The performance of the AT&T single mode ST® connector and its latest enhanced features

The AT&T single mode ST® connector is a low-loss, low-reflection connector suitable for high-speed, wideband digital transmission. This new connector offers enhanced hardware for easier use and more stable connections. In addition, a new backplane-compatible version is introduced for circuit board applications. The insertion loss of AT&T's single mode ST connector averages 0.34 dB with a standard deviation of 0.28. The reflection of an AT&T ST connection (product against product) averages -42.8 dB with a worst case of -34.1 dB. The environmental performance of the connector is characterized by low variations in loss and refection. The AT&T single mode ST connector and its backplane version were subjected to a battery of tests whose results are discussed in this article.     

Pyrene-terminated phenylenethynylene rigid linkers anchored to metal oxide nanoparticles

Phenylenethynylene (PE) rigid linkers (para and meta) were used to anchor pyrene to the surface of TiO2 (anatase) and ZrO2 nanoparticle thin films through the two COOH groups of an isophthalic acid (Ipa) unit. Four chromophore-linker models were studied in solution and bound. Two are novel meta-pyrene-PE linker systems: dimethyl 5-(3-(1-pyrenylethynyl)phenylethynyl)-isophthalate, carrying one pyrene, and dimethyl 5-(bis-3,5-(1-pyrenylethynyl)phenylethynyl)-isophthalate, carrying two. These were compared with para rigid-rods dimethyl 5-(1-pyrenylethynyl)isophthalate and dimethyl 5-(4-(1-pyrenylethynyl)phenylethynyl)-isophthalate, each carrying one pyrene but varying in length. The length of the PE linkers and the para or meta substitution influence the photophysical properties of the compounds. The extinction coefficient increased, and the long wavelength absorbance of the pyrene chromophore was shifted to the red with increasing conjugation. Compared to unsubstituted pyrene, the pyrene-linker systems were characterized by short fluorescence lifetimes (tau approximately 2 ns in tetrahydrofuran solutions), but quantum yields were close to unity. ZINDO/S CI calculations attribute this effect to a switching in the order of the two lowest-lying singlet states of pyrene. High surface coverages, approximately 10(-8) mol/cm2, and carboxylate binding modes on nanostructured TiO2 films were obtained in all cases. The appearance of a pyrene excimer emission on ZrO2, an insulator, indicates that the pyrene-linker system is closely packed (Py-Py < 4 A) on the surface. The fluorescence emission on TiO2 was completely quenched, consistent with quantitative and rapid electron injection into the semiconductor indicating that the pyrene excimer acts as a sensitizer. Photoelectrochemical studies in regenerative solar cells with I3-/I- as the redox mediator indicated near-quantitative conversion of absorbed photons into an electrical current.     

Enhanced nucleation, smoothness and conformality of ultrananocrystalline diamond (UNCD) ultrathin films via tungsten interlayers

Extremely smooth (6 nm RMS roughness over 4 μm²), thin (100 nm), and continuous ultrananocrystalline diamond (UNCD) films were synthesized by microwave plasma chemical vapor deposition using a 10 nm tungsten (W) interlayer between the silicon substrate and the diamond film. These UNCD films possess a high content of sp³-bonded carbon. The W interlayer significantly increased the initial diamond nucleation density, thereby lowering the surface roughness, eliminating interfacial voids, and allowing thinner UNCD films to be grown. This structural optimization enhances the films’ properties and enables its integration with a wide variety of substrate materials.