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Sökning: WFRF:(Wosinski Lech)

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1.
  • Ao, Xianyu, et al. (författare)
  • Polarization beam splitter based on a two-dimensional photonic crystal of pillar type
  • 2006
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:17, s. 171115-
  • Tidskriftsartikel (refereegranskat)abstract
    • Negatively and positively refractive behaviors are achieved in a two-dimensional photonic crystal of pillar type for TE and TM polarizations, respectively, at the same frequency. The photonic crystal is formed by a triangular lattice of silicon pillars of finite height on a silicon substrate. A polarization beam splitter based on such a photonic-crystal slab is demonstrated. Measurements at near infrared wavelengths indicate that two beams of different polarizations can be split with an extinction ratio of over 10 dB in a wide wavelength range.
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2.
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3.
  • Chen, Xi, et al. (författare)
  • Photothermally tunable silicon-microring-based optical add-drop filter through integrated light absorber
  • 2014
  • Ingår i: Optics Express. - 1094-4087. ; 22:21, s. 25233-25241
  • Tidskriftsartikel (refereegranskat)abstract
    • An optically pumped thermo-optic (TO) silicon ring add-drop filter with fast thermal response is experimentally demonstrated. We propose that metal-insulator-metal (MIM) light absorber can be integrated into silicon TO devices, acting as a localized heat source which can be activated remotely by a pump beam. The MIM absorber design introduces less thermal capacity to the device, compared to conventional electrically-driven approaches. Experimentally, the absorber-integrated add-drop filter shows an optical response time of 13.7 mu s following the 10%-90% rule (equivalent to a exponential time constant of 5 mu s) and a wavelength shift over pump power of 60 pm/mW. The photothermally tunable add-drop filter may provide new perspectives for all-optical routing and switching in integrated Si photonic circuits.
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4.
  • Chen, Xi, et al. (författare)
  • Photothermally tunable silicon-microring-based optical add-drop filter through integrated light absorber
  • 2014
  • Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 22:21, s. 25233-25241
  • Tidskriftsartikel (refereegranskat)abstract
    • An optically pumped thermo-optic (TO) silicon ring add-drop filter with fast thermal response is experimentally demonstrated. We propose that metal-insulator-metal (MIM) light absorber can be integrated into silicon TO devices, acting as a localized heat source which can be activated remotely by a pump beam. The MIM absorber design introduces less thermal capacity to the device, compared to conventional electrically-driven approaches. Experimentally, the absorber-integrated add-drop filter shows an optical response time of 13.7 μs following the 10%–90% rule (equivalent to a exponential time constant of 5 μs) and a wavelength shift over pump power of 60 pm/mW. The photothermally tunable add-drop filter may provide new perspectives for all-optical routing and switching in integrated Si photonic circuits.
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5.
  • Dai, Daoxin, et al. (författare)
  • Gain enhancement in a hybrid plasmonic nano-waveguide with a low-index or high-index gain medium
  • 2011
  • Ingår i: Optics Express. - 1094-4087. ; 19:14, s. 12925-12936
  • Tidskriftsartikel (refereegranskat)abstract
    • A theoretical investigation of a nano-scale hybrid plasmonic waveguide with a low-index as well as high-index gain medium is presented. The present hybrid plasmonic waveguide structure consists of a Si substrate, a buffer layer, a high-index dielectric rib, a low-index cladding, a low-index nano-slot, and an inverted metal rib. Due to the field enhancement in the nano-slot region, a gain enhancement is observed, i.e., the ratio partial derivative G/partial derivative g > 1, where g and G are the gains of the gain medium and the TM fundamental mode of the hybrid plasmonic waveguide, respectively. For a hybrid plasmonic waveguide with a core width of w(co) = 30nm and a slot height of h(slot) = 50nm, the intrinsic loss could be compensated when using a low-index medium with a moderate gain of 176dB/cm. When introducing the high-index gain medium for the hybrid plasmonic waveguide, a higher gain is obtained by choosing a wider core width. For the high-index gain case with h(slot) = 50nm and w(co) = 500nm, a gain of about 200dB/cm also suffices for the compensation of the intrinsic loss.
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6.
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7.
  • Dai, Daoxin, et al. (författare)
  • Silicon hybrid plasmonic submicron-donut resonator with pure dielectric access waveguides
  • 2011
  • Ingår i: Optics Express. - 1094-4087. ; 19:24, s. 23671-23682
  • Tidskriftsartikel (refereegranskat)abstract
    • Characteristic analyses are given for a bent silicon hybrid plasmonic waveguide, which has the ability of submicron bending (e.g., R = 500nm) even when operating at the infrared wavelength range (1.2 mu m similar to 2 mu m). A silicon hybrid plasmonic submicron-donut resonator is then presented by utilizing the sharp-bending ability of the hybrid plasmonic waveguide. In order to enable long-distance optical interconnects, a pure dielectric access waveguide is introduced for the present hybrid plasmonic submicron-donut resonator by utilizing the evanescent coupling between this pure dielectric waveguide and the submicron hybrid plasmonic resonator. Since the hybrid plasmonic waveguide has a relatively low intrinsic loss, the theoretical intrinsic Q-value is up to 2000 even when the bending radius is reduced to 800nm. By using a three-dimensional finite-difference time-domain (FDTD) method, the spectral response of hybrid plasmonic submicron-donut resonators with a bending radius of 800nm is simulated. The critical coupling of the resonance at around 1423nm is achieved by choosing a 80nm-wide gap between the access waveguide and the resonator. The corresponding loaded Q-value of the submicron-donut resonator is about 220.
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8.
  • Dainese, Matteo, et al. (författare)
  • Directional coupler wavelength selective filter based on dispersive  Bragg Reflection Waveguide
  • 2006
  • Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 260:2, s. 514-521
  • Tidskriftsartikel (refereegranskat)abstract
    • A new type of wavelength selective filter, based on high differential dispersion between two coupled waveguides, is presented. The Bragg Reflection Waveguide displays high effective refractive index dispersion, due to the interaction of the guided mode with the two confining Bragg reflectors. When coupled with a weakly guided buried channel silica waveguide, a very narrow bandwidth filter (< 1 nm) can be easily produced, in a shorter length, with respect to directional couplers made with standard step index channel waveguides. The complete design methodology, fabrication and characterization are presented.
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9.
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11.
  • Dainese, Matteo, et al. (författare)
  • Influence of Ge content on the optical quality of Plasma CVD deposited Silica films
  • 2002
  • Konferensbidrag (refereegranskat)abstract
    • The feasibility of a full low temperature process, based on Plasma Enhanced Chemical VaporDeposition, for the fabrication of low loss silica-based optical waveguides is investigated.Results from XPS, FTIR, ERDA, isochronal wet etch rate, prism coupler measurements showthat (low frequency) RF power is a critical parameter to improve microstructural properties ofas-deposited SiO2 and minimize Rayleigh scattering. Ge doping of the silica matrix in thecore layer increases network disorder and point defects density, mainly due to the highlyreactive characteristics of the employed gas precursor (germane) and the high stickingcoefficients of its radicals. Measurements on fabricated optical waveguides show that forrelative refractive index differences between core and cladding up to 0.75%, the opticallosses are acceptable for the fabrication of high performance devices.
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12.
  • Dainese, Matteo, et al. (författare)
  • Narrow band coupler based on one-dimensional Bragg reflection waveguide
  • 2003
  • Ingår i: 2003 Optical Fiber Communication Conference. - 1557527466 ; , s. 44-46
  • Konferensbidrag (refereegranskat)abstract
    • A new configuration based on the coupling between a conventional low loss, weakly guiding channel waveguide and a Bragg reflection waveguide (BRW) was discussed. The strong difference between the dispersion of a Bragg reflection waveguide and a channel waveguide was used to create a narrow band coupler. The two-dimensional analysis of the BRW was generally based on the transfer matrix method. The structure consisted of a weakly guiding conventional Ge-doped silica waveguide on the top of which a BRW was stacked. The number of periods in the mirror between the BRW and the silica waveguide affected the coupling length and ultimately the bandwidth.
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13.
  • Dainese, Matteo, et al. (författare)
  • Photosensitivity of boron-codoped PECVD films in application to grating assisted WDM devices
  • 2004
  • Ingår i: INTEGRATED OPTICS AND PHOTONIC INTEGRATED CIRCUITS. - BELLINGHAM : SPIE-INT SOC OPTICAL ENGINEERING. - 0819453749 ; , s. 191-198
  • Konferensbidrag (refereegranskat)abstract
    • UV sensitivity of B-Ge codoped cores in PECVD silica waveguides has been investigated. Photoinduced refractive index changes have been introduced by KrF excimer laser irradiation at 248 rim, without any presensitization method. The effects of B codoping of Ge doped silica have been examined. It has been shown that B addition mildly increases glass network disorder, by broadening the O bridging angle distribution as from FTIR measurements, but on the other hand it does not produce point defects which may contribute to the absorption band at 5eV already generated by the presence of Ge doping. The fabricated channel waveguides show low optical loss even without high temperature annealing. Strong Bragg gratings imprinted into these waveguides confirm that in non thermally annealed Ge doped PECVD silica glass, where a small absorption band still exist at 5eV, B codoping supplies sufficient photosensitivity amplification to make hydrogen loading unnecessary.
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14.
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15.
  • Dainese, Matteo, et al. (författare)
  • Wavelength selective coupler based on Bragg Reflection Waveguide
  • 2005
  • Konferensbidrag (refereegranskat)abstract
    • Highly wavelength selective optical filters are essential components for channel management in modern Dense Wavelength Division Multiplexed communication systems with 50GHz channel spacing and below 0.4nm channel bandwidth. We have designed, fabricated and characterized a new type of wavelength selective directional coupler, based on the high differential dispersion between a Bragg Reflection Waveguide (BRW) and a conventional buried channel silica waveguide.The bandwidth of the device is inversely proportional to the length of the coupler as well as to the differential effective refractive index dispersion of the coupled modal fields, at the wavelength of phase matching. The BRW is made of a high index (amorphous) silicon core layer, surrounded vertically by two periodic Bragg reflectors with alternating layers of silica and silicon. The silica waveguide with a Ge-doped core, vertically stacked with the BRW, allows fiber incoupling loss below 1dB which is essentially the insertion loss of the device. The device is operating within the optical bandgap of the Bragg reflectors. Both the bandwidth and the coupling wavelength can be tuned during the fabrication process: the fields’ overlap and the coupling coefficient between the two waveguide modes are controlled by one of the Bragg reflectors (coarse control) and a spacer layer (fine control); the position of the coupling wavelength is mainly determined by the BRW core thickness.The devices were fabricated by depositing SiO2 and a-Si:H films on a 4” <100> oriented Si substrate, by plasma enhanced chemical vapor deposition, at a temperature of 250ºC. The 5µm wide vertical stack of BRW and silica waveguide were defined by lithography and etched in an inductively coupled plasma reactor. The 8.8µm thick coupler structure was covered with a 16µm thick silica cladding. The device can be easily integrated in a standard silica-based planar lightwave circuit.The measured filter suppression is 14dB and the FWHM is 0.29nm for only a 1.73mm long device, which is close to the estimated value of 0.31nm, and one of the lowest ever reported for this type of coupler.
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16.
  • Fernando, Harendra, et al. (författare)
  • Engineering UV-photosensitivity in planar lightwave circuits by plasma enhanced chemical vapour deposition
  • 2004
  • Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 37:20, s. 2804-2809
  • Tidskriftsartikel (refereegranskat)abstract
    • Ion bombarding conditions were used to modify glass properties in silica-on-silicon systems during plasma enhanced chemical vapour deposition (PECVD). The induced structural modifications in the SiO2/Si system resulted in different photosensitive responses when irradiated by ArF pulsed laser operating at 193 nm wavelength. Fourier transform infrared spectroscopy was used to study the structural modifications triggered by ion bombarding conditions during film growth. The results were further confirmed by additional characterizations with regard to density (etch rate), refractive index and surface topographic measurements. The demonstrated method could be used not only to engineer UV-photosensitivity but also to control and compensate birefringence in planar lightwave devices.
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17.
  • Fernando, H. N. J., et al. (författare)
  • Characterization of ultra-violet-induced changes in planar waveguides
  • 2003
  • Ingår i: Journal of Optics. A, Pure and applied optics. - : IOP Publishing. - 1464-4258 .- 1741-3567. ; 5:4, s. 335-340
  • Tidskriftsartikel (refereegranskat)abstract
    • A simple, low-cost spectrophotometer system operating in reflection absorption mode is used to characterize changes in refractive index and thickness of thin films under 193 nm irradiation. The results indicate overall dilation of the glass and are confirmed by additional surface topographic measurements. We also show that in addition to the net relaxation from laser annealing of the interface, in germanosilicate samples local compaction takes place. Since the net relaxation is triggered by remote interactions, it is not spatially confined to the laser-irradiated area. However, a local positive index change is observed. These results are in agreement with previous hypotheses put forward to explain planar waveguide negative index changes. They also bring to attention the great care necessary in both conducting and interpreting measurements that do not take into account spatial variations arising from the combination of remote and local triggers of both index and thickness changes.
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18.
  • Guan, Xiaowei, et al. (författare)
  • Ultracompact and broadband polarization beam splitter utilizing the evanescent coupling between a hybrid plasmonic waveguide and a silicon nanowire
  • 2013
  • Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 38:16, s. 3005-3008
  • Tidskriftsartikel (refereegranskat)abstract
    • An ultracompact polarization beam splitter (PBS) is proposed based on an asymmetrical directional coupler consisting of a silicon hybrid plasmonic waveguide (HPW) and a silicon nanowire. The widths of the two coupling waveguides are chosen so that the phase-matching condition is satisfied for TE polarization only while the phase mismatch is significant for TM polarization. A sharply bent silicon HPW is connected at the thru port to play the role of polarizer by utilizing its polarization-dependent loss. With the present principle, the designed PBS has a footprint as small as only similar to 1.9 mu m x 3.7 mu m, which is the shortest PBS reported until now, even when large waveguide dimensions (e. g., the waveguide widths w(1,2) = similar to 300 nm and the gap width w(gap) = similar to 200 nm) are chosen to simplify the fabrication process. The numerical simulations show that the designed PBS has a very broad band (similar to 120 nm) with an extinction ratio >12 dB and a large fabrication tolerance to allow a waveguide width variation of similar to 30 nm.
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19.
  • Guan, Xiaowei, et al. (författare)
  • Ultrasmall Directional Coupler and Disk-resonantor Based on Nano-scale Silicon Hybrid Plasmonic Waveguides
  • 2012
  • Ingår i: 2012 Asia Communications And Photonics Conference (ACP). - Washington, D.C. : OSA. - 9781467362740 ; , s. AS2H.4-
  • Konferensbidrag (refereegranskat)abstract
    • Nanophotonic integrated devices based on nano-scale silicon hybrid plasmonic waveguides have been demonstrated experimentally, including directional couplers and disk-resonators. The temperature-dependence of the hybrid plasmonic disk-resonators is also characterized.
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20.
  • Jaskorzynska, Bozena, et al. (författare)
  • Active Si-based photonics via heterogeneous integration
  • 2008
  • Ingår i: ICTON 2008. - NEW YORK : IEEE. - 9781424426256 ; , s. 30-33
  • Konferensbidrag (refereegranskat)abstract
    • We review major breakthroughs in realizing silicon-based active components by heterogeneous integration with III-V semiconductors, or nonlinear organic materials. In more detail we describe examples of our concepts and technological approach addressing this goal. This includes designs for widely tunable filters and new routes for heteroepitaxy and selective area growth of InP on silicon.
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21.
  • Jaskorzynska, Bozena, et al. (författare)
  • Applications of wavelength dispersion in 1D and 2D photonic crystals
  • 2005
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. ; , s. 1-9
  • Konferensbidrag (refereegranskat)abstract
    • One of the most distinctive features of photonic crystals (PhCs) is their unique wavelength dispersion allowing novel device concepts for enhancement of photonic functionality and performance. Here, we present examples of our design and demonstrations utilizing dispersion properties of 1D and 2D photonic crystals. This includes the demonstration of negative refraction in 2D PhC at optical wavelengths, filters based on 1D and 2D PhC waveguides, and the design of a widely tunable filter involving 1D PhC.
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22.
  • Jaskorzynska, Bozena, et al. (författare)
  • Dielectric and Plasmon Slot Waveguides for Photonic Integration
  • 2009
  • Ingår i: ICTON 2009: 11th International Conference on Transparent Optical Networks. - NEW YORK : IEEE. ; , s. 653-656
  • Konferensbidrag (refereegranskat)abstract
    • Slot waveguides formed either in high-index dielectrics or in metals attract great interest because they provide sub-wavelength confinement in the slot region. While this feature is very attractive for devices relying on stimulated emission or nonlinear effects, it does not necessarily improve the integration density. The spacing between dielectric slot waveguides is still limited by diffraction. Although for metal (plasmon) waveguides the total field can be shrunk far beyond the diffraction limit, the associated increase in propagation loss will set practical limits on both the minimum waveguide width and edge-to-edge separation. Here we compare the packing densities for 3D slot waveguides in silicon and plasmon waveguides in gold with a silicon slot. As a reference we also consider silicon photonic wire. We calculate center-to-center waveguide separations (pitch) versus cross-talk level. We show that at ca 24 dB/mu m cross-talk and requiring the attenuation length of at least 5 mu m, plasmon slot waveguides can be packed ca 3.5 times denser than silicon slot waveguides, and ca 2.5 times denser than photonic wires. We also show examples of the fabricated devices.
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23.
  • Jaskorzynska, Bozena, et al. (författare)
  • Silicon-based photonic crystals and nanowires
  • 2008
  • Ingår i: Photonic Crystals. - Milano : Springer. - 9783540244318 ; , s. 149-169
  • Bokkapitel (refereegranskat)abstract
    • This Chapter highlights issues related to dense photonic integration based on silicon platform and reviews two alternatives to achieve this goal within the diffraction limit; photonic nanowires and photonic crystal waveguides. Examples of the device concepts and demonstrators, as well as the fabrication techniques for passive Si based mesostructures, are presented. Promising prospects and recent breakthroughs in heterogeneous integration of silicon with optically active materials are indicated.
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24.
  • Junesand, Carl, et al. (författare)
  • InP overgrowth on SiO2 for active photonic devices on silicon
  • 2010
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering.
  • Konferensbidrag (refereegranskat)abstract
    • ntegrationof III-V materials on silicon wafer for active photonic deviceshave previously been achieved by growing thick III-V layers ontop of silicon or by bonding the III-V stack layersonto a silicon wafer. Another way is the epitaxial lateralovergrowth (ELOG) of a thin III-V material from a seedlayer directly on the silicon wafer, which can be usedas a platform for the growth of active devices. Asa prestudy, we have investigated lateral overgrowth of InP byHydride Vapor Phase Epitaxy (HVPE) over SiO2 masks of differentthickness on InP substrates from openings in the mask. Openingswhich varied in direction, width and separation were made withE-beam lithography allowing a good dimension control even for nano-sizedopenings (down to 100 nm wide). This mimics overgrowth ofInP on top of SiO2/Si waveguides. By optimizing the growthconditions in terms of growth temperature and partial pressure ofthe source gases with respect to the opening direction, separationand width, we show that a thin (~200 nm) layerof InP with good morphology and crystalline quality can begrown laterally on top of SiO2. Due to the thingrown InP layer, amplification structures on top of it canbe well integrated with the underlying silicon waveguides. The proposedELOG technology provides a promising integration platform for hybrid InP/siliconactive devices.
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25.
  • Khan, Salman Naeem, et al. (författare)
  • Optimal design for a flat-top AWG demultiplexer by using a fast calculation method based on a Gaussian beam approximation
  • 2006
  • Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 262:2, s. 175-179
  • Tidskriftsartikel (refereegranskat)abstract
    • Passband broadening of an AWG (array waveguide grating) demultiplexer with an MMI (multimode interference) coupler connected at the end of a tapered input waveguide is considered. An explicit formula based on the field propagation of an approximate Hermit-Gaussian beam is used to calculate quickly and reliably the spectral response of the AWG demultiplexer. The widths of the input waveguide, the output waveguides and the MMI coupler are optimized. The optimal design is verified with the experimental measurement.
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26.
  • Kulbickas, A., et al. (författare)
  • Optical study and structure modelling of PPI liquid crystalline dendrimer derivatives
  • 2007
  • Ingår i: Photonics and Nanostructures-Fundamentals and Applications. - : Elsevier BV. - 1569-4410. ; 5:4, s. 178-183
  • Tidskriftsartikel (refereegranskat)abstract
    • Optical study of two families of poly(propylene imine) (PPI) dendrimers (G = 1-5) are reported. The enlarging of the chain number (generations) of the PPI dendrimer leads to the spectra shift to IR region in solvent until 8 and 19 nm for both families, respectively. The theoretical modelling of the dendrimer structure was performed. The geometric characterization of dendrimer structure demonstrates that the preferable free space for encapsulation is periphery of the PPI dendrimer.
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27.
  • Liu, Liu, et al. (författare)
  • Compact Arrayed Waveguide Grating Demultiplexers Based on Amorphous Silicon Nanowires
  • 2006
  • Ingår i: Integrated Photonics Research and Applications/Nanophotonics 2006, NWB5,April 24–28, 2006, Uncasville, Connecticut, USA..
  • Konferensbidrag (refereegranskat)abstract
    • A novel and flexible technology for ultra compact AWGs based on amorphous silicon nanowires is presented. A 4×4 AWG with a total dimension of 50×50µm was fabricated. 11nm channel spacing and -10dB crosstalk was obtained.
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28.
  • Liu, Liu, et al. (författare)
  • Compact polarization beam splitter employing positive/negative refraction based on photonic crystals of pillar type
  • 2006
  • Ingår i: Optoeletronic Materials and Devices, Pts 1 and 2. - BELLINGHAM, WA : SPIE-INT SOC OPTICAL ENGINEERING. - 0819464473 ; , s. U74-U81
  • Konferensbidrag (refereegranskat)abstract
    • A polarization beam splitter based on a two-dimensional photonic crystal slab is presented. In the designed photonic crystal, the TE polarization is negatively refracted, while the TM polarization is positively refracted. The photonic crystal is composed of silicon pillars in a triangular lattice. The whole device is very compact (20x20 mu m(2)), and is compatible with the planar integration. The measurement results show that the extinction ratio is similar to 15dB from 1530 to 1610nm.
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29.
  • Lobov, Gleb, et al. (författare)
  • Electro-optical effects of high aspect ratio P3HT nanofibers colloid in polymer micro-fluid cells
  • 2017
  • Ingår i: Optics Letters. - : OSA Publishing. - 0146-9592 .- 1539-4794. ; 42:11, s. 2157-2160
  • Tidskriftsartikel (refereegranskat)abstract
    • This Letter reports the electro-optical (EO) effect of Poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofibers colloid in a polymer micro-fluidic EO cell. P3HT nanofibers are high aspect ratio semiconducting nanostructures, and can be collectively aligned by an external alternating electric field. Optical transmission modulated by the electric field is a manifestation of the electro-optical effect due to high inner crystallinity of P3HT nanofibers. According to our results, the degree of alignment reaches a maximum at 0.6 V/μm of electric field strength, implying a big polarizability value due to geometry and electrical properties of P3HT nanofibers. We believe that one-dimensional crystalline organic nanostructures have a large potential in EO devices due to their significant anisotropy, wide variety of properties, low actuation voltages, and opportunity to be tailored via adjustment of the fabrication process.
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30.
  • Lobov, Gleb (författare)
  • Electro-optical properties of one-dimensional organic crystals
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The recent development of photonics and applications puts new challenges for systems using emission, transmission and modulation of light. For these reasons, novel optical materials attract a special interest for their enabling properties for novel technologies.In this work, we performed the research on fundamental properties and the possibility of implementation of electro-optical response of Poly-3-hexylthiophene-2,5-diyl (P3HT) nanofibers, which belong to the class of organic semiconductor crystalline materials. Our research demonstrated that an external electric field allows controlling the orientation of nanofibers dispersed in a solution by changing the electrical properties of P3HT crystals. This method was used to introduce a collective alignment of P3HT nanofibers and to impact the optical properties of the colloid. The spectroscopic and polarization measurements show that P3HT nanofibers possess optical anisotropy in a wide range of visible spectrum. This property combined with the ability to manipulate the orientation of nanofibers dynamically, was used for direct phase and intensity modulation of transmitted light. Along with these investigations, several engineering and technology tasks were solved. We have designed the transverse electro-optical cell using all-optical-fiber approach, as well as the longitudinal electro-optical cell was fabricated using a novel polymer molding technique.The obtained research results demonstrate the potential of P3HT crystalline nanofibers as a material class of large niche of applications, not only limited to photovoltaics but also being implemented in electro-optical systems to control light polarization and propagation.
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31.
  • Lobov, Gleb, et al. (författare)
  • Optical birefringence from P3HT nanofibers in alternating electric field
  • 2016
  • Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580194
  • Konferensbidrag (refereegranskat)abstract
    • AC poling allowing to control the orientation of P3HT nanofibers, result in strong optical birefringence with promising implementation in a novel type of optical modulator, without necessary embedding into any hosting matrix, e.g. liquid crystal.
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32.
  • Lobov, Gleb S., et al. (författare)
  • Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution
  • 2015
  • Ingår i: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 5:11, s. 2642-2647
  • Tidskriftsartikel (refereegranskat)abstract
    • The nanofiber morphology of regioregular Poly-3- hexylthiophene (P3HT) is a 1D crystalline structure organized by π - π stacking of the backbone chains. In this study, we report the impact of electric field on the orientation and optical properties of P3HT nanofibers dispersed in liquid solution. We demonstrate that alternating electric field aligns nanofibers, whereas static electric field forces them to migrate towards the cathode. The alignment of nanofibers introduces anisotropic optical properties, which can be dynamically manipulated until the solvent has evaporated. Time resolved spectroscopic measurements revealed that the electro-optical response time decreases significantly with the magnitude of applied electric field. Thus, for electric field 1.3 V ·μm-1 the response time was measured as low as 20 ms, while for 0.65 V ·μm-1 it was 110-150 ms. Observed phenomenon is the first mention of P3HT supramolecules associated with electrooptical effect. Proposed method provides real time control over the orientation of nanofibers, which is a starting point for a novel practical implementation. With further development P3HT nanofibers can be used individually as an anisotropic solution or as an active component in a guest-host system.
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33.
  • Lobov, Gleb S., et al. (författare)
  • Electro-optical response of P3HT nanofibers in liquid solution
  • 2015
  • Ingår i: Asia Communications and Photonics Conference 2015. - : Optical Society of America. - 9781943580064
  • Konferensbidrag (refereegranskat)abstract
    • AC electric poling introduces in P3HT nanofibers anisotropic electro-optical response and birefringence. Along with birefringence, such material exhibits strong amplitude modulation which makes it more efficient alternative to liquid crystals.
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34.
  • Lobov, Gleb S., et al. (författare)
  • Size Impact of Ordered P3HT Nanofibers on Optical Anisotropy
  • 2016
  • Ingår i: Macromolecular Chemistry and Physics. - : John Wiley & Sons. - 1022-1352 .- 1521-3935. ; 217:9, s. 1089-1095
  • Tidskriftsartikel (refereegranskat)abstract
    • Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline structures with semiconductor properties. When P3HT nanofi bers are dispersed in nonconducting solvent, they react to external alternate electric field by aligning along the field lines. This can be used to create layers of ordered nanofi bers and is referred to as alternating current poling method. P3HT nanofi bers with three different size distributions are fabricated, using self-assembly mechanism in marginal solvents, and used for the alignment studies. Anisotropic absorption of oriented 2 mu m long nanofi bers exponentially increases with the magnitude of applied field to a certain asymptotic limit at 0.8 V mu m(-1), while 100-500 nm long nanofi bers respond to electric field negligibly. Effective optical birefringence of oriented 2 mu m long nanofi bers is calculated, based on the phase shift at 633 nm and the average layer thickness, to be 0.41. These results combined with further studies on real-time control over orientation of P3HT nanofi bers in liquid solution or host system are promising in terms of exploiting them in electroabsorptive and electrorefractive applications.
  •  
35.
  • Lou, Fei, et al. (författare)
  • Design and analysis of ultra-compact EO polymer modulators based on hybrid plasmonic microring resonators
  • 2013
  • Ingår i: Optics Express. - 1094-4087. ; 21:17, s. 20041-20051
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultra-compact EO polymer modulators based on hybrid plasmonic microring resonators are proposed, simulated and analyzed. Comparing with Si slot microring modulator, hybrid plasmonic microring modulator shows about 6-times enhancement of the figure of merit when the bending radius is around 510 nm, due to its much larger intrinsic quality factor in sub-micron radius range. Influences of the EO polymer height and Si height on the device's performance are analyzed and optimal design is given. When operating with a bias of 3.6V, the proposed device has optical modulation amplitude of 0.8 and insertion loss of about 1 dB. The estimated power consumption is about 5 fJ/bit at 100 GHz.
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36.
  • Lou, Fei (författare)
  • Design, fabrication and characterization of plasmonic components based on silicon nanowire platform
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Optical interconnects based on CMOS compatible photonic integrated circuits are regarded as a promising technique to tackle the issues traditional electronics faces, such as limited bandwidth, latency, vast energy consumption and so on. In recent years, plasmonic integrated components have gained great attentions due to the properties of nano-scale confinement, which may potentially bridge the size mismatch between photonic and electronic circuits. Based on silicon nanowire platform, this thesis work studies the design, fabrication and characterization of several integrated plasmonic components, aiming to combine the benefits of Si and plasmonics.The basic theories of surface plasmon polaritons are introduced in the beginning, where we explain the physics behind the diffraction-free confinement. Numerical methods frequently used in the thesis including finite-difference time-domain method and finite-element method are then reviewed. We summarize the device fabrication techniques such as film depositions, e-beam lithography and inductively coupled plasma etching as well as characterization methods, such as direct measurement method, butt coupling, grating coupling etc.Fabrication results of an optically tunable silicon-on-insulator microdisk and III-V cavities in applications as light sources for future nanophotonics interconnects are briefly discussed. Afterwards we present in details the experimental demonstrations and novel design of plasmonic components.Hybrid plasmonic waveguides and directional couplers with various splitting ratios are firstly experimentally demonstrated. The coupling length of two 170 nm wide waveguides with a separation of 140 nm is only 1.55 µm. Secondly, an ultracompact polarization beam splitter with a footprint of 2×5.1 μm2 is proposed. The device features an extinction ratio of 12 dB and an insertion loss below 1.5 dB in the entire C-band. Thirdly, we show that plasmonics offer decreased bending losses and enhanced Purcell factor for submicron bends. Novel hybrid plasmonic disk, ring and donut resonators with radii of ~ 0.5 μm and 1 μm are experimentally demonstrated for the first time. The Q-factor of disks with 0.5 μm radii are                         , corresponding to Purcell factors of . Thermal tuning is also presented. Fourthly, we propose a design of electro-optic polymer modulator based on plasmonic microring. The figure of merit characterizing modulation efficiency is 6 times better comparing with corresponding silicon slot polymer modulator. The device exhibits an insertion loss below 1 dB and a power consumption of 5 fJ/bit at 100 GHz. At last, we propose a tightly-confined waveguide and show that the radius of disk resonators based on the proposed waveguide can be shrunk below 60 nm, which may be used to pursue a strong light-matter interaction.The presented here novel components confirm that hybrid plasmonic structures can play an important role in future inter- and intra-core computer communication systems.
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37.
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38.
  • Lou, Fei, et al. (författare)
  • Experimental demonstration of ultra-compact directional couplers based on silicon hybrid plasmonic waveguides
  • 2012
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:24, s. 241105-
  • Tidskriftsartikel (refereegranskat)abstract
    • Hybrid plasmonic waveguides and directional couplers have been experimentally demonstrated. Using a direct measurement method, the propagation loss of a 170 nm wide waveguide is measured to be 0.08 dB/mu m at 1550 nm when the thickness of low-index region is 56 nm. Ultra-compact directional couplers based on such hybrid plasmonic waveguides are demonstrated with gaps of 140 nm, 185 nm, 235 nm, and 290 nm. The corresponding coupling lengths measured are 1.55 mu m, 2.2 mu m, 3.2 mu m, and 4.8 mu m, respectively, which are in very good agreement with the simulations. These ultra-compact devices can be potentially used in future ultra-dense photonic integrated circuits.
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39.
  • Lou, Fei, et al. (författare)
  • Hybrid plasmonic microdisk resonators for optical interconnect applications
  • 2013
  • Ingår i: Integrated Optics. - : SPIE - International Society for Optical Engineering. - 9780819495839 ; , s. 87810X-
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we present our theoretical and experimental work on hybrid plasmonic microdisks. The 170 nm wide access waveguide is first simulated and characterized, and shows a propagation loss about 0.08 dB/mu m. 3-D FDTD simulations are then used to investigate the lower limit of the bending radius of the hybrid plasmonic microdisk. Microdisks with radius around 500 nm are fabricated, characterized, and analyzed. The 5th and 4th order resonances are experimentally observed around 1412 nm and 1625 nm. The extinction ratios of the two resonances are measured to be 5.5dB and above 10dB, respectively. The measured intrinsic quality factors are 350 and 110, respectively. Comparisons are also made between the theoretical and experimental results. The demonstrated ultra-small hybrid plasmonic microdisk may find applications in low-power-consumption modulators, nano laser cavities with large Purcell-factor, molecule sensors, and others.
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40.
  • Lou, Fei, et al. (författare)
  • Photonic devices based on silicon hybrid plasmonic waveguides
  • 2012
  • Ingår i: 2012 Asia Communications And Photonics Conference (ACP). - Washington, D.C. : Optica Publishing Group. ; , s. AS2H.2-
  • Konferensbidrag (refereegranskat)abstract
    • A 170 nm wide hybrid plasmonic waveguide with a loss of 0,08 dB/mu m is demonstrated experimentally. Directional couplers with different gaps and microdisks with 0.5 mu m radius based on such waveguides are also presented.
  •  
41.
  • Lou, Fei, et al. (författare)
  • Sub-wavelength microdisk resonator based on hybrid plasmonic waveguides
  • 2012
  • Ingår i: Information Optoelectronics, Nanofabrication and Testing, IONT 2012. - 9781557529602
  • Konferensbidrag (refereegranskat)abstract
    • Based on hybrid plasmonic waveguides, microdisk resonators with radii of 0.5 μm and FSRs of about 200 nm are simulated and experimentally demonstrated. Thermal tuning of the devices in 6 nm range is also presented.
  •  
42.
  • Lou, Fei, et al. (författare)
  • Transmission characteristics of a novel grating assisted microring
  • 2011
  • Ingår i: 2011 Asia Communications and Photonics Conference and Exhibition, ACP 2011. - Washington, D.C. : IEEE Computer Society. - 9780819489616 ; , s. 83080A-
  • Konferensbidrag (refereegranskat)abstract
    • We propose a new type of grating-assisted microring (GAMR) structure with Bragg gratings placed on microring's arms. Two Fabry-Perot resonances interact with microring resonance, resulting in GAMR's unique amplitude and phase spectra. The structure's characteristics are analytically studied using coupled mode theory and numerically verified by 2D-FDTD. With proper cavity lengths, GAMR exhibits an electromagnetically induced transparency (EIT)-like spectrum. The ultra-narrow resonance can be used for sensing, modulation, and other applications.
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43.
  • Lou, Fei, et al. (författare)
  • Ultra-sharp bends based on hybrid plasmonic waveguides
  • 2014
  • Ingår i: European Conference on Optical Communication, ECOC.
  • Konferensbidrag (refereegranskat)abstract
    • To explore the potentials of hybrid plasmonics, ultrasharp 90 degree bends and resonators based on silicon waveguide and hybrid plasmonic waveguides are simulated and analyzed. Experimental demonstrations of ring and donut resonators based on hybrid plasmonics are also presented.
  •  
44.
  • Lou, Fei, et al. (författare)
  • Ultracompact polarization beam splitter based on a dielectric-hybrid plasmonic-dielectric coupler
  • 2012
  • Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 37:16, s. 3372-3374
  • Tidskriftsartikel (refereegranskat)abstract
    • An ultracompact polarization beam splitter (PBS) based on a dielectric-hybrid plasmonic-dielectric coupler is proposed. The device utilizes the polarization-dependent nature of hybrid plasmonic waveguides. By choosing proper waveguide parameters, a 2 x 5.1 mu m(2) PBS (including S-bends) with extinction ratios over 15 dB and insertion losses below 1.5 dB in the full C-band should be achievable. The effect of fabrication errors is also investigated.
  •  
45.
  • Lou, Fei, et al. (författare)
  • Whispering gallery mode nanodisk resonator based on layered metal-dielectric waveguide
  • 2014
  • Ingår i: Optics Express. - 1094-4087. ; 22:7, s. 8490-8502
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper proposes a layered metal-dielectric waveguide consisting of a stack of alternating metal and dielectric films which enables an ultracompact mode confinement. The properties of whispering gallery modes supported by disk resonators based on such waveguides are investigated for achieving a large Purcell factor. We show that by stacking three layers of 10 nm thick silver with two layers of 50 nm dielectric layers (of refractive index n) in sequence, the disk radius can be as small as 61 nm similar to lambda(0) / (7n) and the mode volume is only 0.0175 (lambda(0) / (2n))(3). When operating at 40 K, the cavity's Q-factor can be similar to 670; Purcell factor can be as large as 2.3x10(4), which is more than five times larger than that achievable in a metal-dielectric-metal disk cavity in the same condition. When more dielectric layers with smaller thicknesses are used, even more compact confinement can be achieved. For example, the radius of a cavity consisting of seven dielectric-layer waveguide can be shrunk down to lambda(0) / (13.5n), corresponding to a mode volume of 0.005 lambda(0) / (2n))(3), and Purcell factor can be enhanced to 7.3x10(4) at 40 K. The influence of parameters like thicknesses of dielectric and metal films, cavity size, and number of dielectric layers is also comprehensively studied. The proposed waveguide and nanodisk cavity provide an alternative for ultracompact light confinement, and can find applications where a strong light-matter interaction is necessary.
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46.
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47.
  • Saeed, Saba, et al. (författare)
  • Structural and optical characterization of self-assembled Ge nanocrystal layers grown by plasma-enhanced chemical vapor deposition
  • 2014
  • Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 25:40, s. 405705-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a structural and optical study of solid-state dispersions of Ge nanocrystals prepared by plasma-enhanced chemical vapor deposition. Structural analysis shows the presence of nanocrystalline germanium inclusions embedded in an amorphous matrix of Si-rich SiO2. Optical characterization reveals two prominent emission bands centered around 2.6 eV and 3.4 eV, and tunable by excitation energy. In addition, the lower energy band shows an excitation power-dependent blue shift of up to 0.3 eV. Decay dynamics of the observed emission contains fast (nanosecond) and slow (microseconds) components, indicating contributions of several relaxation channels. Based on these material characteristics, a possible microscopic origin of the individual emission bands is discussed.
  •  
48.
  • Shi, Yuechun, et al. (författare)
  • All-optical switching of silicon disk resonator based on photothermal effect in metal-insulator-metal absorber
  • 2014
  • Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 39:15, s. 4431-4434
  • Tidskriftsartikel (refereegranskat)abstract
    • Efficient narrowband light absorption by a metal-insulator-metal (MIM) structure can lead to high-speed light-to-heat conversion at a micro-or nanoscale. Such a MIM structure can serve as a heater for achieving all-optical light control based on the thermo-optical (TO) effect. Here we experimentally fabricated and characterized a novel all-optical switch based on a silicon microdisk integrated with a MIM light absorber. Direct integration of the absorber on top of the microdisk reduces the thermal capacity of the whole device, leading to high-speed TO switching of the microdisk resonance. The measurement result exhibits a rise time of 2.0 mu s and a fall time of 2.6 mu s with switching power as low as 0.5 mW; the product of switching power and response time is only about 1.3 mW.mu s. Since no auxiliary elements are required for the heater, the switch is structurally compact, and its fabrication is rather easy. The device potentially can be deployed for new kinds of all-optical applications.
  •  
49.
  • Shi, Yuechun, et al. (författare)
  • All-optical switching of silicon disk resonator based on photothermal effect in metal–insulator–metal absorber
  • 2014
  • Ingår i: Optics Letters. - : Optica Publishing Group. - 0146-9592 .- 1539-4794. ; 39:15, s. 4431-4434
  • Tidskriftsartikel (refereegranskat)abstract
    • Efficient narrowband light absorption by a metal–insulator–metal (MIM) structure can lead to high-speed light-to-heat conversion at a micro- or nanoscale. Such a MIM structure can serve as a heater for achieving all-optical light control based on the thermo-optical (TO) effect. Here we experimentally fabricated and characterized a novel all-optical switch based on a silicon microdisk integrated with a MIM light absorber. Direct integration of the absorber on top of the microdisk reduces the thermal capacity of the whole device, leading to high-speed TO switching of the microdisk resonance. The measurement result exhibits a rise time of 2.0 μs and a fall time of 2.6 μs with switching power as low as 0.5 mW; the product of switching power and response time is only about 1.3  mW·μs1.3  mW·μs. Since no auxiliary elements are required for the heater, the switch is structurally compact, and its fabrication is rather easy. The device potentially can be deployed for new kinds of all-optical applications.
  •  
50.
  • Sun, Xu, 1987-, et al. (författare)
  • All-Optical Switching Using a Hybrid Plasmonic Donut Resonator With Photothermal Absorber
  • 2016
  • Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 28:15, s. 1609-1612
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel hybrid plasmonic (HP) donut resonator integrated with a photothermal plasmonic absorber has been developed, which can be used as a compact all-optical switch or modulator. The radius of the fabricated HP donut resonator is 1.8 mu m, with a resonant wavelength around 1550 nm and a quality factor (Q factor) around 600. The photothermal plasmonic absorber is directly integrated above the HP device, which can absorb as much as 75% of impinging optical power at 1064 nm wavelength. Since the absorber is in tight contact to the Si ridge of the HP waveguide, the absorbed optical power can efficiently heat up the Si ridge, and hence change the resonant wavelength of the HP donut resonator by Si thermal expansion effect. Experimental results show that the power used for 15 dB amplitude switch is only 10 mW, with rise and fall response times around 18 and 14 mu s, respectively.
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