Supplementary MaterialsSupplementary Materials for High extinction ratio electromagnetically induced transparency analogue

Supplementary MaterialsSupplementary Materials for High extinction ratio electromagnetically induced transparency analogue based on the radiation suppression of dark modes 41598_2017_11920_MOESM1_ESM. coupling SRR arrangement. Finally, the potential multi-channel sensing utility of this device is demonstrated to show the importance of high ER feature. Introduction Electromagnetically induced transparency (EIT) is originally observed in atomic physics and arises due to quantum interference effect, resulting in a narrow transmission window inside an absorption band1. This concept was later extended to classical oscillator systems, such as mechanical spring-mass configurations2, RLC electric circuits3, coupled optical micro-resonators4, 5, and waveguides side coupled to a resonator6, 7. In the field of metamaterials, the transparent and highly dispersive nature of EIT-like effect offers a potential remedy towards low-reduction and high-quality-element resonances, which are crucial for recognizing low-reduction slow-light products8, sensors9, filter systems10, photoluminescence11 and enhancing non-linear interactions12. The classical analogue of EIT in metamaterials depends on the coupling between a broadband bright-mode resonator, which is obtainable from totally free space, and a narrowband dark mode resonator, which can be less-accessible from totally free space13. Because of low radiative lack of the dark setting, the EIT-like resonance can be quite sharp, GSK1120212 manufacturer leading to complete transmission14 or reflection15. The EIT-like impact has been noticed in a number of metamaterial configurations, such as for example nanoring dimer, metallic strips and coupled split ring resonators16C21. Active control and tuning the transparency window as well as its slow slight properties have also been explored in the past few years5, 22, 23. An appealing scheme was to use two polarization dependent split-ring resonators (SRRs) work as bright and dark modes respectively24, 25. However, the extinction ratio (ER) of conventional bright-dark SRR resonance is quite low due to its high radiative losses25, 26. Since high ER resonance is of particular importance for the ultrasensitive resonance sensing or frequency-selective ability in filter applications27, it is necessary to further suppress the radiation loss of bright or dark mode and increase ER in designing such devices. In this work, we propose and demonstrate a mirror-like symmetrical unit cell of metamaterial to generate an EIT analogue with high extinction ratio. The unit cell consists of four SRRs to form the bright-dark-dark-bright modes configuration. Two bright resonators can be strongly excited by the incident wave, while two dark resonators can only be excited through near field coupling with bright SRRs. Compared to the conventional bright-dark coupling of two SRRs, the symmetrical arrangement of two dark modes induces highly suppression of their own electric and magnetic dipole radiation losses, and hence extraordinarily high ER transmission. A theoretical analysis using the coupled-resonator model shows the transmission characteristics, and numerical simulation is adapted to analyze interaction between the four elements in the metamaterial unit cell. The transmission performance is measured for fabricated devices and 11?dB improvement of GSK1120212 manufacturer ER is obtained, which verifies our design. Finally, we demonstrate the sensing ability SEB of our structure and compare the results with conventional bright-dark structure, to further show the potential utility of this multi-channel sensor and the importance of high ER feature. Results and Discussions Figure?1(a) shows the schematic illustration of our proposed symmetrically coupled bright-dark-dark-bright metamaterial unit cell that consists of four SRRs, such unit cell appears periodically to form a metamaterial structure of Fig.?1(b). In each unit cell, the two SRRs with the split gap aligned parallel to the electric field of incident wave are termed GSK1120212 manufacturer as bright resonators (R1 and R4), since their fundamental LC resonances can GSK1120212 manufacturer be excited. On the contrary, the other two orthogonally twisted resonators (R2 and R3) are called dark resonators, as their fundamental LC resonance is less accessible with the same polarization. Therefore, the.