Fiber core mode leakage induced by refractive index variation in high-power fiber laser
Yan Ping, Wang Xuejiao, Huang Yusheng, Fu Chen, Sun Junyi, Xiao Qirong, Li Dan †, Gong Mali
       

(color online) Experimental results for (a) output power (Pcore + Pcladding, black curve), remnant pump power (red curve), and optical efficiency (P1080/P975, blue curve); (b) pure fiber core mode power (black curve) and corresponding core mode optical efficiency (blue curve); (c) cladding mode power (black curve) and corresponding cladding mode optical efficiency in fiber amplifier.