Multiwavelength switchable NDFL based on a dual-stage Mach–Zehnder filter

Abstract This study proposes a switchable and tunable neodymium-doped fiber laser (NDFL) based on a dual-stage Mach–Zehnder (MZ) filter. For the designed fiber laser, the dual-stage MZ filter consists of two 2 × 2 3 dB optical couplers (OCs), resulting in a comb-like interference pattern with a period of 0.5 nm. The two reflective ends of the NDFL cavity are formed by the dual-stage MZ filter and a total reflecting mirror composed of a 1 × 2 3 dB OC. By adjusting the polarization controller, the single-wavelength laser output can be tuned within the range of 1057.59 nm–1064.49 nm, with a linearity of 0.998 and power fluctuation less than 1.39 dB. In the dual-wavelength output mode, the wavelength spacing can be tuned from 1.38 nm to 2.96 nm, and stable triple-wavelength, quadruple-wavelength, and quintuple-wavelength laser outputs have also been achieved. The proposed NDFL based on the dual-stage MZ filter exhibits flexible tuning capabilities and high stability, making it suitable for a wide range of applications in fields such as fiber-optic communications, sensing, and spectral analysis.