ORCID Profile
0000-0003-3962-3726
Current Organisation
University of California, Irvine
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Publisher: American Chemical Society (ACS)
Date: 27-05-2014
DOI: 10.1021/NL500694C
Abstract: Composed of optical waveguides and power-splitting waveguide junctions in a network layout, resonant guided wave networks (RGWNs) split an incident wave into partial waves that resonantly interact within the network. Resonant guided wave networks have been proposed as nanoscale distributed optical networks (Feigenbaum and Atwater, Phys. Rev. Lett. 2010, 104, 147402) that can function as resonators and color routers (Feigenbaum et al. Opt. Express 2010, 18, 25584-25595). Here we experimentally characterize a plasmonic resonant guided wave network by demonstrating that a 90° waveguide junction of two v-groove channel plasmon polariton (CPP) waveguides operates as a compact power-splitting element. Combining these plasmonic power splitters with CPP waveguides in a network layout, we characterize a prototype plasmonic nanocircuit composed of four v-groove waveguides in an evenly spaced 2 × 2 configuration, which functions as a simple, compact optical logic device at telecommunication wavelengths, routing different wavelengths to separate transmission ports due to the resulting network resonances. The resonant guided wave network exhibits the full permutation of Boolean on/off values at two output ports and can be extended to an eight-port configuration, unlike other photonic crystal and plasmonic add/drop filters, in which only two on/off states are accessible.
Publisher: Springer Science and Business Media LLC
Date: 22-08-2017
DOI: 10.1038/S41598-017-08593-8
Abstract: Ultraviolet (UV) irradiation is an effective bacterial inactivation technique with broad applications in environmental disinfection. However, biomedical applications are limited due to the low selectivity, undesired inactivation of beneficial bacteria and damage of healthy tissue. New approaches are needed for the protection of biological cells from UV radiation for the development of controlled treatment and improved biosensors. Aluminum plasmonics offers attractive opportunities for the control of light-matter interactions in the UV range, which have not yet been explored in microbiology. Here, we investigate the effects of aluminum nanoparticles (Al NPs) prepared by sonication of aluminum foil on the UVC inactivation of E . coli bacteria and demonstrate a new radiation protection mechanism via plasmonic nanoshielding. We observe direct interaction of the bacterial cells with Al NPs and elucidate the nanoshielding mechanism via UV plasmonic resonance and nanotailing effects. Concentration and wavelength dependence studies reveal the role and range of control parameters for regulating the radiation dosage to achieve effective UVC protection. Our results provide a step towards developing improved radiation-based bacterial treatments.
Publisher: American Chemical Society (ACS)
Date: 02-09-2016
DOI: 10.1021/ACS.NANOLETT.6B00555
Abstract: Metasurfaces composed of planar arrays of subwavelength artificial structures show promise for extraordinary light manipulation. They have yielded novel ultrathin optical components such as flat lenses, wave plates, holographic surfaces, and orbital angular momentum manipulation and detection over a broad range of the electromagnetic spectrum. However, the optical properties of metasurfaces developed to date do not allow for versatile tunability of reflected or transmitted wave litude and phase after their fabrication, thus limiting their use in a wide range of applications. Here, we experimentally demonstrate a gate-tunable metasurface that enables dynamic electrical control of the phase and litude of the plane wave reflected from the metasurface. Tunability arises from field-effect modulation of the complex refractive index of conducting oxide layers incorporated into metasurface antenna elements which are configured in reflectarray geometry. We measure a phase shift of 180° and ∼30% change in the reflectance by applying 2.5 V gate bias. Additionally, we demonstrate modulation at frequencies exceeding 10 MHz and electrical switching of ±1 order diffracted beams by electrical control over subgroups of metasurface elements, a basic requirement for electrically tunable beam-steering phased array metasurfaces. In principle, electrically gated phase and litude control allows for electrical addressability of in idual metasurface elements and opens the path to applications in ultrathin optical components for imaging and sensing technologies, such as reconfigurable beam steering devices, dynamic holograms, tunable ultrathin lenses, nanoprojectors, and nanoscale spatial light modulators.
Publisher: Walter de Gruyter GmbH
Date: 06-05-2022
Abstract: Plasmonic structural color, in which vivid colors are generated via resonant nanostructures made of common plasmonic materials, such as noble metals have fueled worldwide interest in backlight-free displays. However, plasmonic colors that were withstanding ultrahigh temperatures without damage remain an unmet challenge due to the low melting point of noble metals. Here, we report the refractory hafnium nitride (HfN) plasmonic crystals that can generate full-visible color with a high image resolution of ∼63,500 dpi while withstanding a high temperature (900 °C). Plasmonic colors that reflect visible light could be attributed to the unique features in plasmonic HfN, a high bulk plasmon frequency of 3.1 eV, whichcould support localized surface plasmon resonance (LSPR) in the visible range. By tuning the wavelength of the LSPR, the reflective optical response can be controlled to generate the colors from blue to red across a wide gamut. The novel refractory plasmonic colors pave the way for emerging applications ranging from reflective displays to solar energy harvesting systems.
Publisher: AIP Publishing
Date: 15-09-2008
DOI: 10.1063/1.2982083
Abstract: We present experimental results on coupling to surface plasmon modes on gold nanowires selectively introduced into polarization-maintaining photonic crystal fibers. Highly polarization- and wavelength-dependent transmission is observed. In one s le 24.5 mm long, the transmission on and off resonance differs by as much as 45 dB. Near-field optical images of the light emerging from such a gold-filled fiber show light guided on the wire at surface plasmon resonances. Finite element simulations are in good agreement with the experimental results. These gold-filled fibers can be potentially used as in-fiber wavelength-dependent filters and polarizers and as near-field tips for sub-wavelength-scale imaging.
Publisher: Springer Science and Business Media LLC
Date: 26-02-2019
DOI: 10.1038/S41598-019-39047-Y
Abstract: We demonstrate an electrically tunable ultracompact plasmonic modulator with large modulation strength ( dB) and a small footprint (~1 μm in length) via plasmon-induced transparency (PIT) configuration. The modulator based on a metal-oxide-semiconductor (MOS) slot waveguide structure consists of two stubs embedded on the same side of a bus waveguide forming a coupled system. Heavily n-doped indium tin oxide (ITO) is used as the semiconductor in the MOS waveguide. A large modulation strength is realized due to the formation of the epsilon-near-zero (ENZ) layer at the ITO-oxide interface at the wavelength of the modulated signal. Numerical simulation results reveal that such a significant modulation can be achieved with a small applied voltage of ~3V. This result shows promise in developing nanoscale modulators for next generation compact photonic lasmonic integrated circuits.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-07-2012
Abstract: Optic fibers provide the backbone of communication networks. Controlling light propagation through the fiber is key to maximizing the capacity of information flow. By introducing a literal twist on the photonic crystal fiber, Wong et al. (p. 446 ) show that adding chirality to the cladding surrounding the core may provide another route to manipulating the transmission of light. Coupling between the twisted cladding and the core results in dips in the transmission spectrum, which are dependent on the degree of twist introduced into the fiber. Such twisted microstructure fibers may offer opportunities for coupling, filtering and manipulating light.
Publisher: IOP Publishing
Date: 24-01-2018
Publisher: Springer Science and Business Media LLC
Date: 05-02-2018
DOI: 10.1038/S41598-018-19633-2
Abstract: We report a novel optical waveguide design of a hollow step index fiber modified with a thin layer of indium tin oxide (ITO). We show an excitation of highly confined waveguide mode in the proposed fiber near the wavelength where permittivity of ITO approaches zero. Due to the high field confinement within thin ITO shell inside the fiber, the epsilon-near-zero (ENZ) mode can be characterized by a peak in modal loss of the hybrid waveguide. Our results show that such in-fiber excitation of ENZ mode is due to the coupling of the guided core mode to the thin-film ENZ mode. We also show that the phase matching wavelength, where the coupling takes place, varies depending on the refractive index of the constituents inside the central bore of the fiber. These ENZ nanostructured optical fibers have many potential applications, for ex le, in ENZ nonlinear and magneto-optics, as in-fiber wavelength-dependent filters, and as subwavelength fluid channel for optical and bio-photonic sensing.
Publisher: American Chemical Society (ACS)
Date: 09-06-2021
Publisher: The Optical Society
Date: 13-07-2012
DOI: 10.1364/OL.37.002946
Publisher: American Chemical Society (ACS)
Date: 14-10-2021
Publisher: American Chemical Society (ACS)
Date: 23-04-2018
Publisher: Walter de Gruyter GmbH
Date: 06-03-2023
Abstract: Using electrodynamical description of the average power absorbed by a conducting film, we present an expression for the electric-field intensity enhancement (FIE) due to epsilon-near-zero (ENZ) polariton modes. We show that FIE reaches a limit in ultrathin ENZ films inverse of second power of ENZ losses. This is illustrated in an exemplary series of aluminum-doped zinc oxide nanolayers grown by atomic layer deposition. Only in a case of unrealistic lossless ENZ films, FIE follows the inverse second power of film thickness predicted by S. C ione, et al. [ Phys. Rev. B , vol. 91, no. 12, art. 121408, 2015]. We also predict that FIE could reach values of 100,000 in ultrathin polar semiconductor films. This work is important for establishing the limits of plasmonic field enhancement and the development of near zero refractive index photonics, nonlinear optics, thermal, and quantum optics in the ENZ regime.
Publisher: Elsevier BV
Date: 10-2007
Publisher: Optica Publishing Group
Date: 2006
DOI: 10.1364/OE.14.009451
Abstract: We have written a s led Bragg grating into a highly photosensitive chalcogenide (As(2)S(3)) rib-waveguide using a scanning Sagnac interferometer. The grating exhibits evenly spaced rejection peaks over a 40 nm bandwidth. We estimate the induced refractive index change of the waveguide to be over 0.03 by matching the measured spectrum to numerical solutions of the coupled mode equations while accounting for an induced chirp. The s led Bragg grating presented is comparable in strength and bandwidth to the best s led Bragg gratings obtained to date in silica optical fibre.
Publisher: Optica Publishing Group
Date: 22-08-2022
DOI: 10.1364/OL.461614
Abstract: We study coherent anti-Stokes Raman spectroscopy in air-filled anti-resonance hollow-core photonic crystal fiber, otherwise known as “revolver” fiber. We compare the vibrational coherent anti-Stokes Raman signal of N 2 , at ∼2331 cm −1 , generated in ambient air (no fiber present), with the one generated in a 2.96 cm of a revolver fiber. We show a ∼170 times enhancement for the signal produced in the fiber, due to an increased interaction path. Remarkably, the N 2 signal obtained in the revolver fiber shows near-zero non-resonant background, due to near-zero overlap between the laser field and the fiber cladding. Through our study, we find that the revolver fiber properties make it an ideal candidate for the coherent Raman spectroscopy signal enhancement.
Publisher: Optica Publishing Group
Date: 22-07-2010
DOI: 10.1364/OL.35.002573
Publisher: The Optical Society
Date: 05-02-2019
DOI: 10.1364/PRJ.7.000251
Publisher: American Chemical Society (ACS)
Date: 14-10-2014
DOI: 10.1021/NL502998Z
Abstract: We experimentally demonstrate an ultracompact PlasMOStor, a plasmon slot waveguide field-effect modulator based on a transparent conducting oxide active region. By electrically modulating the conducting oxide material deposited into the gaps of highly confined plasmonic slot waveguides, we demonstrate field-effect dynamics giving rise to modulation with high dynamic range (2.71 dB/μm) and low waveguide loss (∼0.45 dB/μm). The large modulation strength is due to the large change in complex dielectric function when the signal wavelength approaches the surface plasmon resonance in the voltage-tuned conducting oxide accumulation layer. The results provide insight about the design of ultracompact, nanoscale modulators for future integrated nanophotonic circuits.
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3TC02909C
Publisher: IOP Publishing
Date: 03-2022
Abstract: Optical metasurfaces with subwavelength thickness hold considerable promise for future advances in fundamental optics and novel optical applications due to their unprecedented ability to control the phase, litude, and polarization of transmitted, reflected, and diffracted light. Introducing active functionalities to optical metasurfaces is an essential step to the development of next-generation flat optical components and devices. During the last few years, many attempts have been made to develop tunable optical metasurfaces with dynamic control of optical properties (e.g., litude, phase, polarization, spatial/spectral/temporal responses) and early-stage device functions (e.g., beam steering, tunable focusing, tunable color filters/absorber, dynamic hologram, etc) based on a variety of novel active materials and tunable mechanisms. These recently-developed active metasurfaces show significant promise for practical applications, but significant challenges still remain. In this review, a comprehensive overview of recently-reported tunable metasurfaces is provided which focuses on the ten major tunable metasurface mechanisms. For each type of mechanism, the performance metrics on the reported tunable metasurface are outlined, and the capabilities/limitations of each mechanism and its potential for various photonic applications are compared and summarized. This review concludes with discussion of several prospective applications, emerging technologies, and research directions based on the use of tunable optical metasurfaces. We anticipate significant new advances when the tunable mechanisms are further developed in the coming years.
Publisher: American Chemical Society (ACS)
Date: 10-06-2021
Publisher: Walter de Gruyter GmbH
Date: 17-03-2022
Abstract: We demonstrate in-fiber polarization-dependent optical filter by nanopatterning an asymmetric metallic metasurface array on the end-facet of polarization-maintaining photonic-crystal fibers. The asymmetric cross-typed nanoslit metasurface arrays are fabricated on the core of the optical fiber using the focused ion beam milling technique. Highly polarization- and wavelength-dependent transmission with transmission efficiency of ∼70% in the telecommunication wavelength was observed by launching two orthogonal linear-polarization states of light into the fiber. Full-wave electromagnetic simulations are in good agreement with the experimental results. These advanced meta-structured optical fibers can potentially be used as novel ultracompact in-fiber filters, splitters, and polarization converters.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2009
Publisher: The Optical Society
Date: 07-12-2012
DOI: 10.1364/OE.20.028409
Publisher: American Chemical Society (ACS)
Date: 27-01-2018
Publisher: Wiley
Date: 05-01-2023
Abstract: Experimental excitation of a highly confined epsilon‐near‐zero (ENZ) mode in a side‐polished optical fiber coated with a deep subwavelength thick layer of aluminum‐doped zinc oxide (AZO) is reported. The uniform AZO layer on the fiber is fabricated by atomic layer deposition technique and optimized to exhibit close‐to‐zero permittivity at the near‐infrared wavelength. Highly polarization‐ and wavelength‐dependent transmission with strong resonance strength up to 25 dB is observed in a 30‐nm ENZ‐coated fiber that is 17 mm long. Different from the excitation of the ENZ mode in a planar conducting oxide thin film, the hybrid ENZ mode can be excited via direct phase matching between the fundamental mode of the fiber and the ENZ mode supported by the AZO thin film. The hybrid ENZ mode in the fiber exhibits a relatively long propagation/light–matter interaction length which is a few orders of magnitude longer than those on the planar ENZ substrates. It is further shown that the hybrid resonance in the ENZ fiber can be actively tuned through the refractive index of surrounding medium and the large ENZ's nonlinearity. These ENZ‐optical fibers serve as emerging in‐fiber optical devices, such as advanced in‐fiber ultrafast optical switches/modulators, mode‐locked fiber lasers, and in‐fiber optical gas/biomolecule sensors.
Publisher: Springer Science and Business Media LLC
Date: 25-09-2020
DOI: 10.1038/S41598-020-72689-X
Abstract: Understanding of how particles and light interact in a liquid environment is vital for optical and biological applications. MoS 2 has been shown to enhance nonlinear optical phenomena due to the presence of a direct excitonic resonance. Its use in biological applications is predicated on knowledge of how MoS 2 interacts with ultrafast ( 1 ps) pulses. In this experiment, the interaction between two femtosecond pulses and MoS 2 nanoparticles suspended in liquid is studied. We found that the laser pulses induce bubble formation on the surface of a nanoparticle and a nanoparticle aggregate then forms on the surface of the trapped bubble. The processes of formation of the bubble and the nanoparticle aggregation are intertwined.
Publisher: The Optical Society
Date: 08-06-2011
DOI: 10.1364/OE.19.012180
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2008
Publisher: The Optical Society
Date: 14-04-2011
DOI: 10.1364/OE.19.008200
Publisher: MedCrave Group, LLC
Date: 04-2016
Publisher: Optica Publishing Group
Date: 06-03-2009
DOI: 10.1364/OE.17.004533
Abstract: We demonstrate that the efficiency of CO(2) laser writing of long-period fiber gratings in a solid-core photonic crystal fiber (PCF) can be enhanced greatly by applying tension to the fiber during the writing process through the mechanism of frozen-in viscoelasticity. Using this mechanism, we are able to write strong gratings in PCFs with a dosage of CO(2) laser radiation low enough not to cause any significant fiber structure deformation.
Publisher: Optica Publishing Group
Date: 27-07-2020
DOI: 10.1364/OL.396311
Abstract: We present a study of optical modulation by the effect of temperature-induced insulator-to-metal phase transition of vanadium dioxide ( V O 2 ) nanocrystals deposited in an antiresonance hollow-core fiber (AR-HCF). We fabricate such a V O 2 -coated fiber by embedding alkylsilane functionalized V O 2 nanocrystals into the air holes of an AR-HCF. With this fiber, we achieve an optical loss modulation of ∼ 60 % at a temperature above ∼ 53 ∘ C over an ultrabroad spectral range that encompasses the S + C + L band.
Publisher: OSA
Date: 2018
Publisher: American Chemical Society (ACS)
Date: 18-10-2023
Publisher: Wiley
Date: 29-08-2018
Publisher: The Optical Society
Date: 18-07-2019
DOI: 10.1364/OL.44.003653
Publisher: Wiley
Date: 25-06-2020
Publisher: Optica Publishing Group
Date: 02-2021
DOI: 10.1364/PRJ.411583
Abstract: The direct interfacing of photonic crystal fiber to a metallic nanoantenna has widespread application in nanoscale imaging, optical lithography, nanoscale lasers, quantum communication, in vivo sensing, and medical surgery. We report on the fabrication of a needle-shaped plasmonic nanoantenna on the end facet of a photonic crystal fiber using electron-beam-induced evaporation of platinum. We demonstrate the coupling of light from the fiber waveguide mode to the subwavelength nanoantenna plasmonic mode focusing down to the apex of the plasmonic needle using a polarization-resolved far-field side-scatter imaging technique. Our work provides an important step toward widespread application of optical fibers in nearfield spectroscopic techniques such as tip-enhanced Raman and fluorescence microscopy, single-photon excitation and quantum sensors, nanoscale optical lithography, and lab-on-fiber devices.
Publisher: Wiley
Date: 12-04-2011
Abstract: Magneto‐optical glasses are of considerable current interest, primarily for applications in fiber circuitry, optical isolation, all‐optical diodes, optical switching and modulation. While the benchmark materials are still crystalline, glasses offer a variety of unique advantages, such as very high rare‐earth and heavy‐metal solubility and, in principle, the possibility of being produced in fiber form. In comparison to conventional fiber‐drawing processes, pressure‐assisted melt‐filling of microcapillaries or photonic crystal fibers with magneto‐optical glasses offers an alternative route to creating complex waveguide architectures from unusual combinations of glasses. For instance, strongly diamagnetic tellurite or chalcogenide glasses with high refractive index can be combined with silica in an all‐solid, microstructured waveguide. This promises the implementation of as‐yet‐unsuitable but strongly active glass candidates as fiber waveguides, for ex le in photonic crystal fibers.
Publisher: IOP Publishing
Date: 16-01-2013
Publisher: Informa UK Limited
Date: 09-02-2017
Publisher: The Optical Society
Date: 16-12-2019
DOI: 10.1364/OE.27.038098
Publisher: World Scientific Pub Co Pte Lt
Date: 07-2017
DOI: 10.1142/S1793292017500862
Abstract: In most of the reports on nanocrystal (NC) luminescent, the power depedence of luminescent intensity is studied using a continuous-wave laser with low power density, and the slopes of those different emission bands keep unchanged. In this paper, the up/down conversion of monodisperse Yb/Er: NaGdF 4 @Yb: NaGdF 4 @Yb: NaNdF 4 NCs under the excitation of 800[Formula: see text]nm femtosecond laser was detected simultaneously by a home-built optical measurement setup. The power-dependent optical properties under the excitation of femtosecond laser are quite different from the normal situation, which is due to their high peak power and energy transfer processes: Nd[Formula: see text].
Publisher: Walter de Gruyter GmbH
Date: 21-02-2019
Abstract: Conventional optical fiber has excellent performance in guiding light, which has been widely employed for long-distance optical communication. Although the optical fiber is efficient for transmitting light, its functionality is limited by the dielectric properties of the core’s and cladding’s materials (e.g. Ge-doped-silica and silica glasses). The spot size of the transmitted light is erging and restricted by the diffraction limit of the dielectric core, and the numerical aperture is determined by the refractive index of the fiber materials. However, the novel technology of metasurfaces is opening the door to a variety of optical fiber innovations. Here, we report an ultrathin optical metalens directly patterned on the facet of a photonic crystal optical fiber that enables light focusing in the telecommunication regime. In-fiber metalenses with focal lengths of 28 μm and 40 μm at a wavelength of 1550 nm are demonstrated with maximum enhanced optical intensity as large as 234%. The ultrathin optical fiber metalens may find novel applications in optical imaging, sensing, and fiber laser designs.
Publisher: Wiley
Date: 02-2021
Location: United States of America
No related grants have been discovered for Howard (Ho Wai) Lee.