Non-Hermitian systems have recently attracted broad interest and exhibited intriguing physical phenomena, including the non-Hermitian skin effect, which have been widely studied in various fermionic and bosonic system...
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We present a wide class of novel solitary and periodic waves in a non-centrosymmetric waveguide exhibiting second-and third-order nonlinearities. We show the existence of bright, gray, and Wshaped solitary waves as we...
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This article aims to present a general study of the Helmholtz problem in slowly varying waveguides. This work is of particular interest at locally resonant fre- quencies, where a phenomenon close to the tunnel effect ...
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In this work, we prove a theorem that states the electromagnetic (EM) duality correspondence between eigenmodes of complementary structures, induces counterpropagating spin-polarized states in different types of waveg...
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This article aims to present a general study of the Helmholtz problem in slowly varying waveguides. This work is of particular interest at locally resonant frequencies, where a phenomenon close to the tunnel effect fo...
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Curvature-induced effects allow us to tailor the static and dynamic response of a magnetic system with a high degree of freedom. We study corrugated magnonic waveguides deposited on a sinusoidally modulated substrate ...
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Curvature-induced effects allow us to tailor the static and dynamic response of a magnetic system with a high degree of freedom. We study corrugated magnonic waveguides deposited on a sinusoidally modulated substrate prepared by focused electron beam-induced deposition. The curvature of the waveguides with thicknesses comparable to the amplitude of modulation modifies the contributions of dipolar and exchange energies and results in an effective anisotropy term, which is strong enough to overcome the shape anisotropy. At zero external magnetic field, the magnetization of the waveguide then points perpendicular to its long axis in a geometry, which is best-suited to spin-wave propagation. We show, by Brillouin light scattering microscopy, that without the presence of the external magnetic field, spin waves propagate over a distance 10xlarger in the corrugated waveguide than in the planar waveguide. We further analyze the influence of the modulation amplitude on the spin-wave propagation length and conclude that for moderate modulation amplitudes, the spin-wave decay length is not affected. For larger amplitudes, the decay length decreases linearly with increasing modulation. The presented approach opens many possibilities for the design of complex 2D magnonic circuits where the waveguides can be oriented in any direction and placed anywhere on the sample while still allowing spin-wave propagation with the same efficiency.
The increasing number of solution-processed laser compounds that can be implemented as low-cost, flexible, and/or integrated devices, makes necessary the development of reliable methods to delineate all their amplifyi...
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The increasing number of solution-processed laser compounds that can be implemented as low-cost, flexible, and/or integrated devices, makes necessary the development of reliable methods to delineate all their amplifying signatures and thus to open the door to appropriate cross-sample comparisons. Seeking to solve this problem, a new formalism to retrieve the losses and the optical gains from Amplified Spontaneous Emission (ASE) spectra as a function of the excitation density has been recently reported. In this manuscript, we explore the potential of this methodology to unveil relevant information on the photonic properties of the waveguiding devices and on the photophysics of the active materials. We demonstrate that the Variable Pump Intensity method opens the door to understand the relationship between the ASE thresholds and the optical gains and losses, it enables the extraction of the scattering/modal losses of the passive devices, and it can unveil the presence of leaky-modes and excited state absorption. In contrast, it does not perform too well in samples with multiple active species in its current implementation. We have substantiated all these findings using organic semiconductor thin films, several dye-doped polymer thin films and solutions of boron hydride.
Strong acousto-optic interaction in high-index waveguides and cavities generally requires the releasing of the high-index core to avoid mechanical leakage into the underlying low-index substrate. This complicates fabr...
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Strong acousto-optic interaction in high-index waveguides and cavities generally requires the releasing of the high-index core to avoid mechanical leakage into the underlying low-index substrate. This complicates fabrication, limits thermalization, reduces the mechanical robustness, and hinders large-area optomechanical devices on a single chip. Here, we overcome this limitation by employing vertical photonic-phononic engineering to drastically reduce mechanical leakage into the cladding by adding a pedestal with specific properties between the core and the cladding. We apply this concept to a silicon-based platform, due to the remarkable properties of silicon to enhance optomechanical interactions and the technological relevance of silicon devices in multiple applications. Specifically, the insertion of a thick silicon nitride layer between the silicon guiding core and the silica substrate contributes to reducing gigahertz-frequency phonon leakage while enabling large values of the Brillouin gain in an unreleased platform. We numerically obtain values of the Brillouin gain around 300(W m)−1 for different configurations, which could be further increased by operation at cryogenic temperatures. These values should enable Brillouin-related phenomena in centimeter-scale waveguides or in more compact ring resonators. Our findings could pave the way toward large-area unreleased-cavity and waveguide optomechanics on silicon and other high-index photonic technologies.
The importance of transmission, guiding and delivery of electromagnetic waves to the targeted part of a photonic circuit, leads to design couplers with high coupling efficiency. In the present work, we apply two types...
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The importance of transmission, guiding and delivery of electromagnetic waves to the targeted part of a photonic circuit, leads to design couplers with high coupling efficiency. In the present work, we apply two types of photonic crystal-based flat lenses for designing the couplers. The lenses are made of annular 2 rods with a triangular structure embedded in air. To design the lenses, the outer radius of the annular cylinders is kept constant while the inner radius follows two linear and parabolic functions. At the next step, the lenses are placed along a slot waveguide, conventional photonic crystal waveguide and funnel-form photonic crystal waveguide, separately, for creating coupled structures. The incident light is focussed by the graded index flat lenses and transmits through the waveguides. In the following, we study the coupling efficiency of all mentioned structures, using finite-difference time-domain and plane wave expansion methods. The results reveal that the coupled funnel-form waveguide with the linear lens gives the highest coupling efficiency, which is 7.49 and shows great improvement compared to the previous works.
We experimentally demonstrate the observation of a frequency-shift dynamics at a temporal boundary in the terahertz (THz) region relying on a scheme that controls the structural dispersion of a metal-semiconductor wav...
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We experimentally demonstrate the observation of a frequency-shift dynamics at a temporal boundary in the terahertz (THz) region relying on a scheme that controls the structural dispersion of a metal-semiconductor waveguide. Ultrafast structural-dispersion switching is achieved within a subpicosecond timescale by illuminating a waveguide surface with an optical pump pulse during the propagation of a THz pulse in the waveguide. Owing to the relatively high conversion efficiency, up to 23%, under the condition that the frequency shift is sufficiently larger than the bandwidth of the incident pulse, the rapid variation of the THz frequency around the temporal boundary is directly observed in the time domain.
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