Nonlinear dynamics in breathing-soliton lasers

High-repetition-rate (up to GHz) femtosecond mode-locked lasers have attracted significant attention in many applications, such as broadband spectroscopy, high-speed optical sampling, and so on. In this paper, the characteristics of dispersion-managed, polarization-maintaining (PM) 1-GHz mode-locked fiber lasers were investigated both experimentally and numerically. Three compact and robust 1-GHz fiber lasers operating at anomalous, normal, and near-zero dispersion regimes were demonstrated, respectively. The net dispersion of the linear cavity is adjusted by changing types of PM erbium-doped fibers (EDFs) and semiconductor saturable absorber mirrors (SESAMs) in the cavity. Moreover, the long-term stability of the three mode-locked fiber lasers is proved without external control. In order to better understand the mode-locking dynamics of lasers, a numerical model was constructed for analysis of the 1-GHz fiber laser. Pulse evolution simulations have been carried out for soliton, dissipative-soliton, and stretched-pulse mode-locking regimes under different net dispersion conditions. Experimental results are basically in agreement with the numerical simulations.

We present an experimental study of pulse dynamics in a mode-locked Er:fiber laser. By injecting a continuous wave laser with sinusoidal intensity modulation into the fiber laser, we are able to modulate the gain. Measuring the response of the pulse energy, central frequency, central pulse time, and phase to the gain modulation allows determination of the parameters that describe their coupling. Based on the experimentally derived parameters, we evaluate the free running comb linewidth and frequency uncertainty with feedback included, assuming quantum noise is the limiting factor. Optimization of fiber lasers is also discussed.

We demonstrate an all-fiber, Er-doped fiber laser mode-locked with a graphene-based saturable absorber. The resonator is designed using only polarization maintaining fibers and components, which allows to achieve linearly polarized output beam. The laser delivers 595 fs long pulses at 1560 nm center wavelength with 6.3 nm bandwidth and 67 MHz repetition rate. As a saturable a graphene-polymer was used. Full Text: PDF References Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, D. Y. Tang, Atomic-Layer as a Saturable Absorber for Ultrafast Pulsed Lasers, Adv. Funct. Mater. 19, 3077 (2009). CrossRef T. Hasan, Z. Sun, F. Wang, F. Bonaccorso, P. H. Tan, A. G. Rozhin, A.C. Ferrari, Nanotube?Polymer Composites for Ultrafast Photonics, Adv. Mater. 21, 3874 (2009). CrossRef H. Zhang, D. Y. Tang, L. M. Zhao, Q. L. Bao, and K. P. Loh, Large energy mode locking of an erbium-doped fiber laser with atomic layer graphene, Opt. Express 17, 17630 (2009). CrossRef Z. Sun, T. Hasan, F. Torrisi, D. Popa, G. Privitera, F. Wang, F. Bonaccorso, D. M. Basko, A. C. Ferrari, Graphene Mode-Locked Ultrafast Laser, ACS Nano 4, 803 (2010). CrossRef Z. Sun, D. Popa, T. Hasan, F. Torrisi, F. Wang, E. JR Kelleher, J. C Travers, V. Nicolosi, A. C Ferrari, A stable, wideband tunable, near transform-limited, graphene-mode-locked, ultrafast laser, Nano Res. 3, 653 (2010). CrossRef D. Popa, Z. Sun, F. Torrisi, T. Hasan, F. Wang, and A. C. Ferrari, Sub 200 fs pulse generation from a graphene mode-locked fiber laser, Appl. Phys. Lett. 97, 203106 (2010). CrossRef H. Zhang, D. Y. Tang, L. M. Zhao, Q. L. Bao, K. P. Loh, B. Lin, and S. C. Tjin, Compact graphene mode-locked wavelength-tunable erbium-doped fiber lasers: from all anomalous dispersion to all normal dispersion, Laser Phys. Lett. 7, 591 (2010). CrossRef H. Zhang, Q. Bao, D. Tang, L. Zhao, and K. Loh, Large energy soliton erbium-doped fiber laser with a graphene-polymer mode locker, Appl. Phys. Lett. 95, 141103 (2009). CrossRef J. Xu, S. Wu, H. Li, J. Liu, R. Sun, F. Tan, Q.-H. Yang, P. Wang, Dissipative soliton generation from a graphene oxide mode-locked Er-doped fiber laser, Opt. Express 20, 23653 (2012). CrossRef P.L. Huang, S. Lin, C. Yeh, H. Kuo, S. Huang, G. Lin, L. Li, C. Su, W. Cheng, Stable mode-locked fiber laser based on CVD fabricated graphene saturable absorber, Opt. Express 20, 2460 (2012) CrossRef X.H. Li, Y.G. Wang, Y.S. Wang, Y.Z. Zhang, K. Wu, P.P. Shum, X. Yu, Y. Zhang, Q.J. Wang, All-normal-dispersion passively mode-locked Yb-doped fiber ring laser based on a graphene oxide saturable absorber, Laser Phys Lett. 10, 075108 (2013). CrossRef M. Zhang, E. J. R. Kelleher, F. Torrisi, Z. Sun, T. Hasan, D. Popa, F. Wang, A. C. Ferrari, S. V. Popov, and J. R. Taylor, Tm-doped fiber laser mode-locked by graphene-polymer composite Opt. Express 20, 25077 (2012). CrossRef Q. Wang, T. Chen, B. Zhang, M. Li, Y. Lu, and K. P. Chen, All-fiber passively mode-locked thulium-doped fiber ring laser using optically deposited graphene saturable absorbers, Appl. Phys. Lett. 102, 131117 (2013). CrossRef G. Sobon, J. Sotor, I. Pasternak, A. Krajewska, W. Strupinski, K. M. Abramski, Thulium-doped all-fiber laser mode-locked by CVD-graphene/PMMA saturable absorber, Opt. Express 21, 12797 (2013). CrossRef G. Sobon, J. Sotor, I. Pasternak, K. Grodecki, P. Paletko, W. Strupinski, Z. Jankiewicz, K.M. Abramski, Er-Doped Fiber Laser Mode-Locked by CVD-Graphene Saturable Absorber, J. Lightwave Technol. 30, 2770 (2012). CrossRef A. Martinez, K. Fuse, B. Xu, and S. Yamashita, Optical deposition of graphene and carbon nanotubes in a fiber ferrule for passive mode-locked lasing, Opt. Express 18, 23054 (2010). CrossRef Y. M. Chang, H. Kim, J. H. Lee, and Y. Song, Multilayered graphene efficiently formed by mechanical exfoliation for nonlinear saturable absorbers in fiber mode-locked lasers, Appl. Phys. Lett. 97, 211102 (2010). CrossRef A. Martinez, K. Fuse, and S. Yamashita, Mechanical exfoliation of graphene for the passive mode-locking of fiber lasers, Appl. Phys. Lett. 99, 121107 (2011). CrossRef G. Sobon, J. Sotor, K. M. Abramski, All-polarization maintaining femtosecond Er-doped fiber laser mode-locked by graphene saturable absorber, Laser Phys. Lett. 9, 581 (2012). CrossRef J. Sotor, G. Sobon, K. M. Abramski, Scalar soliton generation in all-polarization-maintaining, graphene mode-locked fiber laser, Opt. Lett. 37, 2166 (2012). CrossRef M. L. Dennis, I. N. Duling III, Experimental study of sideband generation in femtosecond fiber lasers, IEEE J. Quantum Electron. 30, 1469 (1994) CrossRef

An L-band mode-locking erbium-doped fiber laser with high pulse energy is presented incorporating 1497 nm pump wavelength. Microfiber-based carbon nanotube saturable absorber is employed to initiate mode-locking operation in ring cavity. This mode-locked laser operates in soliton regime by scheming net anomalous dispersion of laser cavity. We observe mode-locked laser with Kelly's sidebands properties and 860 fs pulse duration at 341 mW pump power. The pulse energy of this mode-locked laser is measured at 1.08 nJ, on account of 20 % laser output excerpted from the laser cavity. This achievement is beneficial for numerous applications demanding on a high energy mode-locked laser source at L-band wavelength region.

We demonstrate an L-band passively mode-locked femtosecond fiber laser with a fundamental repetition rate of 1.013GHz based on a semiconductor saturable absorber mirror. Compared with other reported L-band fiber lasers that use overlong Er-doped fiber, the laser here consists of 10cm heavily doped fiber to increase the fundamental pulse repetition rate to gigahertz level. An output ratio as low as 0.2% is used to make the central wavelength up to 1.6μm. The laser operates at the soliton regime with a 3dB spectral bandwidth of 13.6nm and a pulse duration of 229fs.

We report a study on a hybrid mode-locked fiber laser with two saturable absorbers: slow and fast, integrated in a single device. Amorphous antimony telluride (Sb(2)Te(3)) layer was deposited on side-polished fiber to form the slow saturable absorber due to the third order nonlinear susceptibility of Sb(2)Te(3). Additionally, an unsymmetrical design of the device causes polarization-dependent losses and together with polarization controller allows to use a nonlinear polarization evolution to form the artificial fast saturable absorber. Sub-200 fs soliton pulses with 0.27 nJ of pulse energy were generated in the hybrid mode-locked Er-doped fiber laser. Differences in the dynamics of mode-locked laser are further investigated with the use of slow and fast saturable absorbers solely, and compared with the hybrid device. Joint operation of two saturable absorbers enhances the laser performance and stability. The conducted experiments allowed to define roles of each mechanism on the pulse shaping in the laser cavity.

As a universal phenomenon in nonlinear optical systems, pulsating behaviors of solitons have attracted increasingly more investigations. While pulsating solitons and their likely generation conditions had been widely theoretical studied, their detailed spectro-temporal dynamics had been hardly reported in experiments. Here, three types of pulsating solitons are experimentally generated and observed in a dispersion-managed, hybrid mode-locked fiber laser. By controllably generating such states through intracavity tuning and leveraging the dispersive Fourier transform technique that maps spectral information into the time domain, real-time ultrafast spectro-temporal evolutions of the pulsating behaviors are revealed. The numerical results further show the generation of the pulsating soliton could be caused by the intracavity spectral filtering effect, consistent with the experimental configurations. Our findings could provide further insights into the complex nonlinear dynamics in lasers and potential ways to the design such systems to deliver targeted soliton outputs for potential applications.

The tunable fiber lasers in the soliton regime are attractive ultrashort optical pulse sources. However, problems arise with fiber lasers due to their susceptibility to mechanical and temperature fluctuations affecting the optical path length of the cavities. The resulting instabilities are the major barriers for their applications in communications. The estimations of phase noise properties are important with respect to applications of the sources. Timing jitter is a type of phase noise that can occur in a short time scale. The jitter is consistent with small variations of optical path length in the cavity. We have demonstrated a passively mode-locked erbium-doped fiber laser to generate 60 nm tunable 270 fs pulses with 45.4 MHz repetition frequency. We describe the estimation of timing jitter in this fiber laser.

Pulsating solitons in fiber lasers embody a captivating phenomenon in nonlinear optics, combining the stability of solitons with the dynamic nature of pulsation. In recent years, real-time measurements have revealed a variety of pulsating solitons with distinct pulsation characteristics in fiber lasers, stemming from the intricate properties of dissipative systems. However, there are still rare studies focusing on the dynamical diversity of pulsating solitons in conventional soliton mode-locked lasers. Here, we report soliton pulsations induced by the four-wave mixing (FWM) in a conventional soliton fiber laser. Pulsating solitons including pulsating single solitons, synchronous and asynchronous double-soliton bunches, and soliton molecules (SMs) are observed. They all exhibit peak-dip alternation at the spectral center but present varying types of sidebands. The diversity of spectral pulsation characteristics is related to periodic variations in soliton parameters, the strength of dispersive wave radiation, and the relative phase between the soliton and the dispersive wave. These findings will expand the diversity of pulsating solitons with complicated spectral structures in nonlinear dissipative systems.

We demonstrate a fiber ring laser based on a single-walled carbon nanotube (SWCNT) wall paper absorber. It is found that the proposed Yb-doped fiber laser can either be operated in the mode-locked states or Q-switched states. First, SWCNT wall paper acts as a mode locker when the pump power is below 80 mW. Self-started mode locking can be obtained when the pump power is about 47 mW. The proposed Yb-doped mode-locked fiber lasers can be operated in the dissipative soliton regime that the spectra have a narrow peak. Second, SWCNT wall paper acts as a Q switcher when the pump power is above 80 mW. The Yb-doped fiber laser can work in the Q-switched states at higher pump power which is quite different from the conventional pulse fiber lasers. The repetition rate increases from 30 kHz to 50 kHz and the pulse duration decreases from 2.7 μs to 1 μs with the increase of pump power. This is due to the SWCNT wall paper induced loss in the cavity which leads to Q-switched state at higher pump powers. The combination of the Q-switching and mode-locking in one fiber laser have potential application in the fields that require different pulse fiber lasers.

We report on the application of a 1 μm solid-state passively Q-switched (PQS) laser and 1, 1.5 μm mode-locked (ML) fiber lasers based on ternary chalcogenide Ta2NiS5 saturable absorber (SA), which were successfully fabricated by liquid-phase exfoliation method (LPE). The nonlinear absorption of the Ta2NiS5-SA was characterized by 0.32 GW/cm2 and 0.25 GW/cm2 saturation intensities with 7.3% and 5.1% modulations depths at 1 μm and 1.5 μm, respectively. A PQS solid-state laser operating at 1.0 μm has been realized with the Ta2NiS5-SA. The maximum average output power, shortest pulse width, pulse energy, and pulse peak power from the PQS laser are 0.257 W, 180 ns, 1.265 μJ, and 7 W. Moreover, highly stable femtosecond laser centered at 1.5 μm, and picosecond centered at 1 μm, ML fiber lasers were obtained using the Ta2NiS5-SA. A 70 dB signal-to-noise ML laser with a pulse duration of 781 fs was observed in the telecommunication window, which is better than the duration of the previously reported lasers based on Ta2NiS5. The corresponding maximum single pulse energy and peak power are 0.977 nJ and 1251 W, respectively. The Ta2NiS5-SA fabricated by the LPE method was applied in near-infrared (NIR) ML fiber lasers (evanescent field interactions) and PQS bulk lasers. The results indicate that Ta2NiS5-SA prepared by the LPE method can be applied in a 1 μm bulk PQS laser and improved by the new combination mode (evanescent field interactions) for better output performance of the fiber laser.

The ground-breaking scientific and technological impact of optical frequency combs (OFC) – a bunch of equidistantly spaced narrow spectral lines or pulse train with the stabilized period produced by mode-locked laser – has been recognized by the scientific community sinFce 2005 when Theodor W. Hänsch was awarded the Nobel Prize in Physics. The recent Nobel Prize (2018) in physics corroborates the power of lasers in the context of pulse-shaping techniques for generating high-intensity laser pulses (Gérard Mourou and Donna Strickland: chirped pulse amplification). Though OFC and pulse-shaping techniques have already revolutionized a range of science and technological fields, there are still challenges related to unlocking new vector waveforms based on fast and slowly evolving state of polarization (SOP) in the pulse train. Harnessing vector waveforms will advance OFC-based technologies for applications in optical telecommunications, high-resolution spectroscopy, medical diagnostics, metrology and autonomous driving (LIDARs). Given advantages of the mode-locked fiber lasers vs bulk counterpart, e.g., confinement of pump and signal beams, long interaction length, and control of the propagation properties by the waveguide, make such lasers an ideal testbed for mastering different vector waveforms. This chapter summarizes our recent research results on the experimental characterization of vector waveforms generated by mode-locked fiber lasers in the time scales ranging from a few pulse widths (soliton molecules) to round-trip time (soliton rain, harmonic mode locking). Experimental results on slow and fast fundamental soliton polarization dynamics are presented in the first two sections. Experimental study of multipulsing polarization dynamics in the form of complex of pulses, soliton molecules, soliton rain, and vector rogue waves is described in the next four sections. Next, the experimental characterization of new vector mechanisms of fundamental and harmonic mode-locking is outlined. Finally, the theoretical characterization of the vector dynamics is described.

Here, few-layered W2C nanosheets and microfiber-based few-layered W2C-SA are fabricated by the magnetron sputtering deposition method. The third-order nonlinear optical responses of the prepared 2D W2C nanosheets are investigated by the Z-scan method with βeff and n2 determined to be −88.2 cm/MW and −1.112×10−13 m2/W, respectively, revealing its excellent nonlinear saturable absorption properties and optical modulation capabilities. In addition, by incorporating microfiber based few-layered W2C-SA into Yb-doped and Er-doped fiber lasers (YDFLs and EDFLs), the passively mode-locked operations at the central wavelength of 1035.1 and 1562 nm are realized, respectively. In addition, multi-soliton bound mode-locked operation in EDFLs with soliton pulses up to 36 is realized. Our results not only demonstrate the capability of few-layered W2C as a wideband optical modulator, but also provide a practical approach to explore soliton dynamics in fiber lasers.

Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperature is considerably below one femtosecond at high Fourier frequency. The ultrashort pulse train with ultralow timing jitter enables absolute time-of-flight measurements based on a dual-comb implementation, which is typically composed of a pair of optical frequency combs generated by femtosecond lasers. Dead-zone-free absolute distance measurement with sub-micrometer precision and kHz update rate has been routinely achieved with a dual-comb configuration, which is promising for a number of precision manufacturing applications, from large step-structure measurements prevalent in microelectronic profilometry to three coordinate measurements in large-scale aerospace manufacturing and shipbuilding. In this paper, we first review the sub-femtosecond precision timing jitter characterization methods and approaches for ultralow timing jitter mode-locked fiber laser design. Then, we provide an overview of the state-of-the-art dual-comb absolute ranging technology in terms of working principles, experimental implementations, and measurement precisions. Finally, we discuss the impact of quantum-limited timing jitter on the dual-comb ranging precision at a high update rate. The route to high-precision dual-comb range finder design based on ultralow jitter femtosecond fiber lasers is proposed.

Fiber lasers show several advantages over other types of lasers. They are efficient, compact, and rugged since they require few bulk components and are virtually unaffected by the surrounding environment. Mode-locked mid-infrared (mid-IR) lasers are essential for a wide variety of applications. The promising applications of mode-locked fiber lasers at wavelengths near 3 m include combs generation (metrology), spectroscopic sensors, infrared countermeasures, laser surgery, high-efficient pump sources for longer-wavelength oscillators and mid-IR supercontinuum source pumping. Based on the nonlinear Schrdinger equation (NLSE), a theoretical model of passively mode-locked Er3+-doped fluoride fiber laser using a saturable absorber is set up. Some mechanisms for generating mid-IR ultrashort pulse in fiber lasers are investigated. When the dispersion of the cavity is managed properly, the numerical simulation mainly focuses on the evolution process of mid-IR ultrashort pulse in fluoride fiber oscillators. Influences of the intracavity net dispersion and the small-signal gain on the generation of mode-locked pulses are analyzed in detail. And the reasonable parameter windows are given. Just as the simulated results showed, for a case of 4 m Er3+-doped fluoride fiber, small-signal gain g0= 0.6 m-1 and unsaturated loss l0 = 0.7, the stable mode-locked pulses are achieved by tuning the net intracavity dispersion within a certain range from 0.72 ps2 to 0.83 ps2. As the net intracavity dispersion increases, the output pulse duration increases gradually, while the spectrum width (FWHM) and peak power decrease accordingly. In addition, for the case of 4 m Er3+-doped fluoride fiber, unsaturated loss l0 = 0.7 and net intracavity dispersion of 0.8 ps2, the stable mode-locked pulses can also be obtained by tuning the small-signal gain within a certain range from 0.55 to 0.70 m-1. As the small-signal gain increases, the output pulse duration, spectral width, and peak power increase gradually. This work may be beneficial to the design of experiments for achieving more narrow pulse duration, wide spectral width, and high peak power mid-infrared ultrashort pulse.