Dah-Ching Tzuang

Localized surface plasmon polaritons in Ag∕SiO2∕Ag plasmonic thermal emitter

The reflection dispersion relation and emission spectra of Ag∕SiO2∕Ag trilayer plasmonic thermal emitters with different lattice constant and Ag line width were investigated. The top Ag film is perforated with parallel line-shape hole array. The induced Ag∕SiO2 surface plasmons at both top and bottom Ag∕SiO2 interface are found coupled together. The coupling effect results in the localized surface plasmon polaritons confined at the top Ag∕SiO2 interface which exhibit the Fabry–Perot resonance. The thermal emission peak position coincides with the reflection minimum in the dispersion relation and shifts to long wavelength as the Ag line width increases, which proves that the emission is due to the excitation of localized surface plasmon polaritons. Moreover, the emitted light is polarized perpendicular to the parallel metal lines.

Coupling of surface plasmons between two silver films in a Ag/SiO2/Ag plasmonic thermal emitter with grating structure

The reflection and emission spectra of Ag/SiO2/Ag trilayer plasmonic thermal emitters with different SiO2 thicknesses are investigated. The top Ag film is perforated with periodic slits. It is found that the coupling of surface plasmons at the top and bottom Ag/SiO2 interface results in the redshift in thermal emission peaks. In this Ag/SiO2/Ag plasmonic thermal emitter, the electromagnetic field exhibits either Fabry–Perot resonance or propagating surface plasmons depending on the thickness of SiO2 layer. By varying the thickness of SiO2 layer, transition from localized to grating-coupled propagating surface plasmon modes is observed.

Narrow Bandwidth Midinfrared Waveguide Thermal Emitters

This work describes innovative waveguide thermal emitters with top metal perforated with subwavelength holes arranged in a short period to eliminate Bragg scattered waveguide modes (WMs) and surface plasmon polariton (SPP) modes. A metal-dielectric-metal parallel-plate waveguide with top metal perforated with subwavelength holes arranged in a short period exhibits high output intensities and emission peaks (WMs) with a narrow bandwidth in the midinfrared region under heat treatment. The redundant SPP modes and Bragg scattered WMs are filtered automatically by shifting them to the short wavelength due to a short period where blackbody radiations are too weak to appear.

Surface plasmon on aluminum concentric rings arranged in a long-range periodic structure

The enhanced optical transmission through the annular aluminum metal with different number of concentric rings arranged in a long-range periodic structure on the silicon substrate is investigated. The measured transmission spectra demonstrate that the surface plasmon modes depend sensitively on the structural parameters of the metallic rings. The degenerate (1,0), (1,1), and (2,1) Al∕Si surface plasmon modes are determined by the long periodicity of the structure. The localized modes in cavities with different length can be observed in this structure as well. These phenomena suggest that both surface plasmons and localized cavity modes are excited within super unit cell.

Characteristics of a waveguide mode in a trilayer Ag/SiO 2 /Au plasmonic thermal emitter

A suitably designed trilayer Ag/SiO(2)/Au thermal emitter can be used as the narrow bandwidth infrared light source. The thermal radiation generated in the SiO(2) layer resonates between the two metal films and results in not only the Ag/SiO(2) surface plasmon polaritons but also the waveguide mode (WM) in the Ag/SiO(2)/Au structure owing to the thick SiO(2) layer. This study investigated the influence of dielectric thickness on energy dispersion relations and derived the theoretical dispersion relation, which fit well with experimental results. This WM light source can be applied in the area of gas sensing and probing the response of the animal cells and plants to infrared radiation.

Localized surface plasmons in Al∕Si structure and Ag∕SiO2∕Ag emitter with different concentric metal rings

This paper reports the optical properties of Al∕Si structure and trilayer Ag∕SiO2∕Ag plasmonic thermal emitter with different concentric metal rings on top metal film. It is found that when the metal width is smaller than 40% of the period (=gap+metal width), the (1,0) Al∕Si surface plasmon leads to a maximum in the transmission spectra; otherwise, the opposite is observed. The dispersion relations and emission spectra of the plasmonic thermal emitters were investigated. The emission peaks are independent of the gap width and redshift as annular metal width increases. This phenomenon suggests the excitation of Fabry-Perot type resonance within cavity of Ag∕SiO2∕Ag structure. No (1,0) Ag∕SiO2 surface plasmon was observed.

Enhancement of Thermal Radiation in Plasmonic Thermal Emitter by Surface Plasmon Resonance

The emission spectra of Ag/Si02/Ag tri-layer plasmonic thermal emitters were investigated. It is demonstrated that the top silver film perforated with periodic hole arrays plays a role to amplify the thermal emission in the emitter at a specific wavelength determined by the surface plasmon. Obviously the amplification of the thermal radiation is independent of lattices. The amplification of thermal radiation at specific wavelength was induced by the strong surface plasmon resonance. In addition, it provides a useful tool to be applied in the area of gas sensing and probing the response of cells and plants to the infrared radiation. Furthermore, the emittance spectra with decreasing sized holes were measured and the peak position red shift was observed, the result was attributed to the variation of effective refractive index.

Extraordinary Transmission Through Ag–Si Structure Perforated With Rhombus Lattice Hole Arrays

This investigation elucidates the transmission characteristics of an Ag-Si structure on which an Ag film is perforated with a rhombus-shape of lattice holes. The transmission in the Ag-Si mode depends approximately linearly on the numbers of degenerate modes at long wavelengths at which the couplings between Ag-Si and Ag-air modes are weak. At the shorter wavelengths where Ag-Si and Ag-air modes are coupled together, the transmission intensities are approximately constant without an apparent peak at wavelengths longer than those of the Ag-air modes. The intensities decay rapidly at lower wavelengths owing the asymmetric slope of the Ag-air mode in the spectra.

Enhanced Thermal Radiation Observed in Metal-dielectric-metal Thermal Emitter by Surface Plasmon Resonance

The emission spectra of Ag/SiO2/Ag tri-layer plasmonic thermal emitters were investigated. It is found that the top silver film perforated with periodic hole array acts not only as a filter but also as an optical amplifier. The enhancement of thermal radiation at specific wavelength was induced by the strong surface plasmon resonance. Furthermore, the energy dispersion relation of the surface plasmon and the polar emission of the plasmonic thermal emitter were found.

The Characteristics of Cavity Mode in Trilayer Dielectric/Metal/Dielectric Plasmonic Thermal Emitter

A suitable designed trilayer Ag/SiO2/Au thermal emitter can be used as the narrow bandwidth infrared light source. The thermal radiation generated in the SiO2 layer resonates between the two metal films and results in not only the Ag/SiO2 surface plasmon polaritons but also the cavity mode in the Ag/SiO2/Au waveguide. The interaction between surface plasmon polaritons and the cavity modes was investigated, and the theoretical dispersion relation was derived which fitted well with the experimental results. This cavity mode light source can be applied in the area of gas sensing and probing the response of the animal cells and plants to the infrared radiation.