Synthesis and characterization of cross-linkable polyurethane-imide electro-optic waveguide polymer

The electro-optic (EO) polymers of Y-type polyurethane-imides (PUI-1 and PUI-2) were synthesized by reaction of monomer azo-based chromophores, phenyl diisocyanate and aromatic dianhydride, based on polycondensation mechanism. Molecular structure characteristics for the polymers were evidenced by 1HNMR, FTIR, elemental analysis and gel permeation chromatography. The polymers exhibited a glass transition temperature (Tg) of 185 °C and 192 °C and a temperature of 5% weight loss at 256 °C and 325 °C and showed EO coefficient, γ33, of 43 pm/V and 51 pm/V at 1550 nm wavelength. A type of single-mode embedded PUI polymeric inverted rib waveguide Mach-Zehnder (MZ) interferometer electro-optic modulators was fabricated and measured, and exhibiting favorable electro-optical modulation response and the average propagation loss of the waveguide was less than 2.0 dB/cm at 1550 nm. The experimental results indicated that the PUI were promising candidates for the preparation of comprehensive performance excellent EO polymer waveguide materials, due to their large nonlinear optic effects, thermal stability, good processability and low optical propagation loss.

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/PPIF/TEA polymer has the highest cross-link density (3.07 mmol/g) among all the polyurethanes studied here. It gains 38 °C in thermal stability but loses 50% of EO activity as compared with the CLD-5/TDI/TEA polyurethane material, which has a cross-link density of 1.91 mmol/g. A higher EO coefficient (41 pm/V), lower optical loss of 2.56 dB/cm at 1.3 μm, and the highest dynamic stability (133 °C) were obtained for the CLD-5/PPIF/BPDM polyurethane EO material, which has the lowest cross-link density (1.27 mmol/g) and the most rigid monomers. The results indicate that excessive cross-linking deteriorates electric poling of long chromophores in a cross-linked polymer thin film. Therefore, cross-linking by itself is not necessarily a good approach to achieving high thermal stability of electrical field-induced chromophore alignment in polyurethane systems.

We review recent research using amorphous electrooptic (EO) polymers for generation and detection of broadband terahertz radiation (0.3 THz -30 THz). The advantages of amorphous EO polymers over other materials for broadband THz generation (via optical rectification) and detection (via EO sampling) include a lack of phonon absorption (good transparency) in the THz regime, high EO coefficient and good phase-matching properties, and, of course, easy fabrication (low cost). Our ~12-THz, spectral gap-free THz system based on a polymer emitter-sensor pair is an excellent demonstration of the advantages of the use of EO polymers. This system has been employed as a wideband spectrometer to study dielectric materials in the THz regime.

A new host-guest electro optic (EO) polymer, in which a chromophore can be reacted with the polymer main chain during poling to give the corresponding side-chain EO polymer, has been prepared for improving EO effect and its thermal stability. Polyisoimide (PII) synthesized from 2, 2-bis (4-aminophenyl) hexafluoropropane and oxydiphthalic anhydride and Disperse Red 1 (DR1) were used as a host and a guest, respectively. A model compound reaction and Infrared spectra of the host-guest film after annealing at various temperatures show that the reaction between the isoimide groups in PII and the hydroxyl groups in DR1 occurs around 140 °C. The glass transition temperatures of the resulting EO polyamic aicd ester-imide copolymer with 0, 10, 20 and 30 wt. % of chromophore concentration were 275, 219, 160, and 124 °C, respectively. The EO coefficient obtained at a wavelength of 1.55 νm was 5.3 and 10.5 pm/V from the EO polymer film with 20 and 30 wt. % DR1. The EO signals exhibited only a slight decay at high temperature due to the chemical reaction between the host and guest during poling.

Material processing and device fabrication of many different electro-optic (EO) polymers developed at USC are reviewed. Detailed discussion is given to guest-host CLD/APCs, crosslinking perfluorocyclobutane (PFCB) polymer CX1, and thermally stable side-chain polymers CX2 and CX3. Excellent EO performance (1.4V at 1.31 &mu;m, 2.1 V at 1.55 &mu;m) was achieved in CLD/APC Mach-Zehnder modulators (2-cm, push-pull). CLD/APCs also possess low optical losses (1.2 dB/cm in slab waveguides and in thick core channel waveguides). However, the guest-host materials only have limited thermal stability (110-132 &deg;C in short term, <60 &deg;C in long term) and require special techniques in device fabrication. The crosslinking polymer CX1 was able to provide long-term stability at 85 oC when fully cured. It also has a low optical loss (comparable to CLD/APCs) before curing and decent EO coefficient when poled at 180 &deg;C. However, after the films were poled at the crosslinking temperatures (200 &deg;C or above), the transmissions of the waveguides and EO activity became very poor due to poling-induced chromophore degradation. By judicial molecular design of both chromophore and monomer structures to suppress thermal motion of polymer segments, we were able to realize the same or even better thermal stability in side-chain polymers CX2 and CX3. Since no curing is needed, devices can be poled at their optimal poling temperatures, and all good properties can be obtained simultaneously. Despite the excellent solubility in chlorinated solvents, these side-chain polymers are resistant to some other organic solvents or solutions such as acetone, photoresist and various UV-curable liquids.

The preparation of high-performance electro-optical materials is one of the key factors determining the application of optoelectronic communication technology such as 5G communication, radar detection, terahertz, and electro-optic modulators. Organic electro-optic materials have the advantage of a high electro-optic coefficient (~1000 pm/V) and could allow the utilization of photonic devices for the chip-scale integration of electronics and photonics, as compared to inorganic electro-optic materials. However, the application of organic nonlinear optical materials to commercial electro-optic modulators and other fields is also facing technical bottlenecks. Obtaining an organic electro-optic chromophore with a large electro-optic coefficient (r33 value), thermal stability, and long-term stability is still a difficulty in the industry. This brief review summarizes recent great progress and the strategies to obtain high-performance OEO materials with a high electro-optic coefficient and/or strong long-term stability. The configuration of D-π-A structure, the types of materials, and the effects of molecular engineering on the electro-optical coefficient and glass transition temperature of chromophores were summarized in detail. The difficulties and future development trends in the practical application of organic electro-optic materials was also discussed.

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.

我們合成了兩新型骨架中含N,N,N’,N’-tetraphenyl-phenylenediamine (TPPA)之聚脲。N,N’-bis(4-aminophenyl)-N,N’-bis(4-methoxyphenyl)benzene-1,4-diamin由N,N’-bis(4-methoxyphenyl)benzene-1,4-diamine (1)與4-nitroaniline，CsF做催化劑的環境下進行反應而得到N,N’-bis(4-methoxyphenyl)-N,N’-bis(4-nitrophenyl)benzene-1,4-diamine，再將硝基還原成二胺分子，兩新型全芳香族聚脲PTPAMDI及PTPAPDI由二胺與methylenedi-p-phenyl diisocyanate (MDI) 或p-phenylene diisocyanate (PDI)經由低溫溶液加成聚合反應而製得。合成出之聚脲其黏度介於0.34~0.56 dL/g之間，重量平均分子量與數目平均分子量經由凝膠層析滲透儀(gel permeation chromatography; GPC)測得分別介於25,000~50,000之間。 所得之聚脲皆為非晶形之聚合物，可溶於一般有機溶劑例如：N,N-dimethylacetamide (DMAc)、N,N-dimethylformaide (DMF)、chloroform (CHCl3)且接展現良好的熱穩定性(裂解溫度介於340-360 oC)，以及高玻璃轉換溫度(glass-transition temperatures, Tgs; 139-138 oC)，PTPAMDI之量子效率為4.2 %，而此二系列之HOMO與LUMO可由循環伏安儀測得分別是4.73-4.78 eV對應至HOMO及1.53-1.57 eV對應至LUMO。而PTPAMDI之電洞、電子傳導特性在0.00~1.40 V電壓下展現出由無色中性態轉變為綠、藍色之氧化態。

Electro-optic (EO) polymer modulators with a wide range of thermal stability from −46°Cto95°C for fiber-optic gyroscope applications are reported. The synthesized EO side-chain polymer used has a glass transient temperature (Tg) of 200°C and a large EO coefficient of 25.2pm∕V in a real device measurement. Mach–Zehnder (MZ) intensity and optical phase modulators are implemented based on this high-Tg side-chain EO polymer, exhibiting ∼3.75V half-wave voltage with 1.5cm interaction length and 2.3cm total length at 1.55μm wavelength. The optical fiber-to-lens insertion loss is ∼7.5dB in the MZ interferometers and ∼6dB in the straight waveguides. We examine the long-term thermal stability of these devices and demonstrate their ability to meet the strict requirements of various EO device applications, particularly fiber-optic gyroscopes.

Multimode interference waveguide switch of electro-optic polymer with tapered access waveguides

A series of crossslinked organic and organic/inorganic polymers based on maleimide chemistry have been investigated for second‐order non‐linear optical (NLO) materials with excellent thermal stability and low optical loss. Two reactive chromophores (maleimide‐containing azobenzene dye and alkoxysilane‐containing azobenzene dye) were incorporated into a phosphorus‐containing maleimide polymer, respectively. The selection of the phosphorus‐containing maleimide polymer as the polymeric matrices provides enhanced solubility and thermal stability, and excellent optical quality. Moreover, a full interpenetrating network (IPN) was formed through simultaneous addition reaction of the phosphorus‐containing maleimide, and sol‐gel process of alkoxysilane dye (ASD). Atomic force microscopy (AFM) results indicate that the inorganic networks are distributed uniformly throughout the polymer matrices on a nano‐scale. The silica particle sizes are well under 100 nm. Using in situ contact poling, the r33 coefficients of 2.2–17.0 pm/V have been obtained for the optically clear phosphorus‐containing NLO materials. Excellent temporal stability (100°C) and low optical loss (0.99–1.71 dB/cm; 830 nm) were also obtained for these phosphorus‐containing materials. Copyright © 2004 John Wiley &amp; Sons, Ltd.

A new poly ionic liquid( PIL) type adsorbent, poly( vinyl-benzyl-imidazolium) chloride( P[VBnim]Cl) was prepared facilely with overall yield above 75% through free radical polymerization of1-vinylimidazole at 70 ℃ and cross-linking of the resulting polymer with 1,4-bis( chloromethyl) benzene via quaternization reaction in dimethylformamide( DMF) solvent. The as-prepared PIL was analyzed and characterized with respect to composition,structure,morphology and thermal stability by elemental analysis,gel permeation chromatography( GPC),Fourier transform infrared spectroscopy( FTIR),scanning electron microscope( SEM),physical absorption instrument and thermal gravimetric analysis /differential scanning calorimetry( TGA /DSC) technique. The molar ratio of 1,4-bis( chloromethyl) benzene to 1-vinylimidazole is about1∶ 3 in P[VBnim]Cl. The P[VBnim]Cl is a beige and fluffy fine powder with primary particle size of 50—80nm,being mesoporous material with specific surface area 13. 86 m2/g and average pore size 9. 94 nm. The PIL exhibits good thermal stability with its initial decomposition temperature being about 274 ℃. Adsorptivity for phenol from the model oil of low temperature coal tar was also studied. The P[VBnim]Cl was proved as an excellent adsorbent,being 2 to 10 times superior to the conventional active carbon at fixed other conditions.The excellent adsorptive property is mainly attributed to the chemical adsorption of the IL constituents at dilute phenol concentrations as well as the physical adsorption at higher phenol concentrations due to the porous architecture of P[VBnim]Cl. The used P[VBnim]Cl adsorbent can be regenerated easily with ethyl acetate,and used repeatedly with good adsorptivity.

Synthesis and characterization of a bipyridine-containing electroluminescent polymer with well-defined conjugation length

We used an ellipsometric reflective technique developed by Teng and Man to measure the electrooptic (EO) coefficients of poled thin films in EO multilayer devices with and without a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conductive barrier layer (CBL). The EO coefficients for the device containing PEDOT:PSS were 260 and 215 pm V−1 at 1.31 and 1.55 μm, respectively, which are higher than those for the device without the CBL. Indeed, the highest EO coefficient for the EO polymer poled without TiO2 or the CBL was 166 pm V−1 at 1.55 μm, consistent with that obtained for our modulator devices (160 pm V−1). We investigated the electrical properties, surface morphology, and optical quality of a PEDOT:PSS CBL in EO polymer/TiO2 multilayer-slot waveguide modulators. We demonstrated that the PEDOT:PSS functions as an efficient CBL to pole EO polymers in hybrid EO polymer/TiO2 vertical-slot waveguide modulators.

Large electro-optic response of bulk ferroelectric crystals enhanced by piezoelectric resonance in the high frequency range