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In this paper, we design a multifunctional micro-nano device with a hybrid metamaterial-waveguide system, which leads to a triple plasmon-induced transparency (PIT). The formation mechanisms of the three transparent peaks have their own unique characteristics. First, PIT-I can be switched into the BIC (Friedrich–Wintge bound state in continuum), and the quality factors (Q-factors) of the transparency window of PIT-I are increased during the process. Second, PIT-II comes from near-field coupling between two bright modes. Third, PIT-III is generated by the near-field coupling between a low-Q broadband bright mode and a high-Q narrowband guide mode, which also has a high-Q transparent window due to the guide mode. The triple-PIT described above can be dynamically tuned by the gate voltage of the graphene, particularly for the dynamic tuning of the Q values of PIT-I and PIT-III. Based on the high Q value of the transparent window, our proposed structure can be used for highly sensitive refractive index sensors or devices with prominent slow light effects. [ABSTRACT FROM AUTHOR]

Plasmonic resonators have drawn more attention due to the ability to confine light into subwavelength scale. However, they always suffer from a low-quality (Q) factor owing to the intrinsic loss of metal. Here, we numerically propose a plasmonic resonator with ultra-high Q factor based on plasmonic metal–insulator-metal (MIM) waveguide structures. The resonator consists of a disk cavity surrounded by a concentric ring cavity, possessing an ultra-small volume. Arising from the plasmon hybridization between plasmon modes in the disk and ring cavity, the induced bonding hybridized modes have an ultra-narrow full width at half maximum (FWHM) as well as ultra-high Q factors. The FWHM can be nearly 1 nm and Q factor can be more than 400. Furthermore, such a device can act as a refractive index sensor with an ultra-high figure of merit (FOM). This work provides a novel approach to design plasmonic high-Q-factor resonators and has potential on-chip applications such as filters, multi-spectral sensors and nanolasers. [ABSTRACT FROM AUTHOR]

The realization of the electromagnetically induced transparency (EIT) effect based on guided-mode resonance (GMR) has attracted a lot of attention. However, achieving the multispectral EIT effect in this way has not been studied. Here, we numerically realize a double EIT-ike effect with extremely high Q factors based on a GMR system with the double-bar dielectric grating structure, and the Q factors can reach 35,104 and 24,423, respectively. Moreover, the resonance wavelengths of the two EIT peaks can be flexibly controlled by changing the corresponding structural parameters. The figure of merit (FOM) of the dual-mode refractive index sensor based on this system can reach 571.88 and 587.42, respectively. Our work provides a novel method to achieve double EIT-like effects, which can be applied to the dual mode sensor, dual channel slow light and so on. [ABSTRACT FROM AUTHOR]

We investigate the active control of electromagnetically induced transparency (EIT) analogue based on terahertz (THz) metamaterials integrated with vanadium oxide(VO2). Due to the insulator-to-metal transition of VO2, the amplitude of EIT peak can be actively modulated with significant modulation depth. Meanwhile the group delay within the transparent window can also be dynamically tuned, bringing the active control of slow light effect. Furthermore, we also introduce independently tunable transparent peaks based on double-peak EIT, and the group delay within each transparent window can also be independently controlled. Finally, based on broadband EIT, the active tuning toward quality factor of EIT is also realized. This work introduces active EIT control with multiple degree of freedom by employing VO2, and can find potential applications in future wireless THz communication systems as multi-channel filters, switches, spacers, logic gates and modulators. [ABSTRACT FROM AUTHOR]

An asymmetric grating structure was investigated for realizing mid-infrared (mid-IR) ultra-high resolution dual-band notch filters. The structure is constructed by an asymmetric gold grating on the stack of an Al 2 O 3 layer and a CaF 2 substrate. The grating consists of three gold strips in each unit cell, and the center-to-center distances between two adjacent gold strips are different. The filter provides two high-extinction transmission dips over a broad spectral region. One is at a wavelength of ∼ 3. 8381 μ m with a full-width at half-maximum (FWHM) of ∼ 0.7 nm, and the other is at a wavelength of ∼ 3. 8435 μ m with a FWHM of ∼ 1.7 nm. The quality-factor (Q-factor) of the filter is >2200. It was found that the two transmission dips result from the excited (+1) and (-1) resonance modes, respectively. Thus, there is an interesting feature that either of the two transmission dips does not split at oblique incidence. [ABSTRACT FROM AUTHOR]