64 dB gain Yb-doped fiber amplifier for small-signal lasers based on tandem pump cavity

We propose a high-gain fiber amplifier based on a tandem pump cavity tailored for small-signal lasers. The small-signal laser can obtain high gain when passing through the tandem pump cavity and is then be continuously amplified by the tandem core-pumping process. In our experimental setup, a 50 μW signal laser is amplified to 128.5 W, achieving a maximum gain of 64 dB, surpassing conventional fiber amplifier capabilities. This approach offers a promising pathway toward realizing compact, reliable, and cost-effective high-gain fiber amplifiers.