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2. Turn on the host laser to normal Q-switch operation.
3. Record the output energy of the host laser.
4. Adjust the Marx bank voltage to minimize the feedback from the host laser.
5. If the energy is >10 mJ/pulse after minimizing feedback, turn off the laser system. Contact the
host laser manufacturer or otherwise modify the Marx bank such that the feedback is <10
mJ/pulse. DO NOT PROCEED.
6. Remove the power meter from the optical train.
7. Verify seeder performance by observing the Q-switched build-up reduction time.
8. Turn the seed and host lasers off.
2.2.4 Frequency Overlap Adjustment
The overlap of the seed laser frequency and the host laser frequency is critical for efficient,
consistent injection seeding. There are two procedures for optimizing frequency overlap. The first
method is for customers with a 2nd harmonic generator and a Fabry-Perot etalon. The second
method only requires a chart recorder, but the first method is considerably easier and more effective.
Before beginning, ensure the seed and host beams are properly overlapped, as described in Section
2.2.2.
Method 1: Using 2nd harmonic generator and Fabry-Perot etalon
1. Configure the host laser for second harmonic generation.
2. Turn on the host laser to Q-switched mode. Ensure that the host laser is sufficiently warmed-up
to the extent that external cooling water is flowing. Thus, the gain center frequency of the host
Nd:YAG oscillator rod should be stabilized and fixed.
3. Send the 1.06 µm radiation into a beam dump and route the 532nm radiation through a 3cm
-1
,
0.5 µm Fabry-Perot etalon, as shown in Figure 2-7. Arrange these elements such that the etalon
rings can be observed on a screen while adjustments are made on the seeder assembly. The
harmonic generator can be detuned to ensure that a safe level of 532 nm power is incident on the
etalon. See Section 3.4.2 for an example of the output through the etalon.
Figure 2-7: Optical Layout For Observing Frequency Overlap
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