Experimental Study on the In-Band Amplified Spontaneous Emission in the Single-Mode Continuous-Wave Yb-Doped Fiber Amplifier Operating near 980 nm

Abstract

In this paper, the in-band amplified spontaneous emission (ASE) in the Yb-doped continuous-wave (CW) fiber amplifier operating near 980 nm is experimentally studied for the first time, to the best of our knowledge. A core-pumped single-mode Yb-doped fiber amplifier is fabricated and the effects of pump power, seed power, and active fiber length on the in-band ASE are investigated in the experiment. It is found that a strong in-band ASE around 980 nm can be observed even with no obvious ASE around 1030 nm present. It is also found that with the increment of pump power, the in-band ASE can be enhanced faster than the signal light. By studying the effects of seed power and active fiber length, it is found that, although increasing the seed power and shortening the active fiber can both suppress the in-band ASE, the latter method is less effective than the former one. The theoretical study is also carried out in order to understand the difference between the in-band ASE and 1030-nm ASE. The experimental observations are also discussed qualitatively with the theoretical results. We believe that the pertinent results and discussions can provide significant guidance for understanding the in-band ASE in the Yb-doped fiber amplifier operating near 980 nm.