Measurements for Laser Engineers

Question: Being a Laser Engineer there are many times where I need to catch a pulse train of several hundred pulses at a time.  I am using a pulsing solid state laser operating anywhere between 10 and 20 Hz.  The issue is that I need to catch every pulse and then be able to export the data to Lab View for processing and integration with a full test setup. 

I am using a nanosecond photo detector to look at the widths of each pulse.  I need a scope to be able to detect and record each pulse of the set of pulses and then be able to conduct some basic statistics on the data: min, max, average, standard deviation, # of pulses, etc.

Typical Characteristics of the lasers are:

  • Pulse Width: 8-12 nanoseconds
  • Frequency: 10-20 Hz
  • Amplitude: 5 Volts or less
  • # of Pulses: 100-500 pulses per data set

The pulse shape is a Gaussian shaped pulse, and we would have 500 pulses each with a width of 8-12ns occurring at a frequency anywhere between 10-20Hz.  If it was 500 pulses at 20 Hz total time would be 25 s, 500 pulses at 15 Hz would be 33.33 s, and 500 pulses at 10 Hz, would be 50 s.  So, the total length of time depends on the number of pulses in the data set and the frequency of the pulsed laser.

Which scope would be best for me and is there one that I can control through Lab View?

Answer: First the good news–any Tektronix scope will work with Lab View.  But, here are specifics about making the measurements you need to make.

There are two ways to go about making the measurements you want.   The first way would be to use a lower end bench scope, single shot each pulse, then pull that into data into Lab View. Then you would need to re-arm the scope trigger before the next pulse would occur.  That puts a lot of variables on the PC side to ensure that the scope would be re-armed fast enough to catch the next pulse. 

What we would recommend is using a scope that has FastFrame Acquisition mode.  This mode allows the Oscilloscope to handle (by setup) the number of pulses (trigger event) and the number of data points to store every trigger event.  This allows for high resolution capturing of each pulse, without using up record length saving time in-between each pulse.   The time of trigger is also stored very accurately.  This acquisition mode was designed specifically for the type of acquisition you need.

The recommended Tektronix instrument with this feature is one of our DPO7000 series of oscilloscopes.

Explore posts in the same categories: Ask Scope Guru Q/A

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