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Superconducting transition edge bolometers on micromachined silicon membranes have been fabricated. The optical response is 580 V/W at a time constant of 0.4 ms. The detectivity D* is 3.8×109 (cm Hz1/2 W−1) at a temperature of 84.5 K and within the frequency regime 100<f<300 Hz. This is one of the fastest composite type bolometers ever reported. Upon thermal optimization, this type of detector should be competitive with state-of-the-art quantum detectors.

One-photon ionization by a pulsed VUV laser has been employed to probe infrared multiphoton excitation and dissociation (IR-MPE/D) dynamics in real time, in situ, and collision free during excitation by a CO2− laser pulse. In this first experiment acetic anhydride has been used as the parent molecule to demonstrate the feasibility and to study properties of the method. Using the 118.4 nm radiation from a VUV laser as source for photoionization, ions have been observed mass selectively with time resolution in the nanosecond range, determined by the laser pulse duration. By following production and decay rates of ions, the time dependence of the excitation and decay of parent molecules, and the evolution of neutral intermediates in primary and sequential steps could be observed, from which detailed information on excitation and dissociation pathways was deduced.

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The bolometric performance of a high-Tc transition edge bolometer has been evaluated within the temperature range 80 K<T<300 K. The detectivity D* of the device is peaking at transition midpoint and remains at moderate levels up to room temperature. The bolometric time constant of the device increases from 0.33 ms at transition midpoint to 1.55 ms at ambient temperature. The noise pattern displays 1/f  behavior at low frequency and is scaling with bias current and the thermal resistance coefficient β of the superconducting film.

Silicon represents the material of choice for fast superconducting high quality transition edge bolometers. The performance of these devices sensitively depends on their thermal properties where the heat flux critically affects time constant, optical response and noise behavior. In this work extensive numerical Finite Elementcalculations have been performed for various bolometer configurations, using the ABAQUS-code. A high degree of t h e r m a l i s o l a t i o n c a n b e e s t a b l i s h e d t h r o u g h microstructuring techniques. The bolometric performance of a prototype device is compared with the simulated data.Values of the detectivity D* as high as 1~1 0 '~ cm HzH W 1 already should be feasible, while a time constant in the regime below 10 ms would be retained.degree of thermal isolation of the device from the heat sink [l]. Technologically, this is achieved through a very thin membrane type silicon substrate, where the heat flux is reduced, for example, through a microstructured meandering configuration. The high-T, superconductor-silicon system, however, poses a number of technological challenges, particularly in connection with the required multilayer system. It consists of a silicon membrane substrate, a dielectric lattice matched buffer layer, the thin superconducting film, an additional passivation layer and, finally, an optical absorber film on top of the structure. Critical design parameters are illustrated in eqn 1, where the bolometric response So is shown as a function of the temperature increase AT from the incoming radiation, the optical absorptance q, the bias current i, the resistive temperature coefficient p of the superconducting film, and its resistance r.

Effects of substrate temperature on structural properties of undoped silicon thin films