In this paper, we present one dimensional plasmonic narrow groove nano-gratings, covered with a thin film of VO(2) (Vanadium Dioxide), as novel optical switches. These narrow groove gratings couple the incident optical radiation to plasmonic waveguide modes leading to high electromagnetic fields in the gaps between the nano-gratings. Since VO(2) changes from its semiconductor to its metallic phase on heating, on exposure to infra-red light, or on application of voltage, the optical properties of the underlying plasmonic grating also get altered during this phase transition, thereby resulting in significant switchability of the reflectance spectra. Moreover, as the phase transition in VO(2) can occur at femto-second time-scales, the VO(2)-coated plasmonic optical switch described in this paper can potentially be employed for ultrafast optical switching. We aim at maximizing this switchability, i.e., maximizing the differential reflectance (DR) between the two states (metallic and semiconductor) of this VO(2) coated nano-grating. Rigorous Coupled Wave Analysis (RCWA) reveals that the switching wavelengths - i.e., the wavelengths at which the values of the differential reflectance between VO(2) (S) and VO(2) (M) phases are maximum - can be tuned over a large spectral regime by varying the nano-grating parameters such as groove width, depth of the narrow groove, grating width, and thickness of the VO(2) layer. A comparison of the proposed ideal nano-gratings with various types of non-ideal nano-gratings - i.e., nano-gratings with non-parallel sidewalls - has also been carried out. It is found that significant switchability is also present for these non-ideal gratings that are easy to fabricate. Thus, we propose highly switchable and wide-spectra VO(2) based narrow groove nano-gratings that do not have a complex structure and can be easily fabricated.
A surface-enhanced Raman scattering (SERS) substrate based on plasmonics-active metallic nano-finger arrays grown on arrays of triangular-shaped metal-coated silicon nanowire arrays is proposed. Finite-difference time-domain modeling is employed to numerically calculate the effect of the inter-finger gap and the growth angle of the nano-fingers on the magnitude of SERS enhancement and the plasmon resonance wavelength. Additionally, the polarization dependence of the SERS signals from these novel substrates has been studied. A protocol for the fabrication of the proposed SERS substrate is also discussed.
We present hybrid nanoline-nanoparticle plasmonic substrates which allow easily achievable sub-5 nm gaps and a possibility of large-area fabrication. These substrates--based on plasmonic nanocavities formed by arrays of plasmonic nanoparticle (NP) dimers lying inside periodic metal nanolines (NLs)--can be used as tunable surface enhanced Raman scattering (SERS) substrates due to the tunability of cavity modes in the gap regions. Theoretical studies were conducted, using finite difference time domain (FDTD) modeling, to understand the plasmon resonance tunability as a function of gaps in these hybrid plasmonic substrates. The gaps forming the nanocavities include those between nanolines and nanoparticles (NL-NP) and between two nanoparticles (NP-NP). Our analysis reveals that these gaps play a combined role in tuning the resonance wavelength and the magnitude of electromagnetic field enhancement. Moreover, distinct structure-dependent plasmon resonance peaks are present in addition to material-dependent resonance peaks characteristic to the metal involved. Replacing the spherical particle arrays inside the nanolines with nanorod arrays revealed the possibility of tuning the plasmon resonance in the near-infrared regime. This indicates that there is a possibility of tuning the plasmon resonance wavelength to any region of the visible or near-infrared spectrum by changing the size or shape of the particles assembled inside these plasmonic nanolines.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.