ABSTRACT
Improving the conversion efficiency is particularly important for the generation and applications of harmonic waves in optical microstructures. Herein, we propose to enhance the efficiency of third harmonic generation by integrating a monolayer WS2 with the metal/dielectric/photonic crystal multilayer structure. The numerical simulations show that the multilayer structure enables to generate the Tamm plasmon mode between the metal film and photonic crystal around the telecommunication wavelength, which is consistent with the experimental result. By measuring with a self-built nonlinear optical micro-spectroscopy system, we find that the third harmonic signal can be reinforced by 16-fold through inserting the monolayer WS2 in the dielectric spacer. This work will provide a new way for improving nonlinear optical response, especially THG in multilayer photonic microstructures.
ABSTRACT
Surface plasmon resonance holographic microscopy (SPRHM) has been employed to measure the refractive index but whose performance is generally limited by the metallic intrinsic loss. Herein we first, to our knowledge, utilize guided wave resonance (GWR) with low loss to realize the monitoring of the refractive index by integrating with digital holographic microscopy (DHM). By depositing a dielectric layer on a silver film, we observe a typical GWR in the dielectric layer with stronger field enhancement and higher sensitivity to the surrounding refractive index compared to the silver film-supported SPR, which agrees well with calculations. The innovative combination of the GWR and DHM contributes to the highly sensitive dynamic monitoring of the surrounding refractive index variation. Through the measurement with DHM, we found that the GWR presents an excellent sensitivity, which is 2.6 times higher than that of the SPR on the silver film. The results will pave a new pathway for digital holographic interferometry and its applications in environmental and biological detections.
ABSTRACT
Topological insulators (TIs) are a new type of Dirac material that possess unique electrical and optical properties, enabling the generation of surface plasmons over an extensive spectral range with promising applications in functional devices. Herein, we fabricated antimony telluride (Sb2Te3) TI nanoparticles by using magnetron sputtering and focused ion beam (FIB) lithography techniques, and experimentally demonstrated high-performance refractive index nanosensing. We find that the Sb2Te3 TI nanoparticles can support the excitation of localized surface plasmon resonance (LSPR), which depends on the dimensions of the TI nanoparticle. TI-based LSPR can contribute to the nanoscale sensing of the surrounding refractive index with a high sensitivity of 443 nm RIU-1, which is comparable to that of plasmonic sensors based on metallic nanoparticles. The experimental results are in excellent agreement with finite-difference time-domain (FDTD) numerical simulations. This work will pave a new way to explore TI optical properties and applications in nanophotonic devices, especially plasmonic nanosensors.
ABSTRACT
Photon-exciton coupling behaviors in optical nanocavities attract broad attention due to their crucial applications in light manipulation and emission. Herein, we experimentally observed a Fano-like resonance with asymmetrical spectral response in an ultrathin metal-dielectric-metal (MDM) cavity integrated with an atomic-layer tungsten disulfide (WS2). The resonance wavelength of an MDM nanocavity can be flexibly controlled by adjusting dielectric layer thickness. The results measured by the home-made microscopic spectrometer agree well with the numerical simulations. A temporal coupled-mode theoretical model was established to analyze the formation mechanism of Fano resonance in the ultrathin cavity. The theoretical analysis reveals that the Fano resonance is attributed to a weak coupling between the resonance photons in the nanocavity and excitons in the WS2 atomic layer. The results will pave a new way for exciton-induced generation of Fano resonance and light spectral manipulation at the nanoscale.
ABSTRACT
Symmetric metal-dielectric-metal (MDM) nanocavities based on Fabry-Perot resonance play a crucial role in transmission colors. However, their reflection color gamuts are generally limited owing to the narrow dip of resonance spectrum. In this work, we propose and fabricate symmetric titanium-indium tin oxide-silver (Ti/ITO/Ag) nanocavities to realize the reflection colors. The experimental and simulation results show that reflection color gamut of the asymmetric nanocavity is wider than that of symmetric MDM nanocavity due to the generation of broader resonance spectral dip. Moreover, a grayscale focused ion beam (FIB) etching method is employed to fabricate the thickness-controlled microstructures, and the etching depth satisfies a linear relationship with the gray value. The reflection color image can be observed by fabricating the ITO layer in the asymmetric MDM nanocavity with grayscale FIB etching method, which is more vivid than the image from fabricated symmetric MDM nanocavities. This work will provide a new way for color printing, color display, and ultra-small anti-counterfeiting technology.
