Author Affiliations
Northwestern Polytechnical University, School of Physical Science and Technology, MOE Key Laboratory of Material Physics and Chemistry under Extraordinary Conditions, Key Laboratory of Light-Field Manipulation and Information Acquisition, Ministry of Industry and Information Technology, Shaanxi Key Laboratory of Optical Information Technology, Xi’an, Chinashow less
Fig. 1. TI structures and absorption spectra. (a) 3D diagram of the ultrathin nanocavity with a TI nanofilm coated on a metallic layer. (b) Angle-tilted cross-sectional SEM image of a TI nanocavity deposited on a substrate. The scale bar is 200 nm. Here, and are the thicknesses of and silver nanofilms, respectively. (c) Experimental measurement of the absorption spectrum of the nanocavity with a 42-nm film on a 30-nm silver layer (i.e., and ). (d) 3D diagram of a TI nanocavity on a 1D photonic crystal. (e) Cross-sectional SEM image of a nanocavity on a photonic crystal with alternately stacked and layers. Here, and are the thicknesses of and layers, respectively. is the periodic number. The scale bar is . The inset shows the high-resolution SEM image of and silver films on the photonic crystal. The scale bar is 200 nm. (f) Measured absorption spectrum of the TI nanocavity/photonic crystal structure with , , , , and . The inset depicts a three-level system of the EIT-like effect. stands for the nanocavity resonant frequency. is the frequency detuning between the nanocavity resonance and Tamm plasmons in silver/photonic crystal structure. and are the decaying rates of nanocavity resonance and Tamm plasmons, respectively. is the complex coupling coefficient between the nanocavity resonance and Tamm plasmons with a phase retardation .
Fig. 2. Material characterization and optical constants of TI. (a) TEM image of a grown 42-nm TI film transferred on the supporter of a copper microgrid. (b) SAED pattern of the nanofilm. (c) HRTEM image of the nanofilm. (d) Ellipsometer-measured (circles) and fitted (curves) refractive indices and extinction coefficients of TI at the wavelengths from 230 to 1930 nm. (e), (f) Fitted refractive indices and extinction coefficients of TI surface and bulk states with the layer-on-bulk model [the inset in panel (d)].
Fig. 3. TI thickness-dependent nanocavity resonance and induced transparency. (a) Experimentally measured absorption spectra of the TI nanocavities on the substrate with different film thicknesses when . (b) Corresponding resonance wavelengths of the TI nanocavity with different . The curve, red circles, and blue circles denote the theoretical, experimental, and simulation results, respectively. (c) Corresponding magnetic field distribution of the TI nanocavity with a 42-nm film (i.e., ) at the absorption peak wavelength. (d), (e) Measured and simulated absorption spectra of the TI nanocavity/photonic crystal structures with different when . (f) Corresponding magnetic field distribution of the TI nanocavity/photonic crystal structure with a 42-nm film at the absorption dip wavelength.
Fig. 4. EIT-like response with different silver film thicknesses. (a) Theoretical evolution of absorption spectrum from the TI nanocavity/photonic crystal structures with different silver film thicknesses when . (b) Measured (solid curves) and fitted (dashed curves) absorption spectra of the TI nanocavity/photonic crystal structures with different when . Here, the experimentally measured spectra were fitted with the TCO model. (c) Fitted decaying rates and coupling strengths in the TCO model with different . The inset shows the corresponding decaying rates .