  Generation of high-fidelity amplified pulse bursts with a regular interpulse
interval yields, in the spectral domain, an equidistant pattern of narrowband
spectral modes, similar to frequency combs produced by cw mode-locked lasers,
but with greatly increased pulse energy. Despite their great potential for
nonlinear spectroscopy, material processing, etc., such long frequency-stable
bursts are difficult to generate and amplify because of prominent temporal
intensity modulation even after strong dispersive pulse stretching. This study
presents a burst generation method based on a master-oscillator
regenerative-amplifier system that allows for chirped-pulse amplification (CPA)
with high scalability in pulse number. A gradual smoothing of temporal
intensity profiles at an increasing number of pulses is discovered,
demonstrating an unexpected recovery of the CPA performance at terahertz (THz)
intraburst repetition rates. In consequence, a self-referenced stable burst
spectral peak structure with megahertz (MHz) peak width is generated, without
risk of amplifier damage caused by interference of chirped pulses. This result
eliminates limitations in burst amplification and paves the way for
advancements in ultrashort-pulse burst technology, particularly for its use in
nonlinear optical applications.
