Tsunami - Beckman Institute Laser Resource Center

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Service and Repair
Symptom: The entire STATUS bar display flashes when Model 3930 LOCK is enabled.
Possible Causes
Difference in reference
and cavity frequencies
exceeding 100 Hz.
PZT connections have
not been made.
Tsunami is not properly
aligned and optimized.
Possible Feedback
Corrective Action
Disable the LOCK and adjust cavity frequency to match the reference
frequency to within 100 Hz (the last digit on the display reads tens of Hz).
Disable the LOCK. Inspect all cables and connections from the Model 3930 to
the PZT.
Disable the LOCK. Verify Tsunami is operating properly.
Feedback occurs when a reflection from a flat surface (such as a mirror, fiber,
or the plano surface of a lens) enters the laser cavity. Feedback radiation of a
few mW may disrupt mode locking. To test for possible feedback, set up a fast
photodiode (or the Model 409 autocorrelator) to monitor the Tsunami pulse
using a beam splitter between the Tsunami and the suspected feedback
source. If stable pulse operation is obtained after blocking the beam to the
suspected source, you have a feedback problem. Try realigning the suspected
device to the Tsunami laser. If this does not work, try installing a Faraday or
other isolator in your optical system. When selecting an isolator, be sure it can
accommodate the Tsunami wavelength tuning range.
Symptom: System locked up but drifts out of the capture range of the PZT.
Possible Causes
Ion laser not stable.
Tsunami not stable.
Reference oscillator not
fully warmed up.
Environmental problem.
Corrective Action
Refer to the ion laser troubleshooting section in its user's manual.
Refer to "Long-term stability is poor" in this troubleshooting guide.
The Model 3930 must be warmed up for over 24 hours before stable operation
can be expected.
Avoid temperature swings r + 3°C; avoid turbulent airflow over the entire system.
Do not allow the cooling water to change temperature drastically or to
cycle.
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Symptom: High phase noise in fs operation but the STATUS bar display is normal.
Possible Causes
Tsunami drifted Off alignment.
Pump power too high Or
too low.
Too much prism glass in
the cavity.
'lit width too narrow Or
too wide.
Corrective Action
Refer to chapter 7, 'operation: Optimizing Laser Output."
Monitor the bandwidth for cw breakthrough with either a camera through a
monochromator or a grating, disable the LOCK and adjust the pump power to
get rid of cw breakthrough. Refer to appendix B, "CW Breakthrough."
Monitor the bandwidth for cw breakthrough as above, then disable the LOCK
and back prism glass out of the beam by adjusting the prism pair Pr2/Pr3.
Monitor the autocorrelator trace and adjust the slit and prisms Pr2 and Pr3 to
maximize the signal. (The wider the slit, the larger the amount of prism glass in
the cavity). For a given wavelength, pump power, and prism quantity, there is a
specific slit width that yields maximum bandwidth and power and prevents cw
breakthrough.