All-optical Plasmonic Switch Research Articles

Nanophotonic structure inverse design for switching application using deep learning

Switching functionality is pivotal in advancing communication systems, serving as a paramount mechanism. Despite numerous innovations in this field, optical switch design, fabrication, and characterization have traditionally followed an iterative approach. Within this paradigm, the designer formulates an informed conjecture regarding the switch's structural configuration and subsequently resolves Maxwell's equations to ascertain its performance. Conversely, the inverse problem, which entails deriving a switch geometry to achieve a targeted electromagnetic response, continues to pose formidable challenges and necessitates substantial time and effort, particularly under the constraints of specific assumptions. In this work, we propose a deep neural network-based method to approximate the spectral transmittance of all-optical switches. The findings substantiate the efficacy of deep learning in the design of all-optical plasmonic switches, which are renowned as the fastest switches at the nanoscale. The nonlinear Kerr effect in square resonators is leveraged to demonstrate the switching performance. Juxtaposed with conventional simulations, the proposed model showcases a remarkable improvement in computational efficiency. Furthermore, deep learning can resolve nanophotonic inverse design problems without reliance on trial-and-error or empirical strategies. Compared to simulations, the mean squared error for both forward and inverse models is meager, with values of around 0.03 and 0.02, respectively. The deep learning-proposed switches exhibit excellent suitability for integration into photonic integrated circuits, substantially influencing the progression of all-optical signal processing.

A deep learning method for empirical spectral prediction and inverse design of all-optical nonlinear plasmonic ring resonator switches

All-optical plasmonic switches (AOPSs) utilizing surface plasmon polaritons are well-suited for integration into photonic integrated circuits (PICs) and play a crucial role in advancing all-optical signal processing. The current AOPS design methods still rely on trial-and-error or empirical approaches. In contrast, recent deep learning (DL) advances have proven highly effective as computational tools, offering an alternative means to accelerate nanophotonics simulations. This paper proposes an innovative approach utilizing DL for spectrum prediction and inverse design of AOPS. The switches employ circular nonlinear plasmonic ring resonators (NPRRs) composed of interconnected metal–insulator–metal waveguides with a ring resonator. The NPRR switching performance is shown using the nonlinear Kerr effect. The forward model presented in this study demonstrates superior computational efficiency when compared to the finite-difference time-domain method. The model analyzes various structural parameters to predict transmission spectra with a distinctive dip. Inverse modeling enables the prediction of design parameters for desired transmission spectra. This model provides a rapid estimation of design parameters, offering a clear advantage over time-intensive conventional optimization approaches. The loss of prediction for both the forward and inverse models, when compared to simulations, is exceedingly low and on the order of 10−4. The results confirm the suitability of employing DL for forward and inverse design of AOPSs in PICs.

Ultra-compact all-optical plasmonic switch for three telecommunication windows using a nonlinear Kerr material and Fano resonance.

In this study, an all-optical plasmonic switch based on a metal-insulator-metal (MIM) waveguide coupled to two rectangular cavities that are perpendicularly connected to each other through a vertical stub is proposed and analyzed both theoretically and numerically. Rectangular cavities are filled with a nonlinear Kerr material, and the switching operation is achieved by applying a high-intensity pump input into the MIM waveguide to obtain nonlinear cross-phase modulation (XPM) effect. The proposed structure is designed so that it can realize the switching operation at each of the three telecommunication windows of 850, 1310, and 1550nm. Realizing the switching operation at these three wavelength bands is accomplished by the Fano resonance. In fact, the Fano resonance is utilized to create a band-stop area that is crucial for building a suitable OFF state for the switching operation at two of the three telecommunication windows of 1310 and 1550nm. The theoretical and numerical results are obtained using the transmission-line model (TLM) and the finite difference time domain (FDTD) method, respectively, the results of which comply well. The proposed ultra-compact all-optical switch has significant applications in photonic integrated circuits (PICs).

All-optical plasmonic switches based on Fano resonance in an X-shaped resonator coupled to parallel stubs for telecommunication applications

In this paper, all-optical plasmonic switches based on metal-insulator-metal (MIM) waveguide configurations are proposed. In these structures, a Kerr-type nonlinear material and Fano resonance are used to achieve all-optical switching. Firstly, it is shown that adding two stubs to a MIM waveguide creates a Fano resonance which can be used for switching applications (the first switch) and finally, it is shown that adding a cross-shaped resonator between the identical stubs can improve the switching performance (the second switch). In this work, the finite element method (FEM) is employed to numerically simulate the proposed structures. To validate the FEM simulation results, they are superimposed on the results obtained from the finite difference time domain (FDTD) method, for which a very good agreement is observed. According to our calculations, by applying an optical pump, while the transmission value for the first proposed switch varies from 0.53 to 0.03, this value changes from 0.60 to 0.02 for the second switch. The proposed all-optical switches have various advantages such as working at tele-communication optical wavelengths, having a compact size (390 nm × 675 nm), needing a lower pump intensity (which is approximately equal to 145 mW/μm2 for both switches), and a simple designing mechanism.

Plasmonic all-optical metal–insulator–metal switches based on silver nano-rods, comprehensive theoretical analysis and design guidelines

In this paper, all-optical plasmonic switches are proposed and analyzed. These structures consist of a rectangular resonator filled with a Kerr-type material (AuSiO2) which is coupled to isolated metal–insulator–metal plasmonic waveguides. The resonators contain periodic arrays of nano-rods with rectangular and triangular patterns. The horizontal and vertical waveguides are used for data and control signals, respectively. Using two separate paths for the data and control signals results in suitable isolation between the signals. The finite difference time domain (FDTD) method is used for numerical investigation of the designed structures. To provide more insight, the FDTD results of the building blocks of the switches are compared with transmission line method results. The most important benefits of the proposed topologies are requiring lower pump intensities, needing smaller footprints and having isolated data and control ports. The proposed switch needs a pump intensity equal to 193.2 mW/μm2 and requires a 0.593 μm2 footprint area. A 11.3 dB contrast ratio exists between the On and Off states of the switch. Based on the mentioned advantages, these switches have the potential to be used in complex integrated optical circuits.

Realization of a plasmonic optical switch using improved nano-disk resonators with Kerr-type nonlinearity: A theoretical and numerical study on challenges and solutions

In this paper, a novel all-optical plasmonic switch is presented. For the proposed structure, a nano-disk resonator coupled to parenthesis-shaped adjunctions and perpendicular metal–insulator–metal waveguides are used. The insulator which is used here, is an optically nonlinear Kerr-type material (InGaAsP). The data and control pulses are injected to the horizontal and vertical waveguides, respectively. Allocating two separate waveguides for the data and control signals prevents these signals from interfering with each other. One of the main benefits of the proposed switch is that a single wavelength can be used for the data and control signals. It prevents the amplitude modulation of the output signal and eliminates the need for harmonic suppression filters. The finite difference time domain (FDTD) method is used for numerical investigation of the switch. Based on the numerical simulations, the switch can operate for control pulses as narrow as 3 ps at 1028 nm. In addition to FDTD, analytical formulas have also been presented to model the switch, which are in excellent agreement with FDTD results. To provide a better perspective, besides the conventional frequency domain analysis, the time domain simulations are also presented. The main advantages of the proposed topology are: the ability to use an identical wavelength for data and control pulses (which originates from the novel resonator shape), having separate and isolated input and output data and control ports, requiring a small footprint area of 1.37μm2, the simplicity of fabrication due to its simple and symmetric structure and finally the robustness of the design, where other nonlinear materials with higher Kerr indices can also be easily used to redesign the switch.

All-Optical Plasmonic Switches Based on Asymmetric Directional Couplers Incorporating Bragg Gratings

In this paper, a novel technique for realization of all-optical plasmonic switches is presented. The proposed structure is based on an asymmetric metal-insulator-metal plasmonic directional coupler. A Bragg grating is used on one of the directional coupler’s adjacent waveguides while the other remains intact. Such a modification results in dissimilar input-output transmission spectrums for each of the two input ports. The Bragg grating creates a bandgap region in one of the signal paths while the other path has no bandgap. The directional coupler is filled with a dielectric with high Kerr-type nonlinearity. One of the input ports is used for the data signal and the other port for the control (pump) signal. When the pump signal is present, a small modification in the refractive index of the Kerr material occurs which slightly changes the bandgap region. The input signal’s wavelength is chosen at the bandgap edge so that it can only pass through the structure when the control signal is present. The structure proposed in this paper is numerically simulated using finite difference time domain method. Silver and Ag/BaO composite are used as the metal and dielectric materials. Since the proposed topology incorporates two different input ports for the control and data signals, it has the potential to be used in complex-integrated optical circuits.

Design and implementation of optical switches based on nonlinear plasmonic ring resonators: Circular, square and octagon

In this paper, all-optical plasmonic switches (AOPS) based on various configurations of circular, square and octagon nonlinear plasmonic ring resonators (NPRR) were proposed and numerically investigated. Each of these configurations consisted of two metal-insulator-metal (MIM) waveguides coupled to each other by a ring resonator (RR). Nonlinear Kerr effect was used to show switching performance of the proposed NPRR. The result showed that the octagon switch structure had lower threshold power and higher transmission ratio than square and circular switch structures. The octagon switch structure had a low threshold power equal to 7.77 MW/cm2 and the high transmission ratio of approximately 0.6. Therefore, the octagon switch structure was an appropriate candidate to be applied in optical integration circuits as an AOPS.

Ultra-fast all-optical plasmonic switching in near infra-red spectrum using a Kerr nonlinear ring resonator

In this paper, an all-optical plasmonic switch based on metal–insulator–metal (MIM) nanoplasmonic waveguide with a Kerr nonlinear ring resonator is introduced and studied. Two-dimensional simulations utilizing the finite-difference time-domain algorithm are used to demonstrate an apparent optical bistability and significant switching mechanisms (in enabled-low condition: T(ON/OFF) =21.9 and in enabled-high condition: T(ON/OFF) =24.9) of the signal light arisen by altering the pump-light intensity. The proposed all-optical switching demonstrates femtosecond-scale feedback time (90 fs) and then ultra-fast switching can be achieved. The offered all-optical switch may recognize potential significant applications in integrated optical circuits.

Ultrasmall all-optical plasmonic switch and its application to superresolution imaging.

Because of their exceptional local-field enhancement and ultrasmall mode volume, plasmonic components can integrate photonics and electronics at nanoscale, and active control of plasmons is the key. However, all-optical modulation of plasmonic response with nanometer mode volume and unity modulation depth is still lacking. Here we show that scattering from a plasmonic nanoparticle, whose volume is smaller than 0.001 μm3, can be optically switched off with less than 100 μW power. Over 80% modulation depth is observed, and shows no degradation after repetitive switching. The spectral bandwidth approaches 100 nm. The underlying mechanism is suggested to be photothermal effects, and the effective single-particle nonlinearity reaches nearly 10−9 m2/W, which is to our knowledge the largest record of metallic materials to date. As a novel application, the non-bleaching and unlimitedly switchable scattering is used to enhance optical resolution to λ/5 (λ/9 after deconvolution), with 100-fold less intensity requirement compared to similar superresolution techniques. Our work not only opens up a new field of ultrasmall all-optical control based on scattering from a single nanoparticle, but also facilitates superresolution imaging for long-term observation.

Submicron bidirectional all-optical plasmonic switches

Ultra-small all-optical switches are of importance in highly integrated optical communication and computing networks. However, the weak nonlinear light-matter interactions in natural materials present an enormous challenge to realize efficiently switching for the ultra-short interaction lengths. Here, we experimentally demonstrate a submicron bidirectional all-optical plasmonic switch with an asymmetric T-shape single slit. Sharp asymmetric spectra as well as significant field enhancements (about 18 times that in the conventional slit case) occur in the symmetry-breaking structure. Consequently, both of the surface plasmon polaritons propagating in the opposite directions on the metal surface are all-optically controlled inversely at the same time with the on/off switching ratios of >6 dB for the device lateral dimension of <1 μm. Moreover, in such a submicron structure, the coupling of free-space light and the on-chip bidirectional switching are integrated together. This submicron bidirectional all-optical switch may find important applications in the highly integrated plasmonic circuits.

Simulation and Design of a Submicron Ultrafast Plasmonic Switch Based on Nonlinear Doped Silicon MIM Waveguide

We propose and analyze a submicron stub-assisted ultrafast all-optical plasmonic switch based on nonlinear MIM waveguide. It is constructed by two silicon stub filters sandwiched by silver cladding. The signal wavelength is assumed to be 1550 nm. The simulation results show a ?14.66 dB extinction ratio. Downscaling the silicon waveguide in MIM structure leads to enhancement of the effective Kerr nonlinearity due to tight mode confinement. Also, using O+ ions implanted into silicon, the switching time less than 10 ps and a delay time less than 8 fs are achieved. The overall length of the switch is 550 nm.

All-Optical Plasmonic Switches Based on Coupled Nano-disk Cavity Structures Containing Nonlinear Material

All-optical plasmonic switches based on a novel coupled nano-disk cavity configuration containing nonlinear material are proposed and numerically investigated. The finite difference time domain simulation results reveal that the single-disk plasmonic structure can operate as an “on–off” switch with the presence/absence of pumping light. We also demonstrate that the proposed T-shaped plasmonic structure with two disk cavities can switch signal light from one port to another under an optical pumping light, functioning as a bidirectional switch. The proposed nano-disk cavity plasmonic switches have many advantages such as compact size, requirement of low pumping light intensity, and ultra-fast switching time at a femto-second scale, which are promising for future integrated plasmonic devices for applications such as communications, signal processing, and sensing.