS2-filled liquid-core optical fibres. Octave-spanning supercontinua in the mid-infrared region are observed when pumping the hybrid waveguide with a 460 fs laser (1.95 μm) in the anomalous dispersion regime at nanojoule-level pulse energies. A detailed numerical analysis well correlated with the experiment uncovers clear indicators of emerging hybrid solitons, revealing their impact on the bandwidth, onset energy and noise characteristics of the supercontinua. Our study highlights liquid-core fibres as a promising platform for fundamental optics and applications towards novel coherent and reconfigurable light sources

Carbon chloride-core fibers for soliton mediated supercontinuum generation

We report on soliton-fission mediated infrared supercontinuum generation in liquid-core step-index fibers using highly transparent carbon chlorides (CCl4, C2Cl4). By developing models for the refractive index dispersions and nonlinear response functions, dispersion engineering and pumping with an ultrafast thulium fiber laser (300 fs) at 1.92 μm, distinct soliton fission and dispersive wave generation was observed, particularly in the case of tetrachloroethylene (C2Cl4). The measured results match simulations of both the generalized and a hybrid nonlinear Schrödinger equation, with the latter resembling the characteristics of non-instantaneous medium via a static potential term and representing a simulation tool with substantially reduced complexity. We show that C2Cl4 has the potential for observing non-instantaneous soliton dynamics along meters of liquid-core fiber opening a feasible route for directly observing hybrid soliton dynamics

A colaboração docente em estudos de aula na perspectiva de professores participantes

O artigo analisa a colaboração docente em estudos de aula, encarados como um processo de desenvolvimento profissional. Foram entrevistados sete professores do 1.º ao 3.º ciclo de ensino básico, os quais participaram em três estudos de aula promovidos em escolas públicas de Lisboa em 2013-2014, sob a coordenação de uma equipa de investigadores do Instituto de Educação da Universidade de Lisboa. As entrevistas, semiestruturadas, foram realizadas em junho e julho de 2016 e analisadas na perspectiva qualitativa e interpretativa de pesquisa. Os resultados apontam que no contexto de um estudo de aula a colaboração docente se concretiza no entrecruzamento de três aspetos principais – a partilha, a cooperação e o estímulo pessoal–, manifestando-se em especial no planeamento e realização da aula de investigação e nas atividades profissionais cotidianas.info:eu-repo/semantics/publishedVersio

Generation and processing of complex photon states with quantum frequency combs

The development of technologies for quantum information (QI) science demands the realization. and precise control of complex (multipartite and high dimensional) entangled systems on practical and scalable platforms. Quantum frequency combs (QFCs) represent a powerful tool towards this goal. They enable the generation of complex photon states within a single spatial mode as well as their manipulation using standard fiber-based telecommunication components. Here, we review recent progress in the development of QFCs, with a focus on results that highlight their importance for the realization of complex quantum states. In particular, we outline recent work on the use of integrated QFCs for the generation of high-dimensional multipartite optical cluster states - lying at the basis of measurement-based quantum computation. These results confirm that the QFC approach can provide a stable, practical, low-cost, and established platform for the development of quantum technologies, paving the way towards the advancement of QI science for out-of-the-lab applications, ranging from practical quantum computing to more secure communications

Single mode criterion - a benchmark figure to optimize the performance of nonlinear fibers

Optical fibers with sub-wavelength cores are promising systems for efficient nonlinear light generation. Here we reveal that the single-mode criterion represents a convenient design tool to optimize the performance of nonlinear fibers circumventing intense numerical calculations. We introduce a quasi-analytic expression for the nonlinear coefficient allowing us to investigate its behavior over a large parameter range. The study is independent of the actual value of the material nonlinearity and shows the fundamental dependencies of the nonlinear coefficient on wavelength, refractive index and core diameter, elucidated by detailed case studies of fused silica and chalcogenide tapers and hybrid fibers

Impact of deuteration on the ultrafast nonlinear optical response of toluene and nitrobenzene

Nonlinear pulse propagation inside highly nonlinear media requires accurate knowledge on the temporal response function of the materials used particular in the case of liquids. Here we study the impact of deuteration on the ultrafast dynamics of toluene and nitrobenzene via all optical Kerr gating, showing substantially different electronic and molecular contributions, which was quantified by fitting a multichannel decay model to the data points. Specifically we found that deuteration imposes the time-integrated nonlinearities to reduce particular for toluene which could be caused by both reduced electronic hyperpolarizabilities as well as weaker intermolecular interactions. The results achieved reveal that deuterated organic solvents represent promising materials for infrared photonics since they offer extended infrared transmission compared to their non-deuterated counterparts while maintained strong nonlinear responses

Monolithic optofluidic mode coupler for broadband thermo- and piezo-optical characterization of liquids

We present a monolithic fiber device that enables investigation of the thermo- and piezo-optical properties of liquids using straightforward broadband transmission measurements. The device is a directional mode coupler consisting of a multi-mode liquid core and a single-mode glass core with pronounced coupling resonances whose wavelength strongly depend on the operation temperature. We demonstrated the functionality and flexibility of our device for carbon disulfide, extending the current knowledge of the thermo-optic coefficient by 200 nm at 20 °C and uniquely for high temperatures. Moreover, our device allows measuring the piezo-optic coefficient of carbon disulfide, confirming results first obtained by Röntgen in 1891. Finally, we applied our approach to obtain the dispersion of the thermo-optic coefficients of benzene and tetrachloroethylene between 450 and 800 nm, whereas no data was available for the latter so far