Fig. 1. (a) Constructions of AIFG. FMF, few-mode fiber; PZT, piezoceramic transducer; RF, radio-frequency source. (b) Output beam profiles of 1130 nm laser at different frequencies.

Fig. 2. (a) Transmission spectrum of LP₀₁ mode at different loaded frequencies; (b) fitted curve between eigenfrequency and wavelength.

Fig. 3. (a) Experimental setup of mode controllable RRFL; (b) refractive index of GRIN FMF; (c) four LP modes supported at both 1080 and 1134 nm.

Fig. 4. (a) Output signal power as a function of pump power and beam spots; (b) spectrum at different output power levels for LP₀₁ and LP₁₁ modes.

Fig. 5. (a) Measured and reconstructed beam profiles as well as calculated mode purity at different power levels; (b) content of the LP₀₁, LP₁₁ modes and the other modes at the highest power; (c) MD results of RRFL recorded every 2 min in 20 min.

Fig. 6. (a) Rising and (b) falling edge of the temporal trace.