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A scheme for the direct conversion of millimeter and THz waves to optical signals is introduced. The compact device consists of a plasmonic phase modulator that is seamlessly cointegrated with an antenna. Neither high-speed electronics nor electronic amplification is required to drive the modulator. A built-in enhancement of the electric field by a factor of 35 000 enables the direct conversion of millimeter-wave signals to the optical domain. This high enhancement is obtained via a resonant antenna that is directly coupled to an optical field by means of a plasmonic modulator. The suggested concept provides a simple and cost-efficient alternative solution to conventional schemes where millimeter-wave signals are first converted to the electrical domain before being up-converted to the optical domain., Nano Letters, 15 (12), ISSN:1530-6984, ISSN:1530-6992

Limitations of silicon photonics can be overcome by hybrid integration or by photonic multi-chip systems. We give an overview on recent progress regarding silicon-organic hybrid (SOH) integration as well as multi-chip integration enabled by photonic wire bonding.

A plasmonic Mach-Zehnder modulator array with 4×36 Gbit/s capacity is introduced. The densely packed devices are connected by a multicore fiber demonstrating a highly scalable interconnect solution in a most compact footprint.

We demonstrate for the first time generation of 16-state quadrature amplitude modulation (16QAM) signals at a symbol rate of 40 GBd using silicon-based modulators. Our devices exploit silicon-organic hybrid (SOH) integration, which combines silicon-on-insulator slot waveguides with electro-optic cladding materials to realize highly efficient phase shifters. The devices enable 16QAM signaling and quadrature phase shift keying (QPSK) at symbol rates of 40 GBd and 45 GBd, respectively, leading to line rates of up to 160 Gbit/s on a single wavelength and in a single polarization. This is the highest value demonstrated by a silicon-based device up to now. The energy consumption for 16QAM signaling amounts to less than 120 fJ/bit – one order of magnitude below that of conventional silicon photonic 16QAM modulators.

High-speed optical interconnects rely on advanced wavelength-division multiplexing (WDM) schemes. However, while photonic-electronic interfaces can be efficiently realized on silicon-on-insulator chips, dense integration of the necessary light sources still represents a major challenge. Chip-scale frequency comb sources present an attractive alternative for providing a multitude of optical carriers for WDM transmission. In this paper, we give an overview of our recent progress towards terabit communications with chip-scale frequency comb sources. In a first set of experiments, we demonstrate frequency comb generation based on silicon-organic hybrid (SOH) electro-optic modulators, enabling line rates up to 1.152 Tbit/s. In a second set of experiments, we use injection locking of a gain-switched laser diode to generate frequency combs. This approach leads to line rates of more than 2 Tbit/s. A third set of experiments is finally dedicated to using Kerr nonlinearities in integrated nonlinear microcavities for frequency comb generation. We demonstrate coherent communication using Kerr frequency comb sources, thereby achieving line rates up to 1.44 Tbit/s. Our experiments show that frequency comb generation in chip-scale devices represents a viable approach to terabit communications.

Chip-scale frequency comb sources are likely to become key elements of future terabit/s optical transceivers. We investigated and demonstrate the viability of different comb generation schemes for transmission at data rates beyond 1 Tbit/s.

Micro-ring wavelength filters and resonant modulators using polymer materials at 1300 nm and 1550 nm are analyzed, designed, and demonstrated. The rings are integrated with vertically coupled input and output waveguides. The devices are fabricated using optical lithography. Filters with a finesse of 141 and free spectral range of 5 nm at 1300 nm and finesse of 117 with a free spectral range (FSR) of 8 nm at 1550 nm are demonstrated. Ring resonators with a Q as high as 1.3 /spl times/ 10/sup 5/ at 1300 nm are demonstrated. The filters can be temperature tuned at the rate of 14 GHz//spl deg/C. Resonant ring modulators, which use an electrooptic polymer, are demonstrated. The resonance wavelength voltage tunes at the rate of 0.82 GHz/V. The modulators have a bandwidth larger than 2 GHz. Using the resonant modulator, and open eye diagram at 1 Gb/s is demonstrated.

Polymer optical waveguide devices will play a key role in several rapidly developing areas of broadband communications, such as optical networking, metropolitan/access communications, and computing systems due to their easier processibility and integration over inorganic counterparts. The combined advantages also makes them an ideal integration platform where foreign material systems such as YIG (yttrium iron garnet) and lithium niobate, and semiconductor devices such as lasers, detectors, amplifiers, and logic circuits can be inserted into an etched groove in a planar lightwave circuit to enable full amplifier modules or optical add/drop multiplexers on a single substrate. Moreover, the combination of flexibility and toughness in optical polymers makes it suitable for vertical integration to realize 3D and even all-polymer integrated optics. In this review, a survey of suitable optical polymer systems, their processing techniques, and the integrated optical waveguide components and circuits derived from these materials is summarized. The first part is focused on discussing the characteristics of several important classes of optical polymers, such as their refractive index, optical loss, processibility/mechanical properties, and environmental performance. Then, the emphasis is placed on the discussion of several novel passive and active (electro-optic and thermo-optic) polymer systems and versatile processing techniques commonly used for fabricating component devices, such as photoresist-based patterning, direct lithographic patterning, and soft lithography. At the end, a series of compelling polymer optical waveguide devices including optical interconnects, directional couplers, array waveguide grating (AWG) multi/demultiplexers, switches, tunable filters, variable optical attenuators (VOAs), and amplifiers are reviewed. Several integrated planar lightwave circuits, such as tunable optical add/drop multiplexers (OADMs), photonic crystal superprism waveguides, digital optical switches (DOSs) integrated with VOAs, traveling-wave heterojunction phototransistors, and three-dimensionally (3D) integrated optical devices are also highlighted.

After a brief review on electro-optical (EO) polymers, the recent development of EO dendrimers is summarized. Both single- and multiple-dendron-modified nonlinear optical (NLO) chromophores in the guest–host polymer systems showed a very significant enhancement of poling efficiency (up to a three-fold increase) due to the minimization of intermolecular electrostatic interactions among large dipole moment chromophores through the dendritic effect. Moreover, multiple NLO chromophore building blocks can also be placed into a dendrimer to construct a precise molecular architecture with a predetermined chemical composition. The site-isolation effect, through the encapsulation of NLO moieties with dendrons, can greatly enhance the performance of EO materials. A very large EO coefficient (r33 = 60 pm/V at 1.55 μm) and high temporal stability (85 °C for more than 1000 h) were achieved in a NLO dendrimer (see Figure) through the double-end functionalization of a three-dimensional phenyl-tetracyanobutadienyl (Ph-TCBD)-containing NLO chromophore with thermally crosslinkable trifluorovinylether-containing dendrons.

A new europium (Eu) complex with dendron-substituted diketone ligands was synthesized and found to exhibit a photoluminescence efficiency of 45%. Double-layer light-emitting diodes based on polymer matrices doped with the Eu complex were fabricated. An electroluminescence external quantum efficiency of 0.80% was achieved when a copolymer containing side-chain carbazole and 1,3,4-oxadiazole groups was used as the matrix. The results are analyzed in the context of Forster energy transfer.

August 1, 2002 marked the launch of the National Science Foundation (NSF) Science and Technology Center (STC) on Materials and Devices for Information Technology Research (MDITR). The Center will strive to develop new materials and device concepts that will complement existing semiconductor and inorganic electronic and photonic materials in information technology (IT). An initial five_year award of $18.35 million supports this development and the training of a workforce capable of implementing that technology. Education, human resource development, and technology transfer are also important components of this Center and approximately 30% of the NSF funding is committed to these activities. The motivation for creating such a center is quite obvious. Despite the ‘dot com’ crash, IT continues to be the fastest growing and dominant component of world economy. Computing power and the ability to rapidly move information around the world are, of course, important drivers of that IT economy.

An analytical model for the nonlinear behavior of the electro-optic (EO) coefficient in chromophore–polymeric materials is developed. The sharp decline of the EO coefficient above a threshold chromophore concentration is attributed to a second order phase transition transforming the chromophore dipolar system into an antiferroelectric state. The rise of antiferroelectric correlations between chromophore dipoles deteriorates the efficiency of the poling process aimed at achieving a noncentrosymmetric chromophore ordering by application of an electric field. The location of the phase transition and the magnitude of the EO coefficient are investigated as functions of molecular and thermodynamic parameters. Particularly remarkable observations are made regarding the dependence of the EO coefficient on the macroscopic shape of samples used for poling. Slab shaped samples that are common in practice are least efficient for the poling process. Any degree of sample elongation in the direction of the poling field shifts the antiferroelectric phase transition towards higher chromophore concentrations and radically increases the maximum value of the EO coefficient. The theory is applied to two chromophore systems that are typical of materials used in EO devices. Fine agreement with the experimental data is achieved with little adjustment.

Pure and efficient red light-emitting diodes based on novel europium (Eu) and osmium (Os) complexes were demonstrated. The Eu complex, with dendron substituted diketone ligands, exhibits high photoluminescence efficiency of 45%. When a copolymer containing carbazole and 1,3,4-oxadiazole groups was used as the host, narrow electroluminescence at 617 nm was achieved, with a 'full width at half maximum of 4 nm and a maximum external quantum efficiency (η) of 0.80%, The Os complex shows pure red emission peaking at 650 nm. The Commission Internationale de l'Eclairage (CIE) chromaticity coordinates (x, y) are (0.65, 0.33). Maximum η and brightness achieved were 0.82% and 590 cd/m 2 , respectively.

A photoassisted corona poling technique (PACP) was applied to a binary chromophore system that was composed of YLD-124 and DR1-co-PMMA to enhance the poling efficiency of an electrooptic (EO) polymer device. The DR1 chromophores as a photoaddressable host material were resonantly irradiated by a polarized pumping green laser beam at a wavelength of 532 nm which is within its molecular absorption band. This process caused the DR1 chromophore's reorientation via a cis-trans photoisomerization process. The coupled YLD-124 system's dipoles were then poled with the assistance of a static electrical field applied to the EO core layer. In this letter, we report the experimental demonstration of the photoassisted corona poling scheme in a binary chromophore system that improved Mach-Zehnder optical modulator performance by lowering its Vπ. It was shown that the device's Vπ was reduced by 21%-23% compared to a regular device that was only corona poled without the green light assistance.

Nonlinear optical and gain materials are incorporated into both metallic/semiconductor and dielectric (e.g., organic) metamaterial architectures for active control of light. Potential applications include imaging, sensing, and information management (e.g., telecommunications). New material structures are based on nonlinear optical and gain materials integrated with silicon photonic and plasmonic materials, which are capable of generating substantial local field enhancement and upon one-, two-, and three dimensional metamaterials. Nonlinear optical and gain materials integrated metamaterial architectures include laser dyes and amplifier materials and both second and third order nonlinear optical materials. Both organic and inorganic active materials are explored to achieve desired wavelength control of phenomenon and realize the desired optical effects. Mechanisms for efficient coupling of light into and out of metamaterials (another recognized problem) are investigated.

We propose a bidirectional, polarization-independent, recirculating IQ-modulator scheme based on the silicon-organic hybrid (SOH) platform. We demonstrate the viability of the concept by using an SOH Mach-Zehnder modulator, operated at 10 GBd BPSK and 2ASK-2PSK.

We demonstrate 16QAM and QPSK modulation at symbol rates of 40 GBd and 45 GBd using a silicon-based IQ modulator. The device enables data rates up to 160 Gbit/s in a single polarization with an estimated energy consumption of 120fJ/bit.

We demonstrate a plasmonic Mach-Zehnder-modulator with a record-small length of 10 μm. The modulator is fully integrated into a single silicon waveguide and operates at 72 Gbit s-1. A voltage-length product as low as VπL=50 ±5 Vpm is found.

High-speed optical interconnects rely on advanced wavelength-division multiplexing (WDM) schemes. However, while photonic-electronic interfaces can be efficiently realized on silicon-on-insulator chips, dense integration of the corresponding light sources still represents a major challenge. Chip-scale frequency comb sources present an attractive alternative for providing a multitude of optical carriers for WDM transmission. In this paper, we give an overview on our recent progress towards terabit communications with chip-scale frequency comb sources. In a first set of experiments, we demonstrate frequency comb generation based on silicon-organic hybrid (SOH) electro-optic modulators, enabling transmission data rates of up to 1.152 Tbit/s. A second set of experiments demonstrates Kerr comb generation in nonlinear integrated microcavities, leading to data rates of up to 1.44 Tbit/s. Our experiments demonstrate that frequency comb generation in chip-scale devices represents a viable approach to terabit/s communications.

We give an overview on our recent achievements in the field of SOH integration, covering in-device electro-optic coefficients r 33 in excess of 200 pm/V, highly efficient Mach-Zehnder modulators, IQ modulators, and modulator-based frequency comb generators

Silicon photonics offers tremendous potential for inexpensive high-yield photonic-electronic integration by enabling fabless fabrication and joint processing of photonic and electronic circuitry. Silicon as an optical material, however, falls short of certain properties that are indispensable for high-performance devices. In particular, bulk silicon does not feature any second-order optical nonlinearity due to crystal symmetry, thereby making efficient electro-optic modulators challenging. These deficiencies can be overcome by silicon-organic hybrid (SOH) integration, which combines silicon-on-insulator (SOI) waveguides with electro-optic organic materials. We give an overview on our recent progress in the field of SOH modulators, covering highly efficient devices with energy consumptions of a few femtojoule per bit and modulator-based frequency comb generators that enable WDM data transmission at terabit/s data rates.

CONSPECTUS: Organic glasses containing chromophores with large first hyperpolarizabilities (β) are promising for compact, high-bandwidth, and energy-efficient electro-optic devices. Systematic optimization of device performance requires development of materials with high acentric order and enhanced hyperpolarizability at operating wavelengths. One essential component of the design process is the accurate calculation of optical transition frequencies and hyperpolarizability. These properties can be computed with a wide range of electronic structure methods implemented within commercial and open-source software packages. A wide variety of methods, especially hybrid density-functional theory (DFT) variants have been used for this purpose. However, in order to provide predictions useful to chromophore designers, a method must be able to consistently predict the relative ordering of standard and novel materials. Moreover, it is important to distinguish between the resonant and nonresonant contribution to the hyperpolarizabiliy and be able to estimate the trade-off between improved β and unwanted absorbance (optical loss) at the target device's operating wavelength. Therefore, we have surveyed a large variety of common methods for computing the properties of modern high-performance chromophores and compared these results with prior experimental hyper-Rayleigh scattering (HRS) and absorbance data. We focused on hybrid DFT methods, supplemented by more computationally intensive Møller-Plesset (MP2) calculations, to determine the relative accuracy of these methods. Our work compares computed hyperpolarizabilities in chloroform relative to standard chromophore EZ-FTC against HRS data versus the same reference. We categorized DFT methods used by the amount of Hartree-Fock (HF) exchange energy incorporated into each functional. Our results suggest that the relationship between percentage of long-range HF exchange and both βHRS and λmax is nearly linear, decreasing as the fraction of long-range HF exchange increases. Mild hybrid DFT methods are satisfactory for prediction of λmax. However, mild hybrid methods provided qualitatively incorrect predictions of the relative hyperpolarizabilities of three high-performance chromophores. DFT methods with approximately 50% HF exchange, and especially the Truhlar M062X functional, provide superior predictions of relative βHRS values but poorer predictions of λmax. The observed trends for these functionals, as well as range-separated hybrids, are similar to MP2, though predicting smaller absolute magnitudes for βHRS. Frequency dependence for βHRS can be calculated using time-dependent DFT and HF methods. However, calculation quality is sensitive not only to a method's ability to predict static hyperpolarizability but also to its prediction of optical resonances. Due to the apparent trade-off in accuracy of prediction of these two properties and the need to use static finite-field methods for MP2 and higher-level hyperpolarizability calculations in most codes, we suggest that composite methods could greatly improve the accuracy of calculations of β and λmax.

Novel europium complexes containing either symmetrical or unsymmetrical diphenanthryl β-diketone ligands were synthesized and characterized. The ligand conjugation length has a profound effect on the spectral properties of the complexes and the device performance of the complexes as emitting dopants in light-emitting diodes. The unsymmetrical ligand has a longer conjugation, which red-shifts the absorption of the complex. The longer wavelength absorption facilitates the choice of host material that can efficiently transfer energy to the complex. However, the longer conjugation also results in a less efficient energy transfer from the ligand to the central Eu3+ ion.

Quantum mechanics and new statistical mechanical methods have been employed to optimize macroscopic electro-optic activity for organic chromophore-containing polymeric materials. In particular, statistical mechanical (equilibrium and kinetic Monte Carlo) methods that explicitly take into account many-body, spatially-anisotropic, intermolecular interactions are necessary to understand the variation of macroscopic electro-optic activity with chromophore number density, shape, dipole moment, polarizability, and polymer dielectric constant. With guidance from theory, materials have been prepared that exhibit electro-optic coefficients of greater than 100 pm/V. Halfwave voltages of less than one volt have been realized for devices fabricated from these materials. Low halfwave voltage, ultrahigh bandwidth, and ease of incorporation into sophisticated 3-D circuits are some of the demonstrated advantages of polymeric electro-optic devices; however, for such devices to be commercially viable they must exhibit exceptional stability in harsh environments (high temperature and optical power exposure). Lattice hardening (intermolecular cross-linking) plays a critical role in defining chemical, photochemical, and thermal stability. Optical insertion loss is another issue that requires attention to both material design and device structure. Techniques for reducing insertion loss are cited. New material performance capabilities have led to new device concepts and demonstrations; several examples are given.

A ring-locked, phenyltetraene-based, second-order nonlinear optical chromophore (CLD-1) was synthesized. It shows no drop in decomposition temperature compared to its phenyltriene analogue, while the molecular nonlinearity increases by a factor of 2.25 from 6252 × 10-48 to 14065 × 10-48 esu at 1.9 μm. Thin films and waveguide devices were prepared from CLD-1/PMMA and CLD-1/APC (an amorphous polycarbonate) composites to study its electrooptic (EO) activity, optical loss, and photostability. An average EO coefficient of 92 pm/V at 1.06 μm was achieved in a 25 wt % CLD-1/APC composite. Mach−Zender (MZ) modulators fabricated from CLD-1/APC showed good thermal stability, low optical loss, low modulation voltage, and high extinction ratio. The photochemical stability of the CLD-1/APC modulator can be dramatically improved by operating in an inert gas atmosphere. Evidence shows that the predominant photochemical degradation mechanism of the material in air at 1.55 μm is the reaction between oxygen and photoexcit...

A mean-field model of acentric order of dipolar chromophores in polymeric electro-optic materials is developed by extension of our earlier results [Y.V. Pereverzev, O.V. Prezhdo, Phys. Rev. E 62 (2000) 8324] to allow for position and orientation flexibility of chromophore dipoles with respect of the molecular frame. The extended model quantitatively reproduces the experimental data for two sample chromophore systems. The model indicates that the disappearance of the acentric order and the related turnover and decay of the electro-optic coefficient are associated with a second-order phase transition in the dipolar system from para- to antiferroelectric state.

The first molecular hyperpolarizabilities (β) of a series of charge-transfer nonlinear optical (NLO) chromophores are measured with the hyper-Rayleigh scattering (HRS) technique using two excitation wavelengths at 1064 and 1907 nm. The 1907 nm wavelength is the longest excitation wavelength used for the HRS experiment. For some of these chromophores, β values in excess of 1000×10−30 esu at 1907 nm are obtained, and due to two-photon enhancement, even greater β values are found with the 1064 nm excitation. Chromophores with such large hyperpolarizability are expected to have potential applications in practical electro-optical devices. The dispersion of β is analyzed using a two-vibronic-state model developed previously in our laboratory. The study shows that it is necessary to consider the vibronic structure of the chromophore in the excited state in order to account for the behavior of the first molecular hyperpolarizability of the charge-transfer NLO chromophores.

This paper presents a class of nonlinear optical (NLO) urethane-urea copolymers, where dimethylsiloxane linkages of different length are incorporated into the polymer main chain. For comparison, a urethane-urea polymer having virtually no siloxane units has also been prepared. Results show that for copolymers with siloxane linkages poled samples have exceptional orientational stability, consistent in part with strong hydrogen-bonding effects. By the introduction of siloxane linkages, low optical loss materials suitable for device-quality applications have been obtained. The low optical loss can be attributed to the relatively lower number density of C-H bonds in the polymer matrix. Simultaneous realization of enhanced temporal stability and lower optical loss has been achieved in a single polymer system.

Based on a nonlinear optical polymer with a highly nonlinear chromophore (CLD) dispersed in an amorphous polycarbonate (APC), we have developed electrooptic (EO) polymer modulators operating at 1550-nm wavelength with low loss and good thermal stability. By incorporating polymer insulation layer, push-pull poling was successfully performed without film damages. We also demonstrated that the propagation loss of the EO polymer waveguide could be reduced as low as 1.2 dB/cm at 1550 nm when the large core waveguide structure was incorporated. The long-term reliabilities of the EO polymer modulator made of CLD/APC polymer were investigated. When the modulator was hermetically sealed in an inert gas, the V/sub /spl pi// change of a Mach-Zehnder modulator was negligible over 30 d of operation with 20-mW exposure to the waveguide input. In the thermal stability measurement, 25% V/sub /spl pi// increase was observed from the sample heated to 60/spl deg/C over 40 d, though the sample left at room temperature showed no decay of nonlinearity.

Diethyl 5-formyl-2-thienylmethylphosphonate is synthesized via the formylation of 2-thienylmethylphosphonate, and has been demonstrated to beane efficientintermediate thienylvinylene elongation of electron-rich conjugate systems.

A high μβ isophorone-derived phenyltetraene chromophore (denoted CLD-5) was synthesized. The chromophore was modified with a hexyl group at the middle of the π-conjugate bridge to improve solubility and processability and was dihydroxy-functionalized for covalent incorporation into various cross-linked PU polymer systems. Its electrical poling and relaxation behavior in PU polymer thin films were studied. First, the chromophore was incorporated into conventional TDI/TEA polyurethane, and an electrooptic (EO) coefficient of 57.6 pm/V at 1.06 μm was obtained, which is 28% higher than that obtained from nonhexylated chromophore (CLD-2) in the same polyurethane system. Two new polyurethane systems, poly[(phenyl isocyanate)-co-formaldehyde] (PPIF)/triethanolamine (TEA) and PPIF/bisphenyl-1,1‘-dimethanol (BPDM), were designed to study the influence of cross-link density and monomer rigidity on electrical field poling of chromophore dipoles and relaxation behavior of poling-induced chromophore alignment. CLD-5/P...

A novel trilinkable thiophene-containing second-order nonlinear optical (NLO) chromophore [(HO)3FTC] was synthesized from a trilinkable donor bridge and a tricyanofuran electron acceptor (TCF). The TCF acceptor was modified with two butyls which greatly increased solubility and processability of the trihydroxy-functionalized chromophore and inhibited strong chromophore−chromophore interaction. A thermal stability study of (HO)3FTC indicates that the free hydroxyl group located close to the cyano acceptor causes the chromophore to decompose at a much lower temperature than FTC chromophores with no free hydroxyl groups. Significantly improved thermal stability of the chromophore in polyurethane film was obtained by masking the free hydroxyl groups with toluene diisocyanate. New polyurethane prepolymer synthetic schemes were designed and studied in detail to improve electric field induced dipole alignment. Enhancement of over 150% in poling efficiency was achieved by reducing the degree of chromophore attach...

We used femtosecond nearly degenerate four-wave mixing (nDFWM) to measure the instantaneous third-order nonlinear optical susceptibility function χ 1111 [−( ω − δω ), ω , ω ,−( ω + δω )] near the absorption edge of C 60 films with absorption reaching up to 2.0×10 4 cm −1 . The frequency shift was set to ℏ δω =0.07±0.01 eV, smaller than the width of the spectral feature studied but large enough to suppress non-instantaneous signal contributions. Our data are orders of magnitude below previous DFWM results but connect smoothly to data at longer wavelengths where absorption is low ( −1 ).

Control of the spatial arrangement of atoms over nanoscale dimensions can be used to achieve electronic isolation of chromophores, to control electronic delocalization, to control the spatial variation of material indices of refraction, and to achieve spatially controlled energy transfer. Such control can, in turn, be exploited to avoid quenching of luminescence, to control optical absorption and emission characteristics, to achieve morphological resonances and photonic bandgap phenomena, and to achieve light harvesting and transfer to an active center. Examples of control of optical properties using nanostructured dendimers, block copolymers, and polymer microspheres are given.

The synthesis of poly(4-vinylpyridine) block copolymers containing a poly(4-(4-(4-fluorophenyl)sulfonylphenyl)sulfonyl-4‘-N-ethyl-N-2-(4-hydroxyphenolic)ethylazobenzene) (PNLO) segment with a MW between 7300 and 19 300 was carried out by the reaction of the 4-fluorophenyl end group of the PNLO segment with a low molecular weight (DP = 33 or less) phenol end-functionalized P4VP under basic conditions. Self-assembly of this diblock copolymer occurs with polystyrene-b-poly(vinylphenol) (PS-b-PVPh) or PMMA-b-poly(2-hydroxyethyl methacrylate) (PMMA-b-PHEMA) block copolymers, having short H-bond donor blocks, through the formation of H-bonds with the acceptor P4VP blocks. This process was studied by the increased solubility of the P4VP-b-PNLO copolymer in toluene/CH2Cl2 (99/1, v/v) or in ethyl acetate due to the formation of the more soluble block copolymer complexes. The increases in solubility were monitored by visible absorption at about 456 nm, the absorption maximum of the PNLO segment. The apparent bindin...

An acoustic spectrum analyzer based on electrooptic (EO) polymer integrated optics is presented. The device is used in a scanning heterodyne geometry by zero biasing a Michelson interferometer. It is capable of detecting vibrations from DC to GHz range. The novelty of the work is applying EO polymers to high frequency acoustic sensing applications. EO polymers have been extensively used for communication devices. However, their use in high frequency sensing applications remains unexplored. The sensor presented is designed to analyze thin film structure by utilizing high frequency capabilities of EO polymers. The advantage of this approach over existing methods is in its potential to detect vibrations over 100 GHz with low drive voltages (V/sub /spl pi// less than 1 V), using a device that is completely electrically controlled with no mechanical moving parts. Low frequency tests indicate good agreement between experimental results and theoretical predictions. Acoustic vibrations excited by pulsed Nd-YAG laser are detected to frequencies up to 200 MHz using the device presented.

A novel poly-4-vinylpyridine-b-PNLO (nonlinear optical material)-b-polystyrene-b-poly(4-vinylphenol) tetrablock copolymer (P4VP-b-PNLO-b-PS-b-PVPh) was synthesized containing an NLO polymeric segment prepared by step polymerization. The tetrablock copolymer is designed to form an asymmetric lamellar structure by self-assembly prompted by the interactions between the donor and acceptor blocks which are expected to help to align the dipole moments of PNLO block into one direction. The synthesis was carried out by reaction of a P4VP-b-PNLO−Ph−NH2 block copolymer containing an aniline end group with a poly(4-tert-butyldimethylsiloxy)styrene-b-PS−CO2H (PBDMSS-b-PS−COOH) diblock copolymer containing a tert-butyldimethylsilyl-protected polyvinylphenol endowed with a carboxylic end group in the presence of diphenylphosphoryl azide (DPPA) in N,N-dimethylacetamide. After the formation of the P4VP-b-PNLO−PhNH−CO−PS-b-PBDMSS tetrablock copolymer the PVPh block was obtained by deprotection of tert-butyldimethylsilyl g...

We have synthesized a novel electrooptic (EO) polymer based on a high /spl mu//spl beta/ chromophore incorporating tricyanobutadiene acceptors. A crosslinked polyurethane network was also adopted to enhance its thermal stability. In order to find the optimum poling condition for the polymer, the influence of the electric poling profile on optical characteristics such as the EO effect, thermal stability, and damage was investigated. Then a high-speed intensity modulator using the EO polymer was designed and fabricated. The measured half-wave voltage V/sub /spl pi// was 4.5 V at the wavelength of 1.31 /spl mu/m. Accordingly, the achieved EO coefficient r/sub 33/ was as high as 25 pm/V, and the thermal stability of the poled polymer was as high as 95/spl deg/C. Finally, the modulator was successfully operated up to 40 GHz.

Monte Carlo statistical mechanical computer simulations of the electric-field poling of second-order nonlinear optical chromophores, characterized by large dipole moments, polarizabilities, and hyperpolarizabilities, are presented. Such theoretical analysis is critical to defining the structure/function relationships that permit maximization of electro-optic activity for π-electron chromophore-containing polymeric materials. Polymeric electro-optic materials may, in turn, be important for high-bandwidth telecommunications, new forms of radar, and high-speed data processing. The experimentally observed maxima in plots of electro-optic activity versus chromophore number density (loading) in polymer matrices are theoretically reproduced, as are the shifts of the maxima to lower loading with increasing chromophore dipole moment. Modification of the chromophore shape to realize the maximum achievable electro-optic activity for a given π-electron structure is discussed, as is the role of polymer electrical perm...

Electro-optic (EO) modulators encode electrical signals onto fiber optic transmissions. High drive voltages limit gain and noise levels. Typical polymeric and lithium niobate modulators operate with halfwave voltages of 5 volts. Sterically modified organic chromophores have been used to reduce the attenuation of electric field poling–induced electro-optic activity caused by strong intermolecular electrostatic interactions. Such modified chromophores, incorporated into polymer hosts, were used to fabricate EO modulators with halfwave voltages of 0.8 volts (at a telecommunications wavelength of 1318 nanometers) and to achieve a halfwave voltage-interaction length product of 2.2 volt-centimeters. Optical push-pull poling and driving were also used to reduce halfwave voltage. This study, together with recent demonstrations of exceptional bandwidths (more than 110 gigahertz) and ease of integration (with very large scale integration semiconductor circuitry and ultra-low-loss passive optical circuitry) demonstrates the potential of polymeric materials for next generation telecommunications, information processing, and radio frequency distribution.

Amination of 5-bromo-2-thiophenecarboxaldehyde with an acyclic secondary amine - bis(2-methoxyethyl)amine was effected by using weak base sodium bicarbonate. The resulting 5-N,N-bis(2-methoxyethyl)amino-2-thiophenecarboxaldehyde was treated with boron tribromide to give 5-N,N-bis(2-hydroxyethyl)amino-2-thiophenecarbox- aldehyde.

We present here a class of processible donor-embedded nonlinear optical (NLO) polyimides exhibiting the high glass-transition temperature and exceptional thermal and chemical stability. Due to the rigidity of the donor-embedded structure, the stability of the electric field induced dipole orientation of the NLO chromophores was enhanced. A sizable second-order nonlinear optical coefficient was obtained.

An ω-amino carboxylic acid monomer that contained a nonlinear optical (NLO) chromophore was prepared by a convergent synthesis. Strategies for selective protection/deprotection of the amino and carboxylic acid functionalities were developed. The protected monomer, 4-[N-(4-benzyloxycarbonyl)butyl-N-methylamino]-4′-[2″,5″-bis(decyloxy)-4″-(phthalimidomethyl)benzylsulfonyl]azobenzene, could be deprotected selectively or sequentially to give HOOC-monomer-N-phthaloyl, benzyl-OOC-monomer-NH2, or HOOC-monomer-NH2. Sequential synthesis was performed to yield main-chain NLO dimers and tetramers. This was accomplished by selective deprotection and dicyclohexylcarbodiimide coupling. The HOOC-monomer-NH2 was polymerized by treatment with diphenylphosphoryl azide to give a main-chain NLO polyamide. The monomer, dimer, tetramer, and polymer NLO materials were characterized by 1H, 13C, IR, and UV–visible spectroscopy as well as by gel permeation chromatography, differential scanning calorimetry, and elemental analysis. The NLO properties of these materials were measured. Thin films of the oligomers and polymer were prepared by spin casting on indium-tin oxide coated glass. The second-order NLO properties of the oligomers and polymer thin films were studied by in situ corona poling/second-harmonic generation and attenuated total reflection methods. The optimal poling temperatures were significantly lower than the melting temperatures or glass-transition temperatures of the oligomers and polymer. The poling efficiency increased in the following order: monomer, oligomers, and polymer. An electro-optic coefficient of 4 pm/V at 1.06 μm was obtained for the polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 546–559, 2000

An efficient approach to thienylmethylphosphonates has been established through the combination of thienylcoppers with the commercially available diethyl iodomethylphosphonates in a one-pot process.

A protected ω-secondary amino carboxylic acid monomer which contains the 4-dialkyl- amino-4'-(alkylsulfonyl)azobenzene nonlinear optical (NLO) chromophore has been prepared by a convergent synthesis. The carboxylic group is protected as a benzyl ester, while the N-benzyl secondary amino group is protected as a 9-fluorenylmethyl carbamate (Fmoc). Selective deprotection of the protected monomer benzyl-OOC-monomer-N(benzyl)-Fmoc was carried out. Treatment with piperidine selectively removed the Fmoc-protecting group to give benzyl-OOC-monomer-NH(benzyl). Alternatively, treatment with HCl-acetic acid removed the benzyl-protecting group to yield HOOC-monomer-N(benzyl)-Fmoc. The mono-protected monomers were coupled with dicyclocarbodiimide (DCC) to afford a protected dimer, benzyl-OOC-dimer-N(benzyl)-Fmoc. In the same way, selective deprotection followed by DCC coupling of the mono-protected dimers yielded a protected tetramer, benzyl-OOC-tetramer-N(benzyl)-Fmoc. Monomers, dimers and tetramer have been fully ch...

Isoxazolone (ISX) acceptor based chromophores terminated with hydroxyl functional groups were synthesized, spin cast into optical quality 1−2 μm thick films, poled in the presence of an electric field, and thermoset into polyurethane networks to lock in the poling-induced acentric chromophore order. Alkyl groups were introduced into the chromophore backbone (π-electron bridge) to increase chromophore solubility and to inhibit electrostatic interactions between these “high μβ” chromophores. Thermosetting polyurethanes containing alkyl-substituted chromophores exhibited much (1.7−1.9 times) higher electrooptic coefficients than polymers containing unsubstituted chromophores. Chromophores with hydroxyl groups on only the donor end of the molecule were processed into hardened “themoset” materials, exhibiting a dynamic thermal stability (temperature at which the macroscopic optical nonlinearity is first observed to decrease in a thermal ramping experiment) of poling-induced dipolar order of ∼80 °C, while chrom...