NORTHROP GRUMMAN Patara I User Manual page 66

© 2018 Cutting Edge Optronics, Inc.
Figure 7-1 – Typical Beam Profile at Beam Waist, Farfield at Operating Current
If the beam profile is abnormal, such as a roundness below 90%, a split beam or
alternate beam structure, follow the steps below to improve beam quality:
 Not Operating at Correct Parameters: Verify that all operating parameters
match the values on the ATP Test Report Data Summary. If all settings are
correct, proceed to Misalignment.
 Misalignment: If the laser is misaligned, the output power will be low. The
beam profile may be distorted. The threshold will be higher. Perform the laser
power optimization procedures as described in the Optimize Laser
Performance section in Chapter 5: Maintenance to optimize laser output
power and beam profile. After optimization, the beam profile and laser output
power may be restored at a higher operating current and the laser threshold
may be higher, as well. This is normal for aging laser diodes (see the Optimize
Laser Performance section of Chapter 5: Maintenance).
 Failed Laser Diode Bar: If the output power is similar to the ATP Test
Report Data Summary value, but the beam profile is still distorted, this could
be caused by an uneven pumping light distribution. This could be due to a
failed laser diode bar. Measure the voltage at the output of the diode current
source compared to the diode module voltage on the ATP Test Report Data
Summary.
 Contaminated Coolant: Indications that the coolant is contaminated are the
operating current is higher and the beam profile may be distorted. Refer to
SVC-FSB-0001 for chiller cleaning procedures.
 Damaged Optics: Optimization will not recover laser output power lost due
to damaged optics. Internal and external damaged optics can both cause
distortion of the output laser beam, but only damaged optics inside the laser
cavity will increase the threshold current. Verify laser output window and all
external optics are clean and free of damage. If no damage is found, move the
Chapter Seven: Troubleshooting
54 Patara I and II Laser User Manual