Precision II Operation and Maintenance Manual C
5-14
996-0255 rev. b
E. Oscillator optimization (with an oscilloscope)
For the Precision series lasers that employ the “Gaussian” oscillator,
optimizing cavity alignment using an oscilloscope can be very useful.
If the oscillator is well aligned the output pulse width is at its narrowest
( 5-8 ns). The converse is also true. When the cavity is misaligned the
pulse width will broaden. Therefore monitoring the pulse width while
making oscillator adjustments will allow you to achieve optimum cavity
alignment.
Equipment needed:
• Burn paper
• clear plastic bags
• high density Styrofoam beam dump
• Photodiode with ~1 ns risetime
• BNC cable
• >350 MHz oscilloscope with enhanced view
screen
The following is a procedure for optimizing the oscillator by monitoring
the pulsewidth:
NOTE:
This procedure should be done in conjunction with the
alignment procedure described previously in this section.
1) Turn on the flashlamps and let the system warm up ~20
min.
2) Place the beam block in the beam path after the first
turning mirror 7c.
3) Set up the oscilloscope:
a. Plug in photodiode to 50 Ω termination.
b. Run a trigger BNC cable from the “Seeder Trigger”
BNC (located on the side of the laser bench) to the
time base of the scope.
c. Set the triggering of the scope to trigger off the +15
sync pulse.
d. Adjust the time base to view a 5-10 ns pulse. The
trigger pulse will occur ~90 ns before lasing.
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