Spectra-Physics Tsunami - Operating in the Broad Picosecond Regime; Tsunami System Verification

Tsunami Mode-Locked Ti:sapphire Laser
7-8
6. Use the prism dispersion compensation control to adjust Pr
2
and Pr
3
so
the beam also passes through them about 2 mm from the their apices.
7. Verify the beam is in the center of M
10
. Adjust M
5
if necessary, then
repeat Steps 5 and 6.
8. Refer to “Optimizing Laser Output” earlier in this chapter to “walk the
beam” and optimize laser output.
9. Purge the system with clean, dry nitrogen gas when you are operating
within water and oxygen absorption regions (Figure 7-1).
10. Push the STATUS mode locker enable button (the ENABLE LED should
be on).
11. Set up an autocorrelator such as the Model 409-08 according to its
user's manual, then maximize the signal by adjusting the angle of the
nonlinear crystal for the optimum phase-matching condition.
12. Maximize the intensity of the autocorrelated waveform by adjusting
the coarse and fine PHASE controls.
Refer to Chapter 6, “Alignment: Coarse Phase Adjustment...,” for
information on setting the coarse and fine PHASE controls.
13. Adjust the GTI POSITION control to obtain a pulse.
14. Optimize system performance by iterating between the following
adjustments:
a. Adjust the fine PHASE control.
b. Adjust the pump laser output power to obtain a stable pulse.
c. Adjust the GTI POSITION control, prisms Pr
2
and Pr
3
, the slit width,
and pump source to obtain the desired pulse width.
These controls operate interactively on the output pulse width, and
an iterative approach is necessary.
Typically, the pulse width can be varied with these controls by a
factor of 2 to 3.
Operating in the Broad Picosecond Regime
The Tsunami laser is capable of producing pulses in the range 2 – 80 ps by
using special GTIs and either a 2- or 3-plate bi-fi.
Tsunami System Verification
Verify the following before you start the conversion process for broad
pulses:
1. Verify the coarse and fine PHASE settings on the Model 3955 are cor-
rect.
Description Typical Setting
Millennia Xs Millennia Vs
Pump Laser Power 7–9 W 4–5 W
Slit Width 1.8–2.2 mm 1.8–2.2 mm