Tsunami Mode-Locked Ti:sapphire Laser
3-4
Tsunami Laser Description
Pump Laser
Specifications for the Tsunami laser are guaranteed only when pumped by
a Millennia
®
V, VIII or X diode-pumped, cw solid-state laser operating in
power mode.
A Millennia X can supply 10 W of 532 nm power to Tsunami while the
Millennia V provides 5 W. Performance values given in this manual are
provided for various Millennia pump powers. For optimum performance,
the optics need to be changed to accommodate different pump powers.
Refer to Chapter 10, “Options and Accessories,” for a list of available
optics.
The Folded Cavity
Because Tsunami is a mode-locked laser, a cavity longer than that in a cw
laser is required in order to allow it to run at convenient repetition frequen-
cies near 80 MHz. Spectra-Physics modeled, analyzed, and optimized the
cavity design for optimum performance in minimal space. For the fs con-
figuration, the result was a ten-mirror, folded cavity as shown in Figure 3-3.
A six-mirror folded cavity design resulted for the ps configuration shown
in Figure 3-4.
While folding the cavity optimizes space utilization, it makes pumping
more complex. A focusing mirror used at an angle other than normal inci-
dence creates astigmatism in the beam unless corrected by some other ele-
ment, e.g., a Brewster-angle rod. In folded cavities where this astigmatism
is not eliminated, output beams are elliptical and hard to focus. But by
carefully choosing the angles of the cavity focus mirrors and the rod length,
astigmatism in the Tsunami output beam is virtually eliminated.
Figure 3-3: Beam Path for Tsunami Models 3960 and 3941 Femtosecond Configurations
Output
Brewster
Window
Fast
Photodiode
Beam
Splitter
M
10
M
8
Pr
4
AOM
M
9
Pr
3
Pr
2
Tuning
Slit
M
6
Pr
1
M
7
M
5
P
2
M
3
M
4
PZT (optional)
Ti:sapphire Rod
P
1
M
2
Residual
Pump
Beam Dump
Motorized (optional)
Input
Brewster
Window
Pump
Beam
Model 3955
AOM Driver Electronics
Model 3930
Lok-to-Clock Electronics
Optional
HR
OC
M
1
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