Download Spitfire - Spectra

Operation
Re-Optimization
A change in room temperature or similar environmental factors may make
re-optimization necessary. To do this:
1. Disable OUT 2 DELAY on the SDG II, and monitor the intracavity pulse
as it builds up. It should look like that shown in Figure 6-4.
2. Block the seed beam into the Spitfire, and observe the intracavity Qswitched pulse (Figure 6-3) as it builds up.
3. If the Q-switched pulse is unstable in amplitude or time, make slight
adjustments to end mirrors CM1 and CM4. With the oscilloscope triggered by the SYNC OUT DELAY on the SDG II, the Q-switched buildup
time reduction should be approximately 100–150 ns.
4. Unblock the seed beam into the Spitfire. The pulse train should look
like that shown in Figure 6-4. Make small, iterative adjustments to
mirrors M3 and M4 to reduce the pulse buildup time as much as possible; that is, adjust it so that the pulse train shifts from right to left on
the oscilloscope screen.
By alternatively blocking and unblocking the seed beam into the Spitfire, the difference between the unseeded Q-switched time and the
seeded pulse train time can be measured. This difference in buildup
time should be approximately 50–80 ns.
5. Re-enable OUT 2 DELAY on the SDG II. Again, the intracavity pulse
train should look like that shown in Figure 6-5. If it does not, adjust
OUT 2 DELAY so that the highest amplitude pulses in the train remain.
6. Position the photodiode at the output port of the Spitfire to look at the
ejected pulse. Make slight adjustments to OUT 2 DELAY to eject the
pulse that has the best stability. Adjust OUT 1 DELAY slightly if there is
evidence of a secondary pulse being ejected.
6-7