Engineered Absorption Enhancement and Induced Transparency in Coupled Molecular and Plasmonic Resonator Systems

Abstract Here we present a graphene-based long-wavelength infrared modulator characteristic of extra-high contrast, where the frequency detuning degree of magnetic and electric surface plasmons (SPs) is controllable by the gated graphene Fermi energy. If the device is designed to work in a strong SP-coupling regime by selecting an appropriate low-lossy gate dielectric thickness, a modulation depth (MD) up to ~100% but insertion loss (IL) as low as ~-0.37 dB is achievable. Moreover, a compromised MD >90% with IL <-1.0 dB is still retainable in two broadband ranges. The disclosed underlying mechanism to the device working state in the strong, electromagnetic-induced transparency (EIT), or weak SP-coupling regime, indicates the coupling regime shows a strong dependence on the dielectric thickness, which is related to the magnetic-SP mode volume, while the working wavelength can be selected in a broader spectral range by scaling the device geometry. These findings are helpful to construct those optoelectronics for infrared absorption enhancement, EIT, and strong coupling spectral characteristic itself.

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Plasmon-assisted interaction of Si with light, for cancer hyperthermia and electromagnetic energy harvest

The European Physical Journal Applied Physics ◽

10.1051/epjap/2020200071 ◽

2020 ◽

Vol 92 (2) ◽

pp. 20101

Author(s):

Behnam Kheyraddini Mousavi ◽

Morteza Rezaei Talarposhti ◽

Farshid Karbassian ◽

Arash Kheyraddini Mousavi

Keyword(s):

Silicon Nanowires ◽

Metallic Nanoparticles ◽

Near Infrared ◽

Optical Transition ◽

Electromagnetic Energy ◽

Energy Harvest ◽

Absorption Enhancement ◽

Ir Absorption ◽

Absorption Mechanism ◽

Near Ir

Metal-assisted chemical etching (MACE) is applied for fabrication of silicon nanowires (SiNWs). We have shown the effect of amorphous sheath of SiNWs by treating the nanowires with SF6 and the resulting reduction of absorption bandwidth, i.e. making SiNWs semi-transparent in near-infrared (IR). For the first time, by treating the fabricated SiNWs with copper containing HF∕H2O2∕H2O solution, we have generated crystalline nanowires with broader light absorption spectrum, up to λ = 1 μm. Both the absorption and photo-luminescence (PL) of the SiNWs are observed from visible to IR wavelengths. It is found that the SiNWs have PL at visible and near Infrared wavelengths, which may infer presence of mechanisms such as forbidden gap transitions other can involvement of plasmonic resonances. Non-radiative recombination of excitons is one of the reasons behind absorption of SiNWs. Also, on the dielectric metal interface, the absorption mechanism can be due to plasmonic dissipation or plasmon-assisted generation of excitons in the indirect band-gap material. Comparison between nanowires with and without metallic nanoparticles has revealed the effect of nanoparticles on absorption enhancement. The broader near IR absorption, paves the way for applications like hyperthermia of cancer while the optical transition in near IR also facilitates harvesting electromagnetic energy at a broad spectrum from visible to IR.

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