Y. M. Chen

A new guest-host system : towards stable second-order optical nonlinearity

Abstract A new guest-host system based on the azo dye disperse red 1 and phenyl siloxane polymer has been investigated. The second order susceptibility of the polymer cured at 200° C was found to be stable at room temperature and decayed to 60% of its original value after being maintained at a temperature of 100°C for nearly 30 hours. The linear and second-order nonlinear optical (NLO) properties of this material are measured and reported. Curing at higher temperature is expected to lead to greater stability of NLO properties.

Novel Crosslinked Guest-Host System with Stable Second-Order Nonlinearity

Abstract An epoxy-based nonlinear optical (NLO) polymeric material incorporating 4-(4′-nitrophenylazo) phenylamine has been synthesized and subsequently functionalized with acryloyl groups. A glass transition temperature (T 8)of 108°C and a degradation temperature (air) of 251°C were recorded. After crosslinking at 160°C for 2 hours, the T 8 of the polymer increased to 146°C. In order to increase the nonlinear optical chromophore concentration and the crosslinking density, the crosslink-able NLO dye, 2,4-acryloyloxy (4′-phenylazo nitrobenzene), was processed and poled in this epoxy-based NLO material matrix in a manner similar to a typical guest-host system, and thermally crosslinked under the above condition in the poled phase. The crosslinked guest-host material was found to be amorphous with a T 8 of approximately 132°C. It also exhibits a second-order nonlinear optical coefficient d 33 of 14.14 pm/V at a maximum doping level of 33% by weight of the NLO dye, and retains 93% of its original d 33 value a...

Photocrosslinkable Polymers with Stable Second Order Optical Nonlinearity

Abstract Linear and nonlinear optical properties of photocrosslinkable polymers are reported. These polymers exhibit relatively stable second order nonlinearity. Electro-optic and second harmonic generation coefficients are reported for these new materials.

Thin film processing of NLO materials—I. Studies on relaxation behaviour of corona poled aromatic dipolar molecules in a polymer matrix

Abstract A number of corona poled guest-host systems have been investigated to elucidate the nature of interaction between the guest and the host molecules, their compatibility and relaxation behaviour. This study has been carried out by examining the relaxation response of the nonlinear optical effects. Styrene/acrylonitrile copolymer was found to be the ideal matrix studied, since the polymer itself relaxes slowly subsequent to poling and it accommodates a wide range of nonlinear optical molecules differing in molecular structure and polarity. Retention of the second-harmonic intensity has been emphasized as a measure of the relaxation and decay of the order parameters with time. Absorption characteristics of the poled and the unpoled film are also described.

Cerenkov type phase-matched second harmonic generation in polymeric channel waveguides

Abstract Fabrication of polymer channel waveguides by etching on glass is reported. Results on second harmonic generation (SHG) in the Cerenkov mode from stable poled polymeric channel waveguides are presented. The waveguide conversion efficiency for doubling of Nd:YAG laser beam was estimated to be 0.1%/W with a total efficiency of 4.9×10 −7 %/W.

Langmuir-Blodgett films of polymers containing nonlinear optical molecules in the side chains

Abstract Langmuir-Blodgett (LB) film formation has been investigated for two different types of polymers in which nonlinear optical (NLO) moieties are attached in the side chain of polymethacrylate (PMA) and polyvinylalcohol (PVA) backbones. The LB films, where the polymer backbone is polymethacrylate were characterized by pressure-area isotherms, polarized UV-visible spectra and second harmonic generation measurements. The NLO moieties in the side chain are inclined to the plane of the substrate at a shallow angle. The second order nonlinear coefficient and molecular hyperpolarizability were also calculated.

A relaxation study of poled nonlinear optical polymers by infrared reflection-absorption spectroscopy

Abstract The relaxation of poled nonlinear optical (NLO) chromophores in polymer films was characterized by infrared (i.r.) reflection-absorption spectroscopy. Both a guest-host system and a photocrosslinkable polymer system were investigated. Polymethylmethacrylate doped with either 2-methyl-4-nitroaniline or 4(4′-nitrophenylazo)aniline was studied. The photocrosslinkable polymer system, polyvinylcinnamate doped with 3-cinnamoyloxy-4-[4-(N,N-diethylamino)-2-cinnamoyloxy phenyl azo]nitrobenzene was also investigated. Doped NLO active molecules were aligned using the corona poling technique. i.r. spectra as a function of time were used to monitor the relaxation behavior of the oriented dyes after poling. Relaxation of NLO molecules was followed at various characteristic vibrational frequencies. The relaxation behavior of both systems were found to be consistent with those studied by the second harmonic generation technique.

Photocross-Linked Second Order Nonlinear Optical Polymers

We report a novel method to obtain stable second order nonlinear optical (NLO) properties in polymeric thin films. Photocross-linking between the NLO active molecules and a photoreactive polymer is achieved by UV irradiation subsequent to poling. The thin film exhibits a nonlinear coefficient d 33 of 16.5 pm/V at a doping level of 20% by weight of NLO active molecules and possesses quite stable second order nonlinear optical properties

Stable second-order optical non-linearity in novel photocrosslinkable polymers

Optical characterization of novel photocrosslinkable second-order nonlinear optical (NLO) polymers are presented. These polymer systems have been designed with nonlinear optical moieties in the polymer main chain. When poled and sufficiently photocrosslinked these polymers exhibit relatively stable second-order optical nonlinearity at room temperature. The linear optical and second-order NLO properties of these recently synthesized polymers have been investigated. Second harmonic generation (SHG) was utilized to monitor the temporal stability of the nonlinearity. The linear electro-optic coefficients were measured with a modified Michelson interferometer. 1.