# High Repetition Rate, TEM\({}_{00}\) Mode, Compact Sub-Nanosecond 532 nm Laser
## 3 Experimental Results
### Two-Pass Amplification Characteristics  
Figure 4 shows that the output power of the amplifier was a function of the seed's output power and the amplifier's pump power. The output power of the amplifier was 1.26 W, as the seed-injected power was 317.8 mW at 16 kHz and the pump power of the amplifier was at 7 W. The maximum output average power reached 2.3 W when the seed-injected power was 0.477 W at 21 kHz and the pump power of the amplifier was at 9 W.  
Figure 4: The amplified power of the fundamental amplifier versus the power of the seed and the input pump power of the amplifier.  
Figure 3: The single-pulse profile and pulse width of the seed.  
The spatial profile of the fundamental beam was recorded with a LASERCAM HRII camera from Coherent. Figure 5 shows the seed's beam profiles at different pump powers, and the circularity levels we measured were 0.876, 0.829, and 0.779, corresponding to seed pump powers, respectively, of 2.4, 3.3, and 3.9 W.  
The beam profiles after amplification under different seed pump powers are shown in Figure 6. As the pump power of the amplifier was at 7 W, the circularity levels we measured were 0.661, 0.747, and 0.927, corresponding to the seed pump powers of 2.4 W, 3.3 W, and 3.9 W, respectively. After amplification, the beam distortion of the seed was compensated well. The beam profile was more circularly symmetric. The circularity of the amplified beam with a pumped power of 7 W versus different seed pump powers are shown in Table 1. With the increase in pump power, the beam distortion of the seed was severe because of the increase in thermal loading. The distribution of the seed beam was divergent in the horizontal direction. For obtaining the ideal distribution of the fundamental amplifier, the cylindrical lens L2 was used for adjusting the pump distribution of the amplifier in the horizontal direction. We can conclude that the pump distribution of the amplifier was orthogonal to the distribution of the seed beam, since the pump power of the amplifier was constant. The beam distortion of the seed was compensated well owing to the restraint of the horizontal direction amplification and the enhanced vertical direction, as the pump power of the seed was 3.9 W. Therefore, as pertains to this experiment of amplification, the regulation of the pump distribution of the amplifier was effective in compensating the thermal-induced distortion of the seed beam. It would be helpful for the design of a high-beam-quality laser with a compact size.  
Figure 5: The beam profiles of seeds at different pump powers. (**a**) Beam profile of the seed with a pump power of 2.4 W (the circularity was 0.876). (**b**) Beam profile of the seed with a pump power of 3.3 W (the circularity was 0.829). (**c**) Beam profile of the seed with a pump power of 3.9 W (the circularity was 0.776).  
Figure 6: The amplified beam profile of the fundamental laser with a pump power of 7 W at different pump powers of the seed. (**a**) Beam profile with circularity of 0.661, as the pump power of the seed was 2.4 W; (**b**) beam profile with circularity of 0.747, as the pump power of the seed was 3.3 W; (**c**) beam profile with circularity of 0.927, as the pump power of the seed was 3.9 W.