Rise time

About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.

Time-walk-compensated SPAD: multiple-photon versus single-photon operation

Abstract: The SPAD has proven already its capability of timing single- photon events with picosecond accuracy; it does that also for multi-photon events, but introduces here a time walk effect: with received energies of 1000 photons and more, the measured epoch time is shifted 200 ps or more towards earlier times; although the specific SPAD type used shows the lowest time walk effect of all measured silicon avalanche diodes, this effect still might introduce range errors of up to 30 mm, when measuring distances to satellites. It has been shown that this time walk effect is connected with a very small change of the avalanche rise time; this effect has been successfully used to develop an electronic circuit which measures this rise time difference, and uses it to compensate automatically almost all of the time walk effect. Some prototypes have been built and tested successfully in the satellite laser ranging station Graz; improved versions of the circuit are operated or tested now successfully in other SLR stations. It has been shown that the time walk effect can be reduced to more or less zero, for a dynamical range from single photon up to more than 1000 photons. For best time walk compensation, the circuit is adjusted for a specific laser pulse length; it has been shown however, that this adjustment also gives good time walk compensation for other laser pulse lengths.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The electrical breakdown in vacuum

Abstract: Experiments have been performed in order to get information about the phenomena preceding the electrical breakdown in small vacuum gaps. Most experiments have been made with impulse voltages of different rise times; some complementary results obtained with alternating voltage are also presented. The effect of surface layers on the breakdown voltage and on the pre-breakdown current is discussed. It has been found that the rise time of the voltage affects both the breakdown voltage and the pre-breakdown current. The experiments seem to indicate that breakdown in the underlying circumstances is the result of a discharge in metal vapour, originating from the anode. The vapour is thought to be generated by the heating of the anode by a bombardment of field-emission electrons. The transition of the pre-breakdown current to a sudden discharge may occur when the vapour density passes a critical value.

Truly balanced step recovery diode pulse generator with single power supply

Abstract: A space efficient and simple circuit for ultra wideband (UWB) balanced pulse generation is presented. The pulse generator uses a single step recovery diode to provide a truly balanced output. The diode biasing is integrated with the switching circuitry to improve the compactness of the design. Two versions of the circuit with lumped and distributed pulse forming networks have been tested. The pulse parameters for distributed pulse shaping network were: rise/fall time (10-90%) 183 ps, pulse width (50-50%) 340 ps, pulse peak to peak voltage 896 mV (12.05 dBm peak power) and for the lumped case: rise time (10-90%) 272 ps, fall time (90-10%) 566 ps pulse width (50-50%) 511 ps, pulse amplitude /spl plusmn/1.6V (17 dBm peak power). In both cases excellent balance of the two pulses at the output ports can be observed. It should be noted that above parameters were obtained with typical inexpensive RF components. The circuit reduces the complexity of the design because of the lack of broadband baluns required for UWB balanced antennas. The circuit may be used as part of a UWB transmitter.

Design and fabrication of a broadband polymer vertically coupled optical switch

Abstract: This paper presents a detailed design and fabrication of a composite broadband polymer vertically coupled optical switch with a spectral extinction ratio variation less than 1 dB for the cross state and 2.5 dB for the bar state. This switch consists of two pairs of basic three-dimensional (3-D) polymer switches with peak coupling wavelengths located at the two ends of the C-band, respectively. The resultant extinction ratio is shown to be the sum of the individual ratios of the two basic switches that the optical signal propagates through. The rise time and fall time of switching are 1.0 and 1.5 ms, respectively, and the total electric power applied to the electrode heater is about 140 mW.

On the picosecond switching of a high-density current (60 kA/cm2) via a Si closing switch based on a superfast ionization front

Abstract: A silicon closing switch with successive breakdown mode of diode structures based on a superfast ionization front is studied. In a coaxial line with a 48-Ω wave impedance, pulses with an amplitude above 100 kV and a rise time of 40 ps at an amplitude level of 0.3–0.9 are obtained. The maximum output-voltage rise rate is 2 MV/ns at a switching-current peak density of 60 kA/cm2. Numerical simulation shows that the switching time of individual structures of the device is 7–15 ps at a reverse-voltage rise rate of >100 kV/ns per structure under experimental conditions. The electric field in the p-n junction reaches the Zener breakdown threshold (∼106 V/cm) even in the case where the diode structure contains process-induced deep-level centers with concentrations of up to 1013 cm−3.