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[IEEE 2018 Iranian Conference on Electrical Engineering (ICEE) - Mashhad (2018.5.8-2018.5.10)] Electrical Engineering (ICEE), Iranian Conference on - The Proposal of New Fano Structure for Optical Switching Applications
摘要： In this paper, an improved Fano device for optical switching purposes is designed. Proposed structure has better transmission characteristics in terms of quality factor, loss and switching contrast than previous structures announced in the literature. Results show that the Q contrast of the cavities leads to the better performance of the Fano switch.
关键词： Optical Communications,Photonic Crystal,All optical switching,Fano shape spectrume,Fano Structure
更新于2025-09-23 15:22:29
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Micromagnetic Modeling of All-Optical Switching
摘要： The control of the magnetization at the microscale by pure optical means is fundamentally interesting and promises faster speeds for data storage devices. Although several experiments have shown that it is possible to locally reverse the magnetization of a ferromagnetic system by means of laser pulses, a completely theoretical description of these all-optical switching (AOS) processes is still lacking. Here, we develop an advanced micromagnetic solver that is applied to the numerical study of the AOS. The solver is based on the Landau–Lifshitz–Bloch equation that governs the dynamics of the magnetization coupled the microscopic three-temperature model, which describes the temporal evolution of the temperatures of the subsystems as caused by laser heating. The helicity-dependent magnetization switching is evaluated by a magnetooptical effective field caused by the inverse Faraday effect when a circularly polarized laser is applied to the sample. All the other usual terms of a full micromagnetic model are included (exchange, anisotropy, and Dzyaloshinskii–Moriya interaction). As a test, the model is used to describe the local magnetization switching of thin-film samples with high perpendicular anisotropy. The results are in a good agreement with available experimental observations.
关键词： Landau–Lifshitz–Bloch (LLB) equation,three temperatures model (3TM),inverse Faraday effect (IFE),micromagnetism,All-optical switching (AOS)
更新于2025-09-23 15:22:29
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Broadly Tunable Plasmons in Doped Oxide Nanoparticles for Ultrafast and Broadband Mid-Infrared All-Optical Switching
摘要： Plasmons in conducting nanostructures offer the means to efficiently manipulate light at the nanoscale with subpicosecond speed in an all-optical operation fashion, thus allowing for constructing high performance all-optical signal-processing devices. Here, by exploiting the ultrafast nonlinear optical properties of broadly tunable mid-infrared (MIR) plasmons in solution-processed, degenerately doped oxide nanoparticles, we demonstrate ultrafast all-optical switching in the MIR region, which features with subpicosecond response speed (with recovery time constant of ?400 fs) as well as ultrabroadband response spectral range (covering 3.0-5.0 μm). Furthermore, with the degenerately doped nanoparticles as Q-switch, pulsed fiber lasers covering 2.0-3.5 μm were constructed, of which a watt-level fiber laser at 3.0 μm band show superior overall performance among ever-reported passively Q-switched fiber lasers at the same band. Notably, the degenerately doped nanoparticles show great potential to work in the spectral range over 3.0 μm that is beyond the accessibility of commercially available but expensive semiconducting saturable absorber mirror (SESAM). Our work demonstrates a versatile while cost-effective material solution to ultrafast photonics in the technologically important MIR region.
关键词： tunable plasmons,ultrafast photonics,all-optical switching,doped oxide nanoparticles,mid-infrared
更新于2025-09-23 15:21:21
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Externally controlled Lotka-Volterra dynamics in a linearly polarized polariton fluid
摘要： Spontaneous formation of transverse patterns is ubiquitous in nonlinear dynamical systems of all kinds. An aspect of particular interest is the active control of such patterns. In nonlinear optical systems this can be used for all-optical switching with transistorlike performance, for example, realized with polaritons in a planar quantum-well semiconductor microcavity. Here we focus on a specific configuration which takes advantage of the intricate polarization dependencies in the interacting optically driven polariton system. Besides detailed numerical simulations of the coupled light-field exciton dynamics, in the present paper we focus on the derivation of a simplified population competition model giving detailed insight into the underlying mechanisms from a nonlinear dynamical systems perspective. We show that such a model takes the form of a generalized Lotka-Volterra system for two competing populations explicitly including a source term that enables external control. We present a comprehensive analysis of both the existence and stability of stationary states in the parameter space spanned by spatial anisotropy and external control strength. We also construct phase boundaries in nontrivial regions and characterize emerging bifurcations. The population competition model reproduces all key features of the switching observed in full numerical simulations of the rather complex semiconductor system and at the same time is simple enough for a fully analytical understanding.
关键词： all-optical switching,population competition model,nonlinear optical systems,transverse patterns,Lotka-Volterra system,polaritons,semiconductor microcavity
更新于2025-09-23 15:19:57
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Ultrafast Magnetization Reversal in DyFeCo Thin Film by Single Femtosecond Laser Pulse
摘要： The possibility of the local all-optical magnetization reversal in a thin ferrimagnetic rare-earth—transition metal film (DeFeCo) by linearly and circularly polarized 35 fs laser pulses is demonstrated experimentally. Conditions of the exposure to unit pulse and pulse sequence without an applied external magnetic field are used. The found peculiarities of switching in DyFeCo differ substantially from the results obtained previously for rare-earth—transition metal alloys. The minimum nominal fluence for the magnetization reversal is 3 mJ/cm2.
关键词： femtosecond laser,all-optical switching,antiferromagnets
更新于2025-09-16 10:30:52
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All-Optical Switching Based on the Plasma Channel Induced by Laser Pulses
摘要： We display a theoretical and experimental study of all-optical switching for signal lasers based on the plasma channel induced by the control laser. Using the plasma channel generated in the carbon disulfide (CS2) solution, the signal light can be modulated as some spatial distributions including unchanging, ring-shaped beam, and other intensity profiles. The modulation on the signal light can be conveniently adjusted by changing the control light’s incident intensity distribution. We can infer the dark spot shape in the modulated signal laser through the intensity profile of control laser beam. These results provide the great potential of plasma channel induced by lasers as an all-optical switching for various optoelectronic applications.
关键词： all-optical switching,plasma channel,spatial modulation,optoelectronic applications,laser pulses
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Ultrafast All-Optical Switching in III-V Semiconductor Resonant Nanostructures
摘要： All-dielectric high-index resonant nanostructures offer plentiful opportunities for tailoring characteristics of scattered radiation. In fact, the low level of ohmic losses at optical frequencies and the presence of pronounced magneto-dipolar modes in scattering spectra of dielectric nanoresonators pave the way to numerous scattering effects that could be employed for many practical applications [1]. To further advance the performance of dielectric nanophotonic devices, it is crucial to make them reconfigurable, i.e. to provide a method to manipulate optical properties of the material that they are made of. The electron-hole injection, carried out by optical means, is a promising solution for this task (Fig. 1A). Direct-gap semiconductors are perfectly suitable for that purpose, because this class of materials retains advantages typical for dielectrics and, at the same time, is defined by smaller bandgap widths, compared to dielectrics. The latter feature significantly decreases a value of the pumping pulse fluence that is required to noticeably change the optical response of a resonant nanostructure. Indeed, it was numerically shown that the change of the trajectory of the probing pulse constituted 20° for an asymmetric dimer comprised of two silicon (Si) spheres of different radii for the energy fluence of the pumping pulse Φ(cid:3020)(cid:3036) = 1.6 mJ cm(cid:2879)(cid:2870) [2]. On the other hand, there is an experimental study of all-optical switching in gallium arsenide (GaAs) metasurface that indicated the change of its reflection coefficient ?(cid:1844) = 0.35 for the fluence Φ(cid:3008)(cid:3028)(cid:3002)(cid:3046) = 0.31 mJ cm(cid:2879)(cid:2870) [3]. Although there are already some numerical results on the light scattering in the asymmetric dimer, it is still urgent to carry out the corresponding experiment. For that purpose, it is important to change the geometry of the system (cylinders instead of spheres) and its material (GaAs in place of Si). The system has an asymmetric scattering profile in the regular regime owing to its asymmetric geometry. The geometry also stipulates the difference in absorption cross-sections of the cylindrical resonators. Because of this difference in absorption, the change of the material’s optical parameters is not equal for the two cylinders. Therefore, under certain conditions, after the pumping of the nanostructure, the scattering diagram becomes symmetric. Our numeric results demonstrate the symmetrization of the indicatrix for the pumping fluence Φ(cid:2869) = 0.9 mJ cm(cid:2879)(cid:2870) (the corresponding change of the probe scattering direction was calculated to be 7°) for the dimer with following geometrical parameters: radii – 85 nm and 90 nm, height – 200 nm, distance between the centers of the disks – 450 nm. The central wavelength of the pulse spectrum was (cid:2019)(cid:2869) = 820 nm. The dimer nanoantenna is an ultrafast optical switch that can be used, for instance, to distribute optical signals between two waveguides in integrated photonic circuits. The design of the switch makes its fabrication compatible with modern technological methods. The all-optical modulation can be observed not only in single asymmetric nanoantennas, but also in phased-array metasurfaces composed of supercells with resonators of the different size. In particular, we considered a metasurface that could control the intensities (i.e. transmission coefficients) in the diffraction orders that are formed after the scattering on the nanostructure. In our experiments, the most pronounced relative change of the transmission coefficient was detected in the first order: ?(cid:1846) (cid:1846) = 9.7% for the fluence of the pumping pulse Φ(cid:2870) = 0.02 mJ cm(cid:2879)(cid:2870) (Fig. 2B). The metasurfaces of that kind can also be used as all-optical switches.
关键词： ultrafast optics,resonant nanostructures,III-V semiconductor,all-optical switching
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Optical Switching in Microresonators using the Kerr Nonreciprocity
摘要： Photonic circuits are spreading as a viable alternative to conventional electronic circuits. Electro-optic modulators (EOMs) are currently used as switches in telecommunications thanks to their simplicity and speed, however they are driven electrically. Several approaches have been demonstrated to realise all-optical switches such as ring lasers in which the lasing direction is controlled by an input seed, however these devices still require additional electrical or optical pumping. An alternative approach is to exploit the change in resonant frequency of nonlinear resonators with the input power. This has been successfully demonstrated in semiconductor resonators, where the nonlinearity is provided by the carrier generation from two-photon absorption, and in dielectric resonators governed by the Kerr effect. However, this approach needs the input to be in a narrow range of power and detuning from the cavity resonance and is adversely affected by the cavity’s thermal drift due to the high circulating powers. We demonstrate a device that works in a different regime of the Kerr effect. In our case the bistability arises from the twofold contribution of the cross-phase modulation with respect to the self-phase modulation to the refractive index change, Δni ∝ n2(Ii + 2 I j), where i, j are the two possible directions [1,2]. As a consequence, above a threshold power, Pth, light of a given frequency can circulate in just one direction inside the resonator and the switching between the two corresponding states exhibits hysteresis. This regime can be accessed in a much broader range of input powers, from Pth to ～ 5Pth, and the frequency of the laser can drift by up to about 10 GHz thanks to thermal locking [3].
关键词： Kerr nonreciprocity,microresonators,photonic circuits,all-optical switching
更新于2025-09-12 10:27:22
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Theoretical Design of a Pump-Free Ultrahigh Efficiency All-Optical Switching Based on a Defect Ring Optical Waveguide Network
摘要： A theoretical design of a defect ring optical waveguide network is proposed to construct a pump-free ultrahigh efficiency all-optical switch. This switch creates ultrastrong photonic localization and causes the nonlinear dielectric in the defect waveguide to intensely respond. At its ON state, this material defect without Kerr response helps to produce a pair of sharp pass bands in the transmission spectrum to form the dual channel of the all-optical switch. When it is switched to its OFF state, the strong Kerr response induced refractive index change in the high nonlinear defect waveguide strongly alters the spectrum, leading to a collapse of the dual channels. Network equation and generalized eigenfunction method are used to numerically calculate the optical properties of the switch and obtain a threshold control energy of about 2.90 zJ, which is eight orders of magnitude lower than previously reported. The switching efficiency/transmission ratio exceeds 3×1011, which is six orders of magnitude larger than previously reported. The state transition time is nearly 108 fs, which is approximately two orders of magnitude faster than the previously reported shortest time. Furthermore, the switch size can be much smaller than 2.6 μm and will be suitable for integration.
关键词： ultrafast optics,pump-free,all-optical switching,ultrahigh efficiency,nonlinear optics,waveguide network
更新于2025-09-11 14:15:04
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Sub-20 fs All-Optical Switching in a Single Au-Clad Si Nanodisk
摘要： Dielectric nanoantennas have recently emerged as promising elements for nonlinear and ultrafast nanophotonics due to their ability to concentrate light on the nanometer scale with low losses, while exhibiting large nonlinear susceptibilities. In this work, we demonstrate that single Si nanodisks covered with a thin 30-nm thick layer of Au can generate positive and negative sub-20 fs reflectivity modulations of ?0.3% in the vicinity of the first-order anapole mode, when excited around the second-order anapole mode. The experimental results, characterized in the visible to near infrared spectral range, suggest that the nonlinear optical Kerr effect is the responsible mechanism for the observed all-optical switching phenomena. These findings represent an important step toward nanoscale ultrafast all-optical signal processing.
关键词： anapole modes,optical Kerr effect,ultrafast all-optical switching,pump-probe spectroscopy,Dielectric nanoantennas
更新于2025-09-10 09:29:36