Passive amplitude-phase modulations and sensing based on Mach–Zehnder interferometer of spoof surface plasmon polaritons

Abstract

We numerically and experimentally demonstrate an ultrathin and compact Mach–Zehnder interferometer (MZI) for sensing and amplitude/phase modulations of spoof surface plasmon polariton (SSPP) waves. For a specific frequency, the magnitude and phase of the far-field transmission are modulated when a dielectric sample is loaded on one of the MZI arms. The phase difference between the SSPP waves propagating along the sensing and reference arms causes the outputs from both arms to interfere, allowing small perturbations in the sensing arm to be detected. Our study shows that the sensitivity of the proposed SSPP MZI is significantly higher than that of the single-armed SSPP waveguide, and also better than that of the conventional MZI formed with the traditional microstrip lines. The dependence of the sensitivity on the structural parameters such as geometrical parameters of the detected material and the arm length of MZI is discussed, revealing the possibility of realizing miniaturized MZI with high sensitivity.

Logic Gates of Terahertz Spoof Surface Plasmons

“…Due to the limitations of the experimental conditions, the proposed SSPP waveguide structure is designed to be similar to the Mach-Zehnder Interferometer (MZI), where the upper and lower arms are regarded as the two input signals, respectively. [44,45] Thus, the phase difference (Δϕ 0 ) between the upper and lower arms determines the output state and can be written as…”

“…Due to the limitations of the experimental conditions, the proposed SSPP waveguide structure is designed to be similar to the Mach–Zehnder Interferometer (MZI), where the upper and lower arms are regarded as the two input signals, respectively. [ 44,45 ] Thus, the phase difference (Δφ 0 ) between the upper and lower arms determines the output state and can be written as $$\[ \begin{array}{*{20}{c}}{\left| {{A_o}} \right| = \left| {{A_{\rm{i}}}\cos \frac{{\Delta {\varphi _0}}}{2}} \right|}\end{array} \]$$where Ao and A i are the output and input amplitudes of the waveguide, respectively. When the phase difference is (2 k + 1) π ( k = 0, ±1, ±2,…), the output signal is zero.…”

Spoof Localized Surface Plasmon Enhanced Isolation and Circulation

“…[ 5 ] Moreover, the dispersion properties of SSPPs can be engineered by tuning the structures of the surface patterning or the bias voltages/currents of the integrated varactor diodes/positive‐intrinsic‐negative (PIN) diodes, providing flexibility in the design of devices with multiple functionalities or working frequency bands. [ 6–9 ]…”

“…[5] Moreover, the dispersion properties of SSPPs can be engineered by tuning the structures of the surface patterning or the bias voltages/currents of the integrated varactor diodes/positive-intrinsic-negative (PIN) diodes, providing flexibility in the design of devices with multiple functionalities or working frequency bands. [6][7][8][9] The metamaterial approach can also be used to design localized surface plasmons (LSPs) at low frequencies by making corrugations on closed metal surfaces. Spoof LSPs(SLSP) resonators with straight or spiral corrugations have been demonstrated to support multiple resonance modes [10,11] and applied in the design of sensors, [12,13] filters, [14,15] etc.…”

Active spoof plasmonics: from design to applications

“…Following the proposal of CSPs which paves the way for the integration of SSPP devices with conventional microwave circuits [46], we have witnessed a dramatic growth in both the number and scope of SSPP applications. Various planar SSPP devices have been proposed at microwave and THz frequencies, including resonators and sensors [47][48][49][50][51][52][53][54], filters [55][56][57][58][59][60][61][62][63], splitters and couplers [64][65][66][67], and antennas [68][69][70][71][72][73][74][75][76][77]. The unique feature of SSPPs that the dispersion property can be engineered by the geometrical parameters of the structure offers great flexibility in the device design.…”