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Single-cycle all-fiber frequency comb



Sida Xing, Daniel Lesko, Takeshi Umeki, Tsung Han Wu, Alexander Lind, Nazanin Hoghooghi, Scott Diddams


Broad bandwidth mid-infrared frequency combs are important for molecular spectroscopy in a wide range of fundamental and applied research. However, realization of such light sources in a compact and robust format remains a challenge. In this paper, we present the first realization of a 2 µm all-polarization-maintaining-fiber frequency comb at 100 MHz repetition rate that emits single-cycle optical pulses. This is achieved by amplifying seed pulses in highly-doped Tm:fiber, followed by fiber-based self-compression to yield 6.8 fs pulses with 215 kW peak power. The corresponding spectrum, which is generated exclusively in silica fiber, covers more than two octaves from below 700 nm up to 3500 nm. By optimizing the length of nonlinear silica fiber, the region between 2100 and 2700 nm is tailored to provide a relatively flat spectrum with 180 mW of integrated power. We additionally employ intrapulse difference frequency generation in CdSiP\textsubscript2}} and orientation-patterned GaAs crystals to produce few-cycle mid-infrared pulses with corresponding frequency comb coverage from 6 µm to beyond 22 µm. Our work provides a robust all-fiber configuration, built on commercial technology, that generates frequency combs at the limit of a single cycle and multi-octave coverage in the near- and mid-infrared.
APL Photonics


frequency comb, ultrafast laser, fiber amplifier, infrared


Xing, S. , Lesko, D. , Umeki, T. , Wu, T. , Lind, A. , Hoghooghi, N. and Diddams, S. (2021), Single-cycle all-fiber frequency comb, APL Photonics, [online],, (Accessed April 20, 2024)
Created July 8, 2021, Updated November 29, 2022