Spectra-Physics Tsunami - Troubleshooting in the Sub-35 Fs Regime

Operation
7-13
Troubleshooting in the Sub-35 fs Regime
1. If the fluorescent spots do not look like those described in Step 10 of
the sub-35 fs alignment section, the positions of the fold mirrors are
incorrect and the pump beam may not be going through the centers of
M
3
and M
2
. Before proceeding, verify this is not the case.
If the spot from
M
2
is not a bright dot, adjust the M
2
micrometer to
make it bright. When it is as bright as it will get, recenter the beam
using the M
2
adjustments.
If the spot from
M
3
is not rectangular-shaped image or is not the size
described in Step 9, perform the following.
a. With the prisms and slit assembly out of the beam path, remove the
OC and look for the fluorescence outside of the laser.
b. Place a business card approximately 22 in. (55 cm) from the output
bezel.
c. Adjust M
1
so that the fluorescence does not make it out of the laser.
d. Adjust M
3
so that the fluorescence can be seen on the business
card.
e. Slide M
3
back and forth on the dovetail until the fluorescent spot
comes to a focus and secure M
3
.
f. After M
3
is secured, verify the spot from M
2
has not degraded or
moved.
2. If the unit does not lase, check the following:
a. Clean the prisms with acetone or methanol.
b. Verify pump power is optimized according to Table 6-1 on page 4-4.
c. Verify the spots look like those described in Step 10.
d. Verify the fluorescent spots outside the cavity are overlapped.
Make sure the beam (the fluorescence) is going through the prisms
and not over the tops of the prisms.
e. If you have a problem seeing the overlapped spots through
M
8
,
insert a business card in front of
M
5
.
f. If none of the above steps work, chances are that the pump focus is
incorrect. If so, move P
2
one turn in either direction, then adjust the
overlap using the controls on
P
2
. If the unit still does not lase, try
one more turn in the same direction. If the unit still does not lase,
repeat this step, turning the control in the opposite direction.
3. If power is less than 650 mW, try the following:
a. Clean all prisms and mirrors. Also make sure that both sides of the
mode locker are clean.
b. Verify the beam from M
2
to M
1
is not clipping on the bottom of the
P
1
bracket.
c. Adjust P
2
for maximum output power.
d. Adjust
M
2
for maximum output power.