Tsunami Mode-Locked Ti:sapphire Laser
7-14
Because M
2
does not translate along the optical axis, the system
will stop lasing when the micrometer is moved. If this happens,
adjust the horizontal and vertical knobs to return it to lasing opera-
tion, then adjust M
1
for maximum output power.
4. If you cannot get the system to modelock, either the phase is incorrect,
the wrong amount of glass is in the cavity, the fold mirrors are in the
wrong positions or pump power is too high. Try the following:
a. Verify the beam is not going through too much prism glass.
The beam should pass through right at the tips of P
1
and P
4
.
b. Verify pump power is not too high.
Tsunami output should be between 300 and 350 mW. This corre-
sponds to a pump power of approximately 3.2 to 4.0 W.
c. Turn the M
2
micrometer one-eighth turn in either direction, then re-
peak the mirror and try adjusting the prisms again. If the system
does not modelock, try moving the micrometer in the opposite
direction. Make sure that during the adjustments, mode remains
good.
d. Verify the phase is set correctly. While watching the spectrum on
an oscilloscope, adjust the coarse phase knob (inside the Model
3955) until the signal peaks in the vertical direction, then try
adjusting the prisms again. If this fails, adjust the coarse phase
knob one more click and try again. Repeat, turning the coarse
phase knob one click each time until the unit modelocks.
5. If at least 35 nm of bandwidth cannot be attained, try the following:
a. Decrease the pump power and turn P
2
and P
3
one turn clockwise.
b. Turn the slit micrometer counter-clockwise.
c. Open the slit width.
d. Make small adjustments to M
2
as described in Step 4 above.
e. Slide M
3
either in or out slightly, then optimize laser output and
check bandwidth.
Before moving M
3
however, make a mark on the dovetail bracket
so you can return the mirror to this position if this step fails. The
procedure described in Step 1 above should put
M
3
at the right
position. Make very small adjustments to this mirror, no more than
1 mm at a time.
Operating with Lok-to-Clock
Refer to Chapter 8 for installation and operating instructions for the
optional Lok-to-Clock system.
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