Tsunami - Beckman Institute Laser Resource Center

Service and Repair
Symptom: Laser is mode locked but has noisy >2 ps pulses with side lobes or baseline noise
(ps configuration only)
Possible Causes
Poor cavity mode.
Contact your Spectra-Physics Lasers field service representative. Do not at-
GT' might be misaligned' tempt disassembly You will void your warranty.
Pump power is too high.
Possible oxygen or
moisture contamination
from the purge
Corrective Action
Verify M2 and M3 are properly aligned. Refer to chapter 6, "Alignment: Cavity
Alignment."
Reduce pump power until the side lobes or the baseline noise disappears.
Use only dry, oil-free, Electronic Grade 5 nitrogen gas from a cylinder. Avoid
boil-off tanks which might contain oxygen or water vapor. Check the color of
the desiccants in the molecular-sieve assembly in the Model 391 0 and make
sure they are not pink. If they are, replace the assembly (refer to chapter 9).
Symptom: Pulses are broad with low power
Possible Causes
Fine PHASE adjust is not
set properly.
' and photodiode cable(s)
are not the originals.
Pump power is too low.
Possible oxygen or
'Ontamination
from the purge source.
Corrective Action
Use the fine PHASE adjust on the Model 3955 electronics module to set the
system for short, high-power pulses.
Refer to "Coarse Phase Adjustment ..." in chapter 6.
Increase pump power.
Use only dry, oil-free, Electronic Grade 5 nitrogen gas from a cylinder. Avoid
boil-off tanks which might contain oxygen or water vapor. Check the color of
the desiccants in the molecular-sieve assembly in the Model 3910 and make
sure they are not pink. If they are, replace the assembly (refer to chapter 9).
Symptom: Satellite pulses are evident when viewed on an autocorrelator
Possible Causes
Room lights are too
bright.
Pump power is too high
(ps configuration)
Pump power is too high
(fs configuration)
Corrective Action
Turn off the room lights. If the pulses disappear, they are phantom satellite
pulses. To eliminate them, cover the autocorrelator to block room light.
Check for real satellite pulses by turning the GTI POSITION control on the laser
head control panel. If the pulses are real, i.e., they move away from or closer to
the main pulse as the POSITION control is adjusted, they are caused by high
pump power (cw breakthrough). Turn pump power down until the satellites disappear.
Refer to appendix B, "CW Breakthrough." Tsunami power should still
meet specification. If not, contact your Spectra-Physics Lasers service representative
for help.
If the satellite pulses are real, they disappear when you block the pump beam
to the Tsunami. If they are phantom, see "Room lights" above. If you have real
satellites, they are caused by high pump power (cw breakthrough). Turn pump
power down until the satellites disappear. Refer to appendix B, "CW Breakthrough."
Tsunami power should still meet specification. If not, contact your
Spectra-Physics Lasers service representative for help.