Tsunami - Beckman Institute Laser Resource Center

Tsunami
21. Mode lock Tsunami.
Refer to chapter 7, "Operation: Mode Locking the Laser."
This completes the ps to fs conversion.
Coarse Phase Adjustment and
Changing the rf and Photodiode Cables
CAUTION
It is critical to system performance that you use the rf and photodiode
cables provided with the Model 3955. The system was calibrated for
the type and length of these cables. Ifrf and/or photodiode cables other
than those shipped with the Tsunami laser are used, follow the procedure
below to adjust for the difference in cables.
If the cables used to connect the photodiode and rf signals are other than
those shipped with the unit, a coarse phase adjustment might be required
to compensate for any change in cable length.
Before this adjustment can be made, your Tsunami must be lasing and a
photodiode and/or autocorrelator and oscilloscope set up to detect pulses.
Refer to your autocorrelator instruction manual for directions on its setup
and use.
/I
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When the Tsunami laser is oscillating at about 80 MHz, an output pulse is
produced approximately every 12 ns. The fine PHASE control on the front
panel provides a 100 ps delay to provide proper mode locker adjustment in
most cases. However, by changing cables, you change the delay of the
loop and can easily move the delay outside the limits of this control. The
coarse control inside the Model 3955 provides about 14 ns delay and can
be adjusted so the fine PHASE control is once again effective.
1. See if Tsunami is creating short output pulses.
Look for a short output pulse (80 fs or 2 ps, depending on laser configuration)
when the mode locker is enabled (ENABLE is illuminated
on the STATUS panel of the Model 3955 electronics).
If short pulses are present, the laser is aligned and properly mode
locked and you are done. If the pulses are broader than specified for
your configuration, proceed.
2. Remove the cover (4 screws) from the Model 3955 electronics module.