Vincent Ricci

Comparative study of nonlinear-optical polymers for guided-wave second-harmonic generation at telecommunication wavelengths

We report on the linear and nonlinear-optical properties of 4-dimethylamino-4′-nitrostilbene (DANS), 4-diethylamino-1-nitrobenzyl (DANB), and 4-[N-ethyl-N-(2-hydroxyethyl)]amino-4′-nitroazobenzene) (Disperse Red 1;DR1) side chain polymers whose second-harmonic generation at the telecommunication wavelength of 1.55 μm was investigated. Measured ultraviolet–visible–near-infrared spectra were analyzed with an inhomogeneously broadened line-shape model, in particular, in the long-wavelength tail of the electronic transitions, which determines the absorption loss at the second-harmonic wavelength. The nonlinear-optical coefficients were measured at different poling temperatures and poling fields by the Maker fringe technique. On the basis of the measured material parameters we calculated the normalized conversion efficiencies for guided-wave second-harmonic generation at 1.55 μm. The DR1 polymer exhibited the best nonlinearity–absorption trade-off, with a calculated normalized conversion efficiency of several hundred percent per watt, whereas the figures of merit for DANS and DANB are lower and comparable with each other.

Importance of chromophore environment on the near-infrared absorption of polymeric waveguides

The near-infrared absorption of two chromophore functionalized polymers and combinations of seventeen different guest chromophores in seven different organic polymer matrices were investigated to assess the effect of chromophore structure and environment on absorption. The near-infrared absorption losses were found to be dramatically larger by as much as 2-3 orders of magnitude in polymer matrices than in solution. Furthermore, the absorption of the long-wavelength tail appears to be related to the glass transition temperature of the polymer matrix that contains the chromophore. These results are interpreted in terms of inhomogeneous broadening.

Second-order susceptibility of Ga 0.5 In 0.5 P crystals at 1.5 µm and their feasibility for waveguide quasi-phase matching

The second-order susceptibilities (dij) of both ordered and disordered Ga0.5In0.5P semiconductor crystal films epitaxially grown on GaAs substrates are analyzed. Quasi-phase matching based on periodic order–disorder regions is proposed, and the analysis shows that three of the four independent coefficients, namely, d33′,d31′, and d15′, but not d14′, can be modulated. Maker-fringe experiments were performed at 1.57 µm to measure these coefficients in the deposited crystals. However, the crystal-film orientation allowed a definitive determination of the d14′ coefficient (110 pm/V) only and an upper limit of 60 pm/V for d33′. More-sophisticated experimental techniques are proposed for measuring d33′.

Poling of multilayer polymer films for modal dispersion phase matching of second-harmonic generation: effects of glass-transition temperature matching in different layers

The efficiency of multilayered poled polymer devices for parametric mixing depends critically on the creation of large electric fields in the nonlinear layer containing chromophores with large hyperpolarizabilities. The effect of changing the relative glass-transition temperatures of the polymer films constituting a four-layer waveguide has been investigated. An increase in the nonlinearity by a factor of 3.6, as measured by Maker fringes, has been found between an optimized and a nonoptimized combination. Correlation between the poling current density and the propagation losses has also been identified.

Relative electrical resistivities and poling of nonlinear optical polymeric waveguides

A method based on Maker fringe measurements of nonlinear optical coefficients has been used to determine the relative dc electrical resistivities of a series of linear and nonlinear optical polymers. The method can be used to identify low resistivity linear cladding materials for optimized electric field poling of nonlinear optical polymeric waveguides. As an example of the application of the technique we have studied the resistivity of poly(methyl methacrylate)-polystyrene (PMMA-PS) copolymers with varying content of the two components. The resistivity of PMMA was found to be one order of magnitude lower than that of PS.

Second-harmonic generation in reactive-ion etched N′ ethyl N-ethanol-4-(nitrophenylazo)phenylamino polymer waveguides at telecommunication wavelengths

Second-harmonic generation using modal dispersion phase matching has been demonstrated in reactive-ion etched waveguides based on the organic nonlinear polymer poly (methyl methacrylate)-Disperse Red 1 [N′ ethyl N-ethanol-4-(nitrophenylazo)phenylamino]. The measured propagation losses were 6 dB/cm at the fundamental and 10 dB/cm at the second-harmonic wavelength, dramatically less than we obtained previously for the harmonic in photobleached waveguides. A figure of merit of η=0.1%/W for second-harmonic generation was obtained with a modest nonlinearity of 3 pm/V at 1607 nm in a 2 mm long waveguide.

Disperse Red 1-doped solgel planar waveguides for nonlinear optical devices operating at telecommunications wavelengths

We report on linear and nonlinear optical properties of Disperse Red 1-doped solgel waveguides. The refractive-index and optical-propagation losses of the guiding layer were measured between 0.756 µm and 1.64 µm. The spectral broadening of the chromophore charge-transfer transition in the visible is modeled with a Voigt-profile function. In the telecommunications window the attenuation is dominated by the overtones of the O—H bonds vibration bands. The nonlinear optical coefficients were measured at different poling strengths with the Maker-fringe method. The nonlinear coefficient d33 was found to be 4.5 pm V-1 at 1.58 µm for a poling field of 60 V µm-1.

Low loss polymer waveguides fabricated by plasma etching for nonlinear-optical devices operating at telecommunication wavelengths

Summary form only given. Organic materials exhibit large optical nonlinearities and, hence, are attractive for parametric interactions, cascading, and wavelength demultiplexing. In poled polymer waveguides figures of merit comparable to inorganic materials were obtained for second-harmonic generation (SHG) at 1.55 /spl mu/m. However, the absolute conversion efficiency was limited by the high loss of several tens of dBcm/sup -1/ at the second-harmonic wavelength. To reduce the loss of polymer waveguides used for second-order nonlinear effects at telecommunication wavelength is, materials with low intrinsic absorption between 0.6 and 1.6 /spl mu/m have to be combined with techniques allowing one to form waveguides with low scattering losses.

Polymers for telecommunication devices based on /spl chi//sup 2/:/spl chi//sup 2/-cascading

Summary form only given. We envision using polymers in cascading (/spl chi//sup (2)/:/spl chi//sup (2)/) based optical processes at telecommunication wavelengths. The key figure of merit is usually [/spl chi//sup (2)/(2/spl omega/)//spl alpha/(2/spl omega/)] where /spl chi//sup (2)/(2/spl omega/) is the second order nonlinearity /spl alpha/(2/spl omega/) is the harmonic loss coefficient. Chromophore doped, poled polymers such as DANS (4-dimethylamino-4/-nitrostilbene), developed originally for electro-optic applications at 1320 nm, have exhibited larger nonlinearities than LiNbO/sub 3/, but also much higher losses at 2/spl omega/. Here we report on systematic studies of the figure of merit [/spl chi//sup (2)/(2/spl omega/)//spl alpha/(2/spl omega/)] for a series of chromophores in a guest-host system normalized to weight percents of nominally 10%.

Polymer waveguides for second-order nonlinear-optical effects at telecommunication wavelengths

Organic materials exhibit large optical nonlinearities and, hence, are attractive for parametric interactions [1].