arXiv subjects

Michael Mazilu

Publications and source records attributed to Michael Mazilu.

16 recordsLinked to original sources

arXiv2026

Representation-induced superposition breakdown in linear physics

The superposition principle is fundamental to linear wave systems, ensuring that their physical behaviour is independent of the chosen basis representation. While this principle underpins many analytical techniques, including modal decompositions and scattering formulations, we show that superposition expansion can fail in multilayered media when fields are expressed as infinite series of evanescent and inhomogeneous waves. Using the Airy formula and the scattering-matrix formalism, we identify conditions under which the superposition of partial waves diverges, particularly in systems with three or more interfaces. This divergence occurs because evanescent wave components cannot be normalised within the conventional basis and is not a numerical artefact. To address this, we introduce power flux modes corresponding to orthonormal basis wave solutions that preserve energy conservation in scattering events and consequently restore convergence. We prove that in the flux-orthonormal basis, interface scattering is unitary and propagation eigenvalues are bounded guaranteeing convergence. Our approach generalises to scalar, electromagnetic, and elastic wave systems, providing a robust framework for eliminating evanescent mode divergence without regularisation or renormalisation.

physics.class-ph↗

arXiv2019

Eigenmode beam optimisation for optical micro-manipulation

Optical micro-manipulation and trapping of micro-particles delivers a mechanical system in direct interaction with a beam of light. In this interaction, the optical properties such as polarisation, beam profile and wavelength of the trapping beam are important. Different beams are associated with different momentum transfer, trap stiffness and stabilisation properties, for example. One method to determine the best beam profile is through the use of the optical eigenmode approach. To use this method, we employ Mie scattering theory which enables the exact determination of the scattered field as a function of the incident field. More precisely, this approach allows us to calculate the Hermitian relationship between the incident field and the optical forces acting on the scattering objects. This Hermitian relationship defines also a set of orthogonal optical eigenmodes which deliver a natural basis to describe momentum transfer in light-matter interactions. This relationship defines also a set of orthogonal optical eigenmodes. Using these modes it is possible to define, for each numerical aperture, particle size or geometry, the optimal trapping beam.

physics.optics↗

arXiv2018

Wide-Field Multiphoton Imaging Through Scattering Media Without Correction

Optical approaches to fluorescent, spectroscopic, and morphological imaging have made exceptional advances in the last decade. Super-resolution imaging and wide-field multiphoton imaging are now underpinning major advances across the biomedical sciences. While the advances have been startling, the key unmet challenge to date in all forms of optical imaging is to penetrate deeper. A number of schemes implement aberration correction or the use of complex photonics to address this need. In contrast, we approach this challenge by implementing a scheme that requires no a priori information about the medium nor its properties. Exploiting temporal focusing and single-pixel detection in our innovative scheme, we obtain wide-field two-photon images through various turbid media including a scattering phantom and tissue reaching a depth of up to seven scattering mean free path lengths. Our results show that it competes favorably with standard point-scanning two-photon imaging, with up to a fivefold improvement in signal-to-background ratio while showing significantly lower photobleaching.

physics.optics↗

arXiv2017

Light-sheet microscopy with attenuation-compensated propagation-invariant beams

Scattering and absorption limit the penetration of optical fields into tissue, but wavefront correction, often used to compensate for these effects, is incompatible with wide field-of-view imaging and complex to implement. We demonstrate a new approach for increased penetration in light-sheet imaging, namely attenuation-compensation of the light field. This tailors an exponential intensity increase along the illuminating propagation-invariant field, enabling the redistribution of intensity strategically within a sample. This powerful yet straightforward concept, combined with the self-healing of the propagation-invariant field, improves the signal-to-background ratio of Airy light-sheet microscopy up to five-fold and the contrast-to-noise ratio up to eight-fold in thick biological specimens across the field-of-view without any aberration-correction. This improvement is not limited to Airy beam light-sheet microscopy, but can also significantly increase the imaging capabilities of Bessel and lattice light-sheet microscopy techniques, paving the way for widespread uptake by the biomedical community.

physics.optics↗

arXiv2017

Harnessing speckle for a sub-femtometre resolved broadband wavemeter and laser stabilization

The accurate determination and control of the wavelength of light is fundamental to many fields of science. Speckle patterns resulting from the interference of multiple reflections in disordered media are well-known to scramble the information content of light by complex but linear processes. However, these patterns are, in fact, exceptionally rich in information about the illuminating source. We use a fibre-coupled integrating sphere to generate wavelength-dependent speckle patterns, in combination with algorithms based on the transmission matrix method and principal component analysis, to realize a broadband and sensitive wavemeter. We demonstrate sub-femtometre wavelength resolution at a centre wavelength of 780 nm and a broad calibrated measurement range from 488 to 1064 nm. This is comparable with or exceeding the performance of conventional wavemeters. Using this speckle wavemeter as part of a feedback loop, we stabilize a 780 nm diode laser to achieve a linewidth better than 1 MHz.

physics.ins-det↗

arXiv2017

Mie scattering eigenmodes for optical trapping

The Mie scattering theory enables the exact determination of the scattered field as a function of the incident field. Here, we use this approach to calculate the Hermitian relationship between the incident field and the optical forces acting on the scattering objects. This Hermitian relationship defines also a set of orthogonal optical eigenmodes which deliver a natural basis to describe momentum transfer in light-matter interactions.

physics.optics↗

arXiv2015

Quantum conversion

The electromagnetic momentum transferred transfered to scattering particles is proportional to the intensity of the incident fields, however, the momentum of single photons ($\hbar k$) does not naturally appear in these classical expressions. Here, we discuss an alternative to Maxwell's stress tensor that renders the classical electromagnetic field momentum compatible to the quantum mechanical one. This is achieved through the introduction of the quantum conversion which allows the transformation, including units, of the classical fields to wave-function equivalent fields.

physics.optics↗

arXiv2015

Prospects for versatile phase manipulation in the TEM: beyond aberration correction

In this paper we explore the desirability of a transmission electron microscope in which the phase of the electron wave can be freely controlled. We discuss different existing methods to manipulate the phase of the electron wave and their limitations. We show how with the help of current techniques the electron wave can already be crafted into specific classes of waves each having their own peculiar properties. Assuming a versatile phase modulation device is feasible, we explore possible benefits and methods that could come into existence borrowing from light optics where so-called spatial light modulators provide programmable phase plates for quite some time now. We demonstrate that a fully controllable phase plate building on Harald Rose's legacy in aberration correction and electron optics in general would open an exciting field of research and applications.

cond-mat.mtrl-sci↗

arXiv2015

Macroscopic quantum resonators (MAQRO): 2015 Update

Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schrödinger's cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum and microgravity. The proposed mission MAQRO may overcome these limitations and allow addressing those fundamental questions. MAQRO harnesses recent developments in quantum optomechanics, high-mass matter-wave interferometry as well as state-of-the-art space technology to push macroscopic quantum experiments towards their ultimate performance limits and to open new horizons for applying quantum technology in space. The main scientific goal of MAQRO is to probe the vastly unexplored "quantum-classical" transition for increasingly massive objects, testing the predictions of quantum theory for truly macroscopic objects in a size and mass regime unachievable in ground-based experiments. The hardware for the mission will largely be based on available space technology. Here, we present the MAQRO proposal submitted in response to the (M4) Cosmic Vision call of the European Space Agency for a medium-size mission opportunity with a possible launch in 2025.

quant-ph↗

arXiv2011

Complete characterisation of the azimuthal and radial indices of light fields carrying orbital angular momentum

The direct determination of the complete transversal state of an electromagnetic field and accompanying mode indices is essential for the proper quantification of all light-matter interactions. In particular light fields with cylindrical symmetry such as Laguerre-Gaussian beams can possess orbital angular momentum, central to a wide range of emergent applications in quantum cryptography, manipulation, astrophysics and microscopy. A wide array of diffractive structures such as arrays of pinholes, triangular apertures, slits, and holograms have all recently been used to measure the azimuthal index L of individual LG beams. However, all these approaches measure only one single degree of freedom of LG beams, neglecting the radial component or P index and are thus not applicable for a priori unknown beams. Furthermore, it is unclear which is the optimal aperture and scheme needed to determine simultaneously the azimuthal and radial indices nor the extent with which such an aperture can tolerate deviations in beam parameters. Here, we demonstrate a powerful approach to simultaneously measure the radial and azimuthal indices of both pure and mixed LG light fields. We show that the shape of the diffracting element used to measure the mode indices is in fact of little importance and the crucial step is training any diffracting optical system and transforming the observed pattern into uncorrelated variables. Modest fluctuations in beam parameters such as waist size and alignment variations can be tolerated in our scheme. Importantly, beam superpositions can be experimentally decomposed delivering the intensity of each mode and their relative phases. Our results demonstrate the complete characterisation of LG beams. The approach can be expanded to other families of beams and represents a powerful method for characterising the optical multi-dimensional Hilbert space.

physics.optics↗

arXiv2011

Selective and optimal illumination of nano-photonic structures using optical eigenmodes

Using optical eigenmodes defined by the interaction between the electromagnetic fields and photonic structures it is possible to determine the optimal illumination of these structures with respect to a specific measurable quantity. One such quantity considered here is the electric field intensity in the hotspot regions of an array of nano-antennas. This paper presents two possible methods, both based on optical eigenmodes, to determine the optimal and most efficient illumination that couples to a single hotspot on top of a single nano-antenna taken from an array of nano-antennas. The two methods are compared in terms of cross-talk and overall coupling efficiency.

physics.optics↗

arXiv2011

Optical eigenmode imaging

We present an indirect imaging method that measures both amplitude and phase information from a transmissive target. Our method is based on an optical eigenmode decomposition of the light intensity and the first-order cross correlation between a target field and these eigenmodes. We demonstrate that such optical eigenmode imaging does not need any a priori knowledge of the imaging system and corresponds to a compressive full-field sampling leading to high image extraction efficiencies. Finally, we discuss the implications with respect to second-order correlation imaging.

physics.optics↗

arXiv2010

Sub-diffraction Focussing using Quadratic Measure Eigenmodes

For over a century diffraction theory has been thought to limit the resolution of focusing and imaging in the optical domain. The size of the smallest spot achievable is inversely proportional to the range of spatial wavevectors available. Here, we show that it is possible to locally beat the diffraction limit at the expense of efficiency. The method is based on the linearity of Maxwell's equations and that the interaction between light and its surroundings may be considered quadratic in nature with respect to the electromagnetic fields. We represent the intensity and spot size as a quadratic measure with associated eigenmodes. Using a dynamic diffractive optical element, we demonstrate optical focussing to an area 4 times smaller than the diffraction limit. The generic method may be applied to numerous physical phenomena relating to linear and measurable properties of the electromagnetic field that can be expressed in a quadratic form.

physics.optics↗

arXiv2010

Conserving optical currents: angular momentum and spin

Within the first quantisation of Maxwell's equations, we introduce the dynamic energy, linear momentum, angular momentum and optical spin of the electromagnetic fields. We show that these different quantities are conserved during the propagation of light in vacuum and are additive only for eigenmodes of the electromagnetic field.

physics.optics↗

arXiv2009

Spin and angular momentum operators and their conservation

Lorentz's reciprocity lemma and Feld-Tai reciprocity theorem show the effect of interchanging the action and reaction in Maxwell's equations. We derive a free-space version of these reciprocity relations which generalizes the conservation of the momentum-energy tensor. This relation corresponds to the interference conservation of electromagnetic waves. We show that for any transformation or symmetry that leaves Maxwell's equations invariant, we can modify the reciprocity relation to introduce a conserving density, optical flux and stress tensor extending Noether's theorem to a different context. We apply this method to transformations that can be expressed as Hermitian operators and more specifically we define the operators associated with the optical energy, spin, linear and angular momentum.

physics.optics↗

arXiv2005

Singularity dynamics: Action and Reaction

The interaction between singular and regular fields is considered for Lorentz-invariant scalar and vector wave equations. The singular field is generated by a Dirac source term. Its dynamics are deduced from the total field Lagrangian. At non-relativistic speeds, the resulting equations of motion are those of a mass in a scalar potential. Using this method we deduce the relationship between source amplitude (scalar gravitational mass) and dynamic mass (inertial mass). Generalising this method implies Lorentz forces for charge singularities in the electromagnetic field and describes the dynamics and interaction of hypothetical magnetic monopoles.

physics.class-ph↗