[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Controllable Generation of Ultrashort Multi-Bound Solitons in a Mode-Locked Erbium-Doped Ring Laser with a Highly-Nonlinear Resonator

摘要： Mode-locked (ML) ultrashort pulse (USP) fiber lasers can be treated as an ideal platform to expand future applications due to a complex nonlinear dynamics with a presence of a high value of a group velocity dispersion and a third-order dispersion in the laser resonator. Up to now a series of novel ML regimes have been investigated e.g. self-similar pulses, noise-like pulses, multi-bound solitons, and a soliton rain generation. Multi-bound solitons (MBS) generation regime, also known as soliton molecules, is of considerable interest in various fields of applications. For example, the investigation of a MBS generation is very attractive for increasing the data transfer capacity in telecommunications due to coding alphabet extension. The coding concept of MBS suggests a data stream using more than two symbols (2?N symbols, where N is the number of generated solitons in a bound state) [1]. And also, recent research shows that using ultrafast bursts of pulses can improve the quality of laser ablation for medical applications [2]. Moreover, MBS generation can be also used in a coherent pulse staking amplification scheme increasing an amplification efficiency along with a formation of high-energy solitons at a high-repetition-rate [3]. Previously we have obtained a generation of stable low-noise ultrashort multi-bound solitons in a passive mode-locked all-fiber erbium-doped ring laser with a highly-nonlinear resonator [4]. Fig. 1 shows autocorrelation traces and spectrums of MBS generation obtained by pump power variation at a wavelength of 980 nm. The output spectrums are evidently showing high-contrast intensity fringes (up to ~20 dB) and autocorrelation traces having symmetrical form without additional intensity peaks that indicates a stable and strong coherent connection between ultrashort pulses and fixed coherent phase difference in the temporal domain between several identical pulses. It is known that the highest energy of a fundamental soliton in a laser resonator with duration τp is limited by the soliton area theorem Es ~ |β2|/(γ · τp), where γ is the net nonlinear coefficient and β2 is the total cavity dispersion [1]. Soliton energy quantization results in pulse splitting at operation powers higher than the fundamental limit. Here we experimentally demonstrate the formation multi-bound solitons with the controllable number of bound states 7 < N < 17 by pump power variation in the range from ~160 mW to ~377 mW obtained in a highly-nonlinear fiber ring cavity.