• Journal of the Optical Society of Korea
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• v.6 no.3
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• pp.76-82
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• 2002

For dielectric gratings on a flat metal surface, photonic band gaps created by Brags scattering of surface plasmon polaritons are observed. The observation result that directly images this gap is compared with that predicted by a numerical model based on a plane wave expansion. Consistency between the experimental and numerical results is also confirmed by comparison with the well-known calculation method of diffraction, the rigorous coupled wave analysis method.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1283-1288
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• 2018

In this work, we investigate polarization-dependent excitation of the propagating surface plasmon polariton (SPP) modes in gold nanowires (Au NWs) combined with gold nanoparticles (Au NPs). The light coupling from focused light to SPPs on Au NWs is investigated for different structural combinations of Au NWs with Au NPs, using full-wave finite-element numerical simulations. The results show that the excitation of SPPs changes remarkably on varying the orientation of the NP on NW or the polarization angle of the incident light. Metallic NWs combined with NPs can be applied to the polarization-resolved SPP coupling in various optical and optoelectronic devices including photonic circuits and optical sensors.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.176-177
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• 2013

Surface plasmon polaritons (SPPs) have attracted the attention of scientists and engineers involved in a wide area of research, microscopy, diagnostics and sensing. SPPs are waves that propagate along the surface of a conductor, usually metals. These are essentially light waves that are trapped on the surface because of their interaction with the free electrons of conductor. In this interaction, the free electrons respond collectively by oscillating in resonance with the light wave. The resonant interaction between the surface charge oscillation and the electromagnetic field of the light constitutes the SPPs and gives rise to its unique properties. In this papers, we studied theoretical and experimental extraordinary transmittance (T) and reflectance (R) of 2 dimensional metal hole array (2D-MHA) on GaAs in consideration of the diffraction orders. The 2d-MHAs was fabricated using ultra-violet photolithography, electron-beam evaporation and standard lift-off process with pitches ranging from 1.8 to $3.2{\mu}m$ and diameter of half of pitch, and was deposited 5-nm thick layer of titanium (Ti) as an adhesion layer and 50-nm thick layer of gold (Au) on the semiinsulating GaAs substrate. We employed both the commercial software (CST Microwave Studio: Computer Simulation Technology GmbH, Darmstadt, Germany) based on a finite integration technique (FIT) and a rigorous coupled wave analysis (RCWA) to calculate transmittance and reflectance. The transmittance was measured at a normal incident, and the reflectance was measured at variable incident angle of range between $30^{\circ}{\sim}80^{\circ}$ with a Nicolet Fourier transmission infrared (FTIR) spectrometer with a KBr beam splitter and a MCT detector. For MHAs of pitch (P), the peaks ${\lambda}$ max in the normal incidence transmittance spectra can be indentified approximately from SP dispersion relation, that is frequency-dependent SP wave vector (ksp). Shown in Fig. 1 is the transmission of P=2.2 um sample at normal incidence. We attribute the observation to be a result of FTIR system may be able to collect the transmitted light with higher diffraction order than 0th order. This is confirmed by calculations: for the MHAs, diffraction efficiency in (0, 0) diffracted orders is lower than in the (${\pm}x$, ${\pm}y$) diffracted orders. To further investigate the result, we calculated the angular dependent transmission of P=2.2 um sample (Fig. 2). The incident angle varies from 30o to 70o with a 10o increment. We also found the splitting character on reflectance measurement. The splitting effect is considered a results of SPPs assisted diffraction process by oblique incidence.

• Advances in nano research
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• v.2 no.3
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• pp.173-177
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• 2014

This study is aimed to the numerical modeling of the surface plasmon-polariton excitation by a layer of active (electrically pumped) quantum dots embedded in a semiconductor, covered with a metal. It is shown that this excitation becomes much more efficient if the metal has a form of a thin (with thickness of several nanometers) film. The cause of this enhancement in comparison with a thick covering metal film is the partial surface plasmon-polariton localized at the metal-semiconductor interface penetration into air. In result the real part of the metal+air half-space effective dielectric function becomes closer (in absolute value) to the real part of the semiconductor dielectric function than in the case of a thick covering metal film. This leads to approaching the point of the surface plasmon-polariton resonance (where absolute values of these parts coincide) and, therefore, the enhancement of the surface plasmon-polariton excitation. The calculations were made for a particular example of InAs quantum dot layer embedded in GaAs matrix covered with an Au film. Its results indicate that for the 10 nm Au film the rate of this excitation becomes by 2.5 times, and for the 5 nm Au film - by 6-7 times larger than in the case of a thick (40 nm or more) Au film.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.297.2-297.2
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• 2014

Strong exciton-photon coupling in microcavities have generated an intense research effort since quasiparticles called exciton polaritons are produced and shows interesting phenomena. Most of studies have been done with GaAs based microcavities at cryogenic temperature. Recently, GaN material which has large exciton binding energy and oscillator strength has much attention because strong coupling between photon and exciton could be realized at room temperature. However, fabrication of high quality microcavity using GaN is challengeable due to the large mismatch between the lattice and the thermal expansion coefficient in GaN based distributed Bragg mirror. Here, we observed strong coupling regime of exciton-photon in GaN micro-rods which were grown by metalorganic vapour phase epitaxy (MOCVD) on Si substrate. Owing to the hexagonal cross-section of micro-rod, whispering gallery modes of photon are naturally formed and could be coupled with exciton in GaN. Using angle-resolved micro-photoluminescence measurement, exciton polariton dispersion curves were directly observed from GaN micro-rod. We expect room temperature exciton polariton condensation could be realized in high quality GaN micro-rod.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.11.2-11.2
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• 2010

Photovoltaic devices are promising candidates as affordable and large-area renewable energy sources, which can replace the fossil-fuel-based resources. Especially, thin film solar cells have attracted increasing research attention, since they have a great advantage of low production cost. From the physical point of view, the photovoltaic devices can provide us interesting questions, how to enhance the light absorption and the carrier collection efficiency. A lot of approaches would be possible to address these issues. We have focused on two major topics relevant to photovoltaic device physics; (1) light management using surface plasmons and (2) junction characterizations aiming at proper interface engineering. Regarding the first topic, we have investigated the influences of Ag under-layer morphology on optical properties of ZnO thin films. The experimental results suggested that coupling between the surface plasmon polaritons at the ZnO/Ag interface and excitons in ZnO should play important roles in reflectivity of the ZnO/Ag thin films, which are widely used back reflector structures in thin film solar cells. For the second topic, we have carried out scanning probe microscopy studies of Schottky junctions consisting of photovoltaic materials. Such a research is very helpful to understand the correlation between the defects (e.g., grain boundaries) and local electrical properties. We will introduce some of the recent experimental results and discuss the physical significance.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.349-365
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• 2017

Graphene has attracted a lot of attentions due to the unique electrical and optical properties. Compared with the noble metal plasmons in the visible and near-infrared frequencies, graphene can support surface plasmons in the lower frequencies of terahertz and mid-infrared and it demonstrates an extremely large confinement at the surface because of the particular electronic band structures. Especially, the surface conductivity of graphene can be tuned by either chemical doping or electrostatic gating. These features make graphene a promising candidate for plasmonics, biosensing and transformation optics. Furthermore, the combination of graphene and metasurfaces presents a powerful tunability for exotic electromagnetic properties, where the metasurfaces with the highly-localized fields offer a platform to enhance the interaction between the incident light and graphene and facilitate a deep modulation. In this paper, we provide an overview of the key properties of graphene, such as the surface conductivity, the propagating surface plasmon polaritons, and the localized surface plasmons, and the hybrid graphene/metasurfaces, either metallic and dielectric metasurfaces, from terahertz to near-infrared frequencies. Finally, there is a discussion for the current challenges and future goals.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.82-89
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• 2011

In this paper, we numerically study both band-pass and band-stop plasmonic filters based on Metal-Insulator-Metal (MIM) waveguides and circular ring resonators. The band-pass filter consists of two MIM waveguides coupled to each other by a circular ring resonator. The band-stop filter is made up of an MIM waveguide coupled laterally to a circular ring resonator. The propagating modes of Surface Plasmon Polaritons (SPPs) are studied in these structures. By substituting a portion of the ring core with air, while the outer dimensions of the ring resonator are kept constant, we illustrate the possibility of red-shift in resonant wavelengths in order to tune the resonance modes of the proposed filters. This feature is useful for integrated circuits in which we have limitations on the outer dimensions of the filter structure and it is not possible to enlarge the dimension of the ring resonator to reach to longer resonant wavelengths. The results are obtained by a 2D finite-difference time-domain (FDTD) method. The introduced structures have potential applications in plasmonic integrated circuits and can be simply fabricated.

• Korean Journal of Optics and Photonics
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• v.19 no.6
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• pp.429-434
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• 2008

We propose a wavelength filter based on long-range surface plasmon-polaritons (LR-SPP) supported by a asymmetric doubleelectrode LR-SPP structure. For the case of the asymmetric double-layered LR-SPP waveguide, LR-SPPs exist with a much broader range of index mismatches between core and clad materials. Thus, the asymmetric double-electrode LR-SPP waveguide is adequate to form a plasmonic band-gap device as we report in this paper by studying Bragg-reflection wavelength filter based on it. The structure for wavelength filter operating telecommunications wavelength is designed by using the method of line (MoL) and the transfer matrix method. The fabricated device shows a relatively high extinction ratio of 50 dB with a bandwidth of 2 nm, and the performance is very consistent with numerical simulations.

• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.371-380
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• 2006

We design and fabricate a novel tunable wavelength filter, which utilizes long-range surface plasmon-polaritons excited along nm-thick-metal strips. A gold metal strip, with $\sim$ cm length, 20 nm thickness, and $\sim$ 5$\mu$m width, is embedded in thick thermo-optic Polymer films supported by a silicon wafer. A dielectric Bragg grating structure is Placed on the metal strip, so that transmission signals at telecom wavelength are selected by thermal effect of the thermo-optic polymer. High extinction ratio of 25 dB and total insertion loss of $\sim$25 dB/cm can be measured by single-mode coupling of optical fibers. We also verify that wavelength tuning of the long-range surface plasmon-polariton filters can be achieved by electric current directly applied to the metal-strip waveguides.