Organic materials that exhibit large real third-order optical nonlinearities, |Re(χ(3))|, and that also have low linear and nonlinear losses at telecommunication wavelengths may be useful for a range of all-optical signal-processing (AOSP) applications. Based on their solution linear and nonlinear optical characteristics, polymethine dyes in general, and chalcogenopyrylium-terminated heptamethines in particular, are a promising class of materials for AOSP, but the translation of their microscopic nonlinearity to device-relevant materials is hindered by significant aggregation of the molecules in high-chromophore density films. An approach to minimize aggregation these dyes, in which bulky and rigidly out-of-plane groups are introduced both in the center of the polymethine bridge and on the heterocyclic end groups, has been developed and can lead to thin-film materials exhibiting combinations of large |Re(χ(3))|, large two-photon figure-of-merit, and low linear loss that are suitable for AOSP.
 Hales J. M., Matichak J., Barlow S., Ohira S., Yesudas K., Brédas J.-L., Perry J. W. and S. R. Marder, Science, 2010, 327, 1485.
 Barlow S., Brédas J.-L., Getmanenko Y. A., Gieseking R. L., Hales J.M., Kim H., Marder S.R., Perry J. W., Risko C., Zhang Y., Materials Horizons, 2014, 1, 17.
Electro-optic (EO) polymer modulators have demonstrated high speed external modulation of optical signals. Additionally, EO polymers have closely matched refractive indices at optical and microwave wavelengths, which enables high bandwidth operation. An EO polymer includes a polymer matrix and an organic "push-pull" chromophore that can be modified to give poled polymers with high EO activity. This high EO activity and optical-microwave velocity match offer the promise of accomplishing broadband, high speed optical modulation with low drive voltage. Such optical signal modulation is critical for applications in phased array radar and RF photonics. Practical issues such as electrode design, optical fiber coupling, and hermetic packaging are critical in final device performance. Herein, we report on high-speed electrode parameters as well as electro-optic performance versus frequency of packaged modulators fabricated with novel, highly photostable chromophores.
Host polymers play an important role in determining the thermal, optical and electrical properties of guest-host electro-optic (EO) polymers. In this study, a series of novel polymers, polyaryletherketones (PEKs) and polyarylethersulfones (PES'), were synthesized. After an initial screening on EO modulator fabrication-related properties, a PEK, LP120, was identified as a good candidate to host the highly stable chromophores (DH6 and DH52) developed in the company. Further optimization indicated that solvents in chromophore/polymer solutions have a strong impact on the quality of spin-coated films. DH6/LP120 and DH52/LP120 films spun from cyclopentanone gave lower optical losses of 1.97 and 1.55 dB/cm, respectively, when compared with 2.84 dB/cm for DH6/APC and 1.96 dB/cm for DH52/APC. Moreover, poling efficiencies as being reflected by EO coefficient were also improved by using LP120 compared to APC.
Polymeric electro-optical modulators have the advantages in bandwidth, driving voltage, and cost over lithium niobate
modulator for potential industrial, military and space applications. There are strict requirements on electro-optical
polymer materials to be used for practical device fabrication: large EO response, high thermal and photochemical
stability, low optical loss, high long-term stability and good processibility. Lots of progress in material design,
modification and optimization has been made based on theoretical calculation and actual material processing. However it
is very challenging to put all good properties into one material. We report the development of a chromophore series
based on 3,4-ethylenedioxythiophene structure and two host polymers based on 4,4'-(3,3,5-trimethylcyclohexylidene)
diphenol monomer. EO activity and optical loss at different chromophore loadings were systematically studied and
compared on various guest/host combinations. Specifically, DH-52/APC system was compared with DH-6/APC system,
showing improved overall electrical and optical properties. LP-116, with higher glass transition temperature than that of
APC, exhibits excellent mechanical property and compatibility with various chromophore guests. Especially, DH-67/LP-
116 has optical loss of 0.87 dB/cm. This indicates that LP-116 can substitute APC as an improved host polymer and DH-
52/LP-116 is highly feasible for the fabrication of EO devices with enhanced performance.
Electro-optic (EO) polymer modulators have demonstrated high speed external modulation of optical signals. Additionally, EO polymers have closely matched refractive indices at optical and microwave wavelengths, which enables high bandwidth operation. An EO polymer includes a polymer matrix and an organic "push-pull" chromophore that can be modified to give poled polymers with high EO activity. This high EO activity and optical-microwave velocity match offer the promise of accomplishing broadband, high speed optical modulation with low drive voltage. Such optical signal modulation is critical for applications in phased array radar and RF photonics. However, practical fabrication of optical modulators that realize the potential of EO polymers requires clad materials with optimized properties such as conductivity, dielectric constant, optical loss, and refractive index. In addition, other practical issues such as electrode design, optical fiber coupling, and hermetic packaging are critical in final device performance. We report on high-speed electrode parameters as well as electro-optic performance versus frequency of modulators fabricated on 6" silicon wafers. The r33 values measured on single layer thin films are compared with those resulting from Vπ measurements on devices. We compare the effect of EO polymer morphology on device fabrication and optical loss for different EO polymers.
Low drive voltage Mach-Zehnder modulators were designed and fabricated using proprietary EO polymers with high electro-optic coefficients. We report on drive voltage and high-speed electrode parameters of modulators fabricated on silicon wafers with high yield. Special attention was paid to designing claddings to match the electro-optic core conductivity and dielectric constant. The r33 values measured on single layer thin films are compared with those resulting from drive voltage measurements on devices. Half-wave voltage measured on devices is compared with theoretical values derived from equations defined for poling of the core through bottom and top claddings. We compare results obtained from devices fabricated using commercially available UV-curable epoxies with devices fabricating using proprietary clad polymers developed at Lumera Corporation.
The electro-optic coefficient and long-term dipole alignment stability are two major factors in the development of high performance NLO materials for the application of high-speed EO devices. We have developed a high performance non-linear organic chromophore and incorporated it into a crosslinkable side-chain polyimide system. The polymer was synthesized through stepwise grafting of the crosslinker followed by the chromophore onto the polyimide backbone via esterification. Different chromophore loading levels were achieved by adjusting the crosslinker/chromophore feeding ratio. The polyimides films were contact-poled with second-harmonic generation monitoring. A large EO coefficient value was obtained and good long-term thermal stability at 85°C was observed.
1,4-Bis(4-aminostyryl)benzene derivatives have been shown to exhibit large two-photon cross-sections at ca. 730-745 nm and are typically highly fluorescent in organic solvents. For biological imaging applications, we have been interested in identifying water-soluble dyes with high two-photon cross-sections and fluorescence quantum yields. Four new bis(aminostyryl)benzene chromophores have been synthesized; these chromophores are functionalized with phosphate, sulfonate, and sulfate hydrophilic groups. In some cases, this substitution pattern renders the chromophores water-soluble and, for the sulfonate and sulfate cases, moderate fluorescence quantum yields are retained in water.
New crosslinked clad polymers were developed for electro-optic polymer modulators with special attention paid to properties such as refractive index tunability, optical loss, and conductivity. These cured polymers showed relatively low optical loss at 1550 nm and desirable conductivity. The clads were used to fabricate electro-optic devices having mode profiles closely matched to that of optical fibers in order to reduce insertion loss. A new hardmasking technique was developed to define Mach-Zehnder rib waveguides by photolithography and dry etching with high reliability and surface smoothness. The hardmasking technique demonstrated flexibility in defining waveguides made with electro-optic polymers having different reactivity towards etchant gasses.