Tsunami Mode-Locked Ti-sapphire Laser
6-16
Rotate M
10
vertically in one direction a small amount and optimize
output power using M
1
. If power increases, continue the same
direction until power reaches a new maximum. However, if power
decreases, turn M
10
the other way and optimize with M
1
.
b. Repeat the last step using the horizontal controls.
c. Iterate the last two steps to obtain maximum power in both axis.
5. Reiterate Steps 2 through 4 above until M
4
, M
5
and M
10
are centered and
power is maximized. When reading the beam position on mirrors, put
your line of sight normal to the mirror axis to avoid parallax error.
6. Install and align the bi-fi according to “Selecting, Installing, and
Aligning the Birefringent Filter...”, then adjust the bi-fi for output peak
wavelength. Consult Table 7-1 and the tables in Chapter 10 for the
proper filter type for the installed optic set.
7. Set up a spectrometer to view the wavelength. In order to see the effect
of modelocking, reduce the signal level to avoid saturation using ND
filters and/or a variable OD attenuator.
8. Tune to the specified wavelength for the tuning range of the installed
optic set, but tune to 890 nm for the long set in order to stay away from
the water absorption region.
9. Align the photodiode pc board.
a. Loosen the two mounting screws on the photodiode pc board.
b. Move the photodiode pc board around until the maximum signal is
observed on the photodiode bar graph on the front of the Model
3955, then tighten the mounting screws. If the LED bar graph is
saturated, reduce the pump power to bring the signal below satura-
tion before aligning the pc board.
10. Test for proper modelocking.
Refer to “Test for Proper Modelocking” later in this chapter.
Continue with the next section.
Aligning the A/O Modulator (AOM)
The photodiode pc board must be aligned before you align the
AOM. This
assures a maximum photodiode signal for reliable modelocking. If you
have not just done this, refer to “Aligning the Photodiode PC Board” later
in this chapter.
If you have not already done so, perform the “Test for Proper Modelock-
ing” later in this chapter before you attempt this alignment. If the laser
modelocks properly, you do not have to perform this procedure.
Proper AOM alignment is critical for both ps and fs Tsunami lasers. This
procedure assures good AOM beam alignment for optimum modelocking.
Figure 5-2 is a system interconnect diagram to assist you in verifying cor-
rect cable connections. Figure 6-13 shows the location of the
AOM.
1. Verify the output beam is centered on M
10
.
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