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Sep 15, 2015 - Daojing Li, Dingyuan Tang, Member, OSA, Luming Zhao, Senior Member, IEEE, and Deyuan Shen. Abstract—Numerical simulations on.
JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 33, NO. 18, SEPTEMBER 15, 2015

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Mechanism of Dissipative-Soliton-Resonance Generation in Passively Mode-Locked All-Normal-Dispersion Fiber Lasers Daojing Li, Dingyuan Tang, Member, OSA, Luming Zhao, Senior Member, IEEE, and Deyuan Shen

Abstract—Numerical simulations on dissipative-solitonresonance generation in an all-normal-dispersion fiber ring laser are presented. Situations with monotonic and periodical saturable absorption are both considered. The multipulse operation in dissipative soliton laser is found to be caused by the spectral filtering effect that limits the spectral maximum width, and the multipulsing can be fully circumvent by inducing strong peak-power-clamping effect of a sinusoidal saturable absorber in the cavity. When the cavity peak-power-clamping effect is strong enough that the pulse peak power and the pulse spectral width are both confined at a low value, the spectral filtering effect induced multipulse operation is prevented and the dissipative-soliton-resonance is generated. Otherwise, the spectral filtering effect causes pulse breaking before the pulse peak power reaches the saturation point. Further results show that under the dissipative-soliton-resonance, the generated pulse peak power can be directly controlled by the cavity peak-power-clamping effect, which is determined by the saturation power of the saturable absorber. Index Terms—Dissipative-soliton-resonance, multipulse operation, optical solitons, ultrafast optics.

I. INTRODUCTION ASSIVELY mode-locked fiber lasers have been extensively investigated in the past two decades because of their compactness, alignment-free operation and excellent pulse stability [1]–[11]. Different operation regimes were explored to achieve higher pulse energy. When a fiber laser consists of purely anomalous-dispersion components, conventional soliton forms in the cavity as the result of the balance between anomalousdispersion and nonlinearity. However, the pulse energy for single soliton is limited, due to the soliton energy quantization effect [1]. With high pump power, multipulse operation is always obtained, and in the steady state all the pulses are identical. In recent years, dissipative soliton formed in the all-normal-

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Manuscript received April 20, 2015; revised June 17, 2015; accepted June 22, 2015. Date of publication June 24, 2015; date of current version August 9, 2015. This work was supported in part by the National Natural Science Foundation of China under Grant 61177045, in part by the Priority Academic Program Development of Jiangsu Higher Education Institutions, and in part by the Minister of Education under Grant 35/12, Singapore. (Corresponding author: Luming Zhao). D. Li and D. Shen are with the Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China (e-mail: daojingli12 @fudan.edu.cn; [email protected]). D. Tang and L. Zhao are with the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (e-mail: [email protected]; [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/JLT.2015.2449874

dispersion fiber laser was reported, attracting researchers as it favors larger pulse energy compared to the soliton formed in the anomalous-dispersion regime and the dispersion-managed regime [2]–[5]. The pulse dynamics of the dissipative soliton is not only determined by the cavity dispersion and nonlinearity, but also gain and loss. In spite of different pulse dynamics, the multipulse operation in dissipative soliton lasers was still experimentally observed [5], [12]. A saturable absorber (SA) is generally needed to mode-lock the laser. Either physical or artificial SA can be employed in the cavity. The former includes semiconductor saturable-absorber mirrors (SESAMs) [6], carbon nanotubes [7], graphene [8] etc., while the latter includes nonlinear polarization rotation (NPR) [2], nonlinear optical loop mirror (NOLM) [11], and their variants. Despite of different mode-locking techniques used, the multipulse operation always generated in the cavities. The formation of the multipulse operation was both theoretically and numerically studied. Tang et al. proposed that in the anomalous dispersion regime the formation of the multiple solitons was caused by the peak-power-clamping effect of the laser cavity [13]. Komarov et al. [14] and Haboucha et al. [15] theoretically showed that in the normal dispersion regime additional spectrally selective losses or spectral gain filtering were necessary to achieve the multiple pulsing formation in a fiber laser passively mode-locked through the NPR technique. Weill et al. studied the multipulse formation in the framework of the statistical light-mode dynamics theory [16]. Li et al. built a simple iterative model quantifying the interaction of saturable gain and nonlinear loss in a mode-locked laser cavity [17]. Ding et al. [18] generated the sinusoidal Ginzburg–Landau equation by incorporation of the full transmission of wave plates and polarizers in the cavity. Their results well characterizes the generic multi-pulsing instability. The multipulse operation imposes a fundamental limitation on the achievable single pulse energy. To achieve high energies, methods to circumvent or suppress the multipulse operation is highly needed. Inspired by their own work, Li et al. [19]–[21] suggested ways to engineer the nonlinear losses in the cavity in order to achieve an enhanced performance theoretically. However, as they also pointed out in their manuscript, modification of the loss curve needs precise control in practice and may be difficult to achieve. Very recently, in the frame of complex cubic-quantic Ginzburg–Landau equation with certain parameter selections, Chang et al. [22], [23] proposed a new concept of soliton formation, the so called “dissipative soliton resonance” (DSR). In this case, the pulse peak power remains constant, while the pulse width could be

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Ginzburg–Landau equation iβ2 ∂ 2 u g ∂2 u g ∂u 2 =− u + + iγ|u| u + ∂z 2 ∂t2 2 2Ω2g ∂t2 Fig. 1.

Schematic of an all-normal-dispersion fiber laser.

arbitrarily broad and the pulse energy could be theoretically high at will. The multipulse operation is circumvented. Ding et al. proved that the DSR was achievable with realistic laser settings [24]. Komarov et al. investigated the competition and coexistence of ultrashort laser pulses under the DSR conditions [25]. They found that the number of the DSR pulses in steadystate operation depended on the initial conditions, but would not change with increasing pump power. The DSR generation has also been experimentally observed in fiber lasers modelocked by the NPR [26] and the NOLM [27]–[29]. In spite of considerable studies mentioned above, the physical mechanism of the multipulse operation and the DSR generation in dissipative laser remains unclear. None of them have managed to show in what physical ways the DSR is generated instead of the multipulsing in the cavity. The role of spectral balance on the single pulse stability has been recognized by researches [14], [15]. Liu showed that temporal and spectral balances plays the key roles on the pulse evolution in large net-normal-dispersion and high nonlinearity fiber mode-locked laser [30]. However, no DSR generation has been concerned. The transition from the multipulse operation to the DSR generation has not been characterised. And for the DSR generation, the management of the generated pulse peak power is not yet studied theoretically. In this manuscript we present results of numerical simulations on the mechanism of the multipulse operation and the DSR generation in a typical mode-locked all-normal-dispersion fiber ring laser. In our model, we considered the cases of both monotonic and periodical absorption induced by different mode-locking techniques. The monotonic absorption was adopted to model the physical SAs. Instead of explicitly incorporation of wave plates and polarizers, we used the sinusoidal transmission function of the NOLM to model artificial SAs, as to focus on the effect of the periodical absorption on the generation of DSR. The theoretical model used is presented in Section II. Simulation results and discussions are given in Section III. Conclusions are made in Section IV. II. THEORETICAL MODEL A typical mode-locked all-normal-dispersion ytterbiumdoped fiber (YDF) ring laser was considered as shown schematically in Fig. 1. The simulated laser contains a 0.6-m-long YDF, followed by 3-m-long single mode fiber. After the fiber, a SA and a Gaussian-shape spectral filter were placed. A 10% coupler was used to output the light. The pulse-tracking technique was adopted to simulate the pulse evolution in the fiber laser [13]. Briefly, the simulation started with an arbitrary weak pulse, the pulse circulated in the laser cavity until a steady state was established. The pulse propagation in fiber section was modeled by the complex nonlinear

(1)

where u is the normalized electric field envelope; β2 = 22 ps2 /km is the second-order dispersion coefficient, and γ = 0.0058 (Wm)−1 represents the nonlinearity of the fiber; t is the pulse local time and z is the propagation distance. g is the saturable gain of the fiber and Ωg is the gain bandwidth. A parabolic gain shape with 40 nm bandwidth was assumed. For un-doped fibers g = 0. For the YDF, the gain saturation was considered as g=

1+



G0 |u|2 dt/Esat

(2)

where G0 is the small-signal-gain coefficient and Esat = 1 nJ is the saturation energy. The integration was carried out over the whole round-trip period. The gain of the cavity could be controlled by the parameter G0 or Esat . In this manuscript, the small-signal-gain G0 was chosen. Two different transmission functions were used to model the SA effect induced by different mode-locking techniques. For artificial SAs, the sinusoidal transmission curve of NOLM was adopted [16], [31]    π(1 − Φ0 ) 1 I(t) + Φ0 π 1 − q cos T = 2 Isat

(3)

where q is the modulation depth, I(t) is the instantaneous pulse power, Isat is the saturation power when the periodical transmission reaches its first peak, and Φ0 stands for linear bias in the NOLM. Other artificial SAs, such as the NPR technique, might be described by a more complex model. However, their transmission has similar oscillating pattern. With this sinusoidal SA, the growth of the pulse peak power is limited primarily by the saturation power Isat . We note that in the following simulation, the modulation depth and the linear bias of the transmission curve mainly affect the starting mechanism. In the manuscript we focus on the transition from multipulse operation into DSR generation. In the stable mode-locking regime changing Φ0 or q has little impact on the pulse behavior, which is primarily determined by the filter bandwidth BW and the saturation power Isat . So as for simplification and without loss of generality, we set q = 0.4 and Φ0 = 0. For physical SAs such as SESAMs and graphene, an ideal monotonically increasing transmission function was assumed T =1−

q0 1 + I(t)/Isat

(4)

where q0 was set as 0.7 such that two transmission functions had the same unsaturated loss, I(t) is the instantaneous pulse power, and Isat is the saturation power. Fig. 2 shows the two transmission curves. After propagating through the spectral filter and the output coupler, the pulse went back into the YDF again.

LI et al.: MECHANISM OF DISSIPATIVE-SOLITON-RESONANCE GENERATION IN PASSIVELY MODE-LOCKED ALL-NORMAL-DISPERSION

Fig. 2.

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Monotonic and sinusoidal SA transmission curves.

III. SIMULATION RESULTS A. Case for Monotonic SA Curve The cavity with the monotonically increasing SA transmission function was first studied. As for the monotonically increasing SA transmission function, the higher intensity part of light always experiences higher transmission. This monotonic SA curve shows no limitation the intensity growth. The filter bandwidth was firstly set as BW = 10 nm, and the saturation power Isat = 300 W for the SA. Fig. 3(a) shows the generated stable dissipative solitons with increasing pump. The pulse peak power keeps growing as the pump increases, leading to the selfphase modulation induced spectrum broadening. The high side peaks on the spectra are due to the accumulated nonlinear phase shift during the propagation of the positive chirped pulse along the fiber [32]. The nonlinear phase shift ΦN L = γP L is closely related to the pulse peak power. The more nonlinear phase shift accumulated, the broader and more oscillatory structured the spectrum gets. Therefore, with higher pulse peak power, the spectrum becomes broader and the side peaks sharper as shown in Fig. 3(b). Further increasing the pump G0 to 4.5 m−1 , the pulse spectrum becomes too wide that the spectral filtering effect imposes extra loss on it. The pulse cannot be further amplified. Single dissipative soliton is no longer stable. With extra pump, the background starts to raise up and two smaller pulses are quickly built up in the cavity as observed from Fig. 3(c). Due to the gain competition, two pulses evolve until with identical parameters. In this way the original pulse breaks into two stable pulses with lower peak power and narrower optical spectrum. Thus two pulses are stable again in the cavity. Since no peak power limitation was induced by the monotonic SA, we attribute the multipulse operation to the spectral filtering effect. In order to confirm the spectral filtering effect on pulse breaking, the spectral filter bandwidth was varied while the other parameters remained unchanged. In stable mode-locking regime, multipulsing was always obtained. Results of BW = 14 nm are displayed in Fig. 4 as a comparison. With larger spectral filter bandwidth, the laser supports the pulse with larger pulse peak power and broader spectrum with more oscillatory structured side peaks compared to the case of BW = 10 nm. Further increasing the pump, the pulse spectrum is confined by the spectral filtering effect, and the background is amplified. Single

Fig. 3. (a) Pulse temporal profiles, (b) optical spectra, versus the pump G 0 increased from 2.5 to 4 m −1 . (c) Pulse evolution when the pump G 0 increased from 4 to 4.5 m −1 . BW = 10 nm. Isa t = 300 W. Monotonically increasing SA transmission function was assumed.

pulse breaks into two identical pulses. These two multipulse formations exhibit similar pulse evolution except that for the cavity with larger spectral filter bandwidth, broader spectrum and higher peak power are favored, indicating that the spectral filtering puts eventual limitation on the achievable pulse energy. The simulation results show that the multipulse operation in dissipative soliton fiber lasers is caused by the spectral filtering effect that limits the pulse spectral width. In this manuscript we refer to the edge-to-edge width as the pulse spectral width. It is worth noting that this limitation on the pulse spectral width cannot be removed, that is, the finite filter bandwidth is required for the formation of dissipative soliton. Once the filter bandwidth was assumed infinite, no mode-locking could be achieved.

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Fig. 4. (a) Pulse temporal profiles, (b) Optical spectra, versus the pump G 0 increased from 3 to 9 m −1 . (c) Pulse evolution when the pump G 0 increased from 9 to 10 m −1 . BW = 14 nm. Isat = 300 W. Monotonically increasing SA transmission function was assumed.

B. Case for Sinusoidal SA Curve The cavity was re-simulated with the sinusoidal SA transmission function. For the sinusoidal SA transmission curve, the growth of the pulse peak power is limited by the saturation power Isat . The simulation also began with Isat = 300 W, BW = 10 nm. Results are shown in Fig. 5. The pulse dynamics with the increasing pump is similar to that displayed in Fig. 3. As expected, the multipulse operation is finally obtained because of the spectral filtering effect. The simulation started over with varied Isat . We found that with low Isat , which means strong peak power limitation, DSR

JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 33, NO. 18, SEPTEMBER 15, 2015

Fig. 5. (a) Pulse temporal profiles, (b) optical spectra, versus the pump G 0 increased from 2.5 to 4 m −1 . (c) Pulse evolution when the pump G 0 increased from 4 to 5 m −1 . BW = 10 nm. Isat = 300 W. Sinusoidal SA transmission function was assumed.

can be generated in the cavity. Fig. 6 shows the results of Isat = 150 W. With increasing pump G0 , the pulse peak power increases at first but then remains constant due to the peakpower-clamping effect induced by the sinusoidal SA curve. The peak power here (∼ 220 W) is far lower than the case of Figs. 3 and 5, which reaches 400 W. Pulses of lower peak power accumulate smaller nonlinear phase shift in the cavity, thus less SPM-induced spectral broadening. And the spectrum here is less oscillatory. The high spectral side peaks caused by large nonlinear phase shift are not observed. As one can see from Fig. 6(a), the spectral width is around 14 nm, while in Figs. 3

LI et al.: MECHANISM OF DISSIPATIVE-SOLITON-RESONANCE GENERATION IN PASSIVELY MODE-LOCKED ALL-NORMAL-DISPERSION

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Fig. 6. (a) Pulse temporal profiles, (b) optical spectra, versus the increasing pump G 0 . BW = 10 nm. Isat = 150 W. Sinusoidal SA transmission function was assumed.

and 5 the spectral width extends to around 20 nm. The spectrum here is confined at a low value and within the transmission window of the cavity filter. Therefore, unlike the case of multipulse operation, the spectral filtering effect here does not impose extra loss on the pulse. With increasing pump, the pulse continues to be amplified. But the pulse peak power is still clamped. Instead pulse begins to extend in the time-domain (see Fig. 6(a)). And in the spectral domain, the newly generated energy is accumulated in the center part of the pulse spectrum (see Fig. 6(b)). In this way, the spectral filtering effect induced pulse breaking is circumvented. Further results show that with lower SA saturation power, stable DSR is always achieved. Otherwise multipulse operation is observed in the cavity. We varied both the saturation power Isat and bandwidth BW , and recorded the operating states as shown in Fig. 7(a). Qualitatively, under fixed filter bandwidth, when the Isat was set at a low value as the blue diamonds region in Fig. 7(a), the DSR was generated in the cavity. When it was set larger into the red dots region, the cavity operated in multipulsing state, until it overpassed the red dots towards the gray triangles where no stable mode-locking was achieved in the cavity. With smaller filtering bandwidth, the cavity needs stronger peak-power-clamping effect, lower Isat to confine the spectrum within the filtering window so that the DSR can be generated. The results suggest two ways to achieve DSR in dissipative soliton fiber lasers: increase spectral filtering bandwidth; and induce strong pulse peak power limitation. However, as we have

Fig. 7. (a) Different laser operating state with varying saturation power Isat and filter bandwidth BW . ML: Mode-locking. Blue diamonds repent the cavity working at DSR generation, red dots multipulsing, gray triangles no stable modelocking. (b) Pulse temporal profiles, (c) optical spectra, versus the saturation power Isat , under fixed pump G 0 = 10 m −1 . BW = 10 nm. Sinusoidal SA transmission function was assumed.

pointed out that the finite filter bandwidth is required for the formation of dissipative soliton. The saturation absorption effect is much more tunable in fiber lasers. This is particularly true for lasers mode-locked by NOLM. The NOLM relies on nonlinear interference of the counterpropagating fields so the saturation power of NOLM is inversely proportional to product of splitting ratio and loop length. In a fiber laser mode locked by a NOLM, Zhao et al. reported pulses well consistent with the DSR, which we believed, based on our model were due to a large splitting ratio thus a small saturation power of the NOLM [28].

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By simply increasing the loop length, saturation power can also be reduced. Mei et al. [29] generated square-wave pulse from a fiber laser passively mode-locked by a nonlinear amplifying loop mirror (NALM). The NALM had a loop length of 250 m, thus a very low saturation power. Their works agree well with our simulation results that strong peak-power-clamping is the key to achieve the DSR. Apart from the splitting ratio and loop length, the saturation can be engineered in other ways. Pottiez et al. demonstrated a particular design of the NOLM, relying on NPR, which allows adjusting the saturation power through input polarization control [33]. And the saturation power of the NALM can also be controlled by the gain [34]. Figs. 7(b) and (c) demonstrates the generated DSR pulses with different saturation powers under fixed pump. The results indicate that under the DSR generation, the generated pulse peak power can be directly controlled by the SA saturation power, which provides methods for amplitude tuning. This also agrees well with [29]. By using a pump at each loop, the authors were able to adjust not only the cavity gain, but also the saturation power of the NALM, which allowed they to tune the pulse peak power approximately from 4 to 8 W. The results of the two cases evidently show the key role of the peak-power-clamping effect of the sinusoidal SA for the DSR generation. Pulses propagating in the fiber experience nonlinear spectral broadening. High peak power leads to broader spectral width. In fiber cavities without the peak-power-clamping effect of the sinusoidal SA, the multipulse operation is always obtained with strong pump, due to the spectral filtering effect that limits the spectral maximum width. In fiber cavities with this peak-power-clamping effect, the peak power of a steady pulse will be clamped at the position depending on the SA saturation power. When the cavity peak-power-clamping effect is strong enough that the pulse peak-power is clamped at a sufficient low value, the spectrum is thus clamped within the transmission window of the spectral filter. The spectral filtering effect induced pulse breaking is thus circumvented. The DSR is generated. Otherwise, when the saturation power is set too high, the spectral filtering effect causes pulse breaking before the pulse peak power reaches the saturation point. IV. CONCLUSION In recent years, DSR attracts much attention as a promising way to achieve high energy pulse. In this manuscript, we build a simple model and study the cases of monotonic and sinusoidal saturable absorption for DSR generation in an all-normaldispersion fiber ring mode-lock laser. By comparing results of two cases, we manage to show physically how DSR generation circumvents multipulse operation. Pulses propagating in the fiber experience nonlinear spectral broadening. High peak power leads to broader spectral width. For lasers with monotonic saturable absorption, the spectral filtering effect, which limits the spectral maximum width, causes the multipulse operation in the dissipative soliton laser. Laser cavities with larger spectral filter bandwidth favor pulses with broader spectrum and higher peak power. To achieve the DSR generation in the cavity, strong peak-power-clamping effect of a sinusoidal SA is

required. When the cavity peak-power-clamping effect is strong enough that the pulse peak power and the pulse spectral width are both confined at a low value, preventing the spectral filtering effect induced multipulse operation, the DSR is generated. Otherwise, the spectral filtering effect causes pulse breaking before the pulse peak power reaches the saturation point. All the simulation results are based on our previous experience on experiments, for example, the modulation depth, the saturable energy. Although we focus on the qualitative analysis on DSR generation, we believe our results are practical for experiments. As a result of this work, a method to achieve DSR in practice is suggested [28], [29]: inducing strong peak-power-clamping effect, for example, using a very long NOLM as the mode-locking technique. Our numerical results further show that under DSR generation, the generated pulse peak power can be directly controlled by the cavity peak-power-clamping effect, which is also demonstrated experimently. REFERENCES [1] A. Grudinin, D. Richardson, and D. Payne. (1992, Jan.). Energy quantisation in figure eight fibre laser. Electron. Lett. [Online]. 28(1), pp. 67–68. Available: http://digital-library.theiet.org/ content/journals/10.1049/el_19920042 [2] K. Tamura, H. Haus, and E. Ippen. (1992, Nov.). Self-starting additive pulse mode-locked erbium fibre ring laser. Electron. Lett. [Online]. 28(2), pp. 2226–2228. Available: http://digitallibrary.theiet.org/content/journals/10.1049/el_19921430 [3] K. Tamura, E. P. Ippen, H. A. Haus, and L. E. Nelson. (1993, Jul.). 77-fs pulse generation from a stretched-pulse mode-locked allfiberring laser. Opt. Lett. [Online]. 18(13), pp. 1080–1082. Available: http://ol.osa.org/abstract.cfm?URI=ol-18-13-1080 [4] L. M. Zhao, D. Y. Tang, and J. Wu. (2006, Jun.). Gain-guided soliton in a positive group-dispersion fiber laser. Opt. Lett. [Online]. 31(12), pp. 1788–1790. Available: http://ol.osa.org/abstract.cfm?URI=ol-31-121788 [5] A. Chong, W. H. Renninger, and F. W. Wise. (2007, Aug.). All -normal-dispersion femtosecond fiber laser with pulse energy above 20nj. Opt. Lett.[Online]. 32(16), pp. 2408–2410. Available: http://ol.osa.org/abstract.cfm?URI=ol-32-16-2408 [6] L. Gomes, L. Orsila, T. Jouhti, and O. Okhotnikov, “Picosecond sesambased ytterbium mode-locked fiber lasers,” IEEE J. Sel. Topics Quantum Electron., vol. 10, no. 1, pp. 129–136, Jan. 2004. [7] S. Y. Set, H. Yaguchi, Y. Tanaka, and M. Jablonski. (2004, Jan.). Laser mode locking using a saturable absorber incorporating carbon nanotubes. J. Lightw. Technol. [Online]. 22(1), pp. 51–56. Available: http://jlt.osa.org/abstract.cfm?URI=jlt-22-1-51 [8] H. Zhang, D. Y. Tang, L. M. Zhao, Q. L. Bao, and K. P. Loh. (2009, Sep.). Large energy mode locking of an erbium-doped fiber laser with atomic layer graphene. Opt. Exp. [Online]. 17(20), pp. 17 630–17 635. Available: http://www.opticsexpress.org/abstract.cfm?URI=oe-17-20-17630 [9] V. J. Matsas, D. J. Richardson, T. P. Newson, and D. N. Payne. (1993, Mar.). Characterization of a self-starting, passively mode-locked fiber ring laser that exploits nonlinear polarization evolution. Opt. Lett. [Online]. 18(5), pp. 358–360. Available: http://ol.osa.org/abstract.cfm?URI=ol-18-5-358 [10] M. Nakazawa, E. Yoshida, T. Sugawa, and Y. Kimura. (1993, Jul.). Continuum suppressed, uniformly repetitive 136 fs pulse generation from an erbium-doped fibre laser with nonlinear polarisation rotation. Electron. Lett. [Online]. 29(2), pp. 1327–1329. Available: http://digitallibrary.theiet.org/content/journals/10.1049/el_19930890 [11] D. Richardson, R. Laming, D. Payne, V. Matsas, and M. Phillips. (1991, Mar.). Selfstarting, passively modelocked erbium fibre ring laser based on the amplifying sagnac switch. Electron. Lett. [Online]. 27(2), pp. 542–544. Available: http://digital-library.theiet. org/content/journals/10.1049/el_19910341org [12] L. M. Zhao, D. Y. Tang, T. H. Cheng, H. Y. Tam, and C. Lu. (2006, Jun.). Generation of multiple gain-guided solitons in a fiber laser. Opt. Lett. [Online]. 32(11), pp. 1581–1583. Available: http://ol.osa.org/abstract.cfm?URI=ol-32-11-1581

LI et al.: MECHANISM OF DISSIPATIVE-SOLITON-RESONANCE GENERATION IN PASSIVELY MODE-LOCKED ALL-NORMAL-DISPERSION

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Daojing Li received the B.S. degree in electronic science and technology from Shandong University, Jinan, China, in 2012. He is currently working toward the Ph.D. degree at the Department of Optical Science and Engineering, Fudan University, Shanghai, China. His current research includes ultrafast optics, mode-locked fiber lasers, and soliton dynamics.

Dingyuan Tang received the B.Sc. degree in physics from Wuhan University, Hubei, China, in 1983, the M.Sc. degree in laser physics from the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai, China, in 1986, and the Ph.D. degree in physics from Hannover University, Hannover, Germany, in 1993. From 1993 to 1994, he was a Scientific Employee at the Physikalisch-Technische Budesanstalt, Braunschweig, Germany. From 1994 to 1997, he was a university Postdoctoral Research Fellow, and from 1997 to 1999, he was an Australian Research Council Postdoctoral Research Fellow, both at the University of Queensland, Australia. From 1999 to 2000, he was a Research Fellow in the Optical Fiber Technology Center, the University of Sydney, Australia. He is currently an Associate Professor at the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore. He is a Member of the Optical Society of America and the Australian Optical Society.

Luming Zhao received the B.Eng. and M.Eng. degree in engineering physics from Tsinghua University, Beijing, China, in 1999 and 2002, respectively, and the Ph.D. degree in microelectronics from Nanyang Technological University, Singapore, in 2007. His research interests include ultrafast optics, fiber oscillators, fiber amplifiers, and soliton dynamics.

Deyuan Shen received the Ph.D. degree in physics from Shandong University, Jinan, China, in 1996. He subsequently joined the Institute for Laser Science, University of Electro-Communications, Tokyo, Japan, as a Postdoctoral Research Fellow, where he worked on laser-diode pumped high-power solid-state lasers. From 2000 to 2002, he was with the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, developing high-power visible and infrared solid-state lasers for industrial applications. He joined the Optoelectronics Research Centre (ORC), University of Southampton, Southampton, U.K., in 2002, and promoted to a Senior Research Fellow in 2005. His research activities at ORC included eye-safe high-power fiber lasers, fiber-bulk hybrid solid-state lasers, and novel fiber laser sources. He is currently a Professor at the Department of Optical Science and Engineering, Fudan University, Shanghai, China. His current research interests include power and brightness scaling of cladding pumped fiber lasers and amplifiers, nonlinear frequency conversion, and laser applications.