Direct Frequency-Mode-Stable Laser Amplification at Terahertz Burst Rates

TL;DR

This paper introduces a scalable method for amplifying high-energy pulse bursts at terahertz rates with stable spectral features, overcoming previous challenges related to temporal intensity modulation and amplifier damage.

Contribution

It presents a novel burst generation technique using a master-oscillator regenerative-amplifier system enabling high scalability and stable spectral peaks at THz repetition rates.

Findings

Temporal intensity modulation decreases with increasing pulse number.

Stable spectral peak structure achieved with MHz width.

Amplifier damage risk eliminated by chirped pulse interference control.

Abstract

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.