Today, we wanted to charatrize the green produced by SHG. But we found the power changes very fast. Our metphor laser becomes unstable after turn-on and change-current. But after roughly 1hour this fluctuation will becoms stable. We characterize this fluctuation by the coefficient of variation.

The power fluctuation after turn-on is 0.01 with a period of around 15min. This range of power change is comparable with the current change of 0.03A. This means the power change of 0.03A corresponds to roughly 25mW of infrared produced by main laser.

The power fluctuation after 3 hours is 0.001 and doesn't have a clear frequency.

The power fluctuation after change current is 0.0045 with a very long period. For this period, I didn't have enough time to monitor it.

So for a better measurement of green laser power produced by SHG, we should operate main laser after a long enough time to stabilize. Then measure infrared just the moment after the measurement of green.