Yu-Wei Jiang

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.

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.

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.

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.

Emission properties of Ag/dielectric/Ag plasmonic thermal emitter with different lattice type, hole shape, and dielectric material

The emission spectra of the trilayer Ag/dielectric/Ag plasmonic thermal emitter (PTE) with different lattice type, hole shape, and dielectric material were investigated. It is found that the position and number of thermal emission peak of the PTE are determined by the lattice type not by the hole shape and dielectric materials. The PTE with hexagonal lattice generates only one strong (1,0) Ag/dielectric emission peak, whereas a similar PTE with square lattice generates two strong (1,0) and (1,1) Ag/dielectric emission peaks, their relative intensities follow the blackbody radiation law. This phenomenon suggests the coupling of Ag/dielectric and Ag/air modes.

Wavelength selective plasmonic thermal emitter by polarization utilizing Fabry-Pérot type resonances

The experimental results of dispersion relations and thermal emittance spectra of a metal/insulator/metal (MIM) structure with rectangle metallic patch arrays as top layer are demonstrated. The structure exhibits wide-angle, multipeak and polarized emission characteristics caused by Fabry-Perot type resonances of surface plasmons. Emission modes in x- and y-polarization are totally distinct, and their position depends on the width and length of the rectangular metallic patch. Therefore the designing of mode positions has two degrees of freedom and could be applied to wavelength selective light sources.

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.

Narrow bandwidth and highly polarized ratio infrared thermal emitter

Polarized infrared thermal emitters consisting of a waveguide thermal emitter combined with silver grating structure were studied. For a device containing a perforated silver film under the grating, polarized infrared light was emitted only when the wavelength satisfied the standing wave condition, therefore the broad bandwidth SiO2 phonon vibration modes were suppressed in the thermal radiation spectrum. The polarized ratio with different grating thickness was investigated and the highly polarized ratio up to 0.875 was achieved. This study demonstrated that the integrated structure can be used as a narrow bandwidth and highly polarized ratio infrared light source.

A thermal emitter with selective wavelength: Based on the coupling between photonic crystals and surface plasmon polaritons

A thermal emitter with selective wavelength has been demonstrated in which the dielectric layers formed one-dimensional photonic crystals are sandwiched between two Ag films. The top Ag film is perforated periodically with hexagonal hole array. The selected thermal radiation of the photonic crystals resonates between two metal films and surface plasmon polaritons are generated on the top Ag and converted to light radiation. It is found that when leakage modes adjacent to the optic band gap of photonic crystals meet the resonant modes of surface plasmom polaritons, an enhanced thermal emission with maximum intensity can be obtained. The hybrid photonic and plasmonic thermal emitters are selective, which should be very useful for the creation of high power infrared light sources.