The interest in terahertz photometric and imaging measurements has motivated the development of bandpass resonant filters to be coupled to multiple-pixel devices such as bolometer arrays. Resonant grids are relatively simple to fabricate, exhibiting high transmission at the central frequency, a narrow bandpass, and good rejection of the side frequencies of the spectrum. We have fabricated filters centered at different frequencies between 0.4 and 10 THz, using photolithography and electroforming techniques. Transmission measurements have shown center frequencies and bandwidths close to the design predictions. The performance of the filters was found not to be critically dependent on small physical deformations in the mesh, becoming more noticeable at higher frequencies (i.e., for smaller physical sizes). Wider bandwidths, needed to attain higher sensitivities in the continuum, were obtained by changing the design parameters for filters at 2 and 3 THz.

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The solar submillimeter-wave telescope (SST) is the only one of its kind dedicated to solar continuous observations. Two radiometers at 0.740 mm (405 GHz), and four at 1.415 mm (212 GHz) are placed in the Cassegrain focal plane of the 1.5-m dish at El Leoncito high altitude site, San Juan, Argentina. The aperture efficiencies are close to design predictions: 20% and 35% for 2 and 4 arcminutes beam sizes at 405 and 212 GHz, respectively. The positioner absolute pointing accuracy is 10 arcseconds. Spectral coverage is complemented by ground-based mid-infrared telescopes developed for high cadence observations in the continuum 10 micron band (30 THz), using small apertures and roomtemperature microbolometer cameras. Using the system, a new solar burst spectral component was discovered, exhibiting fluxes increasing for smaller wavelengths, separated from the well known microwave component. Rapid subsecond pulsations are common for all bursts. The pulsations onset times of appear to be connected to the launch times of CMEs. Active regions are brighter for shorter submillimeter-waves. Mid-IR bright regions are found closely associated with calcium plages and magnetic structures near the solar photosphere. Intense and rapid 10 micron brightening was detected on active centers in association with weak flares. These results raise challenging difficulties for interpretation

We have measured the temperature dependence of the energy ͓E 0 (T)͔ and broadening parameter ͓⌫ 0 (T)͔ of the fundamental gap for GaSb and four samples of Ga 1Ϫx In x As y Sb 1Ϫy ͑lattice matched to GaSb͒ using infrared photoreflectance. The parameters that describe the temperature variation of the energy ͑including thermalexpansion effects͒ were evaluated using both the semiempirical Vashni relation as well as an equation that incorporates the Bose-Einstein occupation factor. The behavior of ⌫ 0 (T) was described by a Bose-Einsteintype equation.

Chemical and electrochemical synthesis techniques have been the principal methods of obtaining polymers in industry and scientific research laboratories. However, during the last two decades, photochemical synthesis, although poorly studied, has been reported to present several advantages, in that it is a fast and cheap technique, and it is not aggressive to the environment. The technique has been applied to the production of some conducting polymers. In this study, semiconducting polymeric blends composed of PT3AA-K-PVDF and PT3MA-PVDF were respectively obtained by photochemical polymerization in aqueous solutions of 3-thiophene acetic acid and 3-thiophene methyl acetate monomers using PVDF microporous matrices and potassium dichromate as catalyst. The percentage of products and by-products incorporated in the host matrix was obtained by gravimetric analysis. The chemical structures of the polymers synthesized were analyzed by FTIR, UV-vis and 1 H NMR. GPC analysis indicated the formation of oligomers composed of 5-6 mers. The morphology of the matrices and polymeric blends was observed by SEM-EDS and their electric behavior evaluated by measures of electric conductivity. The SEM images show the presence of polythiophene in the pores of the PVDF microporous membrane. The thermal properties of the polymers and their blends were evaluated by DSC and TGA. Thermal analysis by DSC demonstrated an increase in melting temperature of the blends, attributed to the confinement of PVDF crystalline phases for the polymer photosynthesized. The results of volumetric conductivity measurements of polymeric blends show an increase in conductivity in the matrices from 10 À15 to 10 À11 S cm À1 .