All-fiber configuration makes single-cycle pulses more accessible

Recent research has welcomed advances in the control of ultrashort, single-cycle light pulses. However, single-cycle light sources remain confined to complex and expensive setups. Xing et al. demonstrate a new single-cycle pulse source that utilizes a simpler and less costly all-fiber, turnkey format.

The laser source, which is also a frequency comb, generates 6.8 femtosecond pulses at a 100-megahertz repetition rate, outperforming previous fiber attempts. “The pulse duration of current all-fiber lasers are typically tens of femtoseconds,” author Sida Xing said. “For the first time, we show that single optical cycle pulses could be generated with all-fiber structure.”

In the frequency domain, the comb features a two-octave spectrum, while the time domain peak power exceeds 200 kilowatts. Even further, the laser’s deterministic carrier envelope phase makes it a promising tool for studying light-matter dynamics on timescales shorter than the period of light.

Synthesizing a pulse of these characteristics requires a broadband spectrum that consists of in-phase components. The researchers achieved this by combining solition self-compression with a high-gain amplifier. To prove the laser’s frequency comb nature, they produced mid-infrared light by difference frequency generation and resolved their electrical fields using electro-optical sampling.

Alongside its impressive specs, Xing highlights the comb’s accessibility. “Being an all-fiber laser design, this invention is inherently much more robust and compact than previous lasers with free-space components,” he said. “Moreover, all components in this laser are commercially available from multiple providers, making it easily repeatable in the optics community.”

The researchers foresee manifold applications of this technology. Supercontinuum generation, attosecond electronics, and light-matter interaction are just a few of the fields they list as possible beneficiaries.

Source: “Single-cycle all-fiber frequency comb,” by Sida Xing, Daniel M. B. Lesko, Takeshi Umeki, Alexander J. Lind, Nazanin Hoghooghi, Tsung-Han Wu, and Scott A. Diddams, APL Photonics (2021). The article can be accessed at https://doi.org/10.1063/5.0055534 .