Oscillator Optimization (With An Oscilloscope) - Continuum Surelite I 10 Operation And Maintenance Manual

Continuum Surelite Laser
11. Once normal power has been restored, shut down the system, remove the interlock
defeat bracket and reinstall oscillator housing cover.
12. Resume normal operation.

Oscillator optimization (with an oscilloscope)

For the Surelite 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 pulsewidth is at its narrowest (5-8 ns). The converse
is also true. When the cavity is misaligned the pulsewidth will broaden. Therefore,
monitoring the pulse width while making oscillator adjustments will allow you to achieve
optimum cavity alignment.
N E
ECESSARY QUIPMENT
Burn paper
•
Clear plastic bags
•
High density Styrofoam beam dump
•
• Photodiode with ~1 ns rise time
BNC cable
•
>350 MHz oscilloscope with enhanced view screen
•
This procedure optimizes the oscillator by monitoring the pulsewidth.
Note: This procedure should be done in conjunction with the alignment
procedure described previously in this section.
1. Remove harmonic crystals.
2. Place the beam block in the beam path after the output port.
3. Set up the oscilloscope:
• Plug in photodiode to 50 Ω termination.
• Run a trigger BNC cable from the " Fixed sync out" BNC (located on the PCU
front panel display) to the time base of the scope.
• Set the triggering of the scope to trigger off the +5 V TTL sync pulse.
• Adjust the time base to view a 5-10 ns pulse. The trigger pulse will occur ~90 ns
before lasing.
• Place the photodiode on the bench so that it will be able pick up the laser light
scattered off the beam block.
Be sure that the voltage setting on the power unit is set to the laser's normal operating
voltage.
76
CAUTION!
Never attempt to adjust the output coupler
(the mirror mount nearest to the exit port).
996-0207