The vast majority of lasers used today in industrial applications are pulsed ones. Except for the very high power (multi kilowatt-level) CW lasers used for cutting, welding and cladding of metals, all other industrial uses of lasers need short and energetic pulses. Micromachining, drilling, scribing, marking or repairing of precision electronic components are only a few examples of the large variety of processes enabled by short pulsed lasers. In the bio-medical field, pulsed lasers are found in almost all applications: from laser surgery and medical implant fabrication to non-linear imaging of tissues and aesthetics. What these applications have in common is the requirement to deliver the pulse energy to the target in a precise timing. The temporal characteristics of the pulses such as pulse duration, pulse shape and profile, pulse timing jitter and repetition frequency are key parameters which need to be measured and monitored if one wants to guarantee the success of the application.
Short pulses lasers can be grouped into three different classes, depending on their temporal regime of operation. Nanosecond pulses are typically emitted from Q switched lasers, but picosecond and femtosecond pulse duration are a feature of mode-locked lasers.
To address the need for short pulse characterization, Ophir introduced the FPD series of fast photodetectors. In combination with a suitable oscilloscope or RF spectrum analyzer, the temporal performance of short pulsed lasers can be quantified. For pulse durations of nanoseconds down to a few tens of picoseconds, Ophir's fast photodiodes output signal can be directly sampled by an oscilloscope and the temporal characteristics can be obtained. For pulse duration shorter than a few tens of picoseconds, the fast photodiodes can be used to monitor the pulse train repetition rate and amplitude jitter.
For a complete characterization of the pulse duration, an Autocorrelator should be used. Spectra Physics' new PulseScout2 Autocorrelator is a great solution for ultrafast pulse measurements from 35 picoseconds down to 20 femtoseconds.