Proceedings Volume 5517

Linear and Nonlinear Optics of Organic Materials IV

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Proceedings Volume 5517

Linear and Nonlinear Optics of Organic Materials IV

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Volume Details

Date Published: 15 October 2004
Contents: 10 Sessions, 26 Papers, 0 Presentations
Conference: Optical Science and Technology, the SPIE 49th Annual Meeting 2004
Volume Number: 5517

Table of Contents

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Table of Contents

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  • Third Order Materials and Devices
  • Second Order Materials I
  • Linear Properties and Waveguides I
  • Nonlinear Processes and Photoluminescence
  • Linear Properties and Waveguides II
  • Optical Interconnects
  • Novel Optical Materials
  • Structures and Devices
  • Poster Session
  • Second Order Materials I
  • Second Order Materials II
Third Order Materials and Devices
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Advances in polymer optical devices and waveguide fabrication techniques
Warren N. Herman, Wei-Yen Chen, Younggu Kim, et al.
We report progress in the development of polymer waveguides and devices for photonic applications in three areas: non-photolithographic techniques for polymer waveguide fabrication, bistability in laterally-coupled polymer microring resonators, and ultrafast photoconductive switches fabricated from semiconducting polymers. The non-photolithographic techniques for waveguide fabrication under development include laser milling with an excimer laser and programmable automatic dispensing of multimode polymer waveguides using an Essemtech automatic dispenser. Asymmetric diffraction gratings fabricated using phase masks and the interference of two excimer laser beams have exhibited concentration of optical power into the 1st diffraction order. Polymer micro-ring resonators laterally coupled to a bus line were fabricated by lithography from benzocyclobutene with radii as small as 10 μm and free spectral ranges on the order of 20 nm. These devices exhibit bistability in the frequency domain which can arise from thermal or nonlinear optical changes in refractive index and that may have application for all-optical switching. Metal-polymer-metal switches fabricated with interdigitated electrodes in an inverted structure exhibited fast transient photoconductive pulsewidths under 20 ps in response to femtosecond pump laser pulses, but the measurement was bandwidth limited by the oscilloscope. Here we report pump-probe measurements that indicate carrier lifetimes on the order of 2 ps.
Third-order nonlinear optical properties of soluble Cr(III)-dioxolene complexes
Shin-ichiro Noro, Takafumi Sassa, Tetsuya Aoyama, et al.
We synthesized novel ligand-based mixed valence (LBMV) CrIII-dioxolene complexes, [Cr(X4SQ)(X4Cat)(4,4'-di-tert-butyl-2,2'-bpy)] (SQ = semiquinone, Cat = catecohol, 2,2'-bpy = 2,2'-bipyridine; X = Cl (2a) and Br (2b)) and [Cr(X4SQ)(X4Cat)(4,4'-dinonyl-2,2'-bpy)] (X = Cl (3a) and Br (3b)), and prepared thin films for investigating their third-order nonlinear optical (NLO) properties in terms of the mixed valence states. Electronic absorption spectra of these complexes in solution and solid states showed an intervalence charge-transfer (IVCT) band from Cat2- to SQ•- at the IR region, indicating of a coexistence of SQ and Cat ligands, namely, LBMV state of the complexes. These complexes were well soluble in nonpolar organic solvent, which allowed us to prepare thin films by spin coating. The obtained films showed the electronic absorption spectra similar to those in solution and were amorphous because of steric hindrance of halogen and alkyl substituents in o-dioxolene and 2,2'-bpy moieties, respectively. The x(3) values of the films of 3a and 3b with a thickness of 30 ~ 40 nm were determined for 1.0 × 10-12 esu at 1.907 μm.
Second Order Materials I
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Chiral chromophore-functionalized polybinaphtalenes for second-order nonlinear optics
Isabel Picard, Guy Koeckelberghs, Thierry Verbiest, et al.
Here we report on the second-order nonlinear optical properties of chiral chromophore-functionalized polybinaphtalenes. These materials are designed from chiral binaphtalene units, connected with rigid groups. This molecular architecture gives rise to a rigid, rod like (helical) structure. Chromophores which moderate to good hyperpolarizabilities were incorporated to induce a strong second-order nonlinear optical response. The polymers are soluble in common organic solvents and spincoated films of high optical quality can be readily obtained. The spincoated films were subsequently poled by an external electric field and analyzed by second-harmonic generation. The films showed excellent second-order nonlinearities, as high as 100 pm/V. Maybe even more important was the observation that the nonlinearity of these materials increases linearly with increasing chromophore content, in contrast to what has been observed for traditional side-chain polymers. This is due to the rigid character of the polymer backbone which effectively prevents detrimental chromophore aggregation at high chromophore concentrations. This property opens up perspectives to achieve materials with very high second-order nonlinearities. Another interesting observation was the fact that chiral contributions to the nonlinear optical response can be observed, which may further increase the nonlinearity.
Improved transparency-nonlinearity trade-off with boroxine-based octupolar molecules
Claudine Katan, Olivier Mongin, Gilles Alcaraz, et al.
Over the last two decades, a substantial effort has been devoted to the design of molecules with enhanced NLO responses. It has become increasingly clear over recent years that multipolar structures offer challenging possibilities in this respect. In particular, the octupolar framework provides an interesting route towards enhanced NLO responses and improved nonlinearity-transparency trade-off. In this perspective, we have implemented an innovative route based on octupolar structures derived from the boroxine ring. By grafting three electron-donating appendices on the electron-deficient boroxine core, octupolar quasi-planar molecules displaying markedly improved nonlinearity-transparency trade-off, as compared to the prototypical octupole (TATB) or the extensively studied triazine derivatives, were designed. This route indeed led to octupolar molecules showing beta(0) values (from calculations and solution measurements) larger than that of TIATB while remaining blue-shifted by nearly 100 nm and totally transparent in the visible region. Combined experimental and theoretical investigations reveal that this behavior is related to a periphery-to-core intramolecular charge transfer phenomenon in relation with the low-aromaticity and electron-withdrawing character of the boroxine ring. This study opens a new route for molecular engineering of transparent octupolar derivatives for NLO, including the design of effective materials for SHG in the visible-blue region.
Linear Properties and Waveguides I
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Polymer variable optical attenuator arrays: pathway from material platform to qualified telecom product
A variety of material platforms including glass, lithium niobate, and polymer are being utilized for opto-electronic components. Among these, high performance thermo-optic polymers are particularly advantageous for active telecom applications because they possess a unique suite of properties including large thermo-optic coefficient, high thermal stability, refractive index tenability, and compatibility with high-volume wafer scale processing. In this paper, we discuss our approach for material selection and its relation to device design optimization in a Si-polymer based variable optical attenuator array. We outline the key material and device design trade-offs and show that Si-polymer based devices can meet and exceed the reliability requirements for telecom components. To this end, performance, qualification testing, and key properties that are related to high reliability and device lifetime are addressed.
Polymeric waveguide devices for optical communications
Recently, we developed a wavelength converter, a 16-arrayed electro-optic (EO) Mach-Zehnder (MZ) modulator, polarization adjustable and athermal arrayed waveguide gratings (AWGs), and a wavelength channel selector by using all polymers. We designed and fabricated periodically poled nonlinear optical (NLO) polymer waveguides for the wavelength converter. Difference-frequency generation (DFG) process with a quasi-phase-matching (QPM) scheme was used. An all polymer-based wavelength channel selector composed of 16-channel EO polymer modulator array between two polymer AWGs is proposed and fabricated using chip-to-chip bonding of the three optical polymeric waveguide devices. For this, the 16-arrayed polymeric optical modulator and AWGs are respectively fabricated using EO and low-loss optical polymers. For these two-typed devices, we have synthesized new side chain NLO polymers and used low-loss optical polymers, designed and developed by ZenPhotonics, Inc. The developed these photonic devices were discussed in details from materials to packaging.
Optical waveguides using perfluorinated polyimides and their optical device applications
Buried optical waveguides were fabricated using perfluorinated polyimides (FLUPI-PFs) and their optical properties evaluated. These polyimides have excellent optical transparency in the near-infrared wavelength region for optical telecommunications, because there are no carbon-hydrogen bonds that absorb light in that region. They also have high thermal stability and allow precise refractive index control. The buried waveguides were fabricated using the two perfluorinated polyimides with a different refractive index as the core and cladding materials by spin-casting, conventional photolithographic patterning, and reactive ion etching using oxgen. The waveguides are single-mode and have losses below 0.2 dB/cm in the broad near-infrared wavelength region. A waveguide with a refractive index difference between the core and cladding of 0.5% has a minimum curvature radius of 10 mm. The waveguides were investigated for use as telecommunications components by fabricating a thin film filter-embedded 4-channel coarse wavelength-division multiplexer/demultiplexer with channel spacing of 40 nm and center wavelength of 1470 - 1590 nm. The insertion loss and the crosstalk for each port are less than 5.0 dB and better than -17 dB, respectively. A wavelength-division mutiplexing video transmission system using the fabricated multiplexer/demultiplexers was constructed for use in a local area network.
Nonlinear Processes and Photoluminescence
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Investigations of the mechanism of enhancement in novel two-photon absorption branched macromolecules
The nonlinear optical and excited state dynamics of a branched octupolar molecule (tris-4,4’,4”-(4- nitrophenilethynyl)triphenylamine(T-NPTPA)) with charge transfer character is investigated by combining measurements of two-photon absorption, time-resolved fluorescence, transient absorption, and three-pulse photon echo peak shift. The data are compared with those obtained for the linear molecule dimethylnitroaminotolane (DMNAT) representing a linear building block of the octupolar system. The purpose of this investigation is to understand the mechanism of the enhanced nonlinear optical properties of the trimer system relative to their linear analogs.
Environmental and steric effects on electronic and vibrational properties of pyridinium phenoxide derivatives
Alex Boeglin, Vincent Rodriguez, Catherine Combellas, et al.
Our present understanding of the dependence of non linear optical (NLO) properties of charge transfer compounds on their dielectric environment is generally summarized as a set of universal response functions versus the ground state ionicity. Experimentally, these behaviors are recovered by piece-wise assembling measurements performed in solvents of increasing polarities on series of chromophores with varying acceptor and donor groups and/or conjugation paths. In this work, we will take advantage of the recent success in synthesizing pyridinium phenoxides with or without tert-butyl oxygen protection groups as well as with or without steric methyl groups to modify the twisting of the central diaryl bond. Thus, we are in a position to sweep over a wide range of zwitterionic character with essentially the same chromophore. This opens up a great opportunity to investigate the relationships between geometrical structure and NLO properties, to examine the validity of current formalisms, and to test numerical simulations at the semi empirical and density functional levels. In this work, we have carried out an experimental and theoretical study combining UV visible, IR, Raman, and Hyper-Rayleigh spectroscopies to extract information concerning the geometry, the electronic structure, and the NLO response of our compounds. In particular, we show that the steric effect is sufficient to push the chromophore to the full zwitterionic limit. More generally, the approach we followed here shows great potential in probing chromophore-environment interactions.
Polarized photoluminescence of highly oriented poly(p-phenylene-vinylene)
Cesare Soci, Davide Comoretto, Franco Marabelli, et al.
We report on the anisotropic photoluminescence (PL) properties of stretch-oriented free standing films of poly(p-phenylene-vinylene) (PPV) at different temperatures. The PL quantum efficiency is strongly dependent on the pump polarization; it is higher when the pump is polarized perpendicularly to the polymer chain orientation. Independently of the pump polarization, we find that the PL emission spectra are mainly polarized along the polymer chain axis. The PL spectra show high-energy features, close to the onset of the HOMO-LUMO transition, that are significantly affected by self-absorption of the emitted light in the optically thick samples as well as by refractive effects at the polymer-air interface. In order to clarify the origin of these features, we have made a detailed characterization of the anisotropic optical constants of the PPV film. The optical constants have been derived from polarized reflectance and transmittance measurements and were used for the renormalisation of the PL spectra using the Fresnel equations. Frank-Condon analysis for the absorption oscillator strength and for the corrected emission spectra suggests that two different emitting states contribute to the optical properties. The connection of these states with film morphology and intermolecular interactions is described.
The molecular origins of optical nonlinearity: beyond charge-transfer effects
Garth J. Simpson, Andrew J. Moad
A remarkably simple methodology is described for quantitatively relating virtually all nonlinear optical phenomena directly back to intuitive molecular processes, including absorption, Raman polarizability, and two-photon absorption. The dramatic reduction in complexity resulting from this approach provides new routes for predicting and optimizing the molecular nonlinearities in emerging materials and spectroscopic applications without sacrificing mathematical rigor. In combination with experimental measurements, this general approach is shown to be particularly useful in interpreting the unique polarization-dependent nonlinear optical properties of chiral materials and surfaces.
Linear Properties and Waveguides II
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Highly transparent silicone materials
Jon V. DeGroot Jr., Ann Norris, Shedric O. Glover, et al.
Silicone based polymers possess a unique set of properties that makes them highly suitable for optical applications. In addition to their excellent thermal stability, mechanical properties, and ease of processing, they are highly transparent in the ultraviolet, visible, and selected bands of the near-IR spectra. The loss and absorption characteristics for a variety of silicone based polymers are examined and an example of a recently developed ultra-violet transparent polymer coating that is UV cured illustrates the flexibility of the silicone polymer family to be tailored to meet specific application needs.
Optical polymers: critical requirements for optical access applications
Optical access networks currently present some of the most exciting potential applications for integrated photonic devices, in particular those based on polymers. With fiber-to-the-premise (FTTP) initiatives at leading metropolitan area carriers well underway, there is keen interest in the development of low cost, highly integrated components that can withstand an outside plant environment (-40°C to 85°C). As opposed to polymers that have been developed for complex highly integrated optical circuits, polymers suitable for optical access deployment will need to address numerous optoelectronic packaging integration issues, notably alignment with active devices, compatibility with high-volume electronics manufacturing and management of thermal loads. We discuss the critical requirements that optical polymers must meet to address optical access applications, and identify those that can be met by existing technologies and those presenting gaps to be bridged for successful development of optical access components.
Optical Interconnects
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A polymer-based platform technology for integrated photonics
Polymers have been studied as an alternate material to silica for optical interconnects and photonic devices for the last decade. In this paper we review the work performed at GE Global Research in the area of polymer based material systems for photonic applications. A description of the application of the technology to several different areas is presented. Some of these application areas include optical interconnects, optoelectronic integration and electro-optical devices using polymer material systems. The overall effort includes areas of research from the basic chemistry of polymer optical materials to the development of photonic components. Specifically the use of polymer materials as a platform technology for hybrid integration in the development of multi-functional sub systems is reviewed.
Polymeric multimode waveguide arrays for one- and two-dimensional optical interconnects
Jang-Joo Kim, Joon-Sung Kim
Polymeric optical multimode waveguide arrays with micromirrors have been fabricated for one- (1-D) and two-dimensional (-2D) optical interconnects between 1-D or 2-D arrayed VCSELs and detectors. Contact printing lithography was adopted for simple and low cost process using UV-curable epoxy based polymers. Micromirrors for 1-D optical interconnects were fabricated by dicing a waveguide array using a dicing saw with a 45° diamond blade and showed the excess loss of 1.1 dB. For 2-D interconnects, fabricated waveguides were diced of same size and stacked one by one with lateral positional errors less than ± 20 μm. Two kinds of mirrors were fabricated; single-reflection mirror and double-reflection mirror. Double reflected mirrors resulted in lower losses with 1.2 dB than single reflected mirrors with 2.1 dB. The average insertion losses of 16-channel arrayed waveguides with two single-reflection mirrors and with two double-reflection-mirrors were measured to be 6.1 dB and 4.4 dB for 6 cm long waveguides at a wavelength of 830 nm, respectively. The crosstalk between the waveguides was less than -25 dB. The characteristics of the waveguide arrays are good enough for applications to optical interconnects.
Novel Optical Materials
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Fast photoresponse in organic semiconductors: understanding the mechanisms and structure-property relationships
Oksana Ostroverkhova, Svitlana Shcherbyna, David G. Cooke, et al.
We present a comprehensive study of ultrafast time-resolved photconductivity in pentacene and functionalized pentacene single crystals and thin films measured using optical pump-terahertz probe technique. By investigating the wavelength and temperature dependence of the transient photoconductivity, we reveal a sub-picosecond wavelength-independent charge carrier photogeneration and band-like charge transport in both single crystal and thin film samples. The amplitude and decay dynamics of the photoconductivity transients are correleated with the morphology of the films, assessed by atomic force and electron microscopy.
Rapid techniques for the characterization of polymer materials for optical waveguides
Techniques for the rapid evaluation of material properties of interest in the design of polymer integrated optical devices that have recently been developed in our laboratory are described. These include methods for determining optical loss and electrical resistivity. The use of the techniques is demonstrated with polyimide materials as an example. The level of precision that is reasonably attained from each technique is discussed, along with the relative merits of these techniques compared to other potential approaches to obtaining similar information.
Structures and Devices
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Photonic crystal and air trench approaches to realize small-area bends and splitters in low index contrast waveguides
The ability to make small-area bends and splitters in low index contrast waveguide materials is a critical enabler to realize densely integrated planar lightwave circuits (PLCs) in such materials. We discuss two approaches, the first based on photonic crystal (PhC) structures of limited spatial extent and the second on single air trenches. In each case, PhC or air trench regions are used to augment conventional waveguides (CWGs) to permit drastic reductions in overall device size while preserving the traditional advantages of CWGs such as straightforward design for single mode operation, low propagation loss, low fiber coupling loss, low dispersion, and mature microfabrication processes. We show how these approaches can be used to realize example devices having a very small footprint, including Mach-Zender interferometers and ring resonators.
Second- and third-order nonlinear properties of chiral phthalocyanine films
Tsuyoshi Muto, Takafumi Sassa, Tetsuya Aoyama, et al.
Vanadyl phthalocyanine derivatives having optically active side chains and the corresponding racemic isomers were synthesized and examined as nonlinear optical materials. These dyes were soluble in organic solvents and gave uniform thin films using spin coating. The thin films (neat or polymer doped) of each phthalocyanines showed the second- and third-order nonlinear optical responses under appropriate experimental conditions. The nonlinear optical susceptibilities of the optically active derivatives are larger than those of the corresponding racemic isomers. To clarify this enhancement phenomenon, we measured the electronic absorption- and circular dichloic spectra, and X-ray diffraction of the thin films. These results suggested that the optically active dyes forms one-dimensional columnar aggregates with one-handed helical sense and the columns further aligned into honeycomb-like chiral superstructures. It was surmised from the experimental results that the chiral superstructures enhance the nonlinear optical responses relative to the racemic analogues.
Temperature-dependent kinetics of diffraction gratings formation in a polymer matrix doped with azobenzene chromophores: Monte Carlo simulations and experiment
We review, in a light of recent results, the relevance of Monte Carlo simulations of simple kinetic models of processes accompanying the recording and erasure of diffraction gratings in a polymer matrix doped with azobenzene chrompohores under the illumination with spatially modulated and linearly polarized light, in modelling the temperature-dependent processes observed in real degenerate two-wave mixing (DTWM) experiments. We comment on the perspectives of Monte Carlo based design of effective photonic devices operating on photochromic systems.
Elaboration of optical integrated devices by multiphoton polymerization processes in doped photopolymers
Kokou D. Dorkenoo, Stephane Klein, Alberto Barsella, et al.
Nonlinear optical photopolymers are of special interest for the realization of permanent integrated optical circuits via polymerization induced by one or two-photon absorption processes. In this context, we have explored the possibilities to create integrated devices by the 1D and 3D control of the photopolymerization. The various growth forms of self-written wave guides created in the bulk of photopolymerizable resins are presented and analyzed, both experimentally and theoretically. Under quasi-solitonic propagation conditions, the control of the refractive index during the photopolymerization progression allows the elaboration of wave guides over large distances (typically a few cm). We have also taken advantage of the high spatial selectivity of the two-photon absorption procedure for the design of controlled polymerized pathways. By using a two-photon confocal microscopy technique with a femtosecond laser source to activate the polymerization, we demonstrate how it is possible to create optical circuits in the bulk of doped photopolymers. Moreover, the permanent freezing of the orientation of push-pull chromophores embedded in the polymeric matrices opens up the possibility to design integrated circuits with different optical functions. Thus, by combining non linear optical properties and multi-photon polymerization technique, active 3D optical devices can be created in functionalized photopolymers.
Poster Session
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Computational modeling of supercontinuum generation in fused silica by a femtosecond laser pulse of a few optical cycles
Numerical solution of the wave equation describing the propagation of laser pulse of a few optical cycles in fused silica is obtained. Our numerical simulations follow closely the published experimental data. We observed a shifting of the spectrum peak of the broadened pulse depending on the input pulse central wavelength.
Method of multirange models by near-infrared spectral analysis for nonlinear optics of organic materials
Near-infrared (NIR) spectroscopy has gained wide spread acceptance in recent years as a powerful diagnostic tool, particularly for the concentrations of Components of Organic Materials. Unfortunately, most systems in practice are not perfectly linear; they show non-linear behavior of different types. Any model's capacity of information is not infinity, and it is founded that the calibration model is of a strong selectivity caused by non-linear, i.e. the model will provide satisfactory predict results for the samples in the appropriate ranges of the measurements, but make poor ones for the samples in the regions, especially for the extremes of the measurements. Reality has thus created a need for methods that can handle such non-linearities. A new technique of Multi-Region Model (MRM) instead of unique model is presented in the work. To validate the calibration, 198 milk samples were employed in this study, the comparison with the MRM method was based on the root mean square error of prediction (RMSEP) and Correlation coefficient (R2). The study result shows that the MRM accuracy for individual component's prediction is reliable. The predicted results of MRM exhibit values of R2 of 98.63% and 95.07%, and RMSEP of 0.116% and 0.101% for fat and protein, respectively.
Measurement and temperature dependence of the electro-optic coefficient of a range of cross-linked DR-19 doped polyester films
Carl E. Bonner Jr., Stephen Charter, Jedidah Isler, et al.
The optical and electro-optic properties and the temperature stability of those properties has been measured for DR-19 doped polymer films with a range of cross-linking agents. The films show good transmission in the optical communication range due to the lack of OH and NH bonds in the material. The refractive index and field dependent indices are comparable with those previously reported. However, the temperature stability of the films is high. It is this temperature stability that makes the material attractive for electro-optic switching applications.
Second Order Materials I
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Transmission properties and spectral trimming of polymer photonic crystals
Manfred Eich, Markus Schmidt, Gunnar Boettger, et al.
We present a novel concept to trim the transmission properties of finite two dimensional photonic crystal slab waveguide structures by UV photobleaching. Systematic fabrication inaccuracies may be compensated due to the shift of the spectral properties during the bleaching process. To prove our concept experimentally, we measured the transmission of UV sensitive photonic crystal structures for different doses. A shift of band edges and defect resonance peaks depending on UV dose is observed due to changes in refractive index and geometry.
Second Order Materials II
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Biochemical sensors based on polymer microring resonators
L. Jay Guo, Chung-Yen Chao, Wayne Fung, et al.
Photonic microring resonators have great potential in the application of highly sensitive label-free biosensors due to high Q-factor resonances. Design consideration, device fabrication techniques, methods to increase the resonance Q-factors, and preliminary experimental data on biomolecular detections are discussed in this paper.