Walking The Cavity - NORTHROP GRUMMAN Iklwa II TEM00 Service Manual

Walking the Cavity

© 2019 Cutting Edge Optronics
7. Release the pressure in the laser by pressing the center of the COOLANT
OUT quick disconnect.
Walking the cavity is sometimes required to optimize the laser and involves
combining mirror mount and SHG crystal temperature adjustments.
WARNING
. Making mirror adjustments can be non-reversible. Do this step only when all
the steps above have been completed and the laser does not meet the specifications
with the correct settings.
1. Locate the access holes for high-reflection (HR) and harmonic mirrors (HM).
Notice the positions of HR and HM mirrors with respect to the direction of the
laser output in Figure 3-3.
2. Remove screws from access holes only in a dust free environment.
3. Use a 1/8" ball driver to make adjustments. A fine adjustment is a 1° or less
rotation. A small adjustment is about a 2 degree rotation. A coarse adjustment
is 15 degrees to 20 degrees rotation. If coarse adjustments are needed to obtain
performance, reduce operating current by 2 A. Return to normal operating
current when making small and fine adjustments.
4. The screws for the adjustments of the vertical tilt angle and the horizontal tilt
angle are illustrated in Figure 3-3.
5. Make a horizontal adjustment to the HM mount. Recover the laser power by
making a similar adjustment to the horizontal control of the HR mount. Check
and adjust the temperature of SHG crystal. Do not adjust TEC in more than
.2°C increments. Adjusting TEC at full power can cause optical damage to the
SHG crystal.
6. Continue if improvement is noted. If there is no improvement, try the opposite
direction.
7. Perform the same procedure with the vertical adjustments of the HM and HR
mount.
8. Typically, SHG temperature adjustment is not needed when adjusting
vertically. Periodically check for hold off when making these adjustments (see
Check Hold Off section in this chapter).
9. If laser power is within +/-5% of nominal (typical power meter accuracy), and
it has good beam shape and stability, stop and replace the access screws in the
cover.
Chapter 3: Tuning and Testing Procedures
46 Patara II and Iklwa II Service Manual