High-energy wavelength-tunable pulse bursts: on the commutability of spectral filtering and burst-mode amplification

We discuss the commutability of burst generation and spectral filtering, as predicted by linear time-invariant (LTI) signal theory. While LTI indicates that spectral filtering may be applied either before or after burst formation, our experimental investigation shows that this equivalence is not valid in the presence of strong burst-mode amplification. Front-end spectral filtering reduces the seed energy, impacting the nonlinear gain dynamics of the optical amplifier, leading to incomplete gain depletion and the formation of a parasitic background. As a consequence, the spectral filter placement influences the achievable efficiency and background suppression, making it a critical design choice for high-energy wavelength-tunable sources.