Hung-Hsin Chen

Angle and polarization independent narrow-band thermal emitter made of metallic disk on SiO2

It is shown that the metallic disk structure can be used as an efficient narrow-band thermal emitter in the IR region. The absorption spectra of such structure are investigated both theoretically and experimentally. Calculations of thermal radiation properties of the metallic disk show that the metallic disk is a perfect emitter at a specific wavelength, which can be tuned by varying the diameter of the disk. The metallic disk exhibits only one significant localized surface plasmon polariton (LSPP) mode for both TM and TE polarizations simultaneously. The LSPP mode can be tuned by either varying the disk diameter or the spacer (made of SiO2).

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.

White Organic Light-Emitting Diode With Linearly Polarized Emission

An organic light emitting diode (OLED) with a linearly polarized white light emission is demonstrated using a nanograting structure. The aluminum based grating structure is fabricated by laser interference lithography and formed on the back side of the glass substrate of the OLED. The nanograting structure functions as a polarizer to select the transverse magnetic wave in the wavelength range of 400-700 nm. The polarization characteristics are studied experimentally and theoretically in detail. The experimental results agree well with the simulation by a rigorous coupled wave analysis. The polarization ratio of the polarizer can reach as high as 93.4%.

Double wavelength infrared emission by localized surface plasmonic thermal emitter

A double wavelength infrared emission by plasmonic thermal emitter using stacked Au/SiO2/Au/SiO2/Au structure was investigated. The effective refractive index of sandwiched SiO2 is higher than normal value due to the coupling of surface plasmons at the top and bottom Au/SiO2 interfaces. Two different localized surface plasmon modes were excited with the same metal width, but different SiO2 layer thicknesses in top and bottom Au/SiO2/Au tri-layer structures. The measured dispersion relation diagram and simulation demonstrated that the resonances were localized resonance and the distribution of magnetic field was concentrated at the central SiO2 layer between two Au layers.

Extraordinary transmission through a silver film perforated with bowtie-shaped aperture array in midinfrared region

The transmission spectra of bowtie aperture consisting of opposing triangular holes arranged in rectangular array on silver/silicon structure were investigated. It is found that the second order surface plasmon polaritons mode is much stronger than the fundamental one. In addition, by increasing the separation and angles of the tips or silver film thickness, the second order modes decrease gradually. These phenomena suggest magnetic field coupling between metal tips which results in higher order mode enhancement.

A plasmonic infrared photodetector with narrow bandwidth absorption

A plasmonic infrared photodetector with narrow bandwidth infrared absorption was investigated. The structure is constructed by a hydrogenated amorphous silicon (a-Si:H) film covered on a patterned Au layer consisting of the Au disk resonators and Au interdigitated electrodes on an Al2O3/Au substrate. This device exhibited narrow bandwidth infrared absorption corresponded to the localized surface plasmon resonance in the Au-disk/Al2O3/Au tri-layers resonators. The absorption of infrared energy heats up the top hydrogenated amorphous silicon film and reduces the film resistance which can be detected. The optical and electrical characteristics of the photodetector were studied. It was founded that the peak responsivities appeared at the wavelength which coincided with the localized surface plasmon resonance.

Enhanced Transmission of Higher Order Plasmon Modes With Random Au Nanoparticles in Periodic Hole Arrays

The enhanced transmission of higher order plasmon modes with random gold nanoparticles embedded in periodic hole arrays using asymmetric pair aperture as a unit is investigated in the midinfrared regime. Different thicknesses of gold film were deposited inside holes and then annealed to form randomly sized and distributed nanoparticles. The holes deposited with thin gold film exhibit significantly enhanced transmission in higher order modes after thermal annealing. The enormous local electric field around the nanoparticles enhances the scattering effect that contributes to the enhanced infrared transmission. This unique design, which integrates localized and propagating surface plasmons, provides an easy way for midinfrared applications in need of enhanced transmission in higher order modes.