Spectra-Physics Tsunami - Coarse Phase Adjustment and Cable Management

Tsunami Mode-Locked Ti-sapphire Laser
6-40
a. Close the shutter.
b. Place the tuning slit assembly into the laser head and onto the
micrometer shaft. Refer to Figure 6-8.
c. Rotate the slit width adjustment screw until the dowel pin on the
mating shaft can slide into the slot.
d. Seat the slit assembly against the micrometer stop.
e. Tighten the screw.
21. Open the shutter and tune the laser to the desired wavelength.
Refer to Chapter 7, “Operation: Selecting Wavelength, fs Configura-
tion.”
22. Modelock the Tsunami.
Refer to Chapter 7, “Operation: Modelocking the Laser.”
This completes the ps to fs conversion.
Coarse Phase Adjustment and
Changing the RF and Photodiode 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, the Tsunami must be lasing and a pho-
todiode and/or autocorrelator and oscilloscope must be set up to detect
pulses. Refer to your autocorrelator instruction manual for directions on its
setup and use.
When the Tsunami laser is oscillating at about 80 MHz, an output pulse is
produced every 12.5 ns. The fine PHASE control on the front panel pro-
vides a 100 ps delay to provide proper mode locker adjustment in most
cases. However, by changing cables, the loop delay is changed and can eas-
ily be 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.
To avoid damaging nearby optics when installing the slit, carefully
move it into place and use your hand to support it while you tighten the
mounting screw.
Warning!
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. If RF and/or photodiode cables other
than those shipped with the Tsunami laser are used, follow the proce-
dure below to adjust for the difference in cables.
Caution!