Nonelectrical Poling Research Articles

The role of chemisorption for push-pull chromophores on SiO2 surfaces in non-electrically poling host-guest NLO polymers

Abstract For decades, host-guest nonlinear optical (NLO) polymers have been studied because of their versatilities. NLO polymers do not display second-order nonlinearities in as-prepared conditions because the guest chromophores are randomly oriented in the host polymers and they are centro-symmetric. We report non-electrical poling behaviors of push-pull guest chromophores that consist of a π-conjugated phenylene vinylene bridged by an electron-accepting tricyanofuran moiety and electron-donating phenyl amine derivatives in poly (methyl methacrylate). When the phenyl amine moieties were substituted either by hydroxyl or carboxyl groups, enhanced emissions of second harmonic generations (SHG) were observed after annealing at temperatures above the glass transition point of the host polymers in the absence of external electric fields. The number of hydroxyl or carboxylic groups exerted significant influence on the polar ordering of the chromophores. The orientation behaviors of the chromophores were examined using heterodyne SHG, polarized linear absorption and polarized SHG spectroscopies.

Second-order nonlinear optical susceptibilities in nonelectrically poled guest–host polymers with tricyanofuran chromophores

In this manuscript, we describe the current manuscript describes the second-order nonlinear optical susceptibility of guest–host polymers possessing chromophores with strongly electron-accepting tricyanofuran (TCF). Chromophores substituted with different numbers of hydroxyl groups were prepared. Our experimental results demonstrated that the guest–host polymers exhibited nonlinear optical susceptibilities simply upon annealing at temperatures higher than the glass transition point of the host polymers even in the absence of applied external DC electric fields. Nonelectrical poling behaviors were only available for the materials possessing hydroxyl-group-functionalized chromophores. The results indicate that chemisorption of the hydroxyl groups on the substrate led to the orientation order of the guest chromophores. The orientation order of the chromophores was reproduced well by the model of poled polymers in previous studies.

Second-Order Nonlinear Optical Susceptibilities of Nonelectrically Poled DR1–PMMA Guest–Host Polymers

Guest-host nonlinear optical polymers have attracted considerable interest due to their applications in fast electro-optical modulators and wavelength converters. In general, the electrical poling procedures, for which high DC external fields are applied, are necessary for aligning guest chromophores in polar order and activating the second-order nonlinearity. We present the nonelectrical poling behaviors for guest-host polymers: DR1 (4-[ethyl (2-hydroxyethyl) amino]-4'-nitroazobenzene) is the guest, and PMMA (poly (methyl methacrylate)) is the host. Second-order nonlinear optical susceptibility was induced in the conventional guest-host polymers after annealing at temperatures above the glass transition points of the host polymer even without applying the external fields. This phenomenon did not occur in the side-chain polymers, where the guests were directly bonded to the host chains. The guest polar alignments were most likely generated from the guest hydroxyl groups chemisorbing on the substrates. The polar alignments of the guest formed not only near the surface of the substrate, but also inside the host polymers. The optimized conditions for the SHG conversion were examined in the context of the polymer film thickness and guest concentration. The nonelectrical poling techniques described in this study are useful for enhancing the surface nonlinearity in the several materials, and they will be useful for further developments in nanophotonics and plasmonics.

Self-organizing second-order nonlinear susceptibility in NLO-chromophore-doped amorphous ferroelectric poly-(cyano phenylene sulfide) polymers [Invited

We present the second order nonlinear optical properties of the Disperse Red 1 (DR1)-doped poly (cyano phenylene sulfide) (PCPS) - novel ferroelectric amorphous polymers. The PCPS possess self-organized long-range polarizations when they are annealed at temperatures higher than their glass transition point. From the unique nonelectrical poling effect, the second-order nonlinear susceptibility was obtained without the conventional poling procedures. The optimized conditions to create the second-order nonlinear optical susceptibility were also investigated in terms of the sample thicknesses and the annealing temperatures.

Piezoelectricity of vinylidenefluoride–trifluoroethylene copolymer films in various poling conditions

AbstractPiezoelectricity of ferroelectric thin polymer films strongly depends on the poling condition. We can classify them as conventional electrical and novel nonelectrical poling. These experiments show the comparative results on piezoelectricity induced from various poling processes (i.e., electrical corona poling, nonelectrical surface‐energy poling, and a combination of both methods simultaneously in various poling conditions). The most interesting result confirmed that the piezoelectricity increased significantly when the combination poling was applied with appropriate metal substrate and temperature decreasing rate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 856–860, 2004

Non-Electrical Poling in Novel Ferroelectric Polymers

AbstractNon-electrical poling was proposed in novel ferroelectric polymers including such as polythioureas, polycyanophenylenesulfides, and polyvinyfluorides. This poling method utilizing the cooperativity of molecular dipoles can be called “surface energy poling” and takes agvantage of the energy difference inthe top and bottom surface of apolar aggregate (dipole glass) to form a remanent polarization. A ferroelectric polymer film sandwiched between a metal with higher surface energy and PTFE film with lower surface energy were heated to Tp=Tc (glass tramsition temperature or ferroelectric transition) × 1.2 and cooled slowly to room temperature. In the thin films less than 10μm, we observed the remanent polarization which gives a large pyroand piezo-electric constant as well as that obtained by electrical poling. This poling is effective for homogenious structures such as amophous ferroelectric polymers.