From long haul, metro access and intersystem links the trend goes to applying optical interconnection technology at increasingly shorter distances. Intrasystem interconnects such as data busses between microprocessors and memory blocks are still based on copper interconnects today. This causes a bottleneck in computer systems since the achievable bandwidth of electrical interconnects is limited through the underlying physical properties. Approaches to solve this problem by embedding optical multimode polymer waveguides into the board (electro-optical circuit board technology, EOCB) have been reported earlier. The principle feasibility of optical interconnection technology in chip-to-chip applications has been validated in a number of projects. For reasons of cost considerations waveguides with large cross sections are used in order to relax alignment requirements and to allow automatic placement and assembly without any active alignment of components necessary. On the other hand the bandwidth of these highly multimodal waveguides is restricted due to mode dispersion. The advance of WDM technology towards intrasystem applications will provide sufficiently high bandwidth which is required for future high-performance computer systems: Assuming that, for example, 8 wavelength-channels with 12Gbps (SDR1) each are given, then optical on-board interconnects with data rates a magnitude higher than the data rates of electrical interconnects for distances typically found at today's computer boards and backplanes can be realized. The data rate will be twice as much, if DDR2 technology is considered towards the optical signals as well. In this paper we discuss an approach for a hybrid integrated optoelectronic WDM package which might enable the application of WDM technology to EOCB.
Since the first observation of the photorefractive (PR) effect in polymers, extensive efforts have been directed toward understanding the physics of the PR process in these systems, as well as optimizing polymer composites and glasses for various applications. Despite remarkable progress both in elucidating the mechanisms and processes contributing to the PR effect and in designing organic materials with high gain and diffraction efficiency, simultaneously attaining high refractive index modulation, fast dynamics, and good thermal properties in one material remains a challenge. Monolithic glasses represent an attractive class of PR organic materials since they possess large nonlinearities and minimal inert volume, which enhances the performance without stability problems. In this paper, we present a complete study of monolithic glasses based on a promising new class of chromophores (containing 2-dicyanomethylen-3-cyano-5,5-dimethyl-2,5-dihydrofuran, abbreviated as DCDHF-derivatives). We describe thermal, photoconductive, orientational, and photorefractive properties of these materials in both red and near infrared wavelength regions. By studying the temperature dependence of various parameters, we analyze the factors that affect photorefractivity in DCDHF-based materials.
Derivatives of 2-dicyanomethylen-3-cyano-2,5-dihydrofuran (DCDHF) have been synthesized by different methods to be used as photorefractive (PR) chromophores. Structure modifications were performed on the donor, acceptor and conjugated π-system for improving properties such as glass formation. Structure-property relationships important for PR applications are discussed from the results of studies including UV-Vis, electrochemistry and DSC.
We seek to improve the performance of organic photorefractive (OPR) systems by implementing two different design philosophies. In one strategy polysiloxane-based charge transport polymers are used to explore the requirement of a low glass transition temperature. These polymers allow construction of low Tg composites without plasticizcer and additionally may have higher charge mobility than poly(n-vinyl carbazole).The other strategy entails the use of small-molecule organic glasses composed of covalently attached charge transport and non-linrar optical chromophore moieties. Both classes of materials are characterized by holographic, photoconductive, and ellipsometric methods.
The realization of all-optical switching schemes is mostly hindered by the lack of suitable materials with a refractive index change that is large and fast enough. The characterization of the linear and nonlinear optical properties of potential materials is therefore of prime importance. Various characterization methods have been proposed and are employed, yielding different parameters of the nonlinear optical response at the involved laser frequencies. However, in most techniques the resulting nonlinearities are measured only at one point in the spectral dispersion. To generate the whole nonlinear spectra, the laser source has to be tuned over the desired wavelength range and consecutive measurements have to be taken. We propose and demonstrate here a novel technique to measure the nonlinear optical response for a broad wavelength region in a pump-probe scheme that requires no laser tuning. In order to detect the two-photon absorption at several wavelengths simultaneously, we use a white-light-continuum as the probe beam. As the pump beam is held constant, the Kramers-Kroenig transformation can be used to calculate the dispersion of the nonlinear refractive index from the two-photon spectra. By delaying the probe beam relative to the pump beam, the temporal behavior of the nonlinearity can be obtained.
Photorefractive polymers have recently shown an attractive combination of high two-beam-coupling gain coefficient (approximately equals 200cm-1), low absorption (approximately equals 5-10 cm-1), and fast response (few ms) at 1W/cm2 writing intensity. Such materials show promise as adaptive beamsplitters for homodyne detection of transient phase shifts due to laser-based ultrasound. The performance of a photorefractive polymer composite is explored for this application.
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