Bandwidth-limited few-cycle pulses by nonlinear compression in a dispersion-alternating fiber
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Bandwidth‑limited few‑cycle pulses by nonlinear compression in a dispersion‑alternating fiber Niklas M. Lüpken1 · Carsten Fallnich1,2 Received: 15 June 2020 / Accepted: 8 October 2020 © The Author(s) 2020
Abstract We demonstrate an improved concept for nearly bandwidth-limited nonlinear pulse compression down to the few-cycle regime in a fiber chain with alternating sign of dispersion. Whereas the normally dispersive fiber segments generate bandwidth via self-phase modulation, the anomalously dispersive fiber segments recompress the broadened spectral bandwidth by an appropriate amount of group velocity dispersion. Nonlinear pulse compression from 80 fs input pulses to nearly bandwidth-limited 25 fs pulses at 1560 nm was achieved, resulting in a pulse compression factor of 3.2. The use of a specific dispersion-compensating fiber eliminated the impact of higher-order dispersion, such that a high spectral coherence was ensured. We show that nonlinear Schrödinger equation simulations were in good agreement with the experimental results and investigated the transfer of input fluctuations to the output. The concept is transferable to longer input pulse durations, resulting in compression factors of 83 for 10 ps input pulses.
1 Introduction Ultra-short pulses deliver high peak power within a very short time interval; therefore, pulse compression is a topic of high interest for a manifold of applications such as highharmonic generation [1–3], supercontinuum generation [4, 5], nonlinear optical microscopy [6], and telecommunication [7]. To generate ultra-short optical pulses, a broad bandwidth is necessary. For instance, gain media like titanium:sapphire crystals offer a broad bandwidth for the generation of pulses with durations down to a few femtoseconds [8]. Gain media doped with chromium ions provide enough bandwidth for the generation of ultra-short pulses in the telecom wavelength range [9], e.g., for high-speed optical time-division multiplexing [7]. However, fiber-based gain media are preferred in many applications such as telecommunications or biological imaging, but do not offer such a broad bandwidth. Due to the limited bandwidth of typical laser gain media such as erbium or ytterbium glass, pulse durations in the order of many tens or even hundreds of femtoseconds are * Niklas M. Lüpken n.luepken@uni‑muenster.de 1
Institute of Applied Physics, University of Münster, Corrensstraß e 2, 48149 Münster, Germany
MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
2
extracted directly from oscillators but the few-cycle regime is hardly accessible. To overcome this problem, nonlinear pulse compression (NLPC) has been well established [10]. This technique utilizes spectral broadening in a Kerr medium with subsequent compensation of the induced frequency chirp. NLPC was achieved within many different schemes using photonic crystal fibers [2, 11–14], highly nonlinear fibers [15], large-mode-area fibers [1, 3], hollow-core fibers [16–18], fiber amplifiers [
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