Fig. 2: Negative energy transfer that is induced by the pump modulation above the TMI threshold, as analyzed via mode reconstruction of the high-speed camera frames.
From: Modal energy transfer by thermally induced refractive index gratings in Yb-doped fibers
a The temporal evolution of the signal output power, which is normalized to the average signal power of 350 W, with a pump modulation with 600 Hz modulation frequency and ±75% (±262.5 W) modulation depth. b The temporal evolution of the relative modal content (FM (LP01) blue, 1st HOM (LP11) red, 2nd HOM (LP02) yellow); the HOM integral is shaded green. c The reconstructed intensity profile (on the left, including the relative modal contents of various transverse modes), measured intensity profile (top right) and residual intensity profile (bottom right) at the time of negative energy transfer during the pump modulation; excerpt from Supplementary Video 2
