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.