575 research outputs found

    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    Acousto-optic systems for advanced microscopy

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    Acoustic waves in an optical medium cause rapid periodic changes in the refraction index, leading to diffraction effects. Such acoustically controlled diffraction can be used to modulate, deflect, and focus light at microsecond timescales, paving the way for advanced optical microscopy designs that feature unprecedented spatiotemporal resolution. In this article, we review the operational principles, optical properties, and recent applications of acousto-optic (AO) systems for advanced microscopy, including random-access scanning, ultrafast confocal and multiphoton imaging, and fast inertia-free light-sheet microscopy. As AO technology is reaching maturity, designing new microscope architectures that utilize AO elements is more attractive than ever, providing new exciting opportunities in fields as impactful as optical metrology, neuroscience, embryogenesis, and high-content screening

    Microscopy of spin hydrodynamics and cooperative light scattering in atomic Hubbard systems

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    Wechselwirkungen zwischen quantenmechanischen Teilchen können zu kollektiven PhĂ€nomenen fĂŒhren, deren Eigenschaften sich vom Verhalten einzelner Teilchen stark unterscheiden. WĂ€hrend solche Quanteneffekte im Allgemeinen schwierig zu beobachten sind, haben sich ultrakalte, in optischen Gittern gefangene atomare Gase als vielseitige experimentelle Plattform zur Erforschung der Quantenvielteilchenphysik erwiesen. In dieser Arbeit setzten wir ein Gitterplatz- und Einzelatom-aufgelöstes Quantengasmikroskop fĂŒr bosonische Rb-87 Atome ein, um Vielteilchensysteme im und außerhalb des Gleichgewichts zu untersuchen. ZunĂ€chst betrachteten wir den quantenmechanischen PhasenĂŒbergang zwischen dem suprafluiden und dem Mott-isolierenden Zustand im Bose-Hubbard-Modell, das nativ durch kalte Atome in optischen Gittern realisiert wird, und zeigten, dass sich die Brane-ParitĂ€t eignet, um nichtlokale Ordnung im konventionell als ungeordnet erachteten zweidimensionalen Mott-Isolator zu identifizieren. Mithilfe eines mikroskopischen Ansatzes zur Realisierung einstellbarer Gittergeometrien und programmierbarer Einheitszellen implementierten wir Quadrats-, Dreiecks-, Kagome- und Lieb-Gitter und beobachteten die Skalierung des PhasenĂŒbergangspunkts mit der mittleren Koordinationszahl des Gitters. In einem eindimensionalen Gitter untersuchten wir zudem den Hochtemperatur-Spintransport im Heisenberg-Modell, das durch Superaustausch in der Mott-isolierenden Phase eines zwei-Spezies Bose-Hubbard-Modells realisiert wurde. Durch Betrachten der Relaxationsdynamik eines als DomĂ€nenwand prĂ€parierten Anfangszustandes fanden wir eine superdiffusive Raum-Zeit-Skalierung mit einem anomalen dynamischen Exponenten von 3/2. Anschließend untersuchten wir die theoretisch vorhergesagten mikroskopischen Voraussetzungen fĂŒr Superdiffusion, indem wir regulĂ€re Diffusion im nicht-integrablen, zweidimensionalen Heisenberg-Modell und ballistischen Transport fĂŒr SU(2)-Symmetrie-gebrochene magnetisierte AnfangszustĂ€nde nachwiesen. Weiterhin maßen wir die ZĂ€hlstatistik der durch die DomĂ€nenwand transportierten Spins; die sich daraus ergebende schiefe Verteilung deutete auf einen nichtlinearen zugrundeliegenden Transportprozess hin, der an die dynamische Kardar-Parisi-Zhang UniversalitĂ€tsklasse erinnert. Mittels Mott-Isolatoren im Limit tiefer Gitter konnten wir darĂŒber hinaus die durch Photonen vermittelten Wechselwirkungen in einem Spinsystem untersuchen, das aus zwei ĂŒber einen geschlossenen optischen Übergang gekoppelten ZustĂ€nden besteht. Durch spektroskopische Untersuchung der Reflexion und Transmission konnten wir die direkte Anregung einer subradianten Eigenmode und kohĂ€rente Spiegelung beobachten, was auf die Realisierung einer effizienten, im freien Raum operierenden, paraxialen Licht-Materie-Schnittstelle hindeutet.The interplay of quantum particles can give rise to collective phenomena whose characteristics are distinct from the behavior of individual particles. While quantum effects are generally challenging to observe, ultracold atomic gases trapped in optical lattices have emerged as a versatile experimental platform to study quantum many-body physics. In this thesis, we employed a site– and single-atom–resolved quantum gas microscope of bosonic Rb-87 atoms to explore many-body systems in and out of equilibrium. We first considered the ground-state quantum phase transition between the superfluid and Mott-insulating state in the Bose–Hubbard model, natively realized by cold atoms in optical lattices, for which we found brane parity to be suitable for detecting nonlocal order in the conventionally unordered two-dimensional Mott insulator. Using a microscopic approach to realizing tunable lattice geometries and programmable unit cells, we implemented square, triangular, kagome and Lieb lattices, and observed the mean-field scaling of the phase transition point with average coordination number. In a one-dimensional lattice, we furthermore studied high-temperature spin transport in the Heisenberg model, realized by superexchange in the Mott-insulating phase of a two-species Bose–Hubbard model. By tracking the relaxation dynamics of an initial domain-wall state, we found superdiffusive space–time scaling with an anomalous dynamical exponent of 3/2. We then probed the predicted microscopic requirements for superdiffusion, verifying regular diffusion for the integrability-broken two-dimensional Heisenberg model and ballistic transport for SU(2)-symmetry–broken net magnetized initial states. Subsequently, we measured the full counting statistics of spins transported across the domain wall; the resulting skewed distribution implied a nonlinear underlying transport process, reminiscent of the Kardar–Parisi–Zhang dynamical universality class. Moving to Mott insulators in the deep-lattice limit, we could moreover study photon-mediated interactions on a subwavelength-spaced, array-ordered spin system consisting of states coupled by a closed optical transition. By spectroscopically probing the reflectance and transmittance, we demonstrated the direct excitation of a subradiant eigenmode and observed specular reflection, indicating the realization of an efficient free-space paraxial light–matter interface

    Roadmap for optical tweezers

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    ArtĂ­culo escrito por un elevado nĂșmero de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboraciĂłn, si le hubiere, y los autores pertenecientes a la UAMOptical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects, ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in the life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nano-particle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space explorationEuropean Commission (Horizon 2020, Project No. 812780

    Spall Characteristics of Additively Manufactured Stainless Steel

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    Additive manufacturing (AM) has rapidly transformed from a novelty prototyping technology into a growing sector of production across a wide range of industries. Much work has been documented in literature to demonstrate the behavior of AM products under static and quasi-static loading conditions. However, the behavior of AM materials under high strain rate loading is not as well understood. This research attempts to advance the fundamental knowledge of the relationship between the unique aspects of AM and the mechanical performance under high velocity impact loading conditions. This project examines the behavior of AM 316L stainless steel (SS) exposed to high velocity impact, the associated shock wave propagation, and the resistance to fracture as a function of orientation and internal engineered features (a design tool unique to AM). This research involves fabrication, characterization, plate impact spallation testing, experiment modeling, and post-mortem analysis of 316L SS samples fabricated using laser powder bed fusion (LPBF). Connections and correlations were established using a variety of data sets. A build-impact orientation study and two engineered porosity studies (one with random distribution across the bulk and the other with single voids strategically placed) were conducted to develop a better understanding of shock wave propagation and spall fracture related to the unique aspects and capabilities of LPBF fabrication. This research demonstrated that impact orientation with respect to build direction influences the extent and location of spall damage due to the relative microstructural anisotropy and collections of powder filled voids slow and weaken the progressing shock front by presenting disturbances in portions of the wave front. An engineering design study based on the findings of the earlier studies further utilized purposeful engineering design to control the propagation of the shock wave (and associated pressure front) through the material. The use of internal features, a capability unique to LPBF, was the primary goal of the study. This study successfully demonstrated that a large, powder-filled void space placed within a solid sample provides damping qualities that both slow the progression of the shock front and reduce the magnitude of the pressure stress realized at the rear free surface (opposite of impact). Overall, the results of this research demonstrate that the anisotropic properties and unique capabilities of LPBF can be leveraged to control shock wave propagation and resultant damage in stainless steel materials. Unique aspects of this research include (1) comparing the spall response of LPBF fabricated samples to shock loading conditions applied at varying orientation relative to the build direction, (2) examining the use of powder-filled engineered void spaces to reduce the magnitude and velocity of the progressing shock front, along with the resulting damage, and (3) in both cases coupling the results of plate impact experiments with as-built and post-mortem sample characterization

    Driven colloidal particles in optical potential energy landscapes

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    The structure and dynamics of colloidal particles in optical potential energy landscapes is studied. Experiments use paramagnetic or optically anisotropic colloidal particles interacting with lines or pairs of time-dependent optical traps. First, the pairwise interactions of the paramagnetic particles are measured using pairs of optical traps. We test a novel data analysis method under various conditions and calculate the magnetic susceptibility of the particles. Next, we measure the structure and dynamics of chains of paramagnetic colloids in a sinusoidal optical potential of varying depth. At well defined chain lengths, we observe a transition from an asymmetric, strongly pinned state to a free-sliding, symmetric state as the optical potential decreases. We then analyse the frictional dynamics of the same system under a constant driving force and observe a transition from low to high friction as the optical potential increases. We model the dynamics of the chains in the low and high friction regimes. The simple hard sphere model developed for the high friction regime is used to derive an equation which predicts the transition point from low to high friction. Next, we drive the chains through a time-dependent optical potential with an oscillating depth. We analyse the synchronisation of the chain’s motion to the oscillations of the potential and characterise the dynamics, observing a novel mode of motion involving the simultaneous nucleation of kinks and anti-kinks. Finally, we study the dynamics of a single optically anisotropic dumbbell particle interacting with a repulsive optical trap controlled by a time-delayed feedback protocol. We observe a transition from diffusive to driven dynamics which is modelled using delay-differential equations. We find that this transition coincides with the maximum work done on the particle and a local minimum in the mutual information between the particle and the trap

    Closed-loop control system and hardware-aware compilation protocols for quantum simulation with neutral atoms in optical trap arrays

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    Quantum materials offer tremendous potential for advancing electronic devices beyond traditional semiconductor-based technologies. Understanding the dynamics of these materials requires the use of quantum simulators. Quantum simulators are controlled many-body quantum systems that mimic the dynamics of a targeted quantum system. The three key features of a quantum simulator are controllability, scalability, and interactability. Controllability denotes the ability to address an individual quantum system. Scalability refers to extending this control to multiple quantum systems while maintaining their interconnectivity with a polynomial increase in resources. Interactability, on the other hand, denotes the capability to establish strong tunable interactions between a pair of quantum systems. This thesis addresses the challenges of attaining controllability and scalability within the current Noisy Intermediate-Scale Quantum (NISQ) era, characterized by limited and error-prone qubits, for a neutral atom-based quantum simulator. The constraints in qubit interconnectivity necessitate the use of additional swap gates for operations between non-adjacent qubits, increasing errors. To reduce these gate-based errors, we improve qubit interconnectivity by displacing atoms during simulation, thus enhancing our simulator’s scalability. We compare approaches with and without atom displacement analytically and numerically, employing metrics like circuit fidelity and quantum volume. Our analysis introduces a novel metric, denoted as ηprotocol\eta_{protocol}, for comparing compilation protocols incorporating atom displacement. Additionally, we establish an inequality involving the ηplatform\eta_{platform} metric to compare operational protocols with and without atom displacement. We conclude from our quantum volume study that protocols assisted by atom displacement can achieve a quantum volume of 2^7, a significant improvement over the 2^6 attainable without atom displacement with the state-of-the-art two-qubit gate infidelity of 5e-3 and atom displacement infidelity of 1.8e-4. Implementing a dedicated closed-loop control and acquisition system showcases our simulator’s controllability. The system integrates machine learning techniques to automate experiment composition, execution, and analysis, resulting in faster and automated control parameter optimization. A practical demonstration of this optimization is conducted through imaging an atomic cloud composed of Rb-87 atoms, the first step in undertaking quantum simulations with neutral atom arrays. The research presented in this thesis contributes to the understanding and advancement of quantum simulators, paving the way for developing new devices with quantum materials

    Platforms for the development of electrochemiluminescent biosensors

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    Electrochemiluminescence (ECL) based biosensors has attracted much attention since they provide high selectivity, controllability, and sensitivity. Therefore, the goal of this work was to study novel gold-based materials for the development ECL platforms using ruthenium based luminophores for future application in bacteria detection. Firstly, 3D Ti electrodes, printed using Ti alloy (Ti-6AI-4V) powder were studied and functionalized with a thin layer of gold and ECL generation was investigated with [Ru(bpy)3]2+ and the co-reactant tri-propyl amine. Results demonstrated that the presence of gold improved the diffusion on the electrode surface as well as ECL intensity, suggesting it can provide a unique and optimizable platform for their potential application for biosensors. Gold has very interesting electrochemical applications, but it also presents optical properties that can be exploited for sensing purpose, such as ECL signal amplification through optically driven plasmon excitation. With this purpose, 10 nm gold nanoparticles (AuNPs) were investigated in solution with different luminophores of [Ru(bpy)3]2+, [Ru(bpy)3-NH2]2+ and [Ru(bpy)2(phen)-NH2]2+ (separately), for the development of a SPR-ECL system. According to the fluorescence emission results, [Ru(bpy)3-NH2]2+ was chosen as the most suitable dye to develop an ECL biosensor for the DNA detection UTI causing Escherichia coli. For this, gold nanoparticles coated glassy carbon electrodes were analyse using impedance and cyclic voltammetry technique in order to investigate the suitability of the system for DNA bacterial detection. Finally, Ferromagnetic-Core/Gold-Shell NPs synthesized by thermal decomposition method were also characterised. Results confirmed that the particles were successfully synthesized and covered with gold, however, SEM images shown an aggregate size >200nm and a heterogenous shape, indicating that the synthesis protocol should be further optimized to achieve better particle properties for a magnetic ECL based biosensor. In conclusion. this thesis demonstrated the how novel platforms and luminophores could be used in conjunction with gold to develop ECL sensing systems. SPR of AuNPs coupled ECL of luminophores can be exploited to amplify the ECL signal, and overall, the analytical performance of the sensing platforms and undoubtedly, the development of highly selective and sensitive biosensors for correct detection and diagnosis of diseases such as bacterial infections
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