Fig. 1. Schematic diagram of the bidirectional output fiber laser. SSYDF, spindle-shaped ytterbium-doped fiber; BPSC, backward pump and signal combiner; LD, laser diode; FBG, fiber Bragg grating; CLS, cladding light stripper; PD, photodetector; OSA, optical spectrum analyzer; PM, power meter.

Fig. 2. Schematic diagram of the longitudinal structure of the SSYDF.

Fig. 3. Comparison of the output power and the spectra of the unidirectional output oscillator and the bidirectional output oscillator under the unidirectional pump configuration. (a) Comparison of total output power and efficiency under the A-end pump configuration. (b) Comparison of the total output power and efficiency under the B-end pump configuration. (c) Comparison of the output spectra under the A-end pump configuration. (d) Comparison of the output spectra under the B-end pump configuration.

Fig. 4. Results of the bidirectional output oscillator in the bidirectional pump configuration. (a) Output power and efficiency at different pump powers. (b) Output spectra of the A-end and the B-end at the maximum output power. (c) Photodetector signals of the A-end and B-end at the maximum output power and the corresponding fast Fourier transform (FFT) results. (d) Beam quality results of A-end and B-end at the maximum output power.

Fig. 5. Beam profiles at the beam waist of the output lasers from the A-end and B-end.