Evolution of invisible soliton pulsation in a mode-locked fiber laser (Invited)
-
摘要: 以锁模光纤激光器为研究平台,利用色散傅里叶变换技术,实时观察到调制频率成比例的三周期隐形孤子脉动现象。通过分析孤子的演化特性,笔者所在课题组认为孤子的调制不稳定性引起了色散波和孤子的参量耦合过程,导致了色散波和孤子的能量交换,从而产生了参量边带和隐形孤子脉动。部分能量在色散波和孤子间的交换使得孤子总能量几乎不变。因此这种孤子脉动难以通过时域脉冲序列分辨。此外,文中实验分析了隐形孤子脉动完整的演化路径,即仅通过增加泵浦功率使得脉动产生至消失的过程。与传统的可见脉动过程相比,这种隐形孤子脉动的调制周期随泵浦功率的变化较小。该工作不仅加强了对孤子脉动动力学现象的理解,还对锁模激光稳定性的提升具有重要意义。Abstract: The real-time observation of the tripling periodic invisible soliton pulsation in a mode-locked fiber laser with the dispersive Fourier transformation technique was reported. Since the three modulation frequencies were commensurate, the soliton pulsating behavior exhibited good periodicity rather than quasi-periodicity. After analyzing the soliton pulsating evolution, it was identified that the soliton modulation instability caused the generation of parametric sidebands and pulsating instability. The parametric process between soliton and dispersive waves induced the energy exchange between them. Consequently, there was no obvious total soliton energy variation during the evolution of soliton pulsation. As a result, the invisible soliton pulsation could not be visualized directly by the pulse train. In addition, by merely increasing the pump power with other cavity parameters unchanged, the entire route from the invisible soliton pulsation generation to stable dual-soliton pulses was systematically analyzed. Compared with the conventional visible soliton pulsation, the modulation periodicities of the invisible soliton pulsation showed weaker variations along with the pump power elevation. Our work not only contributed to understand the soliton pulsating dynamics in depth but also provided great assist to the optimization of laser performance.
-
图 2 当泵浦功率为40.8 mW时,典型稳定孤子序列的特性。(a) RF谱,插图:脉冲序列;(b) 左图:孤子能量和光谱强度的演变,右图:实时光谱演化图;(c) OSA所测量的光谱和DFT所采集的平均光谱;(d) 自相关轨迹
Figure 2. Characteristics of the stationary soliton at pump power of 40.8 mW. (a) RF spectrum, inset: pulse train; (b) Left-shown: variations of soliton energy and spectral intensity, right-shown: shot-to-shot spectral evolution; (c) Spectra and averaged spectra recorded by OSA and DFT; (d) Autocorrelation trace
图 3 当泵浦功率为49.2 mW时,隐形孤子脉动的特性。(a) RF谱,插图:脉冲序列;(b)左图:孤子能量和光谱强度的演变,右图:实时光谱演化图;(c) OSA所测量的光谱和DFT所采集的平均光谱;(d) 自相关轨迹;(e) RT 1-4光谱图;(f) 孤子能量、KS强度和PS强度随着RTN的变化
Figure 3. Characteristics of invisible soliton pulsation under pump power of 49.2 mW. (a) RF spectrum, inset: pulse train; (b) Left-shown: variations of soliton energy and spectral intensity, right-shown: shot-to-shot spectral evolution; (c) Spectra and averaged spectra recorded by OSA and DFT; (d) Autocorrelation trace; (e) Successive single-shot spectra from RT 1 to RT 4; (f) Total soliton energy, KS intensity and PS intensity versus RTN
图 4 泵浦功率分别41.4 mW(a)~(c)、42 mW(d)~(f)、45.4 mW(g)~(i)和 49.2 mW(j)~(l)的孤子脉动特性。(a)、(d)、(g)和(j)为RF谱;(b)、(e)、(h)和(k)为实时光谱演化过程;(c)、(f)、(i)和(l)为光谱3 dB带宽的变化
Figure 4. Characteristics of soliton pulsation under pump power of 41.4 mW (a)-(c), 42 mW (d)-(f), 45.4 mW (g)-(i) and 49.2 mW (j)-(l), respectively. (a), (d), (g) and (j) are RF spectra; (b), (e), (h) and (k) are real-time spectral evolutions; (c), (f), (i) and (l) are variations of spectral 3 dB bandwidth
图 5 隐形孤子脉动从产生到消失的演化特性。(a) 孤子光谱随着泵浦功率的变化;(b) ∆λKS和∆λPS随泵浦功率的变化;(c)中心波长和输出功率的演变;(d)孤子脉动演化过程中的三个调制频率随泵浦功率的变化
Figure 5. Evolution characteristics in the route from the invisible soliton pulsation generation to disappearance. (a) Soliton spectra under different pump power; (b) Variations of ∆λKS
and ∆λPS versus pump power; (c) Variations of center wavelength and output power; (d) Three modulation frequencies versus pump power in the soliton pulsating evolution -
[1] Chang G, Wei Z. Ultrafast fiber lasers: An expanding versatile toolbox [J]. iScience, 2020, 23(5): 101101. doi: 10.1016/j.isci.2020.101101 [2] Liu M, Li T, Luo A, et al. “Periodic” soliton explosions in a dual-wavelength mode-locked Yb-doped fiber laser [J]. Photonics Research, 2020, 8(3): 246-251. doi: 10.1364/PRJ.377966 [3] Du Y, Gao Q, Zeng C, et al. Formation and statistical properties of rogue wave in dispersion-managed fiber lasers [J]. Physical Review A, 2021, 103(6): 063504. doi: 10.1103/PhysRevA.103.063504 [4] Wang X, He J, Shi H, et al. Real-time observation of multi-soliton asynchronous pulsations in an L-band dissipative soliton fiber laser [J]. Optics Letters, 2020, 45(17): 4782-4785. doi: 10.1364/OL.400409 [5] Wang F, Zhang X, Cui J, et al. Evolution of soliton rain in a Tm-doped passive mode-locked all-fiber laser [J]. IEEE Photonics Journal, 2020, 12(4): 1-8. doi: 10.1109/JPHOT.2020.3012571 [6] Chang W, Soto-Crespo J M, Vouzas P, et al. Extreme soliton pulsations in dissipative systems [J]. Physical Review E, 2015, 92(2): 022926. doi: 10.1103/PhysRevE.92.022926 [7] Zhao L, Shu C, Wang Y, et al. Research progress of period doubling bifurcation in ultrafast fiber lasers (invited) [J]. Infrared and Laser Engineering, 2018, 47(8): 0803002. (in Chinese) doi: 10.3788/IRLA201847.0803002 [8] Akhmediev N, Soto-Crespo J M, Town G. Pulsating solitons, chaotic solitons, period doubling, and pulse coexistence in mode-locked lasers: Complex Ginzburg-Landau equation approach [J]. Physical Review E, 2001, 63(5): 056602. doi: 10.1103/PhysRevE.63.056602 [9] Zhao K, Gao C, Xiao X, et al. Real-time collision dynamics of vector solitons in a fiber laser [J]. Photonics Research, 2021, 9(3): 289-298. doi: 10.1364/PRJ.413855 [10] Wang X, Liu Y, Wang Z, et al. Transient behaviors of pure soliton pulsations and soliton explosion in an L-band normal-dispersion mode-locked fiber laser [J]. Optics Express, 2019, 27(13): 17729-17742. doi: 10.1364/OE.27.017729 [11] Zhou Y, Ren Y, Shi J, et al. Breathing dissipative soliton explosions in a bidirectional ultrafast fiber laser [J]. Photonics Research, 2020, 8(10): 1566-1572. doi: 10.1364/PRJ.399998 [12] Zhang Y, Cui Y, Huang L, et al. Full-field real-time characterization of creeping solitons dynamics in a mode-locked fiber laser [J]. Optics Letters, 2020, 45(22): 6246-6249. doi: 10.1364/OL.404778 [13] Wei Z, Liu M, Ming S, et al. Pulsating soliton with chaotic behavior in a fiber laser [J]. Optics Letters, 2018, 43(24): 5965-5968. doi: 10.1364/OL.43.005965 [14] Liu M, Wei Z W, Li H, et al. Visualizing the “invisible” soliton pulsation in an ultrafast laser [J]. Laser & Photonics Reviews, 2020, 14(4): 1900317. doi: 10.1002/lpor.201900317 [15] Zhao L, Tang D, Wu X, et al. Observation of dip-type sidebands in a soliton fiber laser [J]. Optics Communications, 2010, 283(2): 340-343. doi: 10.1016/j.optcom.2009.10.024 [16] Tang D, Zhao L, Wu X, et al. Soliton modulation instability in fiber lasers [J]. Physical Review A, 2009, 80(2): 023806. doi: 10.1103/PhysRevA.80.023806 [17] Dennis M L, Duling I. Intracavity dispersion measurement in mode locked fibre laser [J]. Electronics Letters, 1993, 29(4): 409-411. doi: 10.1049/el:19930274 [18] Agrawal G P. Modulation instability in erbium-doped fiber amplifiers [J]. IEEE Photonics Technology Letters, 1992, 4(6): 562-564. doi: 10.1109/68.141968 [19] Wang Z, Wang Z, Liu Y, et al. Self-organized compound pattern and pulsation of dissipative solitons in a passively mode-locked fiber laser [J]. Optics Letters, 2018, 43(3): 478-481. doi: 10.1364/OL.43.000478 [20] Tang D, Zhao L, Lin F. Numerical studies of routes to chaos in passively mode-locked fiber soliton ring lasers with dispersion-managed cavity [J]. Europhysics Letters, 2005, 71(1): 56-62. doi: 10.1209/epl/i2005-10052-0