Ming-Wei Tsai

High performance midinfrared narrow-band plasmonic thermal emitter

The blackbody radiation spectrum is fundamental to any thermal emitter. However, by properly designing the emitter structure, a narrow bandwidth and high power infrared source can be achieved. This invention consists of a triple layer structure by sandwiching a dielectric SiO2 layer between two Ag metal films on the Si substrate. The top Ag layer is perforated by periodic holes. When the device was heated, the background thermal radiation was suppressed by the bottom Ag whose emissivity is very low. The thermal radiation generated in the SiO2 layer resonant between two metal films and the Ag∕SiO2 and the Ag/air surface plasmon polaritons are induced and converted to light radiation. Strong resonance at Ag∕SiO2 (1,0) degenerate modes results in the coherent light radiation at the wavelength associated with the dielectric constant of SiO2 and the lattice constant of the perforated hole array. The ratio of the full width at half maximum to the peak wavelength is 0.114. This narrow bandwidth and high power in...

Extraordinary transmission through a silver film perforated with cross shaped hole arrays in a square lattice

In this work, the transmission through cross shaped hole with different sizes but the same lattice constant was measured with the polarized light to investigate the variation of localized charge oscillation around the hole. The comparison between the transmission intensities through the similarly arranged periodic hole array with different hole shapes, i.e., cross, square, and rectangular, were also measured. The cross shaped hole gives rise to a larger transmission of light than those perforated with square or rectangular hole.

Reflection and emission properties of an infrared emitter.

The reflection and emission properties of an infrared emitter, which is a plasmonic multilayer structure consisting of a relief metallic grating, a waveguide layer, and a metallic substrate are investigated both experimentally and theoretically. A localized surface plasmon polariton (SPP) mode which is angular-independent in almost the full range of incident angles is observed. The thermal emission of this structure is also measured. It is found that the emission peak coincides with the angular-independent localized SPP mode. In addition, the emission spectrum of the plasmonic emitter can be predicted by investigating the reflectance spectrum.

Wavelength selective quantum dot infrared photodetector with periodic metal hole arrays

In this letter, the effect of extraordinary transmission of periodic metal hole arrays is directly integrated into the quantum dot infrared photodetector with broadband response. It is found that the detector response is strongly modulated by the extraordinary transmission from the excitation of surface plasmon.

Effect of Wood’s anomalies on the profile of extraordinary transmission spectra through metal periodic arrays of rectangular subwavelength holes with different aspect ratio

The extraordinary transmission through silver film perforated with rectangular hole array with different aspect ratio was investigated. It was found that when the aspect ratio exceeded 7, the propagating surface plasmon polaritons (SPPs) transformed to localized resonance mode. The role of the Woods anomaly on the shape of the transmission spectrum is investigated. By designing the rectangular hole arrays in a rectangular lattice, the Woods anomaly can be shifted far apart from the transmission peak, the real localized resonance peak wavelength was identified and fitted well with the theoretical calculation using a simplified transmission-line model.

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.

Dispersion of surface plasmon polaritons on silver film with rectangular hole arrays in a square lattice

Extraordinary optical transmission through a two-dimensional Ag film in the far infrared region was demonstrated. The holes were rectangular and arranged in a square lattice. When either the width or the length size of the rectangular holes was close to the half of the lattice constant a∕2, the degenerate (±1,0) Ag∕Si or (0,±1) Ag∕Si modes split into two peaks. Additionally, the surface plasmon dispersion relations of the square hole array with different aspect ratios of holes were measured. As the aspect ratio increased, the surface plasmon tended to couple strongly with the local charge dipole oscillations in a direction perpendicular to the long edges. The charge dipole oscillation parallel to the long edges gradually disappeared. This is confirmed by experiments using the polarized light. The dynamic properties of the surface plasmon dispersion relations show the interaction among localized surface plasmons and its mechanism.

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.

Bragg scattering of surface plasmon polaritons on extraordinary transmission through silver periodic perforated hole arrays

Extraordinary optical transmission through a two-dimensional periodic perforated Ag film in the far infrared region was demonstrated. When the squared hole size is close to a half lattice constant a∕2, the split of the degenerate (±1,0) Ag∕Si and (0,±1) Ag∕Si modes into two peaks becomes apparent. Surface plasmon polaritons dispersion relations with variously sized square holes are measured to investigate the different surface charge fields at the periodic metal array. Strong scattering of the forward SPP waves, in the (1,0) Ag∕Si mode, leads to a much lower transmission than that of in the (−1,0) Ag∕Si mode. Experimental results demonstrate that the photonic band gap opens up when the size of the squared hole exceeds a half lattice constant a∕2.

Coupling of surface plasmons between two silver films in a plasmonic thermal emitter

The emission spectra of Ag∕SiO2∕Ag trilayer plasmonic thermal emitters with various SiO2 thicknesses were investigated. By analyzing the relationship between emission peaks and thicknesses of SiO2, the coupling of surface plasmons between two silver films in a plasmonic thermal emitter is demonstrated and the coupling length is determined as well. Furthermore, the dispersion relation of plasmonic thermal emitter is detected by measuring the reflection spectra with various incident angles. This confirms that the main mechanism involved in the emission of a plasmonic thermal emitter is due to the excitation of surface plasmons.