Tsunami - Beckman Institute Laser Resource Center

Tsunami
pulses, adjust the coarse control located inside the Model 3955. Refer
to "Coarse Phase Adjustment ..." at the end of this chapter for instruc- --
tions on locating and changing the setting of the coarse control.
The following procedure, steps 6 through 9, applies to both fs and ps
systems. However, the precursor indication (Figure 6-13, a - e) will not be
observed for fs systems. There is no precursor indication for a fs system.
6. Increase the gain on the autocorrelator so a trace is seen on the oscilloscope
(noise on the baseline, Figure 6- 13a).
7. Adjust the fine PHASE control on the Model 3955 to maximize the
amplitude of the pulse (Figure 6-13, b - d).
Small adjustments to the bi-fi @s) or prism pair (fs) may also be necessary:
turn the appropriate micrometer control turn at a time.
8. Adjust the prism dispersion compensation control (fs) until a pulse
occurs (Figure 6-130 or the GTI POSITION control (ps) until a pulse
begins to appear (Figure 6- 13, e - f).
9. Slightly adjust the angular adjustment knobs on the AOM mount
(Figure 6-12) to maximize the amplitude of the autocorrelator trace.
Repeat steps 7,8, and 9 until the pulse locks; the amplitude will drastically
increase and the pulse will be well defined. If the autocorrelator gain is
too high and the signal is saturated (Figure 6-13g), lower the gain until a
clean pulse is present and increase the oscilloscope sweep speed to broaden
the pulse for viewing (Figure 6-13h).
10. Optimize Tsunami output power.
Place a power meter in the Tsunami beam path and adjust Mlo and M1
for maximum output power.
The PHOTODIODE light bar level indicator on the Model 3955 front
panel should indicate maximum for standard wavelengths and > 30%
for x-long wavelengths.
11. Vary pump power to optimize pulse width and stability.
12. Repeat steps 1 through 11 until the Tsunami pulse is optimized and
the test in step 4 of "Test for Proper Mode Locking" is successful.
13. Close the pump laser shutter.
This completes the AOM alignment.