1 PHz of Coherent Bandwidth from a Compact Fiber Device

Abstract

Femtosecond frequency combs uniquely combine high frequency resolution, wide spectral coverage, and the ability to generate single-cycle pulses, rendering them essential for fundamental research and applied photonics. However, effective dispersion management across vast bandwidths remains a major challenge, often requiring complex setups that compromise stability and efficiency. Here, a coherent comb spectrum is presented with an unprecedented bandwidth of 1 PHz, spanning from the deep ultraviolet (280 nm) to the mid-infrared (2700 nm). This output is generated by a compact fiber device pumped by an ultrastable Er:fiber system. By integrating two highly nonlinear fibers with distinct germanium doping and waveguide design, a flat dispersion profile is achieved across the entire mid- and near-infrared spectral region. This pulse purification technology facilitates efficient third-harmonic generation within the same nonlinear device enabling the synthesis of ultrashort pulses with an exceptionally clean temporal envelope. Using a novel spectral filter and customized chirped mirrors, single-cycle near-infrared pulses with a duration of 3.56 fs are obtained. Beat signals between the fundamental dispersive wave and its third harmonic exhibit exceptional long-term passive stability, underpinning the reliability of this concept. This compact and versatile approach marks a significant leap forward in the generation and control of coherent supercontinua.