Spectra-Physics Tsunami - Troubleshooting LTC Systems

Tsunami Mode-Locked Ti:sapphire Laser
11-8
Troubleshooting LTC Systems
Symptom: Satellite pulses are evident when viewed on an autocorrelator
Possible Causes Corrective Action
Fluorescent lights cause
phantom signals that look
like satellite pulses.
Turn off fluorescent room lights.
Cover the autocorrelator to shield the unit from fluorescent room light.
Improper dispersion in the
cavity.
Femto configurations:
Tu r n p r i sm s P r
2
and Pr
3
counterclockwise to get rid of the satellite pulses.
Pico configurations:
Adjust the GTI POSITION control to get rid of the satellite pulses. The satellite
pulses are real if they move in time with respect to the main pulse when the GTI
POSITION control is adjusted.
Pump power is too high (fs
configuration)
Lower the pump power in 5% increments from the recommended setting.
There is a secondary
reflection from the beam
splitter, attenuator, etc.
Avoid thin and unwedged beam splitters or attenuators that may have a second-
ary reflection in the beam that travels toward or into the autocorrelator.
Symptom: Cannot see individual pulse on the oscilloscope
Possible Causes Corrective Action
The system is not mode
locked.
See the troubleshooting symptom: “System will not mode lock.”
Autocorrelator is not prop-
erly aligned to the beam.
Refer to the autocorrelator manual for proper alignment.
The non-linear crystal is not at the proper phase matching angle.
The focus lens is not at the correct distance from the non-linear crystal.
Symptom: When LOCK is enabled, only the top and bottom LEDs are illuminated on the STATUS
display.
Possible Causes Corrective Action
The M
4
PZT cable is not
connected.
Verify the driver cable is attached to the M
4
PZT mirror.
The M
4
PZT is bad.
Replace.
Symptom: The entire STATUS bar display flashes when Model 3930 LOCK is enabled.
Possible Causes Corrective Action
Improper cavity dispersion. Femto configuration:
Use the Pr
2
and Pr
3
prisms to add or subtract glass in the cavity.
Pico configuration:
Adjust the GTI POSITION control.
Improper phase adjust-
ment.
Adjust the FINE PHASE control.
Improper pump power. Raise or lower the pump power in 5% increments from he recommended setting.
Tsunami is not properly
aligned and optimized.
Adjust M
1
and M
10
as described in Chapter 6, “Alignment: Cavity Alignment.”
Adjust M
2
in or out to reduce fluctuations in the LED.