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Detection of picosecond laser pulses with nanosecond time resolution by use of Analog-to Digital Converters

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  • 530 Physik


Optical and Quantum Electronics 14 (1982) 67-71 Detection of picosecond laser pulses with nanosecond time resolution by use of analogue-to-digital converters G. NIBLER, A. PENZKOFER, W. BLAU Naturwissenschaftliche Fakultät II - Physik, Universität Regensburg, 8400 Regensburg, Federal Republic of Germany Received 10 August 1981; revised 11 September 1981 A photodetector-analogue-to-digital converter system with 1.8 ns rise and decay time is described. The photodetector waveform is fanned-out with power splitters and sampled with high-speed analogue-to- digital converters. The system is used to detect picosecond light pulses from a mode-locked Nd-glass laser with nanosecond time resolution. 1. Introduction The detection of light signals with nanosecond and subnanosecond resolution is generally performed with fast photodetectors and high-speed oscillo- scopes or transient digitizers (for a review, see [1]). Here we describe the use of high-speed analogue-to-digital converters (ADCs) to register photodetector waveforms with nanosecond time resolution. The input waveform is fanned-out to 16 equal signals using power splitters. The signals are time delayed by fixed increments with coaxial cables (50 £2 impedance) of increasing length. They are inputted to 16 synchronously gated channels of two ADC Camac modules. The delayed waveforms are shifted across the closing gate window. The ADCs accumulate the input signals within the time gate. The contents of the channels are read out by a computer. The differ- .ences of counts between adjacent channels repre- sent the time-resolved waveform (differentiation of integrated signal). The system is inexpensive compared with other computerized waveform digitizers with nano- second time resolution. Up to 11 ADC waveform detection units may be installed in one Camac crate and operated by one minicomputer. The system is applicable to time-resolved detection of nanosecond signals. Subnanosecond signals are broadened to

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