Proceedings Volume 5515

Nanoengineering: Fabrication, Properties, Optics, and Devices

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Proceedings Volume 5515

Nanoengineering: Fabrication, Properties, Optics, and Devices

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Volume Details

Date Published: 8 October 2004
Contents: 5 Sessions, 31 Papers, 0 Presentations
Conference: Optical Science and Technology, the SPIE 49th Annual Meeting 2004
Volume Number: 5515

Table of Contents

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Table of Contents

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  • Nano Cavities and Photonics
  • Nano-Bio and Nano-Sensors
  • Nano Engineered Waveguides and Optics
  • Nanotubes, Proximal Probes, Near Field Optics, Nanoparticles
  • Poster Session
Nano Cavities and Photonics
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High-Q photonic nanocavity
High Q and ultra-small photonic nanocavity operating at optical communication wavelength is developed using a silicon-based two-dimensional photonic-crystal slab. The cavity is designed based on the concept that light should be confined gently in order to be confined strongly, which means that the envelope function of the cavity electric field profile should be gently varying but remain spatially localized. Structure of a cavity is adjusted to fit the envelope to a Gaussian function that fulfill the two conditions, and a Q factor more than 45,000 and a modal volume of 0.07 μm3 are successfully realized.
Chip-scale fully reconfigurable optical add/drop multiplexing subsystem in polymer microphotonic circuits
Tomoyuki Izuhara, Junichiro Fujita, Antonije Radojevic, et al.
We report on a highly integrated photonic circuit using a polymer-based planar waveguide system. The properties of the materials used in this work such as ultra-low optical loss, widely tunable refractive index, and large thermo-optic coefficient, enable a multi-functional chip-scale microphotonic circuit. We discuss the application of this technology to the fabrication of a fully reconfigurable optical add/drop multiplexer. This subsystem includes channel switching, power monitoring, load balancing, and wavelength shuffling functionalities that are required for agile wavelength-division multiplexing optical networks. Optical properties of our material systems and performance characteristics of the implemented optical passive/active elements are presented, and the integration schemes of the devices to achieve a fully integrated reconfigurable optical add/drop multiplexer are discussed.
High-density multimode photonic backplane
The development of a photonic backplane for high-speed and high-bandwidth communications is presented. This hybrid, multimode, multi-channel backplane structure contains both electrical and optical interconnects, suitable for next-generation high-speed servers with terabit backplane capacity. Removable and all-passively aligned high density interconnects on this backplane are achieved by polymer based optical waveguides with integrated micro-optics and VCSEL arrays on conventional printed circuit boards. The fabrication of this photonic backplane requires few additional steps outside a traditional board-manufacturing environment and is largely compatible with existing processes.
Magneto-optic photonic crystals as optical waveguide structures
Miguel Levy, Xiaoyue Huang, Rong Li, et al.
Miniaturized on-chip optical isolators are highly desirable for advanced optical telecommunications to eliminate noise and protect the laser source. This talk will discuss the fabrication and testing of on-chip photonic crystals in ferrite waveguides. Photonic band gap engineering can produce Faraday rotators with highly enhanced polarization rotation for ultra-small integrated optical isolators. The main challenges to such devices are the elimination of linear birefringence and the efficient production of planar photonic band gap nanostructures. These challenges are addressed in the present article. In particular, we demonstrate the presence of stopbands and resonant polarization response in single-defect magneto-optic photonic crystal waveguides. However, waveguide birefringence degrades the magneto-optic response and results in significant ellipticity at resonance. Lower birefringence waveguides are required for enhanced magneto-optic performance.
Cavity-enhanced near-field optical magnetometry
We present the first near-field scanning optical magneto-optic Kerr effect (MOKE) of sub-micron magnetic structures, where a Kerr rotation of 0.11° from a 0.25μm nickel magnet was observed. This is enabled by a cavity based technique to enhance the Kerr rotation of light reflected from a magnetized surface. Spatially resolved magneto-optic measurements are performed involving both conventional microscopy and near-field scanning optical microscopy (NSOM). Cavity enhancement is achieved with either a single dielectric coating or a dielectric-metal bilayer coating applied to the ferromagnetic structure of interest. We present a scattering matrix approach to calculating the enhancement resulting from a multilayer dielectric coating and show good agreement with experiment. This demonstrates a non-invasive optical technique for magnetometry with ultrahigh spatial resolution.
Nano-Bio and Nano-Sensors
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Resonating periodic waveguides as ultraresolution sensors in biomedicine
Optical sensor technology based on subwavelength periodic waveguides is applied for tag-free, high-resolution biomedical and chemical detection. Measured resonance wavelength shifts of 6.4 nm for chemically attached Bovine Serum Albumin agree well with theory for a sensor tested in air. Reflection peak efficiencies of 90% are measured, and do not degrade upon biolayer attachment. Phase detection methods are investigated to enhance sensor sensitivity and resolution. Direct measurement of the resonant phase response is reported for the first time using ellipsometric measurement techniques.
Photonic crystals enable infrared gas sensors
Irina Puscasu, Edward A. Johnson, Martin U. Pralle, et al.
Sensors of trace gases are of enormous importance to diverse fields such as environmental protection, household safety, homeland security, bio-hazardous material identification, meteorology and industrial environments. The gases of interest include CO for home environments, CO2 for industrial and environment applications and toxic effluents such as SO2, CH4, NO for various manufacturing environments. We propose a new class of IR gas sensors, where the enabling technology is a spectrally tuned metallo-dielectric photonic crystal. Building both the emitting and sensing capabilities on to a single discrete element, Ion Optics’ infrared sensorchip brings together a new sensor paradigm to vital commercial applications. Our design exploits Si-based suspended micro-bridge structures fabricated using conventional photolithographic processes. Spectral tuning, control of bandwidth and direction of emission were accomplished by specially designed metallo-dielectric photonic crystal surfaces.
Integrated ARROW waveguides for gas/liquid sensing
Holger Schmidt, Dongliang Yin, David W. Deamer, et al.
We present integrated antiresonant reflecting optical (ARROW) structures with hollow cores as a new paradigm for optical sensing of gases and liquids. ARROW waveguides with micron-sized hollow cores allow for single-mode propagation in low-index non-solid core materials where conventional index guiding is impossible. We review design, fabrication and optical characterization of these devices for possible applications in chemical sensing, single molecule fluorescence and Raman spectroscopy, flow cytometry, and pollution monitoring of picoliter to nanoliter volumes. We describe how to determine and control the waveguide loss and dispersion of the ARROW waveguides and design optimization for realistic structures that are compatible with the fabrication constraints. The technology to realize hollow-core waveguides using conventional silicon microfabrication and sacrificial core layers is discussed. We present the first demonstration of waveguiding in integrated ARROW waveguides with both hollow and liquid cores. Single-mode propagation with mode areas as small as 6mm2 and volumes down to 15 picoliters is observed and the loss characteristics of the waveguides are determined. The observation of fluorescence from dye molecules with concentrations of 10 nmol/l is described. Higher-level integration towards compact, planar, and massively parallel sensors on a chip is discussed.
Fabrication of micro-optical elements and biochip patterns on glass surface by imprint lithography
Yasuhisa Tsubouchi, Takehiko Yamaguchi, Kazuyuki Yao, et al.
Fabrications of free form surface and well array plate demonstrated using glass material by imprint lithography. A metal mold is processed by a Diamond cutting. Using a low Tg glass plate, the mold is pressed to the glass surface and transferred the free form surface. The feature error of the proceed glass surface is within 200nm in 3mm x 6mm field. On the other hand, deep well array for bio-chemical device is transferred on glass surface using ceramics mold. Micro wells with 200 x 200μm in square and 50 μm in depth is achieved without fatal defect using optimized imprint process conditions.
Novel biomedical implant interconnects utilizing micromachined LCP
Robert Neal Dean Jr., Jenny Weller, Michael Bozack, et al.
Micro- and nano-MEMS technology is being increasingly exploited in biomedical applications, such as large electrode-count neural prosthesis probe arrays. However, a bottleneck in fully utilizing this technology has been the interconnect between the implanted MEMS device and the external system connected to the implanted device. Since the implanted MEMS device is capable of having a large number of elements, the interconnect must have a sufficient number of electrical connections to communicate with each and every element. Complicating this is the fact that the interconnect requirements may include electrical signals, microfluidics transport and optical signals, all packaged in a miniature biocompatible interconnect cable. Micromachined liquid crystal polymer (LCP) is a promising technology for this application, due to LCP's biocompatibility, chemical inertness, electromechanical properties and its ability to be micromachined. This paper presents the results from the development of surface micromachining techniques compatible with LCP, and is demonstrated in the realization of a prototype micromachined LCP biomedical interconnect device. In particular, the development of the interconnect device demonstrates the realization of biocompatible connectors with high-density ultra-fine pitch electrical traces.
Manipulation of DNA molecules using optical techniques for optically assisted DNA computing
Yusuke Ogura, Fumika Sumiyama, Takashi Kawakami, et al.
DNA computing is an interesting computational paradigm utilizing reactive nature of DNA. The DNA computing realizes massively parallel computation because a large number of DNAs are processed in parallel. However, the computational functionality is restricted by the number of DNA molecules and DNA reactions that can be employed. As a new computational scheme, we are studying optically assisted DNA computing, which utilizes flexibility in generating light fields and parallelism of DNA reactions. Toward the goal, we experimentally verified methods for translating DNA molecules and controlling DNA reactions locally by using optical techniques. An optical manipulation method with VCSEL array sources is applied to translate DNA. We succeeded to translate two DNA clusters, which consisted of many DNA molecules attached to particles, in different directions simultaneously by switching the emission pattern of the VCSEL array. The reaction of DNA is controlled by irradiating with a laser beam. Experimental results demonstrated that double stranded DNAs, which were immobilized to the surface of a particle or a substrate, were denaturated at a resolution of several micrometer. The methods make possible to deal with a set of DNAs selectively and are useful in executing flexible operations for computing.
Optical detection of single molecules in nanofluidic chips
We present the latest progress on a novel technology for detecting and manipulating solution of single molecules in nanofluidic channels. This paper explains the design and fabrication of nanofluidic chip and its interface, molecule manipulation technique being used, and the optical detection method employed. Single molecule detections are performed using optical imaging as well as metal microelectrodes. The ultimate goal is to get high spatial and spectral resolutions that can lead to molecular identification.
Self-assembled gold nanowires from nanoparticles: an electronic route towards DNA nanosensors
Lifeng Zheng, Shengdong Li, Peter J. Burke
We present a new technique for fabricating gold nanowires using carbon nanotubes as the template. By applying an ac voltage to an electrically contacted single walled carbon nanotube, we generate highly non-uniform ac electric fields in the vicinity of the nanotubes. These ac electric fields serve to polarize 2 nm gold nanoparticles dispersed in solution. The induced dipole moment in the nanoparticles is attracted to the high-intensity field regions at the surface of the nanotube, thus causing a gold nanowire to grow on the surface of the nanotube. Interestingly, we find gold nanowires grow even on nanotubes that are not electrically contacted but in close proximity to the electrodes. Future applications of this work may include DNA sensors based on functionalized Au nanoparticles.
Nano Engineered Waveguides and Optics
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Optical elements with subwavelength structured surfaces
Several optical elements with subwavelength structured (SWS) surfaces have been developed. The SWS has optical features of artificial refractive index, form birefringence, resonance and band-gap effects. This paper describes some applications of form birefringent optical elements and a resonant reflection element. A form-birefringent quarter-wave plate was realized by sputtering the high refractive-index thin film on a SWS substrate. The wavelength dispersion of form birefringence restrains the phase retardance from depending on the wavelength of light. An array of form-birefringent wave-plates is useful for the real-time imaging polarimetry. We developed a real-time polarization imaging system for the visible light. A guided-mode resonant grating with a PLZT wave-guide was designed for optical switches. The PLZT is ferroelectric material with an electro-optic (EO) effect. We made a feasibility study on the optical switching by numerical simulations.
Macroporous silicon-based polarization components
Vladimir Kochergin, Marc Christophersen, Philip R. Swinehart
Currently used transmission-type polarizers exhibit strong limitations in the deep UV and shorter wavelength. We propose an entirely different type of polarizer to solve many of the problems caused by the absence of adequate materials in this spectral range. The new polarizers consist of three-dimensionally ordered Macroporous Silicon (MPSi), with the pores used as waveguide cores separated by the reflective silicon host. Ordered pores serve as a two-dimensional array of optical waveguides. Multilayer coating of the pore walls, together with the rectangular shape of the pores (with the length along one axis being several times greater than that of the second axis) results in polarized transmission. Calculations demonstrate potentially very high extinction. In addition, the extinction achieved by such polarization components does not exhibit degradation with the angle of incidence, permitting operation in tilted and divergent light beams to simplify optical system design and fabrication. The fabrication process is different from that used in the fabrication of multilayer interference filters. It permits the fabrication of deep UV polarizers up to 200mm in diameter, suitable for wavelengths from above 600nm to less than 50nm. Far-UV polarizers can be manufactured as simply and economically as the near UV ones. The theory of light propagation through such MPSi layers is developed, the main predictions of the theory are experimentally validated, and the fabrication procedure for MPSi UV polarizers is described.
Fabrication and characterization of GaAs-based space-variant inhomogeneous media for polarization control at 10.6 µm
Chia-Ho Tsai, Uriel Levy, Lin Pang, et al.
Approaches to create radially and azimuthally polarized light beams usually suffer from issues of integration difficulty and system complexity. In this research, we apply a compact design of space-variant inhomogeneous media (SVIM), providing an even more compact solution with relatively higher conversion efficiency. The device we utilize to convert linear polarization at the wavelength of 10.6 μm to radial/azimuthal polarization is fabricated on a single GaAs substrate, using space-variant subwavelength periodic structure with locally varying form birefringence. Unlike previous approach, this subwavelength periodic structure is designed to be relatively deep in order to introduce a pi phase shift between the TE and the TM components of the input light, and therefore to locally rotate the incident linearly polarized light to the radial/azimuthal direction. To realize the deep space-variant form birefringent structure, we utilize standard photolithography on a GaAs substrate, followed by chemically assisted ion beam etching (CAIBE), rendering an etch profile with high aspect-ratio (6:1) as required by the original design. An optical characterization at 10.6 μm shows a close match between the measured and the theoretical polarization distribution. With proper control of the etch profile it shows that the subwavelength structure also serves as an anti-reflection coating at the sample surface.
Si photonic wire waveguides
Due to their ultrahigh index contrast structure, Si photonic wire waveguides realize various micro-components, which enable us to design and fabricate compact photonic devices and circuits. We have already demonstrated them theoretically and experimentally in some journal papers and two SPIE proceedings. In this work, I pick up other two topics; one is the polarization crosstalk, and the other is a Mach-Zehnder interferometer. The former will be a significant problem that degrades the performance of functional circuits based on polarization-dependent devices. It was experimentally meas-ured, and its reduction method was theoretically investigated by the three-dimensional finite-difference time domain method. The latter device is a basic element of functional circuits. By employing micro-bends and micro-couplers, a high extinc-tion ratio of over 15 dB and a large diffraction order of 300 were achieved within a small foot space of 20 times 20 square microns.
Design of thin-film-coated diffractive optical elements with frequency variant transmission functions
Markus E. Testorf, Ursula J. Gibson
Synthetic optical structures are classified as members of a hierarchy of electromagnetic materials and diffractive elements. Innovations on a system level are strongly related to the introduction of new members of this hierarchy as well as by combining features of two or more hierarchy levels. As an example we focus our attention on the synergy of diffractive optics and optical thin film technology. To this end properties and potential applications of diffractive optical elements coated with nonuniform thin films are investigated. Paraxial and non-paraxial diffraction models based on the Kirchhoff approximation are used to understand the response of these elements. As an important tool to provide an intuitive understanding we employ a reciprocal space representation. Three design problems are discussed, namely the shaping of the spectral response of harmonic diffractive optical elements, the design of color separation gratings, and the implementation of computer generated volume holograms.
Nanostructured diffractive optical elements on SiNX membrane for UV-visible regime applications
Silicon nitride (SiNX) film is a commonly used material in silicon technology. In addition, it has excellent optical properties. It is transparent in both the UV and visible range, with a high refractive index of about 1.7~2. Owing to its superior mechanical and optical properties, we used a silicon nitride membrane as an optical phase element. We will fabricate nano-structured diffractive optical elements, such as wave-plate, polarizer, and polarized beam splitter on SiNXHY membrane by e-beam lithography for the UV-visible regime applications. The SiNXHY membranes were made from SiNXHY films deposited by an plasma enhanced chemical vapor deposition (PECVD) as an alternative method for low stress membrane fabrication used in UV-visible transmittance. The stress of silicon nitride film showed a change from compressive to tensile with increasing working pressure during film deposition. The UV-visible transmittance of the free standing membrane was measured, which showed that UV light is transparent at wavelength as short as 240nm. We will show the feasibility to fabricate nano-structured diffractive optical elements on the SiNXHY membrane combined with microoptoelectromechanical systems (MOEMS) technology for the application in the UV-visible regimes.
Waveguiding light in air with ultralow index metamaterials
Brian T. Schwartz, Rafael Piestun
Metamaterials can be engineered to have the real part of the effective refractive index less than unity at optical wavelengths. These composite materials exhibit total external reflection and hence can be utilized in the cladding of hollow optical waveguides. We investigate the use of one- and two-dimensional silver-dielectric metamaterials in waveguides. In particular, we discuss the effects of scaling down the size of the metal features in the metamaterial.
High-aspect ratio grating fabrication by imprint lithography
Yoshihiko Hirai, Takaaki Konishi, Tomohiro Kanakugi, et al.
A fine grating with high aspect rate pattern is one of the essential elements for advanced nano optical devices such as a quarter wave plate. To fabricate high aspect ratio pattern having sub wavelength feature size, nanoimprint lithography is applied. However, fatal defects caused by mechanical stress and friction between the mold and polymer are significant problems. To eliminate the defects, the process sequence, pressure and temperature conditions are optimized. Using Si based mold, sub wavelength grating having 200nm in width and over 1.7 micron in height is demonstrated using PMMA thin film on quartz substrate. This method is a promising technology for industrial production of advanced nano optical elements having high aspect ratio structure.
Electromagnetic modeling of phase-shifting contact lithography by broadband ultraviolet illumination
Fei Wang, Katherine E. Weaver, Akhlesh Lakhtakia, et al.
Experiments have recently indicated that phase-shifting contact lithography (PSCL) could provide sub-wave-length resolution by using broadband ultraviolet sources of illumination. Electromagnetic modeling of PSCL is performed to characterize absorption features of the photoresist layer one of whose faces is in contact with a quartz binary phase-shift mask. The electromagnetic field of the broadband ultraviolet source is represented as a spectrum of normally incident plane waves, and a rigorous coupled--wave analysis is performed to determine spectral absorption in the photoresist layer. The specific absorption rate in the photoresist layer is calculated and examined in relation to the geometric parameters of experimental samples. As illustrated by the modeling, columnar features are formed in the photoresist layer due to the localization of absorption. Feature resolution and profile are noticeably affected by the phase--shift mask's thickness. Ideally, the feature linewidth can be less than 200 nm for transverse-magnetic mode illumination.
Nanotubes, Proximal Probes, Near Field Optics, Nanoparticles
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Formation of nanoscale dots on glass surface by microprobe ion manipulation
Tetsuji Yano, Shin-ichi Kubota, Hiroaki Kato, et al.
Ion manipulation using micro-probe has been performed to fabricate the nano-scale dots on/or in the glass. Soda-lime-silica glass was subjected to the treatments. Two types of the manipulation treatments were carried out using various probes and electrical conditions. In the Na-extraction treatment, the thick needles and/or STM tips were used as a cathode. At 250°C, Na+ ions were extracted from the inside of the glass towards the cathode tip, and electrochemically reduced to Na-metal. Na-metal are held at the tip/glass interface as liquid state, and grew with the treatment time. After the treatment, they formed the micrometer-size dots of fodium compound on the glass surface, and their size was dependent on the total charge conducting through the tip. In the Ag-migration treatment, Ag-metal probes were prepared and used as an anode at 200°C. Ag atoms on the tip were oxidized to Ag+ ions and migrated into the glass. They could be optically recognized using the luminescence from Ag+ ions under the UV irradiation. a lot of Ag-metal dots with the size 100-300nm were also formed on the glass surface. They are considered to be transferred from the tip of Ag-metal probe onto the glass surface. The size of the Ag+ migrated region was dependent on the total charge of the treatment, and the available small size was found to be defined by the apex of the probe tip. The observed phenomena in these treatments were explained and the possibility of the formation of nano-scale dots on the glass by ion manipulation was discussed.
Observation of nanometer-scale crystal grain orientation in ferroelectric thin films using polarization near-field scanning optical microscopy (NSOM)
Takashi Fuse, Fumiyuki Takahashi, Hiroyuki Tsukahara
We developed an observation technique for crystal orientation in the nanometer-scale grain using polarization near-field scanning optical microscopy (NSOM), and applied it to Pb(Zr,Ti)O3 (PZT) ferroelectric thin films. PZT is a ferroelectric RAM material. Because ferroelectric RAM cell sizes have become smaller and are now, being measured in the submicron scale range, the grain sizes in PZT that constitute the cells are about 100 nm. The observation for crystal grain orientation of such ferroelectric RAM cells has been difficult with current methods such as X-ray diffraction method or micro-Raman spectroscopy. PZT is a uniaxial crystal because of its tetragonal structure and we found that the birefringence retardation of PZT depends on its crystal grain orientation. The nanometer-scale grain was observed by NSOM, which is not limited by the diffraction limit of conventional optical microscopy. To achieve the observation of birefringence retardation, NSOM and polarization optical elements were integrated. For this integration, the optical compensation of polarized light was indispensable because a near-field probe in NSOM might show birefringence. Then, a polarization compensation method at the tip of the near-field probe was developed. Using this polarization NSOM, a new technique for observing the crystal grain orientation by birefringence retardation was developed.
Diffraction effects in honeycomb arrays of multiwalled carbon nanotubes
Brian R. Kimball, Joel B. Carlson, Diane M. Steeves, et al.
Carbon nanotubes were grown on silicon and quartz substrates in a honeycomb configuration using self-assembly nanosphere lithography and plasma enhanced chemical vapor deposition methods. Photonic nanoarrays were fabricated with varying spacing and carbon nanotube height. Both periodic and nonperiodic arrays were produced and evaluated. Optical properties of the arrays were studied and related to array geometry. Three dimensional diffraction maps were created that reveal the manner in which the nanoarrays interact with visible light. The unique optical properties of the arrays combined with the excellent mechanical and electrical properties of carbon nanotubes indicates that these materials may find many uses in the field of optoelectronics.
Enhancement of optical transmission through planar nanoapertures in a metal film
Xianfan Xu, Eric X. Jin, Sreemanth M.V. Uppuluri
The optical transmission mechanism through a ridge nano-aperture in a metal film is discussed based on the waveguide theory and FDTD computations. The transmission enhancement through ridge apertures is associated with the TE10 waveguide propagation mode. In terms of near and far field radiator, the ridge aperture can be represented as a combination of an oscillating electric dipole and two magnetic dipoles. The effects of localized surface plasmon (LSP) excited on the edges of ridge nano-apertures made in silver are discussed. The transmission enhancement and field concentration functions of ridge apertures are confirmed by contact lithography experiments.
Carbon-encapsulated iron nanoparticles prepared by laser pyrolysis: characterization and catalyzers for carbon nanotubes and nanofibers
Florian V. Dumitrache, Victor Ciupina, Ion Morjan, et al.
The embedding of Fe-based nanoparticles in carbon layers allows novel physical and catalyzing properties due to inertness and resistance to external detrimental conditions. We have prepared almost spherical carbon encapsulated iron nanoparticles with narrow size distribution, via laser co-pyrolysis method in which the CW CO2 laser beam irradiates a gas mixture containing iron pentacarbonyl (vapors) and ethylene/acetylene hydrocarbons. Specific flow geometries were used in order to synthesize iron particle first followed by stimulate hydrocarbon decomposition at iron surfaces. High-resolution transmission electron microscopy images reveal the core-shell feature of synthesized nanostructures with around 2 nm thick carbon layers and 3-7 nm diameters iron-based core dimensions. The mean diameter could be experimentally controlled. It was found a decreasing trend of particle size with the decreasing of pressure and total reactant gas flow. EELS, EDAX and Raman spectroscopy analysis confirm the simultaneous presence of carbon and iron. The nanoparticles were seeded onto Si wafer and further used as substrates for laser induced CVD carbon nanotubes growth. Depending on laser power density, nanotubes or nanofibres are formed, in strong dependence with the location of iron based nanoparticles on Si substrates as revealed by SEM analysis.
Poster Session
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Analysis of dual-frequency MEMS antenna using H-MRTD method
Wenge Yu, Xianxin Zhong, Yu Chen, et al.
For applying micro/nano technologies and Micro-Electro-Mechanical System (MEMS) technologies in the Radio Frequency (RF) field to manufacture miniature microstrip antennas. A novel MEMS dual-band patch antenna designed using slot-loaded and short-circuited size-reduction techniques is presented in this paper. By controlling the short-plane width, the two resonant frequencies, f10 and f30, can be significantly reduced and the frequency ratio (f30/f10) is tunable in the range 1.7~2.3. The Haar-Wavelet-Based multiresolution time domain (H-MRTD) with compactly supported scaling function for a full three-dimensional (3-D) wave to Yee's staggered cell is used for modeling and analyzing the antenna for the first time. Associated with practical model, an uniaxial perfectly matched layer (UPML) absorbing boundary conditions was developed, In addition , extending the mathematical formulae to an inhomogenous media. Numerical simulation results are compared with those using the conventional 3-D finite-difference time-domain (FDTD) method and measured. It has been demonstrated that, with this technique, space discretization with only a few cells per wavelength gives accurate results, leading to a reduction of both memory requirement and computation time.
Bandwidth enhancement in difference frequency generation by domain-shifted quasi-phase-matching structure
Bandwidth enhancement in difference frequency generation (DFG) has been investigated using domain-shifted quasi-phase-matching (QPM) structure of electrically poled ferroelectric crystals. The exact periodic QPM condition is relaxed by extending the periodic structure to a more flexible domain-shifted structure. The dependence of bandwidth enhancement and flatness on the positions and number of shifted domains are systematically studied for optimum output efficiency. The results presented here are useful for the fabrication of wide-bandwidth wavelength conversion devices based on the DFG process.
Linear and nonlinear optics of thin metal films with randomly distributed subwavelength holes
Mufei Xiao, Nikifor Rakov
Randomly distributed small holes of various subwavelength sizes were fabricated in a thin gold film. We have studied the optical near-filed transmission of the film. In the wavelength spectrum from 350nm to 650nm, a number of strongly enhanced transmission peaks were observed. These transmission peaks can only been observed in the near field. We attribute the new phenomenon to the surface plasmon coupling inside the holes and between the surfaces on the two sides of the thin film. We have also observed that the thin film support two-dimensional wave guiding and the guided light has a red shift of 200nm. Finally, we have observed strong second-harmonic radiation from the thin films with a pulsed laser of wavelength 1064nm. Strong second-harmonic radiation was observed at the wavelength of 532nm with a halfwidth of 40nm.
Silicon-based guided-mode resonance nanophotonic device
An out-of-plane guided-mode resonance (GMR) filter on a single Si chip using a two-layer polysilicon surface micromachining process was proposed. To the best of our knowledge, this is the first time that a monolithic optical filter has been integrated on a silicon microoptical bench. This device can be used as a bi-directional transceiver filter. The extinction ratio between 1550nm and 1310nm could be as low as 40dB and the channel passband at 1550nm was 20nm.