arXiv subjects

Miguel Levy

Publications and source records attributed to Miguel Levy.

31 records · Page 2Linked to original sources

arXiv2020

Crossed two Higgs-doublet models: reduction of Yukawa parameters in the low-scale limit of left-right symmetry and other avatars

We present new variants of the Two Higgs-Doublet Model where all Yukawa couplings with physical Higgs bosons are controlled by the quark mixing matrices of both chiralities, as well as, in one case, the ratio between the two scalar doublets' vacuum expectation values. We obtain these by imposing approximate symmetries on the Lagrangian which, in one of the cases, clearly reveals the model to be the electroweak remnant of the Minimal Left-Right Symmetric Model. We also argue for the benefits of the bidoublet notation in the Two Higgs-Doublet Model context for uncovering new models.

hep-ph↗

arXiv2019

Effective alignments and the landscape of $S_4$ flavour models

We explore the concept of effective alignments: contractions of multiple flavour symmetry breaking flavon fields. These contractions give rise to directions that are hard or impossible to obtain directly by breaking the flavour symmetry. Within this context, and using $S_4$ as the flavour symmetry to exemplify, we perform a phenomenological check of lepton flavour models built from pairing any two effective alignments up to order 2 (in flavon contractions). The check is performed for each pair of effective alignments in a framework with models of constrained sequential dominance type, in a basis where the charged leptons are diagonal. We thus obtain an indication of which effective alignments are interesting for model building, within this so-called $S_4$ landscape. We find three types of viable topologies and provide examples of models realizing this strategy for each topology.

hep-ph↗

arXiv2019

Faraday-Rotation in Iron Garnet Films Beyond Elemental Substitutions

In previous decades significant efforts have been devoted to increasing the magneto-optical efficiency of iron garnet materials for the miniaturization of nonreciprocal devices such as isolators and circulators. Elemental substitutions or proper nano-structuring to benefit from optical resonances have been pursued. However, all these approaches still require film thicknesses of at least several tens of microns to deliver useful device applications, and suffer from narrow bandwidths in the case of optical resonance effects. This Letter reports on a newly discovered enhancement of the Faraday Effect observed experimentally in nanoscale bismuth-substituted iron garnet films. It is shown here that this enhancement is not due to elemental substitution or compositional variations. Nor is it due to photon trapping or resonance effects. Comprehensive experimental and theoretical analysis of the Faraday rotation reveals a dramatic seven-fold amplification in the magneto-optic gyrotropy within only 2 nm of the air-surface interface, corresponding to just a couple of atomic monolayers as a result of symmetry-breaking at the air-film interface. This finding opens up an avenue to the application of monolayer magnetic garnets for the control of light.

physics.optics↗

arXiv2016

Nonreciprocal Transverse Photonic Spin and Magnetization-Induced Electromagnetic Spin-Orbit Coupling

A study of nonreciprocal transverse-spin angular-momentum-density shifts for evanescent waves in magneto-optic waveguide media is presented. Their functional relation to electromagnetic spin- and orbital-momenta is presented and analyzed. It is shown that the magneto-optic gyrotropy can be re-interpreted as the nonreciprocal electromagnetic spin-density shift per unit energy flux, thus providing an interesting alternative physical picture for the magneto-optic gyrotropy. The transverse spin-density shift is found to be thickness-dependent in slab optical waveguides. This dependence is traceable to the admixture of minority helicity components in the transverse spin angular momentum. It is also shown that the transverse spin is magnetically tunable. A formulation of electromagnetic spin-orbit coupling in magneto-optic media is presented, and an alternative source of spin-orbit coupling to non-paraxial optics vortices is proposed. It is shown that magnetization-induced electromagnetic spin-orbit coupling is possible, and that it leads to spin to orbital angular momentum conversion in magneto-optic media evanescent waves.

physics.optics↗

arXiv2015

Magneto-optical metamaterial

We propose a new class of metamaterials called magneto-optical metamaterials that offer enhanced angle of rotation in polarization compared to bulk magneto-optical materials. In the proposed approach, the permittivity tensor of a magneto-optical material is tailored by embedded wire meshes behaving as artificial plasma. We have shown that the angle of rotation in the magneto-optical metamaterial can be enhanced up to 9 times compared to bulk magneto-optical material alone while the polarization extinction ratio remains below -20dB and insertion loss is less than 1.5dB.

physics.optics↗

arXiv2013

On-chip non-reciprocal optical devices based on quantum inspired photonic lattices

We propose a novel geometry for integrated photonic devices that can be used as isolators and polarization splitters based on engineered photonic lattices. Starting from optical waveguide arrays that mimic Fock space representation of a non-interacting two-site Bose Hubbard Hamiltonian, we show that introducing magneto-optic nonreciprocity to these structures leads to a superior optical isolation performance. In the forward propagation direction, an input TM polarized beam experiences a perfect state transfer between the input and output waveguide channels while surface Bloch oscillations block the backward transmission between the same ports. Our analysis indicates a large isolation ratio of 75 dB after a propagation distance of 8 mm inside seven coupled waveguides. Moreover, we demonstrate that, a judicious choice of the nonreciprocity in this same geometry can lead to perfect polarization splitting.

physics.optics↗

arXiv2010

Nonreciprocal Bloch Oscillations in Magneto-Optic Waveguide Arrays

We show that nonreciprocal optical Bloch-like oscillations can emerge in transversely magnetized waveguide arrays in the presence of an effective index step between the waveguides. Normal modes of the system are shown to acquire different wavenumbers in opposite propagation directions. Significant differences in phase coherence and decoherence between these normal modes are presented and discussed. Non-reciprocity is established by imposing unequal vertical refractive index gradients at the substrate/core, and core/cover interfaces in the presence of transverse magnetization.

physics.optics↗

arXiv2008

Gyrotropic Bandgaps, Degeneracy Lifting and Selective Suppression of Bloch States in Photonic Systems

Birefringent magnetophotonic crystals are found to exhibit degeneracy breaking for asymmetric contradirectional coupling in planar waveguides. Fundamental to high-order local normal mode coupling leads to partially overlapping gyrotropic bandgaps inside the Brillouin zone and partial suppression of Bloch mode propagation. A large magneto-optically active reorientation in polarization state is found for allowed Bloch modes at bandgap edges.

physics.optics↗

arXiv2007

Local Normal Mode Coupling and Energy Band Splitting in Elliptically Birefringent 1D Magnetophotonic Crystals

An analysis is presented of wave-vector dispersion in elliptically birefringent stratified magneto-optic media having one-dimensional periodicity. It is found that local normal-mode polarization-state differences between adjacent layers lead to mode coupling and impact the wave-vector dispersion and the character of the Bloch states of the system. This coupling produces extra terms in the dispersion relation not present in uniform circularly birefringent magneto-optic stratified media. Normal mode coupling lifts the degeneracy at frequency band cross-over points under certain conditions and induces a magnetization-dependent optical band gap. This study examines the conditions for band gap formation in the system. It shows that such a frequency-split can be characterized by a simple coupling parameter that depends on the relation between polarization states of local normal modes in adjacent layers. The character of the Bloch states and conditions for maximizing the strength of the band splitting in these systems are analyzed.

physics.optics↗

arXiv2007

Normal mode coupling and Bloch states in elliptically birefringent 1D photonic crystals

An analysis is presented of frequency versus wave-vector dispersion in elliptically birefringent one-dimensional layered periodic structures. The presence of local normal mode polarization state variations from one layer to the next is found to lead to mode coupling and to affect the wave-vector dispersion and the character of the Bloch states of the system.

physics.optics↗

arXiv2007

Band structure and Bloch states in birefringent 1D magnetophotonic crystals: An analytical approach

An analytical formulation for the band structure and Bloch modes in elliptically birefringent magnetophotonic crystals is presented. The model incorporates both the effects of gyrotropy and linear birefringence generally present in magneto-optic thin film devices. Full analytical expressions are obtained for the dispersion relation and Bloch modes in a layered stack photonic crystal and their properties are analyzed. It is shown that other models recently discussed in the literature are contained as special limiting cases of the formulation presented herein.

physics.optics↗

arXiv2006

Band Edge Effects and Normal Mode Propagation in Waveguide Magnetophotonic Crystals

A study of band edge phenomena in ridge waveguide magnetophotonic crystals is presented. Normal mode analysis is used to examine the near-band edge and Bragg center-wavelength group velocities and their relation to the polarization. Large polarization departures from the input are observed in Bragg gratings patterned by focused-ion-beam milling on liquid-phase-epitaxial (LPE) BiLuIG films on (111) gadolinium gallium garnet (GGG) substrates. Transfer matrix analysis of the spectral response in the photonic crystals allows the determination of the phase of the elliptically polarized normal modes from measured transmittances and polarization rotation. Unlike non-birefringent Faraday rotators a non-linear-relation exists between polarization rotation and the normal mode phase difference. Large phase differences between right- and left-elliptically polarized normal modes and optical slow-down are found near the band edges and at the resonant cavity center-wavelength. Standing-wave photon trapping and optical slow-down are analyzed and compared for these systems.

physics.optics↗

arXiv2006

Polarization rotation enhancement by high-order waveguide mode coupling in magnetophotonic crystals

Inter-modal coupling in photonic bandgap optical channels in magnetic films is used to leverage the transverse-electric (TE) to transverse-magnetic (TM) mode conversion due to the Faraday Effect. The underlying mechanism is traced to the dependence of the grating coupling-constant on the modal refractive index and the mode profile of the propagating beam, a feature that arises in waveguide propagation and is not present in normal-incidence stack magnetophotonic crystals. Large changes in polarization near the band edges are observed in first and second orders as a result of the photonic bandgap structure. Extreme sensitivity to linear birefringence exists in second order.

physics.optics↗