Physique // Physics

Permanent URI for this collectionhttps://hdl.handle.net/10393/22778

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Interferometric imaging of amplitude and phase of spatial biphoton states
(2023) Zia, Danillo; Dehghan, Nazanin; D'Errico, Alessio; Sciarrino, Fabio; Karimi, Ebrahim
High-dimensional biphoton states are promising resources for quantum applications, ranging from high-dimensional quantum communications to quantum imaging. A pivotal task is fully characterizing these states, which is generally time-consuming and not scalable when projective measurement approaches are adopted; however, new advances in coincidence imaging technologies allow for overcoming these limitations by parallelizing multiple measurements. Here we introduce biphoton digital holography, in analogy to off-axis digital holography, where coincidence imaging of the superposition of an unknown state with a reference state is used to perform quantum state tomography. We apply this approach to single photons emitted by spontaneous parametric down-conversion in a nonlinear crystal when the pump photons possess various quantum states. The proposed reconstruction technique allows for a more efficient (three orders of magnitude faster) and reliable (an average fidelity of 87%) characterization of states in arbitrary spatial modes bases, compared with previously performed experiments. Multiphoton digital holography may pave the route toward efficient and accurate computational ghost imaging and high-dimensional quantum information processing.
A general illumination method to predict bifacial photovoltaic system performance
(2023) Tonita, Erin M.; Valdivia, Christopher E.; Russell, Annie C. J.; Martinez-Szewczyk, Michael; Bertoni, Mariana I.; Hinzer, Karin
Bifacial photovoltaic technologies are estimated to supply >16% of global energy demand by 2050 to achieve net-zero greenhouse gas emissions. However, the current IEC bifacial measurement standard (IEC 60904-1-2) does not provide a pathway to account for the critical effects of spectral or broadband albedo on the rear-side irradiance, with in-lab characterization of bifacial devices limited by overestimation of rear incident irradiance, neglecting spectral albedo effects on the rear, or both. As a result, prior reports have limited applicability to the diverse landscapes of bifacial photovoltaic deployments. In this paper, we identify a general bifacial illumination method which accounts for spectral albedo while representing realistic system operating conditions, referred to as the scaled rear irradiance (SRI) method. We describe how the SRI method extends the IEC standard, facilitating indoor testing of cell or module performance under varied albedo with standard solar simulator set-ups. This enables improved comparisons of bifacial technologies, application-specific optimization, and the standardization of bifacial module power ratings.
Experimental realisations of the fractional Schrödinger equation in the temporal domain
(2023) Liu, Shilong; Zhang, Yingwen; Malomed, Boris A.; Karimi, Ebrahim
The fractional Schrödinger equation (FSE) — a natural extension of the standard Schrödinger equation — is the basis of fractional quantum mechanics. It can be obtained by replacing the kinetic-energy operator with a fractional derivative. Here, we report the experimental realisation of an optical FSE for femtosecond laser pulses in the temporal domain. Programmable holograms and the single-shot measurement technique are respectively used to emulate a Lévy waveguide and to reconstruct the amplitude and phase of the pulses. Varying the Lévy index of the FSE and the initial pulse, the temporal dynamics is observed in diverse forms, including solitary, splitting and merging pulses, double Airy modes, and “rain-like” multi-pulse patterns. Furthermore, the transmission of input pulses carrying a fractional phase exhibits a “fractional-phase protection” effect through a regular (non-fractional) material. The experimentally generated fractional time-domain pulses offer the potential for designing optical signal-processing schemes.
Spin–orbit coupling induced by ascorbic acid crystals
(2023) Grenapin, Florence; D'Errico, Alessio; Karimi, Ebrahim
Some anisotropic materials form semicrystalline structures, called spherulites, when observed in a polarisation microscope, exhibit a characteristic “maltese-cross”-like pattern. While this observation has been hitherto considered as a tool to characterize these materials, we show that these patterns are associated with a strong light’s spin–orbit coupling induced by the spherulite structures. We experimentally demonstrate these effects using samples of crystallized ascorbic acid and observing the creation of optical vortices in transmitted laser beams, as well as the formation of inhomogeneous polarisation patterns. Our findings suggest the use of some spherulites based on other materials in frequency ranges, e.g. in the THz domain, where polarisation and spatial shaping of electromagnetic radiation is still a challenging task.
Efficient Wave Optics Modeling of Nanowire Solar Cells Using Rigorous Coupled Wave Analysis
(2019) Robertson, Kyle W.; LaPierre, Ray R.; Krich, Jacob J.
We investigate the accuracy of rigorous coupled wave analysis (RCWA) for near-field computations within cylindrical GaAs nanowire solar cells and discover excellent accuracy with low computational cost at long incident wavelengths, but poor accuracy at short incident wavelengths. These near fields give the carrier generation rate, and their accurate determination is essential for device modeling. We implement two techniques for increasing the accuracy of the near fields generated by RCWA, and give some guidance on parameters required for convergence along with an estimate of their associated computation times. The first improvement removes Gibbs phenomenon artifacts from the RCWA fields, and the second uses the extremely well-converged far field absorption to rescale the local fields. These improvements allow a computational speedup between 30 and 1000 times for spectrally integrated calculations, depending on the density of the near fields desired. Some spectrally resolved quantities, especially at short wavelengths, remain expensive, but RCWA is still an excellent method for performing those calculations. These improvements open up the possibility of using RCWA for low cost optical modeling in a full optoelectronic device model of nanowire solar cells.
Projecting onto any two-photon polarization state using linear optics
(2018) Thekkadath, Guillaume S; Giner, Lambert; Ma, Xinyuan; Flórez, Jefferson; Lundeen, Jeff S
Projectors are a simple but powerful tool for manipulating and probing quantum systems. For instance, projecting two-qubit systems onto maximally entangled states can enable quantum teleportation. While such projectors have been extensively studied, partially-entangling projectors have been largely overlooked, especially experimentally, despite their important role in quantum foundations and quantum information. Here, we propose a way to project two polarized photons onto any state with a single experimental setup. Our scheme does not require optical nonlinearities or additional photons. Instead, the entangling operation is provided by Hong–Ou–Mandel interference and post-selection. The efficiency of the scheme is between 50% and 100%, depending on the projector. We perform an experimental demonstration and reconstruct the operator describing our measurement using detector tomography. Finally, we flip the usual role of measurement and state in Hardy's test by performing a partially-entangling projector on separable states. The results verify the entangling nature of our measurement with six standard deviations of confidence.
Integrating nanopore sensors within microfluidic networks
(2015-05) Tahvildari, Radin; Beamish, Eric; Tabard-Cossa, Vincent; Godin, Michel
Nanopore sensing relies on the application of a voltage across a nano-scale aperture fabricated in a thin, insulating membrane and monitoring the ionic current modulations produced by the passage of target biomolecules (proteins, DNA). While traditional solid-state nanopore fabrication using electron microscopy is time-consuming and expensive, a new technique called controlled breakdown (CBD) has been discovered which generates nanopores using only strong electric fields in an aqueous environment. Subsequent treatment of a nanopore with similar high electric fields allows for the precise control of its size and noise properties. We recently demonstrated that CBD can be used to fabricate an array of solid-state nanopores within a single membrane, each individually addressable both fluidically and electrically, directly in a microfluidic environment. By confining the electric field using micro-vias, nanopore formation is localized to specific regions of a membrane, electrical noise is reduced, and a symmetric electric field is generated around the nanopore for increased molecular detection efficiency.
Integrating nanopore sensors within microfluidic channel arrays using controlled breakdown
(2015-01-19) Tahvildari, Radin; Beamish, Eric; Tabard-Cossa, Vincent; Godin, Michel
Nanopore arrays are fabricated by controlled dielectric breakdown (CBD) in solid-state membranes integrated within polydimethylsiloxane (PDMS) microfluidic devices. This technique enables the scalable production of independently addressable nanopores. By confining the electric field within the microfluidic architecture, nanopore fabrication is precisely localized and electrical noise is significantly reduced. Both DNA and protein molecules are detected to validate the performance of this sensing platform.
Nanopore Fabrication by Controlled Dielectric Breakdown
(2014-03-25) Kwok, Harold; Briggs, Kyle; Tabard-Cossa, Vincent
Nanofabrication techniques for achieving dimensional control at the nanometer scale are generally equipment-intensive and time-consuming. The use of energetic beams of electrons or ions has placed the fabrication of nanopores in thin solid-state membranes within reach of some academic laboratories, yet these tools are not accessible to many researchers and are poorly suited for mass-production. Here we describe a fast and simple approach for fabricating a single nanopore down to 2-nm in size with sub-nm precision, directly in solution, by controlling dielectric breakdown at the nanoscale. The method relies on applying a voltage across an insulating membrane to generate a high electric field, while monitoring the induced leakage current. We show that nanopores fabricated by this method produce clear electrical signals from translocating DNA molecules. Considering the tremendous reduction in complexity and cost, we envision this fabrication strategy would not only benefit researchers from the physical and life sciences interested in gaining reliable access to solid-state nanopores, but may provide a path towards manufacturing of nanopore-based biotechnologies.
Using the fringing electric field in microfluidic volume sensors to enhance sensitivity and accuracy
(2012) Riordon, Jason; M.-Catafard, Nicolas; Godin, Michel
The particle trajectory above impedance-monitoring coplanar electrodes in a microfluidic channel dramatically influences the measuredelectric current change. We use finite element modeling to predict changes in ionic current for microspheres flowing in highly fringing fields, and validate these results by introducing a buoyancy-based particle focusing technique. Using 6 μm polystyrene particles in solutions of varying density, we control the height of the particle trajectories near the sensing electrodes and show that sensitivity can be increased by up to 3.5× when particles flow close to the electrodes compared to particles flowing further away, while simultaneously improving accuracy.
A microscale anisotropic biaxial cell stretching device for applications in mechanobiology
(2013-12-05) Tremblay, Dominique; Chagnon-Lessard, Sophie; Mirzaei, Maryam; Pelling, Andrew E.; Godin, Michel
A multi-layered polydimethylsiloxane microfluidic device with an integrated suspended membrane has been fabricated that allows dynamic and multi-axial mechanical deformation and simultaneous live-cell microscopy imaging. The transparent membrane’s strain field can be controlled independently along two orthogonal directions. Human foreskin fibroblasts were immobilized on the membrane’s surface and stretched along two orthogonal directions sequentially while performing live-cell imaging. Cyclic deformation of the cells induced a reversible reorientation perpendicular to the direction of the applied strain. Cells remained viable in the microdevice for several days. As opposed to existing microfluidic or macroscale stretching devices, this device can impose changing, anisotropic and time-varying strain fields in order to more closely mimic the complexities of strains occurring in vivo.
Precise control of the size and noise of solid-state nanopores using high electric fields
(2012) Beamish, Eric; Tabard-Cossa, Vincent; Kwok, Harold; Godin, Michel
We present a methodology for preparing silicon nitride nanopores that provides in situ control of size with sub-nanometer precision while simultaneously reducing electrical noise by up to three orders of magnitude through the cyclic application of high electric ﬁelds in an aqueous environment. Over 90% of nanopores treated with this technique display desirable noise characteristics and readily exhibit translocation of double-stranded DNA molecules. Furthermore, previously used nanopores with degraded electrical properties can be rejuvenated and used for further single-molecule experiments
Fine-tuning the Size and Minimizing the Noise of Solid-state Nanopores
(2013-12-05) Beamish, Eric; Godin, Michel; Tabard-Cossa, Vincent; Kwok, Harold
Solid-state nanopores have emerged as a versatile tool for the characterization of single biomolecules such as nucleic acids and proteins. However, the creation of a nanopore in a thin insulating membrane remains challenging. Fabrication methods involving specialized focused electron beam systems can produce well-defined nanopores, but yield of reliable and low-noise nanopores in commercially available membranes remains low and size control is nontrivial. Here, the application of high electric fields to fine-tune the size of the nanopore while ensuring optimal low-noise performance is demonstrated. These short pulses of high electric field are used to produce a pristine electrical signal and allow for enlarging of nanopores with subnanometer precision upon prolonged exposure. This method is performed in situ in an aqueous environment using standard laboratory equipment, improving the yield and reproducibility of solid-state nanopore fabrication.
Polarization-dependent femtosecond laser ablation of poly-methyl methacrylate
(2012) Guay, J-M; Villafranca, A; Baset, F; Popov, K; Ramunno, L; Bhardwaj, VR
We show that ablation features in poly-methyl methacrylate (PMMA) induced by a single femtosecond laser pulse are imposed by light polarization. The ablation craters are elongated along the major axis of the polarization vector and become increasingly prominent as the pulse energy is increased above the threshold energy. We demonstrate ~40% elongation for linearly and elliptically polarized light in the fluence range of 4–20 J cm−2, while circularly polarized light produced near circular ablation craters irrespective of pulse energies. We also show that irradiation with multiple pulses erases the polarization-dependent elongation of the ablation craters. However, for line ablation the orientation of the electric field vector is imprinted in the form of quasi-periodic structures inside the ablated region. Theoretically, we show that the polarization dependence of the ablation features arises from a local field enhancement during light–plasma interaction. Simulations also show that in materials with high nonlinearities such as doped PMMA, in addition to conventional explosive boiling, sub-surface multiple filamentation can also give rise to porosity.
Spontaneous Excitation Patterns Computed for Axons with Injury-like Impairments of Sodium Channels and Na/K Pumps
(2012) Yu, Na; Morris, Catherine E.; Joós, Béla; Longtin, André
Nerve cells damaged by trauma, stroke, epilepsy, inflammatory conditions etc, have chronically leaky sodium channels that eventually kill. The usual job of sodium channels is to make brief voltage signals –action potentials– for long distance propagation. After sodium channels open to generate action potentials, sodium pumps work harder to re-establish the intracellular/extracellular sodium imbalance that is, literally, the neuron’s battery for firing action potentials. Wherever tissue damage renders membranes overly fluid, we hypothesize, sodium channels become chronically leaky. Our experimental findings justify this. In fluidized membranes, sodium channel voltage sensors respond too easily, letting channels spend too much time open. Channels leak, pumps respond. By mathematical modeling, we show that in damaged channel-rich membranes the continual pump/leak counterplay would trigger the kinds of bizarre intermittent action potential bursts typical of injured neurons. Arising ectopically from injury regions, such neuropathic firing is unrelated to events in the external world. Drugs that can silence these deleterious electrical barrages without blocking healthy action potentials are needed. If fluidized membranes house the problematic leaky sodium channels, then drug side effects could be diminished by using drugs that accumulate most avidly into fluidized membranes, and that bind their targets with highest affinity there.
The Physical Interaction of Myoblasts with the Microenvironment during Remodeling of the Cytoarchitecture
(2012) Modulevsky, Daniel J.; Tremblay, Dominique; Gullekson, Corinne; Bukoresthliev, Nickolay V.; Pelling, Andrew E.
Integrins, focal adhesions, the cytoskeleton and the extracellular matrix, form a structural continuum between the external and internal environment of the cell and mediate the pathways associated with cellular mechanosensitivity and mechanotransduction. This continuum is important for the onset of muscle tissue generation, as muscle precursor cells (myoblasts) require a mechanical stimulus to initiate myogenesis. The ability to sense a mechanical cue requires an intact cytoskeleton and strong physical contact and adhesion to the microenvironment. Importantly, myoblasts also undergo reorientation, alignment and large scale remodeling of the cytoskeleton when they experience mechanical stretch and compression in muscle tissue. It remains unclear if such dramatic changes in cell architecture also inhibit physical contact and adhesion with the tissue microenvironment that are clearly important to myoblast physiology. In this study, we employed interference reflection microscopy to examine changes in the close physical contact of myoblasts with a substrate during induced remodeling of the cytoarchitecture (de-stabilization of the actin and microtubule cytoskeleton and inhibition of acto-myosin contractility). Our results demonstrate that while each remodeling pathway caused distinct effects on myoblast morphology and sub-cellular structure, we only observed a ~13% decrease in close physical contact with the substrate, regardless of the pathway inhibited. However, this decrease did not correlate well with changes in cell adhesion strength. On the other hand, there was a close correlation between cell adhesion and β1-integrin expression and the presence of cell-secreted fibronectin, but not with the presence of intact focal adhesions. In this study, we have shown that myoblasts are able to maintain a large degree of physical contact and adhesion to the microenvironment, even during shot periods (<60 min) of large scale remodeling and physiological stress, which is essential to their in-vivo functionality.
Left-Shifted Nav Channels in Injured Bilayer: Primary Targets for Neuroprotective Nav Antagonist?
(2012-04-25) Morris, Catherine E.; Boucher, Pierre-Alexandre; Joos, Bela
Mechanical, ischemic, and inflammatory injuries to voltage-gated sodium channel (Nav)-rich membranes of axon initial segments and nodes of Ranvier render Nav channels dangerously leaky. By what means? The behavior of recombinant Nav1.6 (Wang et al., 2009) leads us to postulate that, in neuropathologic conditions, structural degradation of axolemmal bilayer fosters chronically left-shifted Nav channel operation, resulting in ENa rundown. This “sick excitable cell Nav-leak” would encompass left-shifted fast- and slow-mode based persistent INa (i.e., Iwindow and slow-inactivating INa). Bilayer-damage-induced electrophysiological dysfunctions of native-Nav channels, and effects on inhibitors on those channels, should, we suggest, be studied in myelinated axons, exploiting INa(V,t) hysteresis data from sawtooth ramp clamp. We hypothesize that (like dihydropyridines for Ca channels), protective lipophilic Nav antagonists would partition more avidly into disorderly bilayers than into the well-packed bilayers characteristic of undamaged, healthy plasma membrane. Whereas inhibitors using aqueous routes would access all Navs equally, differential partitioning into “sick bilayer” would co-localize lipophilic antagonists with “sick-Nav channels,” allowing for more specific targeting of impaired cells. Molecular fine-tuning of Nav antagonists to favor more avid partitioning into damaged than into intact bilayers could reduce side effects. In potentially salvageable neurons of traumatic and/or ischemic penumbras, in inflammatory neuropathies, in muscular dystrophy, in myocytes of cardiac infarct borders, Nav-leak driven excitotoxicity overwhelms cellular repair mechanisms. Precision-tuning of a lipophilic Nav antagonist for greatest efficacy in mildly damaged membranes could render it suitable for the prolonged continuous administration needed to allow for the remodeling of the excitable membranes, and thus functional recovery.

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