Ultrafast serrodyne optical frequency translator

TL;DR

This paper introduces an ultrafast optical frequency translation method using the serrodyne principle, enabling high-power femtosecond laser pulses to be shifted over several THz with maintained coherence and improved pulse quality.

Contribution

It demonstrates a novel, efficient wavelength shifting technique for high-power lasers based on serrodyne modulation and nonlinear multi-pass cells, extending spectral reach beyond current laser gain bandwidths.

Findings

Successfully shifted a 75 W frequency comb from 1030 nm to 1060 nm and 1000 nm.

Maintained coherence at the few Hz-level during wavelength shifting.

Enhanced temporal pulse quality after frequency translation.

Abstract

The serrodyne principle enables shifting the frequency of an electromagnetic signal by applying a linear phase ramp in the time domain [1]. This phenomenon has been exploited to frequency-shift signals in the radiofrequency (RF), microwave and optical region of the electromagnetic spectrum over ranges of up to a few GHz e.g. to analyse the Doppler shift of RF signals, for noise suppression and frequency stabilization [2-9]. Here, we employ this principle to shift the center frequency of high power femtosecond laser pulses over a range of several THz with the help of a nonlinear multi-pass cell. We demonstrate our method experimentally by shifting the central wavelength of a state-of-the-art 75 W frequency comb laser from 1030\,nm to 1060\,nm and to 1000\,nm. Furthermore, we experimentally show that this wavelength shifting technique supports coherence characteristics at the few Hz-level while improving the temporal pulse quality. The technique is generally applicable to wide parameter ranges and different laser systems, enabling efficient wavelength conversion of high-power lasers to spectral regions beyond the gain bandwidth of available laser platforms.