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ABSTRACT: We report on a novel surface functionalization approach to equip the titanium (Ti) surfaces with osteogenic properties. A key feature of the approach is the treatment of the Ti surfaces with Ti-adhesive nanoparticles that can stably load and controllably release bone morphogenetic protein-2 (BMP-2). Ti-adhesive nanoparticles were prepared by self-assembly of a catechol-functionalized poly(amino acid) diblock copolymer, catechol-poly(L-aspartic acid)-b-poly(L-phenylalanine) (Cat-PAsp-PPhe). The nanoparticles consist of Ti-adhesive peripheral catechol groups, anionic PAsp shells, and PPhe inner cores. Field-emission scanning electron microscopy (Fe-SEM) images showed that the Ti-adhesive nanoparticles could be uniformly immobilized on Ti surfaces. X-Ray photoelectron spectroscopy (XPS) confirmed the successful anchoring of nanoparticles onto Ti surfaces. After surface immobilization of the nanoparticles, the static water contact angle of the Ti substrate decreased from 75.3° to 50.0° or 36.4°, depending on the surface nanoparticle. Fluorescence microscopic analysis showed that BMP-2 could be effectively incorporated onto the Ti surface with adhesive nanoparticles. BMP-2 was controllably released for up to 40 days. The Ti substrate functionalized with BMP-2-incorporated nanoparticles significantly promoted attachment, proliferation, spreading, and alkaline phosphatase (ALP) activity of human adipose-derived stem cells (hADSC). The catechol-functionalized adhesive nanoparticles may be applied to various medical devices to create surfaces for improved performance.
Journal of Controlled Release 05/2013; · 5.73 Impact Factor
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ABSTRACT: Waveguide-typed plasmonic mode converters (WPMCs) at a wavelength of 1.55 μm are presented. The WPMC is composed of an insulator-metal-insulator waveguide (IMI-W), a 1st reversely tapered insulator-metal-insulator-metal-insulator waveguide (RT-IMIMI-W), an insulator-metal-insulator-metal-insulator waveguide (IMIMI-W), a 2nd RT-IMIMI-W with lateral silver mirrors (LSMs), and a metal-insulator-metal waveguide (MIM-W) in series. The mode sizes for the IMI-W, IMIMI-W, and MIM-W via the IMIMI-W with LSMs were not only calculated using a finite element method but were also experimentally measured. The input mode size of 10.3 μm × 10.3 μm from a polarization-maintaining single-mode fiber was squeezed to the mode size of ~2.9 μm × 2.9 μm in measurement by converting an s<sub>0</sub> mode to an Sa<sub>0</sub> mode via an Ss<sub>0</sub> mode. The WPMC may be potentially useful for bridging micro- to nano-plasmonic integrated circuits.
Optics Express 08/2012; 20(17):18636-45. · 3.59 Impact Factor
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ABSTRACT: We designed, fabricated, and characterized a hybrid surface plasmon polariton waveguide (SPP_wg) for mode conversion. The 20-nm-thick silver SPP_wg was fabricated via spin-coating with an aqueous silver ionic complex solution. The structure of the SPP_wg consists of a straight Insulator-Metal-Insulator waveguide (IMl_wg), a lateral tapered Insulator-Metal-Insulator-Metal-Insulator waveguide (tapered_IMIMI_wg), and a straight IMIMI waveguide (IMIMI_wg). An s0 mode size of 12.90 microm x 8.08 microm at a 6-microm-wide IMI_wg was excited by a butt-coupling method at a wavelength of 1550 nm. The s0 mode was converted into an Ss0 mode size of 8.08 microm x 5.65 microm at a 3-microm-wide IMIMI_wg. The mode size was squeezed by approximately 2/3 via a 15-microm-long lateral tapered_IMIMI_wg with a 500-nm-thick central insulator. The coupling loss for mode conversion between the straight IMI_wg and the straight IMIMI_wg was 5.49 dB. The hybrid SPP_wg for mode conversion has the potential to bridge the gap between micron and sub-micron scales in nano plasmonic integrated circuits. In addition, the use of the spin coating method is very cost-effective because films are formed at a low temperature in a short period of time without the need for a vacuum system.
Journal of Nanoscience and Nanotechnology 07/2012; 12(7):5474-8. · 1.56 Impact Factor
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ABSTRACT: We fabricated very thin silver films with thicknesses of 20 nm, 40 nm, and 60 nm on a prism using a spin coating method for surface plasmon resonance (SPR) image sensor module applications. An aqueous silver ionic complex solution was spin-coated and then thermally cured for 10 minutes at 150 degrees C in an oven. The spin-coated solid silver films possessed silver crystallinity. The prism modules with the 20-nm-, 40-nm- and 60-nm-thick thin silver films were applied to an SPR image sensor system. The coefficients of determination for the 20-nm-, 40-nm- and 60-nm-thick silver films were 0.923, 0.990 and 0.989, respectively when standard ethanol solutions with 0.1% intervals in the range of 20.0% to 20.5% were applied. The correlation is high-performed and the coefficients of determination are as close as 1. The spin coating method of very thin silver films for SPR image sensor modules is expected to be a very cost-effective solution because the films can be formed at a low temperature in a short period of time without requiring a vacuum system.
Journal of Nanoscience and Nanotechnology 07/2012; 12(7):5827-9. · 1.56 Impact Factor
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ABSTRACT: Plasmonic mode-size converters (PMSCs) for long-range surface plasmon polaritons (LR-SPPs) at the wavelength of 1.55 μm are presented. The PMSC is composed of an insulator-metal-insulator waveguide (IMI-W), a laterally tapered insulator-metal-insulator-metal-insulator waveguide (LT-IMIMI-W), and an IMIMI-W in series. The mode-intensity sizes of the LR-SPPs for the IMI-W and the IMIMI-W were not only calculated using a finite element method but were also experimentally measured. The propagation losses of the IMI-W and the IMIMI-W as well as the coupling losses between them were analyzed by the cut-back method to investigate the effect of LT-IMIMI-Ws. By using the PMSC with a ~27 ° angled LT-IMIMI-W, the coupling loss between a polarization-maintaining fiber and a 3 μm-wide IMIMI-W was reduced by ~3.4 dB. Moreover, the resulting mode-intensity in the output of the PMSC was squeezed to ~35% of the mode-intensity in the input IMI-W. The PMSC may be potentially useful for bridging micro- to nano-plasmonic integrated circuits.
Optics Express 10/2011; 19(22):21605-13. · 3.59 Impact Factor
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ABSTRACT: We designed, fabricated, and characterized novel long-range surface plasmon polariton waveguides based on Bragg gratings (LRSPPW-BGs) via spin coating of a transparent silver ink on nanoimprinted polymeric patterns at low temperature in the absence of a vacuum system. For 20-nm-thick and 8-μm-wide LRSPPW-BGs of lengths in excess of 500 μ m , the measured reflectances are greater than 90% at a Bragg wavelength of ~1532 nm. For a 20-nm-thick, 8- μ m -wide, and 1000-μ m -long LRSPPW-BG, the full width at half maximum of a reflectance is determined to be 1.89 nm. The use of spin-coatable silver ink combined with the nanoimprint technique may represent a viable new route for cost effective and simple fabrication of LRSPPW-BGs.
IEEE Transactions on Nanotechnology 08/2011; · 2.29 Impact Factor
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ABSTRACT: We present a high-efficiency antireflection structure for both TE and TM polarizations in two-dimensional self-collimating square lattice photonic crystal consisting of air holes in silicon. The design parameters of the optimal antireflection structure can be obtained by using the concept of Fresnel coefficients and the finite-difference time-domain simulations. The photonic crystal operating in almost identical self-collimation frequencies for two polarizations exhibits a large reflection coefficient for TE and a very small one for TM polarization. In this case, the antireflection structure for TE can also improve the transmission for TM polarization. To confirm a highly efficient antireflection structure designed, we investigate the transmission data of three finite photonic crystal samples consisting of 36, 38 and 40 unit cells for the cases without and with the antireflection structures through finite-difference time-domain simulations.
Optics Express 06/2010; 18(12):13083-93. · 3.59 Impact Factor
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ABSTRACT: Silver lenses having super-resolution are analyzed in terms of antisymmetric modes of surface plasmon which have the ability to amplify evanescent waves in UV region. Antisymmetric surface plasmon modes excited by subwavelength grating enhances the resolution and contrast of silver superlens. By using a 20 nm-thick silver superlens, the half-pitch resolution of approximately lambda(0)/8 can be achieved with good contrast at a free space wavelength of 435 nm. The resolution of silver superlens can also be improved using shorter illumination wavelength. We show that the thinner the lens, the better the imaging ability of the silver superlens due to the excitation of antisymmetric surface plasmon modes of higher propagation wave vectors. The thickness of lens is varied from 20 to 40 nm in a three layer system, SiO(2)-Ag-SiO(2). Obtained results illustrate that practical application for patterning periodic structures with good contrast and penetration depth can be achieved by using antisymmetric surface plasmon modes.
Optics Express 03/2010; 18(6):5459-65. · 3.59 Impact Factor
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ABSTRACT: We experimentally demonstrated the enhanced transmission in a fiber-coupled Au stripe waveguide system using a linearly tapered (LT) structure at a telecommunication wavelength of 1.55 ??m. The LT structure consists of two 100- ??m-long tapered regions connecting various widths of input and output waveguides with a waist region. The lowest insertion loss of the 1-cm-long LT-Au stripe waveguide is ~ 4.3 dB, when it has 6-??m -wide input and output waveguides and a 4- ??m-wide waist waveguide. The insertion loss is reduced by ~ 2 dB compared to the 4-??m-wide and 1-cm-long straight Au stripe waveguide, which is achieved by decreasing the coupling loss. The losses of the LT region, which has a tapered angle of less than 0.3?? between the input-output waveguides and the waist waveguide, are smaller than 0.4 dB. We showed that the insertion loss of the Au stripe waveguide can be reduced by introducing the LT structure, which can also provide efficient mode conversion.
IEEE Photonics Technology Letters 02/2010; · 2.19 Impact Factor
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ABSTRACT: Chirped gratings can be readily implemented in uniform-period waveguide Bragg gratings (WBGs) by adopting a tapered profile in the core patterning process. Based on our analysis, we have demonstrated that controlled linear chirps can be generated in WBGs with specifically designed core-taper profiles. By virtue of our established design and fabrication techniques, the measured center wavelengths, bandwidths, and dispersion coefficients of our fabricated straight and tapered polymeric WBGs agree very well with the designed values. We also obtained fairly low polarization-dependent wavelength shifts from the straight WBGs owing to the adopted low-birefringence polymeric materials.
Journal of Lightwave Technology 12/2009; · 2.78 Impact Factor
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ABSTRACT: Polymer-based silver stripe optical waveguides were developed for chip-to-chip optical interconnections, and their optical characteristics were investigated. The lowest propagation loss of 0.8 dB/cm was achieved with a 14-nm-thick 1.5-mum-wide stripe, at a wavelength of 1.3 mum . The 2.5-Gb/s optical signals were successfully transmitted via 10-cm-long silver stripe optical waveguides.
IEEE Photonics Technology Letters 08/2009; · 2.19 Impact Factor
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ABSTRACT: Very low vertical bending loss is demonstrated in a flexible metal waveguide. The waveguide consists of an 8 nm-thick and 68 mm-long Ag strip embedded in a free-standing multilayered low-loss polymer film. The polymer film is composed of a 10 microm-thick inner cladding with a refractive index of 1.524, and a pair of 20 microm-thick outer claddings which both have a refractive index of 1.514, resulting in a total thickness of 50 microm. The measured vertical bending loss is lower than 0.3 dB/180 masculine at a wavelength of 1310 nm for the bending radii down to 2 mm.
Optics Express 02/2009; 17(1):228-34. · 3.59 Impact Factor
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ABSTRACT: We demonstrate sub-dB/cm propagation losses in polymer-based silver stripe waveguides at the wavelength of 1.31 microm. The silver stripe waveguides were fabricated in a low-loss fluorinated polymer clad. To form uniform metal stripe patterns, which are essential for reducing propagation loss, we developed a lift-off process using double layers of photoresist and SiNx. A propagation loss of less than 1.0 dB/cm was obtained with the 11- nm-thick silver stripes in the width range of 1.5 - 4.5 microm. A coupling loss of approximately 1.0 dB with a polarization maintaining single mode fiber was achieved for a width of 4.5 microm. For a width of 2.0 microm, we recorded a minimum propagation loss of 0.4 dB/cm, which is comparable with that of dielectric multi-mode waveguides.
Optics Express 02/2009; 17(2):697-702. · 3.59 Impact Factor
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ABSTRACT: We demonstrate a novel on-board chip-to-chip optical interconnect using long-range surface plasmon polariton (LR-SPP) waveguides that feature 2.5-cm-long gold strips embedded in a low loss polymer cladding. A TM-mode vertical-cavity surface-emitting laser (VCSEL) operating at a wavelength of 1.3 microm was butt-coupled into the waveguides in order to excite a fundamental LR-SPP mode and then the transmitted light was received with a photo-diode (PD). The waveguide width is varied in the range of 1.5-5.0 microm in order to optimize the insertion loss where the 3-microm-wide waveguide provides a minimum insertion loss of -17 dB, consisting of 6 dB/cm propagation loss and 2 dB coupling loss. An interconnect system based on the optimized waveguide with a 4-channel array is assembled with the arrayed optoelectronic chips. It shows the feasibility of 10 Gbps (2.5 Gbps x 4 channels) signal transmission indicating that the LR-SPP waveguide is a potential transmission line for optical interconnection.
Optics Express 09/2008; 16(17):13133-8. · 3.59 Impact Factor
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ABSTRACT: We present characteristics of very thin Au strip waveguides based on long-range surface plasmon polaritons (LR-SPPs) along thin Au strips embedded in polymers. We also report a 10 Gbps optical signal transmission via LR-SPPs with the pig-tailed Au strip waveguide at a telecommunication wavelength of 1.55 mum. We limited the thickness, width, and length up to ~20 nm, ~ 10 mum, and ~5 cm, respectively, for practical applications. At 1.55 mum, loss properties of the Au strip waveguides were theoretically and experimentally evaluated with thickness, width and cladding material. The lowest propagation loss of ~1.4 dB/cm was experimentally obtained with the 14-nm-thick and 2-mum-wide Au strip. With a single-mode fiber, the lowest coupling loss of less than 0.1 dB/facet was achieved with the 14-nm-thick and 7.5-mum-wide Au strip. The lowest insertion loss was obtained 7.7 dB with the 14-nm-thick, 5-mum-wide, and 1.5-cm-long Au strip. The propagation loss was improved approximately 30% for the 17-nm-thick Au strip with lowering the refractive index of the cladding polymer by 0.01. In the 10 Gbps optical signal transmission experiment, the LR-SPP waveguide exhibits an excellent eye opening and a 2.2 dB power penalty at 10<sup>-12</sup> bit error rate. These all results indicate that the LR-SPP waveguide is a potential transmission line for optical interconnects to overcome inherent problems in electric interconnects.
Journal of Lightwave Technology 07/2008; 26(11):1510-1518. · 2.78 Impact Factor
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ABSTRACT: Nonlinear optical (NLO) polymers have been considered promising materials for wavelength conversion at a low pump power. However, they have not been readily adopted to practical applications due to their high absorption coefficients, especially at a shorter interacting wavelength. Our theoretical analysis proves that the influence of absorption coefficients can be mitigated significantly in cascaded wavelength conversion (CWC) processes. According to our example study, maximum conversion efficiencies for CWC can compare even with those for second-harmonic generation in many NLO polymers. Thus CWC can become a pertinent application of NLO polymers. However, to obtain such efficient CWC, several realistic problems should be resolved in practical devices.
Optics Express 07/2008; 16(13):9726-38. · 3.59 Impact Factor
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Macromolecular Chemistry and Physics 11/2007; 209(3):290 - 297. · 2.36 Impact Factor
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ABSTRACT: We demonstrate a high bit-rate optical signal transmission by using long-range surface plasmon polariton (LRSPP) waves in a guided geometry. With a 40 Gbit/s optical communication signal, eye patterns and bit-error-rates were measured to access the quality of the transmission properties of the LRSPP mode. A thin gold strip line embedded in a low loss optical polymer supports a LRSPP mode, which propagates with a 2 dB/cm loss, and couples to standard single mode fibers at 1.55 μm with a 2 dB coupling loss. A 40 Gbit/s optical signal was transmitted via a 4 cm long LRSPP waveguide without any distortion of the eye patterns. The experiment also showed error-free transmissions. These results indicate that the LRSPP waveguide is a potential transmission line for optical interconnections overcoming the inherent problems in electric interconnections.
Applied Physics Letters 10/2007; 91(17):171117-171117-3. · 3.84 Impact Factor
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ABSTRACT: To improve the propagation loss of polymer-based long-range surface-plasmon-polariton (LR-SPP) waveguide devices at the telecom wavelength range, low-loss LR-SPP waveguides were fabricated in an ultraviolet-curable acrylate polymer with a low refractive index and absorption loss. A propagation loss of 1.72 dB/cm at a wavelength of 1.55 mum was achieved with a 14-nm-thick and 3-mum-wide metal stripe.
IEEE Photonics Technology Letters 10/2007; · 2.19 Impact Factor
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ABSTRACT: For optical-electrical (O/E) integration of polymer waveguide devices, a polymer optical bench with embedded-electric-circuits was developed and realized by using the UV-embossing technology. An upside-down mounted polymer waveguide device showed not only more efficient fiber-chip coupling but also a good electrical contact.
IEEE/LEOS Summer Topical Meetings, 2007 Digest of the; 08/2007
