Characteristics of rational harmonic mode‑locked short‑cavity fiber ring laser using a bismuth‑oxide-based erbium‑doped fiber and a bismuth‑oxide‑based highly nonlinear fiber

Abstract

We demonstrate a rational harmonic mode-locked fiber ring laser employing a 151-cm-long bismuth-oxide-based erbium-doped fiber (Bi-EDF) and a 250-cm-long bismuth-oxide-based highly nonlinear fiber (Bi-HNLF). Continuous wavelength tuning covering both the conventional wavelength band and the longer wavelength band can be achieved by utilizing the wide gain bandwidth of the Bi-EDF. The pulse amplitude can also be equalized by adjusting the modulation parameters of the intracavity modulator. Ultra-high nonlinearity of the Bi-HNLF collaborates with spectral filtering by an optical bandpass filter to suppress the supermode noise quite effectively. The total cavity length is as short as 10 m. Stable and amplitude equalized pulses up to 40 GHz can be successfully generated over the entire wavelength tuning range.