Abstract
The quality (Q) factor and tunability of electromagnetically induced transparency (EIT)-like effect in plasmonic systems are restrained by the intrinsic loss and weak adjustability of metals, limiting the performance of the devices including optical sensor and storage. Exploring new schemes to realize the high Q-factor and tunable EIT-like effect is particularly significant in plasmonic systems. Here, we present an ultrahigh Q-factor and flexibly tunable EIT-like response in a novel plasmonic system. The results illustrate that the induced transparency distinctly appears when surface plasmon polaritons excited on the metal satisfy the wavevector matching condition with the guided mode in the high-refractive index (HRI) layer. The Q factor of the EIT-like spectrum can exceed 2000, which is remarkable compared to that of other plasmonic systems such as plasmonic metamaterials and waveguides. The position and lineshape of EIT-like spectrum are strongly dependent on the geometrical parameters. An EIT pair is generated in the splitting absorption spectra, which can be easily controlled by adjusting the incident angle of light. Especially, we achieve the dynamical tunability of EIT-like spectrum by changing the Fermi level of graphene inserted in the system. Our results will open a new avenue toward the plasmonic sensing, spectral shaping and switching.
Highlights
Induced transparency (EIT) is a quantum destructive interference effect that occurs in atomic systems, inducing a narrow transparency window in the original absorption spectrum[1]
We find that the group index exceeds 800 in the plasmonic system with d = 1400 nm, which is one order of magnitude higher than that of plasmonic metamaterials[11] and waveguides[20]
We have presented a flexibly tunable and ultrahigh Q-factor electromagnetically induced transparency (EIT)-like effect in a new plasmonic system composed of a Al2O3 grating and a silver film coated on the SiO2/TiO2/SiO2 layers
Summary
Induced transparency (EIT) is a quantum destructive interference effect that occurs in atomic systems, inducing a narrow transparency window in the original absorption spectrum[1]. A new kind of optical phenomena was observed and regarded as the EIT-like effect due to its remarkable analog of the EIT effect in atomic systems[7,8,9,10]. Exploring new ways to realize flexibly tunable high-Q-factor EIT-like effect in plasmonic systems is meaningful and challenging. The results illustrate that a classical analog of EIT effect can be observed in the absorption spectrum due to the satisfaction of wavevector matching condition between the SPP mode on the metallic film and guided mode in the high-refractive index (HRI) layer. We find that the EIT-like spectrum possesses an ultrahigh Q factor of >2000 and can be significantly tailored by adjusting the grating width, spacer thickness, HRI layer thickness and refractive index of HRI layer. The results may provide a new pathway toward the high-efficiency plasmonic sensing, spectral shaping and switching
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