A non-Hermitian coupled waveguide system with periodically varying parameters, in which the Berry curvature is analogous to a hyperbolic magnetic monopole or antimonopole, is investigated. It is shown to have a purely...
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A non-Hermitian coupled waveguide system with periodically varying parameters, in which the Berry curvature is analogous to a hyperbolic magnetic monopole or antimonopole, is investigated. It is shown to have a purely imaginary Berry connection and is consequently influenced by a geometric multiplier. It is possible for this multiplier to induce net gain or loss in the system, corresponding to the existence of the antimonopole or monopole in parameter space, respectively. For the right choice of parameters, the system will display an apparent nonadiabatic change in behavior, which implies a switch between the dominant eigenstate in the waveguides, leading to a change in parameter space analogous to a charge reversal of the hyperbolic magnetic monopole.
A numerical approach to calculate the power transfer between nanoscale waveguides was proposed. Series of complex power-transfer simulations have been performed when comparing two adjacent waveguides made of different...
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A numerical approach to calculate the power transfer between nanoscale waveguides was proposed. Series of complex power-transfer simulations have been performed when comparing two adjacent waveguides made of different materials. The results showed interesting focusing phenomena when coupling a waveguide sharing a high power confinement factor to a waveguide sharing a low one. In addition, we describe the physical properties of a nanoscale integrable waveguide for smooth integration in the microelectronics industry and analyze two case studies regarding such a possible integration. It seems that due to the lack of ability to confine the mode inside a nanoscale dimensions waveguide, combining waveguides with current size transistor may be, at this stage, difficult to realize without specific fits of the whole module. (C) 2020 Society of Photo-Optical Instrumentation Engineers (SPIE)
Compact chip-scale comb sources are of significant interest for many practical applications. Here, we experimentally study the generation of supercontinuum (SC) in an axially varying integrated waveguide. We show that...
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Compact chip-scale comb sources are of significant interest for many practical applications. Here, we experimentally study the generation of supercontinuum (SC) in an axially varying integrated waveguide. We show that the local tuning of the dispersion enables the continuous blue shift of dispersive waves by more than 200 nm due to their trapping by the strongly compressed pump pulse. This mechanism provides an insight into supercontinuum generation in varying-dispersion integrated waveguides. Pumped close to 2.2 μm in the femtosecond regime and at a pulse energy of approximately 4 pJ, the output spectrum extends from 1.1 μm up to 2.76 μm and shows good coherence properties. Octave-spanning SC is also observed at an input energy as low as approximately 0.9 pJ. We show that the supercontinuum is more robust against variations of the input-pulse parameters and is also spectrally flatter in waveguides with an optimized dispersion profile than in dispersion-engineered ones. This research demonstrates the potential of varying-dispersion waveguides for coherent SC generation and paves the way for integrated low-power applications, such as chip-scale frequency-comb generation, precision spectroscopy, optical-frequency metrology, and wide-band wavelength division multiplexing in the near infrared.
Exceptional points (EPs) in photonics are associated with non-Hermitian Hamiltonians with energy gain or loss, a notable example is EPs in parity-time symmetric Hamiltonians. We show that, counterintuitively, actual e...
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Exceptional points (EPs) in photonics are associated with non-Hermitian Hamiltonians with energy gain or loss, a notable example is EPs in parity-time symmetric Hamiltonians. We show that, counterintuitively, actual energy gain or loss is not required to generate this type of non-Hermitian degeneracy, since the eigenvalue of the optical Hamiltonian is the mode's propagation constant and not the energy. This is demonstrated by a simple three-layer insulator-metal-insulator (I-M-I) plasmonic waveguide, the eigenmodes of which are known to experience degeneracy at a certain point in the parametric space suggested to be used for rainbow trapping. We identify this point to be, in fact, an EP with the coalescence of the eigenmodes, despite the system having neither parity nor time symmetry. Furthermore, we demonstrate the manifestation of a third-order EP, which is generated by merging two separate EPs in the parametric space of the I-M-I waveguide. The presented results reveal unconventional properties of the Hamiltonian of a simple plasmonic waveguide and provide an insight into the nature of EPs in non-Hermitian plasmonic systems in general, suggesting the possibility of accessing even higher-order EP regimes in simple photonic structures without the need for optical gain or loss.
In this paper, we introduce the fractal geometry into the spoof surface plasmon polariton (SSPP) waveguide and splitter design. We propose a novel SSPP waveguide consisting of periodic corrugated Greek-cross fractal u...
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In this paper, we introduce the fractal geometry into the spoof surface plasmon polariton (SSPP) waveguide and splitter design. We propose a novel SSPP waveguide consisting of periodic corrugated Greek-cross fractal units (GCFUs) connected to a microstrip line. The generation process of periodic corrugated GCFUs is described and the dispersion characteristics are studied. We find we can engineer the property of the waveguide at will by tuning the parameters of the GCFU. To validate the proposed design, a wideband lowpass filter based on double-sided DCFUs with ultra-sharp roll-offs is fabricated and tested. Based on this waveguide concept, we design a wideband Y-splitter including an SSPP waveguide with double-sided GCFUs and two SSPP waveguide branches with single-sided GCFUs. To improve isolations and reduce the reflections between output ports of the Y-splitter, a 100 omega resistor is loaded in the middle of two symmetrical branches to construct Wilkinson splitter to equally and efficiently split the energy of the SSPPs into two parts. The simulated and measured results show that the SSPP splitter possesses excellent performance in a passband of 1.5-4.0 GHz with low insertion loss (S21, S31 > -4 dB), high reflection loss (S11, S22, S33 < -10 dB), and high isolation (S32 < -10 dB). This work may open up a new door for the development of various plasmonic integrated functional devices.
Dyakonov surface waves are an example of surface electromagnetic waves propagating along a plane interface between isotropic and anisotropic dielectric media. Here we investigate the spectrum and radiative losses of D...
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Dyakonov surface waves are an example of surface electromagnetic waves propagating along a plane interface between isotropic and anisotropic dielectric media. Here we investigate the spectrum and radiative losses of Dyakonov waves at the curved interface considering both cases of “positive” and “negative” curvature of anisotropic medium. We demonstrate how Dyakonov waves at a plane interface continuously transform to the leaky or guided modes of an anisotropic cylindrical waveguide and derive asymptotic equation for radiative losses. All analytical results are confirmed by solving the exact dispersion equation numerically. We believe that our work extends the potential practical application of Dyakonov surface waves at a curved interfaces, e.g., anisotropic cylindrical waveguides, in optics and photonics devices.
The generation of Amplified Spontaneous Emission (ASE) is routinely used to assess the performance of active materials prior to developing thin film lasers. The Variable Stripe Length method has been profusely used fo...
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The generation of Amplified Spontaneous Emission (ASE) is routinely used to assess the performance of active materials prior to developing thin film lasers. The Variable Stripe Length method has been profusely used for decades to measure the optical gain in these materials and devices, but experimental and theoretical evidences cast doubts upon its reliability. With the advent of an ever increasing number of solution-processed laser compounds that can be implemented as low-cost, flexible, and/or integrated devices, there is now more than ever a need to develop an alternative and trustful method to delineate all their amplifying signatures. Herein, a new formalism to fully characterize the ASE properties, based on the most frequent Variable Pump Intensity method, is reported. An analytical expression taking into account the most relevant spatiotemporal and photophysical effects has been found that can be fitted to ASE spectra. This expression allows retrieving, from a single ASE experiment, the spectrally resolved losses coefficient and net optical gains at all pump values, as well as to calculate, instead of visually finding, the ASE threshold. The reported formalism serves as a tool to categorize the best candidates for a given laser application through a reliable, robust, time-saver, and standardized methodology.
We employ complex index modulation to manipulate light scattering in a waveguide and achieve different kinds of singularities in the system. The singularities refer to poles or zeros in the scattering and transfer mat...
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We employ complex index modulation to manipulate light scattering in a waveguide and achieve different kinds of singularities in the system. The singularities refer to poles or zeros in the scattering and transfer matrices. By using spatially complex index modulation, we realize unidirectional zero-reflection singularities, which can be manipulated by adjusting the modulation phase difference between the real and imaginary parts. Laser-coherent perfect absorber singularities with both diverging reflectance and transmittance are also achieved by cascading two waveguides with different modulation phases. Meanwhile, bidirectional zero-reflection singularities with reflectionless light transporting on both sides of the waveguides are also demonstrated. In addition, we utilize temporally complex modulation to obtain transfer matrix singularities and achieve nonreciprocal light transmission. The study may find great applications in light amplification, attenuation, and absorption, as well as constructing nonreciprocal optical devices.
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