Search Results (337)

Using advanced optical modelling, we quantify how sinusoidal corrugation and emitter dipole orientation jointly govern light extraction from OLED thin-film stacks into a glass substrate for red, green, and blue emission. Irrespective of emission colour, the corrugation aspect ratio (AR = height/period) is the dominant geometric parameter controlling extraction, with absolute period and height playing secondary roles, as periods of 600–1000 nm deliver similar gains across all colours. Extraction peaks at AR ≈ 0.2 for predominantly horizontal dipoles, AR ≈ 0.5 for vertical dipoles, and AR ≈ 0.3 for isotropic orientations. For the isotropic case, extraction improves by up to 40%, 34%, and 20% relative to flat red, green, and blue devices, respectively. Absorption analysis attributes the principal gains to suppression of surface-plasmon-polariton losses of vertical dipoles, supported by local dipole reorientation, waveguide disruption, and scattering. Because practical texturing can alter dipole orientation, optimum conditions must be re-evaluated; if orientations follow the sinusoidal profile, an AR of approximately 0.2–0.3 is favoured for isotropic to moderately horizontal orientations, whereas higher ARs benefit strongly vertical orientations. The results provide guidelines for co-optimising corrugation geometry and dipole orientation for high-efficiency OLEDs. Full article

Photonic crystal waveguides (PhCWs) have emerged as a leading platform for integrated optical sensing due to their ability to engineer dispersion, enhance light–matter interaction, and exploit slow-light effects. This review provides a comprehensive analysis of the fundamental physics, performance metrics, device architectures, and application domains that define the current state of PhCW-based sensing. Key mechanisms governing sensitivity, figure of merit, detection limit, and dynamic range are examined, with emphasis on the intrinsic trade-offs introduced by slow-light operation, including disorder-induced scattering, linewidth broadening, and thermal susceptibility. Advances in dispersion engineering, such as hole shifting, gentle confinement, and width modulation, are highlighted alongside novel architectures including slot PhCWs, hybrid material platforms, and plasmonic–photonic configurations. Their respective capabilities in enhancing analyte overlap, improving spectral stability, and expanding functional integration are critically assessed. Emerging applications in biochemical detection, environmental monitoring, and nanoscale particle sensing further illustrate the versatility of PhCWs within modern optofluidic and lab-on-chip systems. The review concludes by outlining key challenges and future directions, including disorder-resilient slow-light design, inverse-engineered structures, and platform-level integration, which collectively chart a path toward next-generation high-performance photonic crystal sensing technologies. Full article

A polarization-insensitive compact optical modulator based on a graphene-hybrid surface plasmon polariton waveguide is proposed. The inverted U-shaped structure enables the synchronous control of TE/TM modes via Fermi level tuning, achieving a maximum attenuation of 0.247 dB/μm (E_f = 0.3 eV) and a minimum attenuation of 0.026–0.028 dB/μm (E_f = 1.0 eV) at 3 THz, with a polarization-dependent modulation error of only 0.002 dB/μm. The 100 μm × 30 μm device operates effectively at 2.5 THz (120 μm), demonstrating its potential for integrated photonic circuits. Additionally, the proposed modulator is compatible with Complementary Metal-Oxide-Semiconductor (CMOS) technology. The excellent ultra-broadband modulation performance of the graphene-hybrid plasmonic waveguide (GHPW) thereby paves the way for high-speed communication, non-destructive testing, biomedical sensing and optical computing. Full article

This paper presents a systematic numerical investigation of a hybrid plasmonic–photonic Panda-ring antenna with an embedded gold grating, designed to enable efficient dual-mode radiation for optical and terahertz communication systems. The proposed structure integrates high-Q whispering-gallery mode (WGM) confinement in a multi-ring dielectric resonator with plasmonic out-coupling at the metal–dielectric interface, allowing controlled conversion of resonantly stored photonic energy into free-space radiation. The electromagnetic behavior is analyzed through a hierarchical structural evolution, progressing from a linear silicon waveguide to single-ring, add–drop, and Panda-ring resonator configurations. Gold is modeled using a dispersive Drude formulation with complex permittivity to accurately capture frequency-dependent plasmonic response at 1.55 µm. Power redistribution within the resonator system is described using coupled-mode theory, with coupling and loss parameters evaluated consistently from full-wave numerical simulations. Full-wave simulations using OptiFDTD and CST Studio Suite demonstrate that purely photonic resonators exhibit strong WGM confinement but negligible radiation, while plasmonic gratings alone suffer from low efficiency due to the absence of coherent photonic excitation. In contrast, the proposed hybrid Panda-ring antenna achieves stable and directive far-field radiation under WGM excitation, with a realized gain of approximately 8.05 dBi at 193.5 THz. The performance enhancement originates from synergistic hybrid SPP–WGM coupling, establishing a WGM-driven radiation mechanism suitable for Li-Fi and terahertz wireless applications. Full article

This paper presents a nanoscale sensor based on a metal–insulator–metal (MIM) waveguide coupled with a composite resonant cavity, where the ring resonator is embedded with triangular, semicircular, and rectangular structural elements. The transmission characteristics and sensing performance of the structure were systematically analyzed using the finite element method. The results indicate that the interference between the continuous mode in the waveguide and the discrete mode in the resonant cavity generates a distinct asymmetric Fano resonance. The optimized sensor achieves a sensitivity of 2960 nm/RIU and a figure of merit (FOM) of 59.79. Experimental verification confirms that the structure exhibits high responsiveness in temperature sensing, providing an effective solution for integrated photonic devices. Full article

This study introduces an innovative sensor architecture predicated on surface plasmon polaritons (SPPs), comprising a metal–insulator–metal (MIM) waveguide in conjunction with a cat-faced circular split resonator (TCRSW). The efficacy of the proposed nanosensor was meticulously evaluated utilizing the finite element method (FEM). It was determined that the TCRSW configuration significantly impacts the sensor’s performance. By means of a comprehensive optimization of the structural parameters, the sensor attained an apex sensitivity of 3380 nm/RIU and a figure of merit (FOM) of 56.33 in its optimal configuration. Furthermore, the study comprehensively evaluated the sensor’s applicability for temperature sensing, demonstrating a measured temperature sensitivity of 1.673 nm/°C. Meanwhile, the application of the proposed structure in biosensing was comprehensively evaluated. When employed as a concentration sensor for detecting sodium and potassium ion solutions, the maximum achievable sensitivities reached 0.49 mg·d/L and 0.6375 mg·d/L, respectively, which highlights its significant potential not only for high-precision temperature monitoring but also for sensitive and reliable biosensing applications. Additionally, the proposed nanosensor holds considerable promise for applications in other nanophotonic fields. Full article

In this paper, a flower-shaped spoof surface plasmon polaritons (SSPPs) unit with strong slow-wave effect is proposed to construct bandpass filters (BPFs). Benefiting from extended current path induced by addition of rotated stubs around rectangular unit, the proposed SSPPs unit exhibits reduced asymptotic frequency. Following this, a single-band filter boasting multiple transmission zeros (TZs) in its upper stopband is developed by embedding the unit into half-mode substrate integrated waveguide (HMSIW). To improve suppression of the lower stopband, a pair of open circuited stubs are loaded to produce TZs and enhance its frequency selectivity. Consequently, the single-band BPF realizes an impressive roll-off rate of 0.116 dB/MHz. Subsequently, geometric dimensions of the open-circuited stubs are modified to dispose the TZs into passband and acquire dual-band operation. In addition, defected ground structures (DGSs) are loaded to broaden the bandwidth of notch between two passbands. Finally, a dual-band filter with a wide suppression band of 0.50 GHz is developed. With roll-off rates of 0.096 and 0.119 dB/MHz, the filter demonstrates good selectivity as well. Full article

Surface plasmon resonance (SPR) sensors based on photonic crystal fibers (PCFs) hold significant promise for high-precision detection in biochemical and chemical sensing. However, achieving high sensitivity in low-refractive-index (RI) aqueous environments remains a formidable challenge due to weak light-matter interactions. To address this limitation, this paper designs and proposes a novel dual-channel D-shaped PCF-SPR sensor tailored for the refractive index range of 1.34–1.40. The sensor incorporates a dual-layer gold/titanium dioxide film, with gold nanoparticles deposited on the surface to synergistically enhance both propagating and localized surface plasmon resonance effects. Furthermore, a D-shaped polished structure integrated with double-sided microfluidic channels is employed to significantly strengthen the interaction between the guided-mode electric field and the analyte. Finite element method simulations demonstrate that the proposed sensor achieves an average wavelength sensitivity of 5733 nm/RIU and a peak sensitivity of 15,500 nm/RIU at a refractive index of 1.40. Notably, the introduction of gold nanoparticles contributes to an approximately 1.47-fold sensitivity enhancement over conventional structures. This work validates the efficacy of hybrid plasmonic nanostructures and optimized waveguide design in advancing RI sensing performance. Full article

Fano resonance sensors based on metal–insulator–metal (MIM) waveguides often face the challenge of balancing high sensitivity (S) and a high figure of merit (FOM). In this work, a high-performance refractive index sensor is proposed, consisting of a straight MIM waveguide side-coupled to a novel ring–bridge–rounded square (RBS) resonator. The transmission characteristics and the formation mechanism of Fano resonance are systematically analyzed using the finite element method (FEM). The results demonstrate that the synergistic introduction of rounded square units and an internal bridge structure significantly enhances electromagnetic field localization and optimizes the coupling strength. The optimized device achieves a remarkable refractive index sensitivity of 3268 nm/RIU (refractive index unit, RIU) and a high FOM of 55.4. Furthermore, by employing ethanol as the filling medium, the proposed configuration functions as a temperature sensor, exhibiting a high linear sensitivity of 1.644 nm/°C over the range of −70 °C to 70 °C. The proposed RBS resonator holds promise for compact and high-precision nanophotonic sensing applications. Full article

Plasmonic- or metamaterial-based multi-narrowband perfect absorbers hold significant potential applications in filtering, photodetection, and spectroscopic sensing. However, it is rather challenging to realize multi-peak and narrowband absorption simultaneously only using plasmonic metallic materials due to the single or dual resonance and large optical losses in the metallic nanostructure. Here, we numerically demonstrate a new multi-narrowband perfect absorber based on the strong coupling between the Fabry–Perot cavity modes and the surface plasmon polariton waveguide modes in a nanostructure consisting of periodic Ag grating and Ag film separated by a SiO₂ waveguide layer. Six absorption peaks, an ultranarrow absorption resonance with FWHM as narrow as 8 nm, and an absorption peak amplitude surpassing 95% have been achieved. Furthermore, the optical properties of the designed nanostructures can be precisely tuned by modulating the grating period, slit width, height, as well as the thickness and refractive index of the waveguide layer. This approach establishes a versatile platform for designing high performance multi-narrowband absorbers, with promising applications in optical filters, nonlinear optics, and biosensors. Full article

Photodetectors are critical components in a wide range of applications, including military, communications, medical, and aerospace fields. With ongoing advancements in optoelectronics, the strategy of integrating multiple optical structures with photodetectors has led to substantial improvements in detection performance. This review summarizes recent research progress in optically coupled photodetectors, providing a systematic analysis of the operational mechanisms and performance characteristics of five key coupling configurations: optical waveguides, surface plasmon resonance structures, microcavities, gratings, and integrated metasurfaces. Furthermore, the main limitations of current coupling technologies and challenges facing the development of future coupled devices are discussed. Recent studies indicate that heterogeneous integration, multi-physical field coupling, and automated fabrication processes are paving the way for high-performance photodetectors with enhanced bandwidth, sensitivity, functional integration, and spectral control capabilities. Full article

Reversible gates theoretically do not result in energy loss during the calculation process. The Toffoli gate is a universal reversible logic gate, and any reversible circuit can be constructed from the Toffoli gate. This paper presents a hybrid electro-optic Toffoli logic that uses an HSPP Switch (hybrid surface plasmon polariton switch), waveguide coupler, and Y-shaped splitter. The hybrid electro-optic Toffoli logic operation is applied via voltage regulation, and the FDTD simulation is used for this research. The modeling and simulation results show that the device’s operating speed is up to 61.62 GHz; the power consumption for transmitting 1 bit is only 13.44 fJ; the average insertion loss is 6.4 dB, and the average extinction ratio of each output port is 19.7 dB. Full article

This article investigates how to exploit the high-frequency mmWave for 5G-advanced and beyond, which requires new filters for the wide bandpass and its multi-sub-band. Based on the substrate-integrated waveguide (SIW), spoof surface plasmon polariton (SSPP), and metastructures, like complementary split-ring resonators (CSRRs), the development of a wide bandpass filter and a multi-sub-band filter is proposed, along with an experimental realization to verify the model. The upper and lower cutoff frequencies of the wide bandpass are controlled through an SIW-SSPP structure, whereas the corresponding wide bandpass and its multi-sub-band filters are designed through incorporating new metastructures. The frequency range of 24.25–29.5 GHz, which covers the n257, n258, and n261 bands for 5G applications, was selected for verification. The basic SIW-SSPP wide bandpass structure of 24.25–29.5 GHz was designed first. Then, by incorporating an Archimedean spiral configuration, the insertion loss within the passband was reduced from 1 dB to 0.5 dB, while the insertion loss in the high-frequency stopband was enhanced from 40 dB to 70 dB. Finally, CSRRs were integrated to effectively suppress undesired frequency components within the bandpass, thereby achieving multi-sub-band filters with low insertion losses with a triple-sub-band filter of 0.5 dB, 0.7 dB, and 0.8 dB in turn. The experimental results showed strong agreement with the design scheme, thereby confirming the rationality of the design. Full article

Based on the theory of optical sensing, we propose a high-precision plasmonic refractive index nanosensor, which consists of a symmetric rectangular waveguide and a circular ring containing a rectangular cavity. The designed novel tunable micro-resonant circular cavity filter based on surface plasmon excitations is able to confine light to sub-wavelength dimensions. The data show that different geometrical factors have different effects on sensing, with the geometry of the rectangular cavity and the radius of the circular ring being the key factors affecting the Fano resonance. Furthermore, the resonance bifurcation enables the structure to achieve a tunable dual Fano resonance system. The structure was tuned to obtain optimal sensitivity (S) and figure of merit values up to 3066 nm/RIU and 78. The designed structure has excellent sensing performance with sensitivities of 0.4767 nm·(mg/d${\mathrm{L}}^{-1}$) and 0.6 nm·(mg/d${\mathrm{L}}^{-1}$) in detecting Na⁺ and K⁺ concentrations in the electrolyte solution, respectively, and can be easily achieved by the spectrometer. The wavelength accuracy of 0.001 nm can be easily achieved by a spectrum analyzer, which has a broad application prospect in the field of optical integration. Full article

Magneto-plasmonic structures have been a subject of tremendous attention of researchers in recent decades as they provide unique approaches regarding the efficient control of optical, magneto-optical, and nonlinear-optical effects. Among others, magneto-plasmonic crystals (MPCs) have become one of the most studied structures, known for their high-quality tunable resonant optical properties. Here, we present the results of experimental and numerical studies on the functional magneto-optical (MO) response of planar 1D plasmonic crystals composed of Co/Au stripes of submicron period on the surface of a 3 μm thick rare-earth garnet layer. The experimental and numerical studies confirm that the wavelength–angular spectra of such structures contain a set of tunable resonant features in their optical and magneto-optical response, associated with the excitation of (i) surface plasmon polaritons at the Co/Au grating–garnet interface, as well as (ii) waveguide (WG) modes propagating in the garnet slab. A comparison of the MO effects in the transversal and longitudinal magnetization of the plasmonic structures is presented. We show that the most efficient Fano-type MPC magneto-optical response is realized for the WG modes of the first order for the longitudinal magnetization of the structure. Further perspectives regarding the optimization of this type of plasmonic crystal are discussed. Full article