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Model 2520 Continuous Pulse Mode
Keithley Instruments, Inc.
28775 Aurora Road Release Notes
Cleveland, Ohio 44139
(440) 248-0400
www.keithley.com
Continuous Pulse Mode
In addition to LIV characterization, laser diodes typically require some type of wavelength or spectrum measurement.
In these cases, the 2520 can be used as a current pulse generator, driving the laser diode with a current pulse train
while a spectrometer or other instrument makes measurements. As a pulse generator, the 2520 provides a fixed pulse
current level with control over pulse width and pulse off time to provide a desired duty cycle. As with conventional,
single purpose pulse generators, no measurements are made when using the 2520 in the continuous pulse mode.
Ensure that the 2520 is using the latest firmware, B06 as of this writing, before using the continuous pulse mode.
Pulse Test Advantage
Testing in the pulse regime is done to minimize the heating of the diode junction, so duty cycles are typically 1% or
less. By minimizing the heating, testing can be performed on the laser diode as soon as the lasing cavity is defined, at
the wafer level for VCSELs and at the bar level for edge-emitting laser diodes. This early testing permits pass/fail and
other grading decisions to be performed before any additional process or packaging costs are added to the device.
Duty Cycle
The 2520 supports a wide range of duty cycles. There are two different maximum duty cycles based on the current
source level:
For I 1.00A, Maximum Duty Cycle = 4 %
For I < 1.00A, Maximum Duty Cycle = 99.6 %
The duty cycle (DC) is controlled by adjusting the pulse width (PW) and pulse delay (PD) values. The pulse delay is
the pulse off time. This gives:
DC % = PW