No abstract

Improving the temporal resolution of single photon detectors has an impact on many applications 1 , such as increased data rates and transmission distances for both classical 2 and quantum 3-5 optical communication systems, higher spatial resolution in laser ranging and observation of shorter-lived fluorophores in biomedical imaging 6 . In recent years, superconducting nanowire single-photon detectors 7,8 (SNSPDs) have emerged as the highest efficiency time-resolving single-photon counting detectors available in the near infrared 9 . As the detection mechanism in SNSPDs occurs on picosecond time scales 10 , SNSPDs have been demonstrated with exquisite temporal resolution below 15 ps [11][12][13][14][15] . We reduce this value to 2.7±0.2 ps at 400 nm and 4.6±0.2 ps at 1550 nm, using a specialized niobium nitride (NbN) SNSPD. The observed photon-energy dependence of the temporal resolution and detection latency suggests that intrinsic effects make a significant contribution.Temporal resolution in SNSPDs, commonly referred to as jitter, is characterized by the width of the temporal distribution of signal outputs with respect to the photon arrival times. This statistical distribution is known as the instrument response function (IRF), and its width is commonly evaluated as

Electrical communication between the flavin adenine dinucleotlde redox centers of glucose oxidase and a conventional carbon paste electrode has been achieved by using electron-transfer relay systems based on polyslloxanes. Six materials for amperometric biosensors are described In which ferrocene and dlmethylferrocene electron relays are covalently attached to Insoluble slloxane polymers. Sensors containing these polymeric relay systems and glucose oxidase respond rapidly to glucose, with steady-state current responses achieved In less than 10 s. The response to glucose under N2 saturation shows apparent Michaells-Menten constants, *VPP, In the range 16-71 mM and limiting current densities, ymax, of 29-275 µ /cm2. The dependence of the sensor response on the nature of the slloxane polymer and the type of polymer-bound relay Is discussed.

No abstract

defined by the remaining five ring atoms. In 2 the corresponding displacement is 0.62 A. This type of distortion is attributed to the presence of the transannular ferrocenyl unit."The coordination of the lithium atom to N(3) in the solid state is consistent with a significant amount of the negative charge in 3 residing on the skeletal nitrogen atoms adjacent to P(3). Interestingly, the N M R spectra for 3 (see above) show that N(3) and N(2) are equivalent, which indicates that the lithium ion either dissociates from N(3) or fluctuates rapidly between N(3) and N(2) in solution at room temperature. These possibilities, together with the reactivity and mechanism of formation of 3, are under investigation.Acknowledgment. W e thank the U.S. Army Research Office for financial support.Supplementary Material Available: An ORTEP drawing of 3 and tables of positional and displacement parameters and bond distances and angles (1 3 pages). Ordering information is given on any current masthead page.

To assess the suitability of bismuth germanate as an electro-optic material for high precision applications, we have confirmed and extended previous data on its refractive index, electro-optic tensor element r(41), and thermal expansion coefficient. In addition, we have measured the thermo-optic coefficient dn/dT, the temperature dependence of the electro-optic coefficient, and the stress-optic tensor elements. From the stress-optic tensor elements and previously published data, we have computed the strain-optic tensor elements. The index of refraction is given, to a good approximation, by the single-term Sellmeier equation, n(2) - 1 = S(0)λ(0)(2)/[1 - (λ(0)/λ)(2)], with S(0) = 95.608 µm(-2) and λ(0) = 0.1807 µm. The thermo-optic coefficient is 3.9 × 10(-5)/°C at 632.8 nm and 3.5 × 10(-5)/°C at 1152.3 nm. The electro-optic tensor element varies between approximately 1.05 and 1.11 pm/V over the spectral range of 550-1000 nm; its normalized effective change with temperature is approximately 1.54 × 10(-4)/°C. The thermal expansion coefficient is 6.3 × 10(-6)/°C over the range 15-125 °C. Values of the stress-optic tensor elements are q(11) - q(12) = -2.995 × 10(-13) m(2)/N and q(44) = -0.1365 × 10(-12) m(2)/N. The strain-optic tensor elements are p(11) - p(12) = -0.0266 and p(44) = -0.0595.

No abstract

No abstract