36 results found
Saba M, Wong S, Elman M, et al., 2020, Nature of topological protection in photonic spin and valley Hall insulators, PHYSICAL REVIEW B, Vol: 101, ISSN: 2469-9950
Wong S, Saba M, Hess O, et al., 2020, Gapless unidirectional photonic transport using all-dielectric kagome lattices, Physical Review Research, Vol: 2
Kerber R, Fitzgerald J, Oh S, et al., 2018, Orbital angular momentum dichroism in nanoantennas, Communications Physics, Vol: 1, ISSN: 2399-3650
When light interacts with matter, dichroism with respect to the handedness of circularly polarized light is well established. But what happens if the light further possesses an orbital angular momentum? In this paper, we discuss possible definitions of orbital angular momentum dichroism and define a new type of dichroism, the class dichroism. By numerically calculating the scattering cross-section spectra, we study the dichroism of a plasmonic nanostructure interacting with orbital angular momentum light. By considering the exemplary case of twisted, stacked nanorods, we show that the orbital angular momentum dichroism can be as strong as dichroism induced by circular polarization. We present a detailed classification of the different types of orbital angular momentum dichroism, which paves the way for new chiroptic spectroscopic techniques.
Giannini V, Maier S, Xiao X, et al., 2018, Interaction of an Archimedean spiral structure with orbital angular momentum light, New Journal of Physics, Vol: 20, ISSN: 1367-2630
Complementing the research of surface plasmon polariton vortices for Archimedean spiral structures grooved in gold platelets, we here study the analogous positive structure of an Archimedean spiral consisting of bent gold nanorods. We consider spirals of two different sizes, for which we perform numerical calculations with the boundary element method. For a micrometer-sized metallic structure we show that the scattered electric field forms a vortex in the centre of the spiral. When the spiral is illuminated by orbital angular momentum light, the topological charge of the vortex can be controlled. For a nanometer-sized plasmonic Archimedean spiral we find that the response to optical excitation is governed by several resonances. When the nanostructure is excited by orbital angular momentum light, different resonances appear compared to the excitation with plane waves. Our results highlight that the distinct architecture of the Archimedean spiral responds in a unique way to the excitation with orbital angular momentum light.
Bittner S, Guazzotti S, Zeng Y, et al., 2018, Suppressing spatiotemporal lasing instabilities with wave-chaotic microcavities, Science, Vol: 361, Pages: 1225-1230, ISSN: 0036-8075
Spatiotemporal instabilities are widespread phenomena resulting from complexity and nonlinearity. In broad-area edge-emitting semiconductor lasers, the nonlinear interactions of multiple spatial modes with the active medium can result in filamentation and spatiotemporal chaos. These instabilities degrade the laser performance and are extremely challenging to control. We demonstrate a powerful approach to suppress spatiotemporal instabilities using wave-chaotic or disordered cavities. The interference of many propagating waves with random phases in such cavities disrupts the formation of self-organized structures such as filaments, resulting in stable lasing dynamics. Our method provides a general and robust scheme to prevent the formation and growth of nonlinear instabilities for a large variety of high-power lasers.
Bittner S, Yilmaz H, Kim K, et al., 2018, Suppressing laser instabilities with microcavities exhibiting chaotic ray dynamics
© 2018 OSA. We demonstrate experimentally that spatio-temporal instabilities of broad-area semiconductor lasers are strongly suppressed in microcavities with chaotic ray-dynamics. This stabilization of lasing dynamics is attributed to the modifications of the nonlinear interaction of the lasing modes.
Kim T-T, Kim H-D, Zhao R, et al., 2018, Electrically Tunable Slow Light Using Graphene Metamaterials, ACS PHOTONICS, Vol: 5, Pages: 1800-1807, ISSN: 2330-4022
Kim M, Oh SS, Hess O, et al., 2018, Frequency-domain modelling of gain in pump-probe experiment by an inhomogeneous medium, JOURNAL OF PHYSICS-CONDENSED MATTER, Vol: 30, ISSN: 0953-8984
Bittner, Guazzotti S, Hu X, et al., 2018, Suppressing spatio-temporal lasing instabilities with wave-chaotic microcavity lasers
© 2018 The Author(s). The suppression of spatio-temporal instabilities of broad-area semiconductor lasers is demonstrated for microcavities with chaotic ray dynamics. We attribute the stabilization to the disruption of coherent instabilities by complex wave interference.
Kim T-T, Oh SS, Kim H-D, et al., 2017, Electrical access to critical coupling of circularly polarized waves in graphene chiral metamaterials., Science Advances, Vol: 3, ISSN: 2375-2548
Active control of polarization states of electromagnetic waves is highly desirable because of its diverse applications in information processing, telecommunications, and spectroscopy. However, despite the recent advances using artificial materials, most active polarization control schemes require optical stimuli necessitating complex optical setups. We experimentally demonstrate an alternative-direct electrical tuning of the polarization state of terahertz waves. Combining a chiral metamaterial with a gated single-layer sheet of graphene, we show that transmission of a terahertz wave with one circular polarization can be electrically controlled without affecting that of the other circular polarization, leading to large-intensity modulation depths (>99%) with a low gate voltage. This effective control of polarization is made possible by the full accessibility of three coupling regimes, that is, underdamped, critically damped, and overdamped regimes by electrical control of the graphene properties.
Kerber R, Fitzgerald J, Reiter D, et al., 2017, Reading the orbital angular momentum of light using plasmonic nanoantennas, ACS Photonics, Vol: 4, Pages: 891-896, ISSN: 2330-4022
Orbital angular momentum of light has recently been recognized as a new degree of freedom to encode information in quantum communication using light pulses. Methods to extract this information include reversing the process by which such twisted light was created in the first place or interference with other beams. Here we propose an alternative new way to directly read out the extra information encoded in twisted light using plasmonic nanoantennas by converting the information about the orbital angular momentum of light into spectral information using bright and dark modes. Exemplarily considering rotation-symmetric nanorod nanoantennas, we show that their scattering cross section is sensitive to the value of the orbital angular momentum combined with the polarization of an incident twisted light beam. Explaining the twist dependence of the excited modes with a new analytical model, our results pave the way to twisted light nanoplasmonics, which is of central importance for future on-chip communication using orbital angular momentum of light.
Choi HJ, Baek IH, Kang BJ, et al., 2017, Control of terahertz nonlinear transmission with electrically gated graphene metadevices, SCIENTIFIC REPORTS, Vol: 7, ISSN: 2045-2322
Baek IH, Hamm JM, Ahn KJ, et al., 2017, Boosting the terahertz nonlinearity of graphene by orientation disorder, 2D MATERIALS, Vol: 4, ISSN: 2053-1583
The conical band structure is the cornerstone of graphene's ultra-broadband optical conductivity. For practical use of graphene in nonlinear photonics, however, substantial increases of the light–matter interaction strength will be required while preserving the promising features of monolayers, as the interaction of light with a single atomic layer is limited due to the extremely short interaction length and low density of state, particularly for the long-wavelength region. Here, we report that this demand can be fulfilled by random stacking of high-quality large-area monolayer graphene up to a requested number of layers, which leads to the electronic interaction between layers being effectively switched off due to turbostratic disorder. The nonlinear characteristics of randomly stacked multilayer graphene (RSMG), which originates from a thermo-modulational feedback mechanism through ultrafast free-carrier heating and temperature-dependent carrier-phonon collisions, show clear improvements in the terahertz (THz) regime with increasing layer numbers, whereas as-grown multilayer graphene (AGMG) exhibits limited behaviors due to strong interlayer coupling. This controllable nonlinearity enhancement provides an ideal prerequisite for developing efficient graphene-based THz photonic devices.
Oh SS, Wood JJ, Kim SH, et al., 2016, Localized toroidal dipole moment of spoof surface plasmon polaritons
© 2015 IEEE. At infrared wavelengths, we demonstrate subwavelength scale localization of spoof surface plasmon polaritons. Based on an analytical model and numerical simulations, we show that the defect mode has toroidal dipole moment and high Q factor.
Pusch A, Oh S, Wuestner S, et al., 2015, A highly efficient CMOS nanoplasmonic crystal enhanced slow-wave thermal emitter improves infrared gas-sensing devices, Scientific Reports, Vol: 5, ISSN: 2045-2322
The application of plasmonics to thermal emitters is generally assisted by absorptive losses in the metal because Kirchhoff’s law prescribes that only good absorbers make good thermal emitters. Based on a designed plasmonic crystal and exploiting a slow-wave lattice resonance and spontaneous thermal plasmon emission, we engineer a tungsten-based thermal emitter, fabricated in an industrial CMOS process, and demonstrate its markedly improved practical use in a prototype non-dispersive infrared (NDIR) gas-sensing device. We show that the emission intensity of the thermal emitter at the CO2 absorption wavelength is enhanced almost 4-fold compared to a standard non-plasmonic emitter, which enables a proportionate increase in the signal-to-noise ratio of the CO2 gas sensor.
Oh SS, Hess O, 2015, Chiral metamaterials: enhancement and control of optical activity and circular dichroism, Nano Convergence, Vol: 2, ISSN: 2196-5404
The control of the optical activity and ellipticity of a medium has drawn considerable attention due to the recent developments in metamaterial design techniques and a deeper understanding of the light matter interaction in composite metallic structures. Indeed, recently proposed designs of metaatoms have enabled the realisation of materials with unprecedented chiral optical properties e.g. strong optical activity, broadband optical activity, and nondispersive zero ellipticity. Combining chiral metamaterials with nonlinear materials has opened up new possibilities in the field of nonlinear chirality as well as provided the foundation for switchable chiral devices. Furthermore, chirality together with hyperbolicity can be used to realise new exciting materials such as photonic topological insulators. In this review, we will outline the fundamental principles of chiral metamaterials and report on recent progress in providing the foundations for promising applications of switchable chiral metamaterials.
Yudistira HT, Tenggara AP, Oh SS, et al., 2015, High-resolution electrohydrodynamic jet printing for the direct fabrication of 3D multilayer terahertz metamaterial of high refractive index, JOURNAL OF MICROMECHANICS AND MICROENGINEERING, Vol: 25, ISSN: 0960-1317
Kim S-H, Oh SS, Kim K-J, et al., 2015, Subwavelength localization and toroidal dipole moment of spoof surface plasmon polaritons, PHYSICAL REVIEW B, Vol: 91, ISSN: 2469-9950
Kim T-T, Oh SS, Park H-S, et al., 2014, Optical Activity Enhanced by Strong Inter-molecular Coupling in Planar Chiral Metamaterials, Scientific Reports, Vol: 4, ISSN: 2045-2322
The polarization of light can be rotated in materials with an absence of molecular or structural mirrorsymmetry. While this rotating ability is normally rather weak in naturally occurring chiral materials,artificial chiral metamaterials have demonstrated extraordinary rotational ability by engineeringintra-molecular couplings. However, while in general, chiral metamaterials can exhibit strong rotatorypower at or around resonances, they convert linearly polarized waves into elliptically polarized ones. Here,we demonstrate that strong inter-molecular coupling through a small gap between adjacent chiralmetamolecules can lead to a broadband enhanced rotating ability with pure rotation of linearly polarizedelectromagnetic waves. Strong inter-molecular coupling leads to nearly identical behaviour in magnitude,but engenders substantial difference in phase between transmitted left and right-handed waves.
Salvatore S, Demetriadou A, Vignolini S, et al., 2013, Tunable 3D Extended Self-Assembled Gold Metamaterials with Enhanced Light Transmission, Advanced Materials, Vol: 25, Pages: 2713-2716
The optical properties of metamaterials made by block copolymer self-assembly are tuned by structural and environmental variations. The plasma frequency red-shifts with increasing lattice constant and blue-shifts as the network filling fraction increases. Infiltration with dielectric liquids leads also to a red-shift of the plasma edge. A 300 nm-thick slab of gyroid-structured gold has a remarkable transmission of 20%.
Oh SS, Demetriadou A, Wuestner S, et al., 2013, On the Origin of Chirality in Nanoplasmonic Gyroid Metamaterials, ADVANCED MATERIALS, Vol: 25, Pages: 612-617, ISSN: 0935-9648
Demetriadou A, Oh SS, Wuestner S, et al., 2012, A tri-helical model for nanoplasmonic gyroid metamaterials, NEW JOURNAL OF PHYSICS, Vol: 14, ISSN: 1367-2630
Hyun WJ, Lee HK, Oh SS, et al., 2011, Two-Dimensional TiO2 Inverse Opal with a Closed Top Surface Structure for Enhanced Light Extraction from Polymer Light-Emitting Diodes, ADVANCED MATERIALS, Vol: 23, Pages: 1846-+, ISSN: 0935-9648
Kim S-H, Kim T-T, Oh SS, et al., 2011, Experimental demonstration of self-collimation of spoof surface plasmons, PHYSICAL REVIEW B, Vol: 83, ISSN: 2469-9950
Oh SS, Wuestner S, Demetriadou A, et al., 2011, Circular dichroism in gold helix metamaterials and gold gyroid structures at optical frequencies, IEEE Nanotechnology materials and Devices Conference
Oh SS, Choi CG, Kim YS, 2010, Fabrication of micro-lens arrays with moth-eye antireflective nanostructures using thermal imprinting process, Microelectronic Engineering, Vol: 87, Pages: 2328-2331
Kang YH, Oh SS, Kim YS, et al., 2009, Fabrication of antireflection nanostructures by hybrid nano-patterning lithography, Microelectronic Engineering, Vol: 87, Pages: 125-128
Oh SS, Choi CG, 2009, Photonic Crystal Slab Type Guided Mode Resonance Filters in Infrared Range, IEEE Photonics Technology Letters, Vol: 21, Pages: 316-318
Oh SS, Choi CG, 2008, Photonic Crystal Type Infrared Filters for Gas Senso, Journal of Korea Physical Society, Vol: 52, Pages: 1671-1674
Oh SS, Lee SG, Kim JE, et al., 2007, Self-collimation phenomena of surface waves in structured perfect electric conductors and metal surfaces, Optics Express, Vol: 15, Pages: 1205-1210
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