Surface Plasmon Polariton Waveguide Research Articles

Additive and subtractive hybrid manufacturing assisted by femtosecond adaptive optics

Advanced micro–nano devices commonly require precise three-dimensional (3D) fabrication solutions for pre-designing and integrating 0D to 3D configurations. The additive–subtractive hybrid manufacturing strategy dominated by femtosecond laser direct writing has become an increasingly interesting technical route for material processing. In this study, a novel approach termed femtosecond adaptive optics-assisted hybrid manufacturing was proposed, which integrates subtractive (femtosecond laser ablation) and additive (two-photon polymerization) fabrication. In this hybrid manufacturing method, the introduction of adaptive optics offers parallel direct writing and wide-area material processing capabilities. To demonstrate the validity of the hybrid approach, on-chip surface plasmon polariton waveguides with strong sub-wavelength field confinement and enhanced functionality were successfully fabricated. In comparison with the terahertz-wave devices fabricated based on the focused ion beam technique, the functional tests in terahertz near-field microscopy show a rival performance fabricated with our hybrid approach. Besides, our cost-effective solution also dramatically reduces the fabricating time of excitation regions by a factor >16. Our work provides a new inspiration in integrated photonics.

Reconfigurable dual-mode meta-waveguide

With the rapid growth of information flux, integrating more channels in limited spaces has been a critical requirement for highly-integrated long-range parallel transmissions. Although meta-waveguides, such as spoof surface plasmon polariton (SSPP) waveguides, can suppress crosstalk between adjacent channels, it is still urgent to seek new methods to further increase the number of channels without occupying additional space. Here, we propose a reconfigurable dual-mode meta-waveguide (RDMMW) by integrating diodes into meta-units, which supports two independent channels using two orthogonal modes. The RDMMW can be switched among dual-mode, even-mode, odd-mode and cutoff states by controlling the diodes, which provides more freedom to manipulate the channel features. The RDMMW possess two outstanding merits in highly-integrated long-range parallel transmissions, including lower coupling between two channels than conventional single-mode waveguides and constant mode coupling in longer waveguides. Thus the proposed RDMMW has advantages of multi-mode, reconfiguration, low coupling and high integration density, providing a new avenue to realize highly-integrated multi-functional systems.

A microwave permittivity sensor on a Mach–Zehnder Interferometer of: Spoof surface plasmon polariton waveguides

A microwave Mach–Zehnder Interferometer (MZI) sensor for the permittivity characterization of liquids is presented in this paper. Two spoof surface plasmon polariton (SSPP) waveguide transmission lines (TLs) composed of compact spiral units is utilized in a differential architecture. Loading a dielectric material on the sensing arm induces a phase difference between the two arms, leading to periodic interference dips on the transmission curve. The spectral positions and magnitudes of these dips change with different dielectric materials. Due to the nonlinear dispersion characteristics of the SSPP TL, the proposed SSPP-based MZI sensor achieves improved sensitivity compared with microstrip-based MZI sensor. To validate the sensor’s performance, six different oil samples and a set of adulterated oils were measured, incorporating a polydimethylsiloxane (PDMS) channel on the sensing arm. The variations in the spectral position and magnitude of the interference dip centered at 3.2 GHz are employed to determine the dielectric constants and loss tangents of the tested oils. The sensitivity in measuring the dielectric constant is 3.61 %. The maximum errors for measuring the dielectric constant and the loss tangent are 4.3 % and 6.7 %, respectively. Compared to other sensors for liquid oil detection, the proposed sensor provides a relatively high sensitivity while maintaining a low liquid volume, making it a promising candidate for permittivity measurements of liquid analytes and solid materials with similar dielectric constants.

Double-layer graphene-based wedge and groove SPP waveguides with ultra-long propagation length

This study investigates long-range surface plasmon polariton (LRSPP) waveguides based on graphene in wedge and groove configurations, comprised of two graphene layers embedded in silica wedges and grooves, respectively. The finite-difference time-domain method is employed for numerical simulations. By combining coupled-mode perturbation theory with numerical results, we demonstrate the excitation of both LRSPP modes and short-range SPP modes when two wedge-shaped or two groove-shaped graphene layers are coupled. Our findings emphasize the significant advantage of the LRSPP fundamental mode, simultaneously achieving an ultra-long propagation length (∼10 μm) and an ultra-deep subwavelength confinement (∼10−7–10−6 times the diffraction-limited mode area). This novel waveguide emerges as a promising candidate for guiding mid-infrared electromagnetic waves in future photonic integrated circuits.

Correction to: Graphene‑Loaded Surface Plasmon Polariton (SPP) Waveguide Surrounded by Uniaxial Chiral (UAC) and Plasma Layers

Correction to: Graphene‑Loaded Surface Plasmon Polariton (SPP) Waveguide Surrounded by Uniaxial Chiral (UAC) and Plasma Layers

Reconfigurable terahertz stretchable spoof surface plasmon polariton waveguide for filter applications

In this paper, a reconfigurable terahertz spoof surface plasmon polariton (SPP) waveguide is proposed on a stretchable polydimethylsiloxane (PDMS) substrate. The SPP unit incorporates a folded stub and a conventional V-shaped SPP groove, enhancing the equivalent capacitance and consequently reducing the cutoff frequency. The cutoff frequency of the proposed SPP unit can be tuned from 285 to 390 GHz with stretchable factors of 1 ∼ 1.2, thereby achieving a reconfigurable operating frequency. The horizontal dimension of the proposed SPP waveguide can be tuned from 6.36 mm to 7.12 mm. Moreover, the SPP waveguide can generate transmission continuous phase shifts of −30°, −60°, −90°, and −120° with stretchable factors of 1.05, 1.1, 1.15, and 1.2, respectively, in the 150–190 GHz band. Applying the characteristic mode theory, a split ring resonator (SRR) functions as the equivalent magnetic dipole, which remains unaffected by stretchable deformation. When loaded with four SRR cells, the proposed SPP waveguide generates a tunable passband with a fixed notched frequency at 193 GHz. Another stretchable SPP resonator serves as the equivalent electric dipole, operating from 284 GHz to 256 GHz in 1∼1.2 stretchable states. By loading three SPP resonators, the SPP waveguide can achieve a passband for the initial state, and a tunable stopband is introduced under 1.1 and 1.2 stretchable states. The proposed stretchable method provides a promising solution for planar terahertz components and systems with reconfigurable functions.

Optical intensity figures of merit of insulator-metal-insulator and metal-insulator-metal thin-film stacks

This paper discusses the quality factors Q and the intensity figures of merit (IFoM) evaluating the intensity and leakage of modes of the reflection flux and of the plane-wave and locally excited transmitted fluxes of insulator-metal-insulator (IMI) and metal-insulator-metal (MIM) 2D planar thin-film stacks, here air-Au-glass and air-Au-SiO2-Au-glass stacks respectively. These thin film stacks sustain a single surface plasmon polariton (SPP) and multiple planar waveguide (PWG) modes. The Q and IFoM of the 3D dispersion graph (in-plane wave vector k ρ /k 0 ∈ [0, 1.52]/frequency ω ∈ [0.5, 2.7] eV/observable dispersion) are calculated and analyzed along 2D cuts where either the in-plane wave vector k ρ /k 0 or the frequency ω are varied the other independent variable being kept fixed. Here these two cuts are called spatial (ω fixed) and frequency (k ρ /k 0 fixed) domains. Due to a lower leakage, the Q and IFoM of the IMI and MIM thin film stack modes are significantly larger in the spatial domain than in the frequency domain. In the spatial domain the IMI and MIM stack modes dominate at low and high frequencies respectively. In the frequency domain, the Q and IFoM of a MIM stack mode is always larger than that of an IMI stack. Our results span a large domain of frequencies in the SPP and RPP region and of the in-plane wave vector whereas the results in the literature presented above concern only particular laser frequencies and limited in-plane wave vector values. Our Q and IFoM of the 2D planar thin film stack modes, obtained with optimized independent variables, are larger than those of other planar thin film stacks but smaller than some 2D/3D nano scale samples with an involved geometry. The simplicity of producing these simple IMI and MIM stacks permit their use in the applications.

An electro-optic half subtractor from a silicon-based hybrid surface plasmon polariton waveguide

Abstract In order to solve the problems of low transmission rate and large device size of electro-optical modulator, an electro-optic half subtractor based on silicon-based hybrid surface plasmon polariton waveguide is proposed in this study. The proposed device utilizes three units metal-oxide-semiconductor capacitor structure to achieve the half subtractor logic function of electro-optic control, improving the transmission rate of the electro-optic half subtractor while also reducing the device size using surface plasmon polariton technology, with a size of only 32 μm × 4.3 μm. At the same time, the use of hybrid silicon waveguides reduces the sharp Ohmic attenuation caused by surface plasmon polaritons and reduces optical insertion losses (ILs). The simulation results show that when the electro-optic half subtractor operates at the wavelength of 1,550 nm, the IL difference is 1.0 dB in each state, the transmission rate of the device is 0.75 Tbit/s, and the energy consumption is 12.69 fj/bit.

Graphene-Loaded Surface Plasmon Polariton (SPP) Waveguide Surrounded by Uniaxial Chiral (UAC) and Plasma Layers

Graphene-Loaded Surface Plasmon Polariton (SPP) Waveguide Surrounded by Uniaxial Chiral (UAC) and Plasma Layers

Power-modulated reconfigurable nonlinear plasmonic devices without DC power supply and feed circuit

High-power electromagnetic (EM) waves can directly modulate the parameters of nonlinear varactor diodes through the rectification and Kerr effects without relying on external sources. Based on this principle, we propose a power-modulated reconfigurable nonlinear device based on spoof surface plasmon polariton (SSPP) waveguide loaded by varactor diodes, without applying DC power supply or feed circuit. Increasing the input power level reduces the effective capacitance of the varactor diode, leading to a blueshift in the cutoff frequency of the SSPP waveguide. This feature can be employed to realize the switching on/off of the input signal depending on the signal power. On the other hand, the transmission state of a low-power signal can be controlled by inputting another independent high-power EM wave simultaneously. Increasing the power of the control wave will enable the low-power signal within a wider bandwidth switched from off to on states. Experimental results are presented to show the excellent performance of the power-modulated reconfigurable SSPP device. This method can reduce the system complexity and provide inspiration for reconfigurable all-passive multifunctional devices and systems.

Non-Markovian quantum interconnect formed by a surface plasmon polariton waveguide

Non-Markovian quantum interconnect formed by a surface plasmon polariton waveguide

Fabrication and characterization of delay lines with spoof surface plasmon polariton waveguide coupled with C-shaped metamaterials for microwave integrated circuits

Abstract Here, we proposed two delay lines consisting of spoof Surface Plasmon Polariton (sSPP) waveguides and C-shaped metamaterials (C-MMs). The delay lines, namely OFF and ON devices, were designed and fabricated. On the OFF device, an sSPP waveguide is capacitively coupled to the C-MMs via an air gap on a high-resistivity silicon substrate. On the ON device, a connection is established between the C-MMs and the sSPP waveguide by metal connectors. The difference in the electrical properties in the coupling between the C-MMs and the sSPP waveguide creates a large phase contrast between the ON and OFF delay lines. The structural design was performed using a numerical calculation based on a commercial finite element solver. We successfully fabricated and characterized delay lines with phase differences equal to tens of degrees between the ON and OFF devices in the target frequency range of 2-6 GHz, while maintaining the original transmittance properties. The promising applications of the delay lines are a phase shifter or modulator when integrating with suitable switches.

Small attenuation negative group delay of spoof surface plasmon polaritons

Spoof surface plasmon polariton (SSPP) waveguides can be used to effectively construct on-chip microwave systems due to the single-side conductor structure. SSPP waveguides usually exhibit normal dispersion, which can introduce large group delays to transmission signal and impair waveform shapes. However, the negative group velocity (NGV) effect may occur in the split modes of coupled surface plasmon polariton waveguides. In this regard, the synthesis wave model of forward and backward transmission waves is applied, which generates a quadrupole vortex wave transmission. In this paper, the SSPP unit structure with folded multi-split rings is proposed to achieve anomalous dispersion with NGV feature in the fundamental mode. The SSPP unit can be equivalent to an epsilon-negative medium, and a maximum negative group delay (NGD) can be reached at the frequency where the NGV begins to appear. For the corresponding SSPP waveguide, a NGD band with lower attenuation can be achieved at the stopband edge. While the SSPP unit structures are loaded as dispersive materials in a microstip line, the similar NGD performance can be obtained. Clearly, the SSPP NGD with lower attenuation provides a new delay equalization method for ultra reliable and low latency communications (URLLC), and can also be used as an effective dispersion compensation means.

Vernier Ellipsometry Sensing with Ultralow Limit‐of‐Detection and Large Dynamic Range by Tuning of Zero‐Reflection Points

AbstractOptical sensors using zero‐reflection points (ZRPs) enable excellent sensitivity due to the accompanying phase singularities and the steepest slope of the reflectivity curve. Here, the collaborative manipulation of three ZRPs in a simple platform formed by a lithography‐free, metal‐dielectric‐metal structure with unsurpassed, experimentally demonstrated, limit of detection ≈2 × 10−8 refractive index unit is reported. The sensor relies on: i) strong coupling between p‐polarized surface plasmon polariton and photonic waveguide, leading to reflection suppression, Rabi splitting and phase singularities; ii) simultaneous implementation of two orthogonally polarized ZRPs, enabling spectral overlap of s‐polarized photonic modes (Rs) with the coupled p‐polarized resonances (Rp); and iii) ellipsometry‐based sensing where the s‐polarized ZRPs provide a stable reference to boost the sensor performance in terms of the amplitude ratio and phase difference of Rp and Rs thereby naturally forming a refinement measuring scale akin to a Vernier scale. Remarkably, the precise manipulation of ZRPs enables resetting the sensor to its optimal sensing point. The capability has been demonstrated for a biosensor of SARS‐CoV‐2 spike (S2) protein that can track the full functionalization process then reset to perform dose‐dependent detection of the S2 protein. This work provides a new strategy for the development of optical sensors and perfect light absorbers.

Compact Muti-Frequency Band-Pass Filters Based on High-Order Mode of Folded Line Spoof Surface Plasmon Polaritons Waveguide

Compact Muti-Frequency Band-Pass Filters Based on High-Order Mode of Folded Line Spoof Surface Plasmon Polaritons Waveguide

Terahertz plasmonic functional devices enabled by multimode interference

Terahertz integrated devices have attracted great attention due to their potential applications in communication systems. Although some functional devices based on terahertz spoof surface plasmon polariton (SPP) waveguides have been studied, multimode waveguides and multimode interference mechanism have rarely been explored. This work investigates several key functional plasmonic devices based on multi-SPP mode interference in the terahertz regime. The feasibility of multimode transmission on terahertz plasmonic waveguides and control of the propagation modes by varying the waveguide parameters are first investigated. Then, the interference mechanism between two or more propagation modes and the self-imaging principle are applied to plasmonic waveguides. Finally, a series of terahertz plasmonic functional devices such as a coupler, wavelength diplexers, and cascaded devices are proposed and simulated by exploring different interference lengths, frequencies, and cascades via the self-imaging principle. These devices have good performance in transmission response, crosstalk, bandwidth, and footprint, and are expected to play an important role in the development of terahertz on-chip communication systems.

Toward Magneto‐Plasmonic Functionality in a Self‐Assembled Device Based on Colloidal Synthesis

The confinement of surface plasmon polaritons (SPPs) offers strong field strengths also for longitudinal field components. Phenomena like spin‐momentum locking can thus be exploited for novel functionality in nanodevices. External control of transport or directional coupling of propagating SPPs would be highly interesting for applications. Herein, the coupling of noble metal and magnetic nanoparticles to a silver nanowire acting as SPP waveguide using a hybrid self‐assembly approach is demonstrated. A designated setup is reported to isolate and investigate magnetically controlled transport in such devices. Various configurations are measured to quantify the required sensitivity for the typically tiny magnet response at moderate strengths of the magnetic field. Although magnetic control cannot be achieved, the required improvements can be estimated based on a heuristic numerical model. It is suggested using an approach to enhance magnetic response using a combination of metal and magnetic nanoparticles. Such devices can be assembled in principle with self‐assembly approach in a multistep process.

Advanced mid-infrared plasmonic waveguides for on-chip integrated photonics

Long-wave infrared (LWIR, 8–14 µm) photonics is a rapidly growing research field within the mid-IR with applications in molecular spectroscopy and optical free-space communication. LWIR applications are often addressed using rather bulky tabletop-sized free-space optical systems, preventing advanced photonic applications, such as rapid-time-scale experiments. Here, device miniaturization into photonic integrated circuits (PICs) with maintained optical capabilities is key to revolutionize mid-IR photonics. Subwavelength mode confinement in plasmonic structures enabled such miniaturization approaches in the visible-to-near-IR spectral range. However, adopting plasmonics for the LWIR needs suitable low-loss and -dispersion materials with compatible integration strategies to existing mid-IR technology. In this paper, we further unlock the field of LWIR/mid-IR PICs by combining photolithographic patterning of organic polymers with dielectric-loaded surface plasmon polariton (DLSPP) waveguides. In particular, polyethylene shows favorable optical properties, including low refractive index and broad transparency between ∼2 μm and 200 µm. We investigate the whole value chain, including design, fabrication, and characterization of polyethylene-based DLSPP waveguides and demonstrate their first-time plasmonic operation and mode guiding capabilities along S-bend structures. Low bending losses of ∼1.3 dB and straight-section propagation lengths of ∼1 mm, pave the way for unprecedented complex on-chip mid-IR photonic devices. Moreover, DLSPPs allow full control of the mode parameters (propagation length and guiding capabilities) for precisely addressing advanced sensing and telecommunication applications with chip-scale devices.

Near-Field Photodetection in Direction Tunable Surface Plasmon Polaritons Waveguides Embedded with Graphene.

2D materials have manifested themselves as key components toward compact integrated circuits. Because of their capability to circumvent the diffraction limit, light manipulation using surface plasmon polaritons (SPPs) is highly-valued. In this study, plasmonic photodetection using graphene as a 2D material is investigated. Non-scattering near-field detection of SPPs is implemented via monolayer graphene stacked under an SPP waveguide with a symmetric antenna. Energy conversion between radiation power and electrical signals is utilized for the photovoltaic and photoconductive processes of the gold-graphene interface and biased electrodes, measuring a maximum photoresponsivity of 29.2mAW-1 . The generated photocurrent is altered under the polarization state of the input light, producing a 400% contrast between the maximum and minimum signals. This result is universally applicable to all on-chip optoelectronic circuits.

A Flexible Amplitude Equalizing Filter Based on Spoof Surface Plasmon Polaritons

In this article, an amplitude equalizing spoof surface plasmon polaritons (AESSPPs) filter deposited on flexible substrate is proposed for the first time. This new hybrid device can realize both the characteristics of amplitude equalization and interference filtering when embedding into a wideband communication system, which brings the compensation process of gain fluctuation back to the microwave front end instead of traditional complex algorithm in digital chip. It is mainly composed of equalizing thin layer and spoof surface plasmon polaritons (SSPPs) waveguide. The equalizing thin layer is realized by ITO (Indium Tin Oxide) and periodically sputtered along the propagation path of SSPPs waveguide to dissipate EM energy at different frequencies. In order to better reveal the nature property of equalization and filtering, an equivalent circuit of AESSPPs unit cell is proposed and analyzed theoretically. The equalizing value and bandwidth can be regulated independently by surface impedance of ITO thin layer and the structural parameter of SSPPs, respectively. Finally, we fabricated and measured three AESSPPs filter prototypes with different critical parameters. All the theory, simulation and measurement results are proved to have achieved the artificial dominated equalizing curve with different equalizing value and bandwidth, which validate that the proposed filter demonstrates the desired flexibility, equalization and filtering capabilities simultaneously.