Plasmonic Ring Resonator Research Articles

Design and optimization of a polarization-insensitive terahertz metamaterial absorber for sensing applications

This study presents dual-band Terahertz (THz) metamaterial absorbers (MA) designed with square resonators for sensing applications. The absorber is made up of a plasmonic ring resonator, a middle polyimide layer, and a lower metal plate, which enhances its absorption capabilities. The position of annular strips and patch units is strategically adjusted to tune and optimize the absorber’s performance precisely. The proposed metamaterial (MA) consistently absorbs over 99 % within the frequency range from 1.4 to 2.8 THz at 1.6 THz for peak-1 and 2.3 THz for peak-2. The peaks labeled as ‘f1’ and ‘f2’ have a spectral width of 0.02 THz and high-quality factors (Q-factors) of 23 for peak-1 and 29 for peak-2, respectively. This makes them remarkably sensitive to variations in the environmental refractive index (RI). It is important to observe that the refractive index of most samples falls within the range of 1.0–2.0, highlighting the potential applications of this sensor.

Optimized hybrid plasmonic waveguide-based ring resonator for advanced refractive index sensing

In this study, we conducted a comprehensive numerical analysis employing the finite element method to explore the characteristics of a hybrid plasmonic waveguide (HPWG)-based ring resonator (RR) structure. Our investigation reveals that the device’s sensitivity can be significantly augmented through strategic geometric modifications. The device exhibits sensitivities of approximately 176 nm RIU−1 and 238 nm RIU−1 when utilizing WG widths of 300 nm and 270 nm, respectively, in forming the ring structure. Through optimization efforts aimed at enhancing the overlap between the dielectric and plasmonic modes, the device’s sensitivity reaches an optimized level of around 316 nm RIU−1 by reducing the ring width to 250 nm. Overall, our findings underscore the potential for leveraging geometric adjustments to enhance the sensitivity and functionality of HPWG-based RRs, thereby advancing their utility in diverse sensing applications.

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.

Plasmonic Ring Resonator Sensor with High Figure of Merit and Sensitivity Using Degenerate N-Doped Silicon for SPP Excitation

Plasmonic Ring Resonator Sensor with High Figure of Merit and Sensitivity Using Degenerate N-Doped Silicon for SPP Excitation

Design of All-Optical Subtractors Utilized with Plasmonic Ring Resonators for Optical Computing

In this paper, a novel plasmonic all-optical half-subtractor and full-subtractor are designed for optical computing. The structure of plasmonic subtractors consists of a metal–insulator–metal (MIM) waveguide and rectangular ring resonators covered by a graphene layer. Due to the nonlinear optical properties of graphene, the states of the plasmonic resonators can be controlled by the pump intensity of a pump beam focused on the graphene layer. The resonators can work as all-optical switches with an ultra-fast response time to constitute optical logic devices according to the directed logic mechanism. A finite-difference time-domain method is utilized to numerically investigate the transmission of the output signals which represent the results of subtraction operations. Simulation results obtained indicate that the proposed plasmonic devices have the ability to implement half-subtraction and full-subtraction with a small feature size and fast response time, and provide a new concept and method for the design and realization of optical computing devices.

Nanoscale Characterization of Individual Three-Dimensional Split Ring Resonator Systems

In this work, we investigate the hybridization of three-dimensional plasmonic split ring resonator (SRR) pairs using focused electron beam nanospectroscopy and model their combined electric and magnetic responses using electromagnetic theory and numerical calculations. Specifically, we fabricate three-dimensional (3D) SRR dimers with varying in-plane rotations and out-of-plane tilts and perform electron energy loss spectroscopy (EELS) measurements to elucidate the impact of their 3D electric and magnetic interactions on the EEL spectrum of each individual SRR dimer. On the basis of the competition between the SRR’s electric and magnetic interactions within our model, we find that varying the 3D tilt angle diminishes the magnetic coupling but increases the level of overall mode mixing. Through further modeling of the experimental data, we determine the system’s electric and magnetic coupling constants, as well as the overall effective coupling constant, a useful metric for characterizing the strength of light–matter interaction. We additionally explore the potential for geometric frustration in the magnetic mode ordering of a coupled SRR trimer using both EELS experiment and companion theoretical modeling. Taken together, the insight gained into the behavior of coupled 3D SRRs serves as a stepping stone to the rational design of 3D photonic metamaterials endowed with even richer optical functionality.

Cylindrical vector beam generator on photonic crystal cavity integrated with metal split ring nanoresonators

We propose a chip-integratable cylindrical vector (CV) beam generator by integrating six plasmonic split ring resonators (SRRs) on a planar photonic crystal (PPC) cavity. The employed PPC cavity is formed by cutting six adjacent air holes in the PPC center, which could generate a CV beam with azimuthally symmetric polarizations. By further integrating six SRRs on the structure defects of the PPC cavity, the polarizations of the CV beam could be tailored by controlling the opening angles of the SRRs, e.g., from azimuthal to radial symmetry. The mechanism is governed by the coupling between the resonance modes in SRRs and PPC cavity, which modifies the far-field radiation of the resonance mode of the PPC cavity with the SRR as the nano-antenna. The integration of SRRs also increases the coupling of the generated CV beam with the free-space optics, such as an objective lens, promising its further applications in optical communication, optical tweezer, imaging, etc.

Plasmonic Ring Resonator Sensor With High Sensitivity and Enhanced Figure of Merit Using an Ag–Si–Ag Bus Waveguide

A plasmonic miniaturized ring resonator based on Ag-analyte-Ag ring cavity coupled with an Ag-Si-Ag input bus waveguide has been numerically analyzed for bulk refractive index and surface adlayer sensing applications. The opto-geometric parameters of the sensor structure have been thoroughly optimized to maximize field confinement in the sensing zone, which significantly improves the sensitivity. Using an Ag-Si-Ag input bus waveguide results in the reduction of propagation loss which offers an improved quality factor and figure of merit due to narrowing of full width at half maximum (FWHM) of the transmission spectrum. The average bulk refractive index sensitivity over biologically relevant refractive index range (1.33-1.38 RIU) and gas-sensitivity (1-1.01 RIU) values are 1757.71 nm/RIU with an FWHM of 37 nm, and 1787.14 nm/RIU with an FWHM of 24 nm, respectively. We have also investigated the optimized sensor's performance as an adlayer biosensor and the maximum adlayer sensitivity obtained is 2.72 nm/nm. We have also analyzed the sensor's optical tolerance by incorporating a 10% change in Ag's and Si's real part of dielectric constants. Owing to excellent sensitivity and high figure of merit the proposed sensor may find applications in designing highly sensitive on-chip nano-sensors with improved detection limit.

Comb-Like Hybrid Plasmonic Ring Resonator for Large and Voltage Tunable Group Delay

A nanophotonic ring resonator based on hybrid plasmonic waveguide is numerically proposed. Introduction of a comb-like structure in the resonator results in large group delay which can be tuned electrically. The proposed silicon-based nanophotonic structure incorporates comb-like design with copper-air subwavelength grating on SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> which supports resonance enhanced propagation of hybrid plasmonic mode confined in 50 nm thick SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The device with its engineered design shows an ultra-large group delay of 208 ps for 1 mm length. The proposed device also exhibits a voltage tunable group delay with a tuning of 48 ps on varying the voltage from −5 V to 5 V. The proposed device with its CMOS compatible and scalable design is useful for integrated optoelectronic circuits. The reported large delay and wide tuning make it a perfect candidate for applications in optical delay lines, signal processing, beam steering in phase array antennas and in microwave photonics.

All-optical NOR and NOT logic gates based on ring resonator-based plasmonic nanostructures

In this paper, compact all-optical plasmonic NOR and NOT gates have been proposed. The structures are based on metal-insulator-metal waveguides coupled to different plasmonic ring resonators. The fundamental structure used for design of the mentioned logic gates is based on T-shaped switches which consists of circular and octagon shaped plasmonic ring resonators (PRR). The simulation results show that the value of contrast ratios of NOR and NOT gates for circular-shaped PRRs are 23.37 and 19.42 dB and the value of contrast ratios of NOR and NOT gates for octagon-shaped PRRs are 24.37 and 23.12 dB, respectively. Also, the maximum transmission ratios of octagon- and circular-shaped PRR at the ON condition are about 82% and 76%, respectively. The proposed logic gates have been simulated using finite difference time domain (FDTD) method. It is observed that the octagon-shaped gates have higher transmission ratios and lower loss than the circular-shaped gates. The size of the NOT gates based on the circular- and octagon-shaped PRRs is 0.4422 µm2 and 0.4775 µm2, respectively. Also, the size of the NOR gate based on the circular- and octagon-shaped PRRs is 0.8645 µm2 and 0.9176 µm2, respectively. These optical logic gates can be used as key components in optical communications and for designing compact plasmonic devices.

Design of low power silicon electro optic modulators based on hybrid plasmonic ring resonator

In this paper, an ITO-based hybrid plasmonic ring resonator modulator has been designed and proposed. Improving the extinction ratio (ER) and the quality factor is considered in designing the modulator. The proposed structure in this paper seeks to reduce the capacitance by reducing the surface between silicon and ITO/HfO2 interface in the ring. Two structures have been proposed based on the ring resonator. In the first structure, high-quality factor, low insertion loss (IL), and low power consumption are obtained, equal to 777, 0.28 dB, and 103fJ. In the second proposed structure, the ER is 12.22 dB, and the quality factor is 514. The finite-difference time-domain (FDTD) method has been used to investigate the modulator characteristic.

Coherent terahertz microscopy of modal field distributions in micro-resonators

Near-field microscopy techniques operating in the terahertz (THz) frequency band offer the tantalizing possibility of visualizing with nanometric resolution the localized THz fields supported by individual resonators, micro-structured surfaces, and metamaterials. Such capabilities promise to underpin the future development and characterization of a wide range of devices, including THz emitters, detectors, optoelectronic modulators, sensors, and novel optical components. In this work, we report scattering-type scanning near-field optical microscopy using a THz-frequency quantum cascade laser (QCL) to probe coherently the localized field supported by individual micro-resonator structures. Our technique demonstrates deep sub-wavelength mapping of the field distribution associated with in-plane resonator modes in plasmonic dipole antennas and split ring resonator structures. By exploiting electronic tuning of the QCL in conjunction with the coherent self-mixing effect in these lasers, we are able to resolve both the magnitude and the phase of the out-of-plane field. We, furthermore, show that the elliptically polarized state of the QCL field can be exploited for the simultaneous excitation and measurement of plasmonic resonances in these structures while suppressing the otherwise dominant signal arising from the local material permittivity.

Compact MIM plasmonic ring resonator for nano-interconnect applications

Abstract In this article, a compact plasmonic metal-insulator-metal ring resonator has been proposed and investigated. The proposed waveguide structure can be turned into a Plasmonic optical filter through alteration in various parameters of the structure geometry, such as radius of ring resonator, width of the waveguide channel, dielectric constant of insulating material and the shifting of the output channel. It is observed that the transmission peaks exhibit redshift with increased radius of the ring resonator and decreased channel width. Several metals have been successfully trialed, in which the silver metal shows high response with near 90% transmission. For the first time, three transmission peaks have been observed in the near infrared regime with air cavity over a wide range of bandwidth, which makes it strong candidate for the significant nano-interconnect and sensing applications.

Hybrid Plasmonic Ring-Resonator Uni-Traveling Carrier Pin-Photodetector on InGaAsP/InP Layer Stack

In this article, for the first time, a hybrid plasmonic (HP) ring resonator uni-traveling carrier pin-photodetector was numerically presented that offers a high responsivity of 0.68 A/W, a high bandwidth of over 125 GHz, and low footprint. This device has the capability of monolithic integration with HP-passive devices on the InP platform at an optical communication wavelength of 1550 nm.

Enhancing the sensitivity of a standard plasmonic MIM square ring resonator by incorporating the Nano-dots in the cavity

We studied the metal-insulator-metal square ring resonator design incorporated with nano-dots that serve to squeeze the surface plasmon wave in the cavity of the ring. The E-field enhances at the boundaries of the nano-dots providing a strong interaction of light with the surrounding medium. As a result, the sensitivity of the resonator is highly enhanced compared to the standard ring resonator design. The best sensitivity of 907 nm/RIU is obtained by placing seven nano-dots of radius 4 nm in all four sides of the ring with a period (ᴧ)= 3r. The proposed design will find applications in biomedical science as highly refractive index sensors. Full Text: PDF

All-optical switching of a dye-doped liquid crystal plasmonic metasurface.

A switchable metasurface composed of plasmonic split ring resonators and a dye-doped liquid crystal is developed. The transmission of the metasurface in the infrared spectral range can be changed by illuminating the dye-doped liquid crystal with light in the visible spectral range. The effect is particularly efficient in the case of hybrid alignment of the liquid crystal, i. e. alignment of the director perpendicular to the surface on one substrate and parallel alignment on the counter substrate. This all-optical switching effect can be attributed to the behavior described in earlier works as colossal optical nonlinearity or surface-induced nonlinear optical effect.

Tunable plasmonic force switch based on graphene nano-ring resonator for nanomanipulation.

Using a plasmonic graphene ring resonator of resonant frequency 10.38 THz coupled to a plasmonic graphene waveguide, we design a lab-on-a-chip optophoresis system that can function as an efficient plasmonic force switch. Finite difference time domain numerical simulations reveal that an appropriate choice of chemical potentials of the waveguide and ring resonator keeps the proposed structure in on-resonance condition, enabling the system to selectively trap a nanoparticle. Moreover, a change of 250 meV in the ring chemical potential (i.e., equivalent to 2.029 V change in the corresponding applied bias) switches the structure to a nearly perfect off-resonance condition, releasing the trapped particle. The equivalent plasmonic switch ON/OFF ratio at the waveguide output is -15.519 dB. The designed system has the capability of trapping, sorting, controlling, and separating PS nanoparticles of diameters ≥30 nm with a THz source intensity of 14.78 mW/µm2 and ≥22 nm with 29.33 mW/µm2.

Record Purcell factors in ultracompact hybrid plasmonic ring resonators.

For integrated optical devices and traveling-wave resonators, realistic use of the superior wave-matter interaction offered by plasmonics is impeded by ohmic loss, which increases rapidly with mode volume reduction. In this work, we report composite hybrid plasmonic waveguides (CHPWs) that are not only capable of guiding subwavelength optical mode with long-range propagation but also unrestricted by stringent requirements in structural, material, or modal symmetry. In these asymmetric CHPWs, the versatility afforded by coupling dissimilar plasmonic modes provides improved fabrication tolerance and more degrees of device design optimization. Experimental realization of CHPWs demonstrates propagation loss and mode area of 0.03 dB/μm and 0.002 μm2, corresponding to the smallest combination among long-range plasmonic structures reported to date. CHPW ring resonators with 2.5-μm radius were realized with record Purcell factor compared with existing plasmonic and dielectric resonators of similar radii.

Microring Switching Control Using Plasmonic Ring Resonator Circuits for Super-Channel Use

The multi-wavelength selection and switching system using the hybrid plasmonic add-drop ring resonator (HPARR) for optical communication is proposed for multi-carrier super-channel-based designed. The plasmonic polariton technique applied in the ring resonator mode to the alternate waveguide interferometer switches the multi-wavelength laser emission in the various ranges. The combination of curvature-coupled plasmon ring and substances with different refractive index allows switching the multi-wavelength emission to shorter the free spectrum range (FSR) and specific wavelengths, without an applied pump signal or adjusted the ring size. It is suitable for the super-channel of wavelength division multiplex (WDM) in the future optical network.

Design of all-optical XOR and XNOR logic gates based on Fano resonance in plasmonic ring resonators

In this paper, compact all-optical XOR and XNOR gates based on different configurations of metal–insulator–metal plasmonic ring resonators (PRRs) have been proposed. Square and octagon-shaped rings have been used in this case. The logic gates have been simulated using the two-dimensional finite-difference time-domain numerical method, with a conventional perfectly matched layer as the absorbing boundary condition of the area under simulation. The phenomenon of Fano resonance is employed by the proposed gates to excite ON/OFF states. As a result, a large value of contrast ratio (C.R.) is obtained. The results show that the values of C.R. of XNOR and XOR gates for square-shaped PRR are 22.66 and 22.9 dB, respectively and the values of C.R. of XNOR and XOR gates for octagon-shaped PRR are 23.01 and 23.52 dB, respectively. Also, it is shown that the octagon-shaped gates have higher transmission ratios than other proposed configurations. The proposed optical logic gates can be used as key components in optical communications and for designing compact plasmonic devices.