Planar waveguide-based silica-polymer hybrid variable optical attenuator and its associated polymers.

We have proposed a silica-polymer hybrid variable optical attenuator that we made by creating two trenches along the core of a straight silica planar waveguide and filling the trenches with a polymer. The polymer, which had a superhigh thermo-optic coefficient, was specially designed and developed in this study to lower the power consumption of the device. We achieved a maximum attenuation of -29 dB for the device by changing the polymer's temperature by only 7 degrees C. The device has a very low power consumption at 2-3 mW/channel, making it a good candidate for integration with arrayed waveguide gratings.

Pattern recognition with generalized centroids and subcentroids.

We propose a class of generalized moment functions (GMFs) that can be used to determine a set of geometric points, namely, generalized centroids (G centroids), within an object. Based on a linear GMF, a mass centroid and its subcentroids can be defined and extracted, which provide information on the location and orientation of an object. Similar to traditional moment functions, GMFs can also be used to describe the global shape of an object, including symmetry and fullness. However, GMFs, along with G centroids and subcentroids, can further serve to construct a feature vector of an object, which is critical for image registration and invariant pattern recognition. One can extract more distinguishing features from the same object by changing the combination of GMFs. We present results that show simulations of pattern recognition from uniform backgrounds.

Volume relaxation in polymers and its effect on waveguide applications.

Volume relaxation in polymers and the effect intrinsic to glassy polymers can significantly affect their refractive index over time. Its beta rate has been found to be related only to relaxation temperature T and the glass transition temperature of the polymer Tg and not to the polymeric chemical structure. Universal values of beta have been obtained for polymers and were used to predict the minimum index change related to volume in polymers. The index change is in the range from 7.86 x 10(-5) to 5.26 x 10(-4) when the Tg - T value of polymers is between 90 and 350 degrees C. These volume-relaxation-induced changes can cause serious deterioration or even failure in corresponding polymer waveguide devices, such as arrayed waveguide gratings and variable optical attenuators, when the Tg of a polymer is not sufficiently high. A minimum requirement is therefore suggested for the Tg of polymers used to fabricate waveguide devices.

Piezoelectric bimorph optical-fiber sensor.

We propose and demonstrate a novel high-voltage optical-fiber sensor. This sensor consists of an emitting fiber, a receiving fiber, and a piezoelectric bimorph transducer. The emitting fiber is fixed in a base, whereas the receiving fiber is mounted on the free end of the piezoelectric bimorph transducer. When a voltage is applied to the piezoelectric bimorph transducer, its free end is displaced over a distance delta. The displacement induces a loss in the optical coupling between the emitting and the receiving fiber. The voltage can be measured by monitoring the coupling loss.

Multilabeling biomolecules at a single site. 1. Synthesis and characterization of a dendritic label for electrochemiluminescence assays.

Ultrasensitive bioanalytical assays are of great value for early detection of human diseases and pathogens. The sensitivities of immunoassays and DNA probing can be enhanced by multilabeling the biorecognition partner used for affinity-based assays. However, the bioreactivity of biomolecules is affected by a high degree of multilabeling at multiple functional sites. It is proposed that dendritic scaffoldings be used to link multiple signal-generating units to a single site with potentially minimum impact on the bioaffinity. A prototype label, a zeroth-generation dendron, bearing three [Ru(bpy)(3)](2+) units for electrochemiluminescence (ECL) assays was synthesized and characterized preliminarily by spectroscopic, electrochemical, and ECL methods. No evidence of interaction between the neighboring [Ru(bpy)(3)](2+) units in the label molecule was found from these characterizations. Both the photoluminescence and ECL of the prototype label have features very similar to those of mononuclear [Ru(bpy)(3)](2+) compounds. Labeling a model protein with a triad of [Ru(bpy)(3)](2+) at one NH(2) position was demonstrated. The results reported here provide support to applying the proposed multilabeling strategy to affinity-based bioanalytical assays.

Relative measurements of second-order susceptibility with reflective second-harmonic generation.

There is a strong demand for a simple and reliable technique for second-order susceptibility measurements of thin films. Since the Maker fringe technique is limited to transparent substrates we propose an experimental protocol based on reflective second-harmonic generation (SHG). The proposed protocol is based on relative measurements of Z-cut quartz. An analytical expression of the reflective SHG intensity dependence of the polarizer, analyzer, and sample azimuth is presented. An error analysis is also presented. Thin organic film of the side-chain polymer poly(Disperse Red 1 Methacrylate-Co-Methyl-Methacrylate) is investigated. Results for different wavelengths are reported.

Visualization of phase objects by use of a differentiation filter.

For the visualization of phase objects by use of a differentiation filter, the phase variation is changed into the intensity variation by differentiation, and then the differentiated image is integrated. In the method used in practice, the differentiated image has been recorded on a film, and then integrated by use of a filter. In this paper, however, the image differentiated by means of a filter is entered into a computer using a CCD camera and then integrated. As a result, the method provides rapid on-line processing. We have performed computer simulations and a detailed analysis of the differentiation filter and also provide the experimental results of three-dimensional image visualization.