Fig. 3: Dependence of the negative energy transfer on the modulation frequency above the TMI threshold.
From: Modal energy transfer by thermally induced refractive index gratings in Yb-doped fibers
a The strength of the negative energy transfer (represented by the HOM integral) as a function of the modulation frequency at 350 W average output power and for ±75% (±262.5 W) pump modulation depth. b The temporal evolution of the relative modal content (FM (LP01) blue, 1st HOM (LP11) red, 2nd HOM (LP02) yellow) for a pump modulation frequency of 1.8 kHz; the HOM integral is shaded green. c The temporal evolution of the relative modal content (FM (LP01) blue, 1st HOM (LP11) red, 2nd HOM (LP02) yellow) for a pump modulation frequency of 2.2 kHz; the HOM integral is shaded green
