Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Z20: Focus Session: Organic Electronics and Photonics - Photonic and Electronic Properties |
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Sponsoring Units: DMP DPOLY Chair: Bryan Boudouris, Purdue University Room: 405 |
Friday, March 7, 2014 11:15AM - 11:27AM |
Z20.00001: Properties of guided modes in plasmonic aluminum quinoline waveguides Niranjala Wickremasinghe, Jonathan Thompson, Xiaosheng Wang, Heidrun Schmitzer, Hans Peter Wagner We investigate the mode properties of aluminum-quinoline (Alq$_{3})$ waveguides with embedded thin (approximately 10 nm thick) Mg$_{0.9}$Ag$_{0.1}$ metal layers at a wavelength of 633 nm using the m-line technique. The plasmonic waveguides were fabricated on a Pyrex substrate by organic molecular beam deposition. Our experiments show that TM$_{0}$ modes in an Alq$_{3}$ waveguides with a single centered metal layer and TM$_{0}$, TM$_{1}$ and TM$_{2}$ modes in a waveguide with three metal layers have higher effective refractive indices as compared to a pure Alq$_{3}$ reference waveguide. These modes are attributed to plasmon-like modes in agreement with model calculations considering a complex dielectric constant for the metal layer. TM modes which possess a node at the location of the metal layer essentially behave like dielectric modes. TE modes are more affected by the embedded metal layer(s). The number of TE modes is reduced and the mode coupling angles are significantly shifted. Only one TE mode is observed in the waveguide containing three metal layers which is in agreement with model calculations. The results show that strategically placed metal layers can be used to selectively excite plasmonic and dielectric TM modes and to shift and suppress TE modes. [Preview Abstract] |
Friday, March 7, 2014 11:27AM - 11:39AM |
Z20.00002: Bragg Reflectors Based on Block Copolymer/ Polyhedral Oligomeric Silsesquioxanes (POSS) and TiO$_{2}$ Hybrid Nanocomposites Cheng Li, Nicholas Colella, James Watkins Maleamic acid functionalized polyhedral oligomeric silsesquioxanes (POSS) can interact with the poly (ethylene oxide) (PEO) block in Pluronics F108 block copolymer via hydrogen bonding to form well-ordered block copolymer nanocomposites. In this study, the block copolymer composites are spin coated into thin films and maleamic acid groups are thermal crosslinked to stabilize the nanocomposite structure. High temperature calcination of the stabilized nanocomposite yields a robust mesoporous silica thin film. By adjusting the loading of POSS into the block copolymer prior to calcination, the refractive index (RI) of mesoporous silica films can be tuned between 1.13 and 1.18. We show these low RI films can be sequentially layered with hybrid TiO$_{2}$ nanocomposite films that exhibit a RI of approximately 2.0 to yield efficient Bragg reflectors. The TiO2 films are prepared by the calcinations of polymer/anatase TiO2 nanoparticle composites with NP loadings as high as 90wt{\%}. Due to the porosity existing in each layer, the wavelength of the reflected light is sensitive to the adsorption of solvent vapors such as toluene, isopropanol, and tetrahydrofuran, or analytes, which suggest applications in sensors. [Preview Abstract] |
Friday, March 7, 2014 11:39AM - 11:51AM |
Z20.00003: Gain enhancement in photorefractive polymers Carl Liebig, Steven Buller, Partha Banerjee, Sergey Basun, Pierre Blanche, Jayan Thomas, Corey Christenson, Nasser Peyghambarian, Dean Evans Photorefractive (PR) polymer materials have shown that they can be successfully used in display applications due to a diffraction efficiency that is close to unity [1]. The polymers rely on the cooperation between several components in order to generate the charge carriers, space-charge field, and the refractive index change as required for both diffractive and beam-coupling applications. The multi-component approach has several unforeseen consequences, such as multiple PR gratings (hole and electron) and sub-optimal phase shifts which decrease the potential (PR) gain [2]. We show that by applying electric fields close to the breakdown potential to PR polymers, the decreased beam coupling and diffraction efficiency can be overcome by reducing the grating competition (hole vs. electron) leading to an enhanced PR gain/efficiency [3]. \\[4pt] [1] P. A. Blanche, et al., Nature \textbf{468}, 80-83 (2010).\\[0pt] [2] P. P. Banerjee, et al., J. Appl. Phys. \textbf{111}, 013108 (2012).\\[0pt] [3] C. M. Liebig, et al., Opt. Exp. (In press 2013). [Preview Abstract] |
Friday, March 7, 2014 11:51AM - 12:03PM |
Z20.00004: Large Area Printing of 3D Photonic Crystals James J. Watkins, Michael R. Beaulieu, Nicholas R. Hendricks, Rohit Kothari We have developed a readily scalable print, lift, and stack approach for producing large area, 3D photonic crystal (PC) structures. UV-assisted nanoimprint lithography (UV-NIL) was used to pattern grating structures comprised of highly filled nanoparticle polymer composite resists with tune-able refractive indices (RI). The gratings were robust and upon release from a support substrate were oriented and stacked to yield 3D PCs. The RI of the composite resists was tuned between 1.58 and 1.92 at 800 nm while maintaining excellent optical transparency. The grating structure dimensions, line width, depth, and pitch, were easily varied by simply changing the imprint mold. For example, a 6 layer log-pile stack was prepared using a composite resist a RI of 1.72 yielding 72 {\%} reflection at 900 nm. The process is scalable for roll-to-roll (R2R) production. [Preview Abstract] |
Friday, March 7, 2014 12:03PM - 12:15PM |
Z20.00005: Tunable photonic multilayer sensors from photo-crosslinkable polymers Maria Chiappelli, Ryan Hayward The fabrication of tunable photonic multilayer sensors from stimuli-responsive, photo-crosslinkable polymers will be described. Benzophenone is covalently incorporated as a pendent photo-crosslinker, allowing for facile preparation of multilayer films by sequential spin-coating and crosslinking processes. Copolymer chemistries and layer thicknesses are selected to provide robust multilayer sensors which can show color changes across nearly the full visible spectrum due to the specific stimulus-responsive nature of the hydrated film stack. We will describe how this approach is extended to alternative sensor designs by tailoring the thickness and chemistry of each layer independently, allowing for the preparation of sensors which depend not only on the shift in wavelength of a reflectance peak, but also on the transition between Bragg mirrors and filters. Device design is optimized by photo-patterning sensor arrays on a single substrate, providing more efficient fabrication time as well as multi-functional sensors. Finally, radiation-sensitive multilayers, designed by choosing polymers which will preferentially degrade or crosslink under ionizing radiation, will also be described. [Preview Abstract] |
Friday, March 7, 2014 12:15PM - 12:27PM |
Z20.00006: Positional Isomer Effects on Photomechanical Response of Azobenzene Functionalized Polyimides Jeong Jae Wie, David Wang, Kyung Min Lee, Loon-Seng Tan, Timothy White Azobenzene-functionalized polyimides (Azo-PIs) are materials capable of a large magnitude photomechanical responses. Recent work from our group has reported that photomechanical effects in these materials are strongly influenced by free volume and crystallinity. In this presentation, we will discuss a recently completed study in which a series of amorphous polyimides were prepared. The connectivity of the backbone of the imide units was intentionally varied to introduce rotational freedom, which is apparent as a $\beta $-transition. Comparatively, materials exhibiting a $\beta $-transition exhibit larger magnitude photomechanical effects. [Preview Abstract] |
Friday, March 7, 2014 12:27PM - 12:39PM |
Z20.00007: Enhanced dielectric properties of electrically poled poly(vinylidene fluoride) (PVDF) and polycarbonate (PC) multilayer films via interfacial polarization Jung-Kai Tseng, Matthew Mackey, Zheng Zhou, Joel Carr, Donald E. Schuele, Eric Baer, Lei Zhu Electrically poled poly(vinylidene fluoride) (PVDF) and polycarbonate (PC) multilayer films can be considered as a polymer electret, which stores quasi-permanent charges (i.e., ions) at PVDF/PC interfaces. In this study, the corresponding dielectric properties of electrically poled PVDF/PC multilayer films are investigated experimentally. First, the bipolar hysteresis loop becomes narrower for the poled PVDF/PC multilayer films upon increasing the poling time, because the impurity ions in PVDF are locked at the PVDF/PC interfaces. Second, asymmetric DC conductivity in poled PVDF/PC multilayer films is observed because of the pre-existing electric field in the electret layers. When the pre-existing field is in the same direction of the applied external field, enhanced DC conductivity is observed in the leakage current measurement. In contrast, if the pre-existing field is opposite to the applied external field, decreased DC conductivity is seen. More experimental evidence of polarized charge at the PVDF/PC interfaces in poled PVDF/PC multilayer films is also manifested by thermally stimulated depolarization current (TSDC) experiments. [Preview Abstract] |
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