CONSIDERATIONS IN MEASURING TRANSIENT LASER PULSES.

One method of extracting information from pulsed laser events is to use oscilloscopes and waveform digitizers. If the process provides a means of converting this information into digital data as well then a transform can be applied to provide frequency versus amplitude information. High-speed repetitive waveforms usually make the job of capturing and storing desired signals much easier. Many other types of signals, however, including single transient events such as those occurring during laser pulsing, are more demanding of measurement instruments. In such cases, instrumentation must perform signal reconstruction in real time from an individual waveform. The problem becomes especially difficult at analog bandwidths at more than 100 megahertz. The two most popular 'fast' techniques used today to convert analog to digital images are called 'flash conversion,' and 'scan conversion. ' Because of basic design limitations, current flash-conversion methods begin to degrade at frequencies above 250 MHz. Instruments that use scan conversion, however, have operated successfully with signals as fast as 6 gigahertz and provided resolutions as fine as 1 picosecond. The author discusses high speed applications and the avoidance of acquisition errors.