Plasmonic Filter Research Articles

Design and Simulation of a High-Selective Plasmon-Induced Reflectance in Coupled Dielectric-Metal-Dielectric Nano-structure for Senor Devices and Slow Light Propagation

A new framework of high-selective plasmonic-induced reflectance (PIR) in a plasmonic-induced transparency (PIT) system is presented by using planar dielectric-metal-dielectric (DMD) metamaterial nano-structure. We used glass as substrate, the first dielectric, gold as metal thin film, and prism as the second dielectric. The proposed plasmonic nano-structure has been investigated based on finite difference time domain (FDTD) method. Results show that by coupling incident light with dark and bright plasmonic modes, without losing the metamaterial structure symmetry, the transparent window is created at 1550 nm and can be tuned. The transmittance (T), reflectance (R), and absorbance (A) coefficients of the presented nano-structure can be considerably varied by changing the thickness of thin films and dimension of the strips. The reflectance coefficients of dip1 (200 THz) and dip2 (265.5 THz) are almost near zero, and the transmittance coefficient of PIR (227.1 THz) is 0.93. Also, the maximum sensitivity and figure of merit are 664 and 3.77 for reflectance dip2, respectively. Similarly, the maximum quality factor (Q) is 10.74 for reflectance dip1. The presented plasmonic metamaterial nano-structure with mentioned unique features is a good candidate for several applications such as multi-channel plasmonic filters, bio and refractive index sensors, optical antenna, and slow-light devices for using in optical nano-electronic circuits and systems.

Ultra-compact graphene plasmonic filter integrated in a waveguide**Project supported by the National Basic Key Research Program of China (Grant No. 2015CB932400), the National Key Research and Development Program of China (Grant No. 2016YFA0201600), the National Natural Science Foundation of China (Grant Nos. 51372045, 11504063, and 11674073), the Key Program of the Bureau of Frontier Sciences and Education, Chinese Academy of

Graphene plasmons have become promising candidates for deep-subwavelength nanoscale optical devices due to their strong field confinement and low damping. Among these nanoscale optical devices, band-pass filter for wavelength selection and noise filtering are key devices in an integrated optical circuit. However, plasmonic filters are still oversized because large resonant cavities are needed to perform frequency selection. Here, an ultra-compact filter integrated in a graphene plasmonic waveguide was designed, where a rectangular resonant cavity is inside a graphene nanoribbon waveguide. The properties of the filter were studied using the finite-difference time-domain method and demonstrated using the analytical model. The results demonstrate the band-pass filter has a high quality factor (20.36) and electrically tunable frequency response. The working frequency of the filter could also be tuned by modifying the cavity size. Our work provides a feasible structure for a graphene plasmonic nano-filter for future use in integrated optical circuits.

Plasmonic color filters fabricated via oxide-based nanotransfer printing

Plasmonic filters have recently become a topic of significant interest because they are suitable for a wide range of applications. However, effective fabrication of plasmonic filters remains a challenge. In this paper, we demonstrate a simple method for fabricating plasmonic color filters based on nanotransfer printing (nTP) , using SiO2 as a hard mask for Al etching. nTP was performed on a 100 nm Al layer deposited on a glass wafer substrate with a 10 nm Al layer and a 20 nm SiO2 layer with a nanohole pattern. The 10 nm Al layer and 20 nm SiO2 layers were previously transferred from a polymer stamp prepared to create patterns of subwavelength-sized holes. The plasmonic filters were ultimately fabricated using the SiO2 layer as a hard mask to selectively etch the Al layer. The optical properties of the fabricated plasmonic filters were evaluated using experimental and simulation tools. In addition, we analyzed the results of nTP on the Al and SiO2 films by varying the temperature, pressure, and SiO2-film thickness. We believe that this technique is a promising method for fabricating nanostructures and for widening the scope of practical application of plasmonics because of its high efficiency and cost-effectiveness.

Transmission Enhancement in Coaxial Hole Array Based Plasmonic Color Filter for Image Sensor Applications

Plasmonic color filters based on the hexagonal arrangement of coaxial hole array in aluminum have been demonstrated as a promising candidate for color filter development due to polarization and incident angle insensitivity. They also comprise a single nanometer thick metal film, demonstrate good line width, CMOS compatibility, and fine color tunability. However, the low transmittance of the coaxial hole array based filters limits their use in potential applications such as image sensors and displays. This paper introduces a new method to increase transmittance in coaxial hole array based filters by tuning localized surface plasmons and surface plasmon polaritons. In this method, coaxial holes of small diameters are filled along with a large size coaxial hole array to form a combined filter geometry with optimized parameters in aluminum film using computational techniques. The simulation results will have potential applications in CMOS image sensors, submicron pixel development, microdisplays, and liquid crystal over silicon devices.

Mid-infrared plasmonic multispectral filters

A miniaturized mid-infrared spectral analyzer will find a wide range of applications as a portable device in non-invasive disease diagnosis, environmental monitoring, food safety and others. In this work, we report an integrated spectral analyzer that can be constructed by using Au subwavelength hole arrays as multispectral filters. The hole arrays were fabricated with CMOS compatible processes. The transmission peak of the subwavelength hole arrays is continuously tuned from 3 μm to 14 μm by linearly increasing the periodicity of the holes in each array. Fourier transform infrared (FTIR) microscopy was applied to spatially map out the transmission of the hole arrays. The results show that each hole array can selectively allow for transmission at a specific wavelength. We further constructed an IR spectral analyzer model based on the microhole multispectral filters to retrieve IR spectral information of two test samples. Our experimental results show that the spectra from the integrated spectral analyzer follow nearly the same pattern of the FTIR spectra of the test samples, proving the potential of the miniaturized spectral analyzer for chemical analysis.

High Efficiency Tunable Graphene-Based Plasmonic Filter in the THz Frequency Range

A tunable plasmonic filter waveguide with indium antimonide activated by graphene layer configuration is proposed and numerically investigated. We demonstrate that the proposed tunable single-stub plasmonic filter using a thin layer of graphene can operate in the terahertz (THz) region as a notch filter. To investigate the transmission response of the structure, finite element method (FEM) calculations are utilized. The designed filter has precise minimum of zero at the notch frequency and also it improves the maximum transmitting light. Moreover, by applying the gate voltage between the graphene sheet and the InSb substrate, it can be seen that the central frequency of the filter is shifted by 32 GHz, and also the maximum of the transmission has been improved by 64% from 0.56 to 0.92 which shows less power loss. Furthermore, a band-stop plasmonic filter is proposed by increasing the number of stubs, which improves the bandwidth of the filter by 33% in compare to a single-stub structure. With such advantages, this structure is promising for future integrated plasmonic devices for applications such as communications, signal filtering, and switching.

Plasmonic filter and sensor based on a subwavelength end-coupled hexagonal resonator.

In this paper, an end-coupled hexagonal resonator inserted with dual parallel metallic blocks is proposed based on subwavelength metal-insulator-metal waveguides. When the blocks are vertically inserted into the resonator, more transmission channels (three peaks) with symmetrical spectral shapes than that (one peak) of the perfect hexagonal resonator are achieved in the same wavelength range. The transmission peaks all have high transmittances; thus, the structure can be performed as an on-chip optical filter. When the blocks are horizontally distributed in the resonator, the antinode and node of the magnetic field for the expected mode will arise inside and outside the blocks, leading to the mode interactions. Subsequently, Fano resonance with an asymmetrical peak is achieved in the structure. High index sensitivity and high figure of merit, which are significant factors for optical sensors, are investigated by using the finite-difference time-domain method. The proposed structure can highly support the development of integrated photonics and find wide applications in the on-chip optical filtering and sensing areas.

Sub-wavenumber linewidth mid-infrared notch filter enabled by a dual-period plasmonic structure

Abstract A transmission notch filter based on surface-plasmon resonance is proposed and numerically studied in the mid-infrared region. The metal structure is a dual-period grating constructed by using smaller-period gold arrays as the duty portions of a larger-period grating. The plasmonic filter shows high transmission of >85% over broad mid-infrared range, and a single notch at ∼ 4. 073 μ m with 24 dB extinction ratio. The stop bandwidth of the filter is ∼ 0.75 nm ( ∼ 0.45 cm−1), corresponding to the quality factor as high as 5400, which is improved by at least one order of magnitude. The rejection wavelength and bandwidth of the filter can be designed by adjusting the structure parameters. Additionally, the angle and polarization of the incidence and refractive index of the surrounding medium affect the performance of the filter.

A Photonic Switch Based on a Hybrid Combination of Metallic Nanoholes and Phase-change Vanadium Dioxide

A photonic switch is an integral part of optical telecommunication systems. A plasmonic bandpass filter integrated with materials exhibiting phase transition can be used as a thermally reconfigurable optical switch. This paper presents the design and demonstration of a broadband photonic switch based on an aluminium nanohole array on quartz utilising the semiconductor-to-metal phase transition of vanadium dioxide. The fabricated switch shows an operating range over 650 nm around the optical communication C, L, and U band with maximum 20%, 23% and 26% transmission difference in switching in the C band, L band, and U band, respectively. The extinction ratio is around 5 dB in the entire operation range. This architecture is a precursor for developing micron-size photonic switches and ultra-compact modulators for thin film photonics.

Transmissive structural color filters using vertically coupled aluminum nanohole/nanodisk array with a triangular-lattice

We demonstrate a configuration to generate transmissive structural colors through triangular-lattice square nanohole arrays in aluminum (Al) film with Al nanodisks on the bottom of the nanoholes. By using a simple nanofabrication process, colors covering the entire visible light with different brightness and saturation are achieved by tuning both the period of arrays and the size of nanoholes. The optical behaviors of the structures are systematically investigated by both experimental and theoretical methods. The results indicate that the localized surface plasmon resonance of nanohole arrays plays the key role in the extraordinary transmission and meanwhile the coupling of disks and holes is also of importance for the enhanced transmission. With the wide color gamut, these kinds of vertically coupled Al nanohole/nanodisk arrays show the capabilities for high-resolution full-color printing. Compared to existing transmissive plasmonic color filters, the configuration in this work has the advantages of a simple fabrication process and using cheap aluminum materials.

Spontaneous Additive Nanopatterning from Solution Route Using Selective Wetting.

Nanopatterns of functional materials have successfully led innovations in a wide range of fields, but further exploration of their full potential has often been limited because of complex and cost-inefficient patterning processes. We here propose an additive nanopatterning process of functional materials from solution route using selective wetting phenomenon. The proposed process can produce nanopatterns as narrow as 150 nm with high yield over large area at ultrahigh process speed, that is, the speed of solution dragging, of up to ca. 4.6 m·min-1. The process is highly versatile that it can utilize a wide range of solution materials, control vertical structures including pattern thickness and multistacks, and produce nanopatterns on various substrates with emerging form factors such as foldability and disposability. The solution patterning in nanoscale by selective wetting is enabled by corresponding surface energy patterns in high contrast that are achieved by one-step imprinting onto hydrophobic/hydrophilic bilayers. The mechanisms and control parameters for the solution patterning are revealed by fluid-dynamic simulation. With the aforementioned advantages, we demonstrate 25 400 pixel-per-inch light-emitting pixel arrays and a plasmonic color filter of 10 cm × 10 cm area on a plastic substrate as potential applications.

Angle-tolerant hybrid plasmonic blue filter with polarization-insensitivity and high transmission

The optical blue filter with the suitable bandwidth, high transmittance and large acceptance angle is usually regarded as a critical optical component for a variety of applications. Here, we propose a polarization-insensitive angle-tolerant hybrid plasmonic blue filter incorporating two-dimensional aluminum (Al) nanodisks on the top of planar waveguide. The proposed plasmonic filter works via hybridization of surface plasmon polariton (SPP) mode, the localized Fabry–Perot resonance and waveguide mode, thus enables high peak transmittance up to 70% with the bandwidth of 30 nm and large acceptance angle up to 20°.

Design and development of aluminum nanoring arrays for realization of dual-mode operation plasmonic color filters

In this paper, engineering the optical characteristics of aluminum nanoring arrays has been investigated with the aim of achieving a practical design approach to the realization of dual-mode plasmonic color filters. In addition to designing a set of subtractive and additive color filters with appropriate properties, an improved approach has also been proposed in order to design different additive/subtractive filters at arbitrary wavelengths. The proposed structures show great optical efficiencies while offering narrowband characteristics and a good color purity. They are CMOS-compatible, cost-effective, easy to fabricate, highly tunable, and polarization insensitive. Moreover, they offer potential applications in displays, CMOS image sensors, color printing, and multispectral imaging.

Polarization-Insensitive Ultra-Narrow Plasmon-Induced Transparency and Short-range Surface Plasmon Polariton Bloch Wave in Ultra-thin Metallic Film Nanostructures

We demonstrate that polarization-insensitive ultra-narrow double plasmon-induced transparency (PIT) can be achieved in the thin-metal-film nanostructures. Ultra-narrow PIT resonance with a bandwidth of 2.5 nm at central wavelength of 768 nm was obtained (~ 1/307 of the peak wavelength). Multispectral PIT can be obtained, and its linewidth and the “on-off” state of the PIT peaks in the system can be adjusted by the metallic nanostructure thickness and particularly the waveguide layer thickness. The narrow transparency window is exhibited to be generated by the coupling and interference between a delocalized hybrid-waveguide photonics mode and the localized surface plasmon (LSP) mode. The angular-dependent dispersion of the system with double PITs is examined and investigated, where the high-order short-range surface plasmon polariton (SRSPP) Bloch waves excited for large incidence angles are indicated and revealed. The multispectral PITs with high quality in the large-area plasmonic system are promising for practical and compact nanophotonics applications such as optical buffers, ultra-sensitive sensor, plasmonic filters, and switches.

Design and Simulation of Compact Band-Pass Filter Using Stub Loaded Plasmonic Mim Waveguide

In this article, plasmonic band-pass filters (BPF) have been studied and numerically analyzed. This filter has been designed based on the two-stubs. Pass-band can be realized by appropriately adjusting the lengths and width of the resonator. Based on the ideal characteristics of the proposed two stubs BPF is allowing the band at THz frequencies. Multiple transmission zeros are generated to improve the selectivity of the filter. All simulated results have been studied using CST Microwave studio suite. Usually, the transmission effectiveness is revealed by the exact resonance condition, whichwill confirmalong with the numerical simulation or theoretical analysis. This article delivers a promising application for plasmonic BPFsin addition to plasmonic integrated circuits (PICs).

Design of a Single-Mode Plasmonic Bandpass Filter Using a Hexagonal Resonator Coupled to Graded-Stub Waveguides

In this paper, a plasmonic filter based on metal-insulator-metal (MIM) configuration is proposed. It uses a hexagonal nano-resonator (HNR) coupled to multi-stub waveguides (MSWs) from both sides. The metal and insulator of the proposed plasmonic filter are silver and air, respectively. Finite difference time domain (FDTD) method is used for numerical simulations. The simulation results indicate that the proposed filter has a single transmission peak at 987 nm with a maximum transmission equal to 67%. The advantages of the proposed structure are a resonance wavelength with high transmission peak and flat transmission spectrum out of the transmission resonance wavelength. The Drude–Lorentz model (DLM) is used for numerical characterization of silver in the proposed structure. Such a model is thereafter compared with Drude and Palik models. To investigate the effect of different structural parameters of HNR and multiple stubs on their transmission spectrums, such structures are simulated by sweeping different parameters. Considering these features, the proposed filter has the potential to be employed in various plasmonic devices such as demultiplexers for optical communication purposes.

Tunable Fano resonance in plasmonic MDM waveguide with a square type split-ring resonator

Plasmonic metal-dielectric-metal (MDM) type waveguide structures with a split ring resonator (SRR) or a complementary split-ring resonator (CSRR) are proposed. The waveguides can support Fano type transmission. It is observed that the asymmetric non-integer modes in addition to the symmetric integer modes can be excited in the SRR structure. Simulation results indicate that the transmission spectra can be efficiently tuned by changing the position of the split as well as other parameters. However, for the symmetrical CSRR structure, the non-integer modes can not be excited. The transmission properties of the proposed structure are numerically studied by the finite element method (FEM). The proposed structures have potential application in the area of the plasmonic filter, the refractive index nanosensor, the integrated slow-light devices, and so on.

Near-Perfect Spectral Transmission Properties for Two Cascaded Plasmonic Ultrathin Nanograting Structures

A high-performance plasmonic transmission structure consisting of two longitudinally cascaded ultrathin metallic nanogratings with a half period lateral dislocated and separated by two heterogeneous dielectric layers is proposed and theoretically studied. Three near-unity spectral transmission peaks are observed for the cascaded plasmonic nanograting structure due to the evanescent field coupling of surface plasmon polariton waves supported by the two neighboring plasmonic nanogratings. The physical mechanism responsible for the near-perfect peak transmissions is discussed based on the corresponding spatial distributions of electromagnetic fields and is found to be two possible ways: by the excitation of hybrid anti-symmetric surface plasmon polariton leaky mode on the incident and transmission surfaces of the cascaded plasmonic nanograting structure or by the formation of localized surface plasmon polariton resonance modes within horizontally butt-jointed metal/insulator/metal coupled waveguides between the two cascaded plasmonic nanogratings. It is the two heterogeneous dielectric layers inserted between the two cascaded plasmonic nanogratings that is indispensable for the formation of the hybrid anti-symmetric surface plasmon polariton leaky mode, resulting in the near-unity transmission peak with an ultra-narrow bandwidth of 20 nm. The high-tunability of spectral transmission behaviors with varying structural parameters and dielectric layer are explored, which promise numerous potential applications in nano-optics devices, such as plasmonic filters, sensors, and nanoscale distance ruler.

Nanosensing and slow light application based on Fano resonance in waveguide coupled equilateral triangle resonator system

Plasmonic Fano resonance effect is investigated in a novel metal-insulator-metal waveguide structure, which consists of a stub MIM waveguide and a triangle shaped resonator. The transmission properties of the proposed plasmonic waveguide structure are numerically investigated by the two dimensional finite-difference-time -domain (FDTD). The coupling between the stub resonator and the triangle resonator results in a Fano resonance. The transmission characteristics and the slow light effect, sensing performance of the proposed plasmonic structure are studies in detail. By proper design, the sensitivity and the optical delay time of the proposed structure can be up to 800 nm/RIU and 0.053 ps. The above characteristics indicate the proposed plasmonic structure may have application in slow light device, plasmonic filter, all optical switch and nanosensing.

Liquid-crystal-based tunable plasmonic waveguide filters

We propose a liquid-crystal-based tunable plasmonic waveguide filter and numerically investigate its filtering properties. The filter consists of a metal-insulator-metal waveguide with a nanocavity resonator. By filling the nanocavity with birefringent liquid crystals (LCs), we could then vary the effective refractive index of the nanocavity by controlling the alignment of the LC molecules, hence making the filter tunable. The tunable filtering properties are further analyzed in details via the temporal coupled mode theory (CMT) and the finite-difference time-domain (FDTD) method. The simulation results show that the resonant wavelengths have linear redshift as the refractive index of the nanocavity increases and the coupling efficiency is more than 65% without considering the internal loss in the nanocavity and waveguides. These achieved results by the FDTD simulations can be also accurately analyzed by CMT. The compact design of our proposed plasmonic filters is especially favorable for integration, and such filters could find many important potential applications in high-density plasmonic integration circuits.