Accurate signal and noise measurements for a high-energy nanosecond Yb-doped all-fiberized amplifier

The monitoring of Amplified spontaneous emission (ASE) is critical in all-fiberized lasers with high pulse energy. The existing measurement scheme is mainly carried out in the spectral and time domain. However, after our verification, these two types of methods have their own applicable conditions and certain errors. In this study, we propose a time-domain precise sampling method to accurately measure the contents of signal and noise with a free space acousto-optic modulator (AOM). We validated our testing approach using two homemade nanosecond pulse systems which contain different ASE and signal contents settings. The measurement result showed the necessity and feasibility of the proposed method. Compared to the spectral method, our method improved the precision of the measurements by at least 25%. In comparison to the AOM gating method, we can directly obtain the signal proportion of the output light. This new method provides a practical alternative for measuring signal and pulse content in a high-energy system.