Open Access
Add to BibSonomy
Abstract
An all-polarization-maintaining (PM) mode-locked fiber laser based upon nonlinear polarization evolution (NPE) that operates around 976 nm is presented. The NPE-based mode-locking is realized using a special section of the laser which comprises three pieces of PM fibers with specific deviation angles between the polarization axes and a polarization-dependent isolator. By optimizing the NPE section and adjusting the pump power, dissipative soliton (DS) pulses with a pulse duration of ∼6 ps, a spectral bandwidth of >10 nm and a maximum pulse energy of 0.54 nJ are generated. Self-starting, steady mode-locking operation is achievable within a pump power range of ∼2 W. Moreover, by incorporating a segment of passive fiber into the appropriate location in the laser resonator, an intermediate regime between stable single-pulse mode-locking and noise-like pulse (NLP) is realized in the laser. Our work expands the dimension of the research on the mode-locked Yb-doped fiber laser operating around 976 nm.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
The lasers operating around 976 nm are increasingly attractive to research communities motivated by the great application demands towards them. Compared with conventional laser sources emitting in the spectral region such as solid-state lasers and diode lasers, 976 nm ytterbium-doped fiber lasers possess superiorities in the aspects like high beam quality, simple thermal management and compact structure [1,2], which make them excellent pump sources for the Yb- and Er-doped fiber amplifiers and solid-state amplifiers [3,4]. In particular, 976 nm pulsed fiber lasers are of great potential to replace the bulky and inefficient argon ion and excimer lasers [5] as the pump sources of nonlinear frequency conversion system.
Although there are two main challenges to generate 976 nm lasing in the Yb-doped fiber lasers, namely the competitive lasing around 1030 nm and the strong reabsorption at 976 nm, the recent decades have still seen unprecedented developments of Yb-doped mode-locked fiber lasers operating around 976 nm. In 2003, O. G. Okhotnikov et al. reported the first mode-locked fiber laser operating in the spectral region around 976 nm, which utilized an in-house-built semiconductor saturable absorption mirror (SESAM) as the mode-locker [6]. Later, they demonstrated the self-started mode-locking operation in a linear cavity [7]. Both lasers include non-fiberized elements and have a relatively low output power. To further enlarge the output power, J. Lhermite et al. employed double-clad ytterbium-doped fiber as the gain medium in their NPE-based mode-locked fiber laser [8]. The mode-locking operation of the laser is activated via management of the pump power and the intracavity polarization state. Thus far, the shortest pulse duration achieved from mode-locked fiber lasers in the spectral region around 976 nm is 180 fs, which is realized by Zhou et al. using a system that combines the NPE-based mode-locking and the diffraction-grating pairs-based pulse compression [9]. To improve the mode-locking performance, the hybrid mode-locking techniques were developed by means of SESAM and NPE techniques [10,11]. Though the output power was scaled dramatically, some problems including complicated configuration and high cost arose as well.
All-fiberize architectures are strongly desired for mode-locked fiber lasers owing to their advantages in compactness and stability [12–19]. Furthermore, the architecture with all-PM fibers is of better stability due to the insensitivity to environmental perturbations, and possesses important applications attributing to the linearly polarized pulse output. Thus, the all-PM mode-locked fiber laser with better performance is more attractive and promising. An all-fiber polarization-maintaining mode-locked laser utilizing SESAM technique was reported, operating around 980 nm [20]. On the other hand, the NPE technique with higher damage threshold, as an artificial saturable absorber, combined with the all-fiber PM configuration, is an excellent solution to the high-performance fiber lasers. In 2017, J. Szczepanek et al. reported an all-fiber PM mode-locked laser operating at ∼1.03 μm using NPE method [21]. The evolution of polarization state and the compensation of polarization mode dispersion mismatch in the cavity were realized by splicing several segments of PM fibers with specific deviation angles. The all-fiber PM NPE mode-locking has aroused wide attention since then [22–25]. Nevertheless, thus far, there is still dearth of an all-PM NPE mode-locked fiber laser around 976 nm.
In this paper, we experimentally demonstrate a 976 nm all-polarization-maintaining mode-locked fiber laser based on nonlinear polarization evolution. Self-started dissipative soliton pulses with a pulse duration of ∼6 ps, a spectral bandwidth of >10 nm and a maximum pulse energy of 0.54 nJ are generated using the laser. Moreover, we established an intermediate regime between stable single-pulse mode-locking and NLP in the laser by inserting a piece of passive fiber into the cavity, and investigated its mechanism via numerical simulation. To our knowledge, this is the first time that such intermediate regime is observed in the 976 nm mode-locked Yb-doped fiber lasers. Our work enriches the research efforts regarding the 976 nm mode-locked fiber lasers, and it will contribute to the further development of the high-performance 976 nm ultra-short pulse sources.
2. Experimental setup
The schematic diagram of the proposed laser is shown in Fig. 1(a). A piece of 15-cm PM Yb-doped double-clad phosphate fiber (YDF, YDF-DC-13/80-PM) with a cladding absorption of 3.4 dB/m at 915 nm is employed as the gain medium, which has a core/cladding diameter of 12/80 μm. The YDF is pumped by a 915 nm laser diode (LD) via a (2 + 1) × 1 combiner (COM). A cladding power stripper (CPS) is connected with the YDF to eliminate the residual pump light. To improve the pump coupling efficiency and reduce the splicing loss, the COM and the CPS are customized with passive PM double-clad pigtail fibers (GDF-DC-10/80-PM), of which the core/cladding diameter is 10/80 μm, respectively. The key component of this cavity is the NPE section consisting of three angle-spliced PM fibers (Nufern, PM1060L) with a beat length of 3.22 mm at 976 nm and a polarization-dependent isolator (PD-ISO). Thereinto, a 100-cm PM1060L fiber is spliced at 23° to the pigtail fiber of the CPS. The other two segments are 210.8-cm long and 110.9-cm long, respectively. It’s worth noting that the length error is within a beat length of the PM1060L fiber. The splicing angle between the first PM fiber, the second one, the last one and the pigtail fiber of the isolator is 90°, 90°, 45°, respectively. The polarization-dependent isolator not only ensures the unidirectional propagation of signal pulses, but polarizes the initial laser pulses. A bandpass filter (BPF) with a full width at half maximum (FWHM) of ∼10 nm around 976 nm is placed after the PD-ISO, aiming to temporally and spectrally compress the pulse, compensating the intracavity dispersion and spectral broadening to sustain the pulse shape from round trip to round trip. 30% of the laser pulses are exported through a 30:70 coupler (OC) placed between the pigtail fiber of the BPF and the signal port of the COM. In order to distinguish different passive PM fibers, the GDF-DC-10/80-PM fiber is colored in blue in Fig. 1(a), and the other passive PM fibers are single mode PM1060L fibers (colored in black) with a core/cladding diameter of 8.5/125 μm. The refractive index difference $\Delta n$ is ∼3.029 × 10−4 between the fast axis and the slow axis of the PM1060L fiber. Note that position 1 represents a fusion splicing point between the BPF and the PD-ISO. The total cavity length is ∼10.04 m, corresponding to a group delay dispersion of ∼0.316 ps2.
Fig. 1. (a) Schematic diagram of the proposed laser. LD, laser diode; COM, combiner; YDF, Yb-doped phosphate fiber; CPS, cladding power stripper; PD-ISO, polarization-dependent isolator; OC, optical coupler; BPF, bandpass filter; position 1: a fusion splicing point between the BPF and the PD-ISO. (b) calculated transmission curve versus phase shift of the NPE-section.
The transmission dependent on the phase shift of the NPE section can be calculated by the Jones matrix [22]. Figure 1(b) depicts the transmission curve versus phase shift, showing a modulation depth $\Delta T$ of 70%, a non-saturable loss ${A_{ns}}$ of 15% and an absorbance ${A_0}$ of 15%.
In the experiment, the output power was monitored by a power meter (Thorlabs, S130C). The spectrum was recorded by an optical spectrum analyzer (Yokogawa, AQ6373) with a resolution of 0.02 nm. The temporal property was recorded by a 20 GHz oscilloscope (Teledyne Lecroy, SDA 820Zi-B) connected with a 12.5 GHz photodetector (EOT, ET-5000F). The radio frequency (RF) spectrum was recorded by the RF spectrum analyzer (Rohde & Schwarz, FSWP8). The autocorrelation trace was measured with a commercial autocorrelator (Femtochrome, FR-103 XL).
3. Results and analysis
The continuous-wave (CW) operation is obtained when the pump power is increased to 5.4 W, switched to the pulsed regime by further increasing the pump power to 8.54 W. In this case, the output characteristics of the mode-locked pulses are illustrated in Fig. 2. The output spectrum is shown in Fig. 2(a), which centers at 976.6 nm with a FWHM of 11.66 nm, revealing the typical spectral profile of DS with steep leading and trailing edges [26–28]. The spectral fluctuation on the top is mainly attributed to the interaction between different polarization components in the NPE section. The spectrum of the pulse in the linear scale is shown in the inset of Fig. 2(a). Figure 2(b) presents the autocorrelation (AC) trace, of which no fine structure is observed, verifying the single-pulse operation. The FWHM of the AC trace is 8.54 ps, fitted with a Gaussian function, indicating a pulse duration of 5.99 ps. The calculated time-bandwidth product (TBP) is 22.38, implying a highly chirped pulse. The pulse train in a range of ± 100 ns is plotted in Fig. 2(c), giving a pulse-to-pulse interval of 48.85 ns. As shown in Fig. 2(d), the fundamental repetition rate is 20.47 MHz with a SNR of 60 dB, consistent with the temporal interval. There is no other RF spectral component on either side of the peak. The wideband RF spectra of 2 GHz are presented in the inset of Fig. 2(d), of which the top envelope is flat without any spectral modulation or the high-order frequency noise, confirming good pulse stability. Under the pump power of 8.54 W, the average output power is 8.32 mW, corresponding to a single-pulse energy of 0.40 nJ and a peak power of 67.6 W.
Fig. 2. Output characteristics at the threshold pump power. (a) output spectrum, inset: the spectrum in the linear scale; (b) autocorrelation trace (blue) and Gaussian fitting curve (red); (c) pulse train; (d) RF spectrum at the fundamental repetition rate, inset: wideband RF spectra of 2 GHz.
To investigate the effect of pump power on the output characteristics, the pump power is increased from 8.54 W to 11.96 W. Figure 3(a) presents the spectral evolution with rising pump power, and the adjacent spectral curves are spaced with a 5-dB ordinate offset to comprehensively display the spectral variations. It is observed that the central wavelength of the spectra remains unaltered at 976.6 nm with a slightly blue-shifted leading edge and a slightly red-shifted trailing edge when the pump power is increased from 8.54 W to 10.53 W. At the pump power of 10.53 W, the cavity operates in a critical regime, in which the CW component is about to appear, and the spectral bandwidth reaches 12.86 nm. The AC traces in the range of 8.54∼10.53 W are shown in Fig. 3(b), where their envelopes keep Gaussian shape. Meanwhile, no pulse splitting occurs, indicating that the laser operates in a single-pulse mode-locking regime. Further rising the pump power, the CW component is observed around 976.3 nm. Note that the bandwidth of BPF is 10 nm, less than the spectral bandwidth of the mode-locking pulses, which is attributed to the self-phase modulation (SPM) effect induced by the pulse propagation between the BPF and the OC. During the whole process of adjusting pump power, the pulse duration fluctuates within 5.8∼6.0 ps, as plotted (solid green line) in Fig. 3(c). The average power (colored in black), pulse energy (colored in red), peak power (colored in blue) versus pump power are also presented in Fig. 3(c), respectively. The variation tendency of three curves is as follows. When the pump power is less than 10.53 W, these curves show an approximately linear growth. However, these curves become smooth once the pump power is beyond 10.53 W. As mentioned above, the CW component appears and its intensity increases continuously with increasing pump power, revealing that the increased pump power makes little contribution to the pulse energy in this case. Thus, the pulse energy and average power increase slowly, close to saturation. Moreover, the pulse duration keeps almost unchanged, which makes the peak power show the same trend as the pulse energy and average output power. As presented in Fig. 3(d), the power fluctuation over 2 hours (acquisition rate = 1 Hz) is measured at the pump power of 10.53 W, which possesses the normalized root-mean-square (RMS) deviation of 0.66%, demonstrating good stability.
Fig. 3. (a) Evolution of the output spectra, (b) evolution of autocorrelation trace, (c) average output power, pulse energy, pulse duration, and peak power versus pump power with the increase of pump power. (d) output power stability under the pump power of 10.53 W.
Furthermore, a peculiar mode-locking regime, namely the intermediate regime between stable single-pulse mode-locking and NLP, is achieved by incorporating a segment of passive fiber into position 1. In this case, the mode-locking threshold is 9.66 W, the average output power is 8.2 mW, and the calculated pulse energy is 0.54 nJ. The corresponding output characteristics are shown in Fig. 4 when a 3.5-m PM1060L fiber is incorporated into the cavity. Considering the fiber cutting and fusion splicing, the actual cavity length is 13.54 m, corresponding to a total group delay dispersion of 0.423 ps2. As presented in Fig. 4(a), the center wavelength of the output spectrum is 976.7 nm with a spectral bandwidth of 12.88 nm. Meanwhile, the spectral envelope is close to that of Fig. 2(a) with relatively deep edges [29]. The RF spectrum is presented in Fig. 4(b) with a peak center of 15.18 MHz and a SNR of 58.8 dB. It is worthwhile noting that a pair of symmetrical intensity noise spikes appear on both sides of the fundamental repetition rate, which indicates the random peak modulation in this regime [30,31]. To certify the pulse properties, the AC trace is measured as shown in Fig. 4(c). It features a double-scale structure with a tiny peak riding on a pedestal, which is a typical characteristic of the intermediate regime [29]. Assuming a Gaussian profile, the pulse duration is 9.98 ps.
Fig. 4. Incorporating a piece of passive fiber at position 1. (a) output spectrum; (b) fundamental repetition rate with a resolution bandwidth of 10 Hz; (c) AC trace (black) and Gaussian fitting curve (red).
In order to verify the feasibility of this method to generate 976 nm intermediate regime, a numerical simulation is necessary. Our simulation results confirm this conversion of the mode-locking regime, consistent with the experimental results, as shown in Fig. 5. When we set the gain saturation energy ${E_s}$ as 6 nJ and no passive fiber is inserted, a stable single pulse is achieved. The evolution of the pulse in spectral and temporal domains is demonstrated in Fig. 5(a) and 5(b), respectively. The corresponding AC trace without any fine structure is presented in Fig. 5(c), and the inset displays the pulse envelope, where the sag on the top results from the group velocity mismatching when two orthogonal polarized pulses synthesize out of the NPE section. Increasing the value of ${E_s}$ to 7.6 nJ and incorporating a 3.5-m long SMF into the cavity, the intermediate regime is realized. As seen in Fig. 5(d) and Fig. 5(e), there are plenty of internal fine structures which are different and localized at every roundtrip in the spectral and temporal domains. Compared with the former, the peak intensity of this situation in the evolution process is higher with larger nonlinear phase shift accumulation. In addition, the AC trace has a typical double-scale structure containing a tiny peak riding on a pedestal [29], as shown in Fig. 5(f).
Fig. 5. Mode-locking characteristics under the different parameter settings. (a) spectral evolution; (b) temporal evolution; (c) AC trace, inset: pulse envelope when Es = 6 nJ. (d) spectral evolution; (e) temporal evolution; (f) AC trace, inset: pulse envelope when Es = 7.6 nJ and inserting a 3.5-m long SMF into cavity.
According to these results discussed above, when the additional passive fiber is incorporated into position 1, the operation state of this laser is converted into intermediate regime and the pulse duration increases as the group delay dispersion of the laser cavity rises. The reason for aforementioned conversion is as follows. In an all-normal-dispersion (ANDi) mode-locked fiber laser, the characteristics of pulses such as amplitude, pulse duration and pulse energy vary significantly with the pulses propagating through different intracavity devices. After the pulse is amplified by the active fiber and compressed by the NPE section, its pulse energy and peak power reach a high level. Therefore, the pulse can accumulate considerable nonlinear phase shift once the passive fiber is inserted at position 1, contributing to the occurrence of the intermediate regime. The simulation results also verify our analysis, matched well with the experimental ones.
Moreover, in the case of Es = 6 nJ, we acquire the spectral evolution and temporal evolution of the pulse circulating inside the cavity. As presented in Fig. 6(a) and Fig. 6(b), the linearly polarized pulse is first amplified by the gain fiber. Subsequently, the linearly polarized pulse enters into the NPE section (comprising three PM fibers and ISO), where the spectral evolution and temporal evolution are both relatively complex. Propagating through the isolator, the intensity of the pulse decreases. The filter compresses the pulse temporally and spectrally, compensating the intracavity dispersion and SPM broadening to sustain the pulse shape. In the OC, the intensity of the pulse decreases and its spectrum slightly broadens. The simulated results are informative to fully understand the pulse evolution in the cavity.
Fig. 6. (a) spectral evolution and (b) temporal evolution of the pulse circulating inside the cavity when Es = 6 nJ.
4. Conclusion
In this paper, we reported an NPE-based, all-polarization-maintaining mode-locked Yb-doped fiber laser operating around 976 nm for the first time. The laser generates self-started DS pulses with a pulse duration of ∼6 ps, a spectral bandwidth of >10 nm and a maximum pulse energy of 0.54 nJ. We also realized an intermediate regime between stable single-pulse mode-locking and NLP from the laser by incorporating a piece of passive fiber into the cavity, and investigated its mechanism via numerical simulation. We hold a view that our work expands the dimension of the research on the 976 nm mode-locked fiber laser, and is informative for the researchers in the area of high-performance 976 nm pulsed lasers.
Funding
National Key Research and Development Program of China (2022YFB3605800); National Natural Science Foundation of China (NSFC) (61975136, 61935014, 62105222, 61775146, 61905151, 62275174, 62105225); Guangdong Basic and Applied Basic Research Foundation (2019A1515010699); Shenzhen Science and Technology Innovation Program (JCYJ20210-324094400001, CJGJZD20200617103003009, GJHZ20210705141-801006).
Disclosures
The authors declare that there are no conflicts of interest related to this article.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. M. E. Fermann and I. Hartl, “Ultrafast fibre lasers,” Nat. Photonics 7(11), 868–874 (2013). [CrossRef]
2. W. Shi, Q. Fang, X. Zhu, R. A. Norwood, and N. Peyghambarian, “Fiber lasers and their applications,” Appl. Opt. 53(28), 6554–6568 (2014). [CrossRef]
3. F. Roeser, C. Jauregui, J. Limpert, and A. Tünnermann, “94 W 980 nm high brightness Yb-doped fiber laser,” Opt. Express 16(22), 17310–17318 (2008). [CrossRef]
4. J. Boullet, Y. Zaouter, R. Desmarchelier, M. Cazaux, F. Salin, J. Saby, R. Bello-Doua, and E. Cormier, “High power ytterbium-doped rod-type three-level photonic crystal fiber laser,” Opt. Express 16(22), 17891–17902 (2008). [CrossRef]
5. M. Ghotbi and M. Ebrahim-Zadeh, “990 mW average power, 52% efficient, high-repetition-rate picosecond-pulse generation in the blue with BiB3O6,” Opt. Lett. 30(24), 3395–3397 (2005). [CrossRef]
6. O. G. Okhotnikov, L. Gomes, N. Xiang, T. Jouhti, and A. B. Grudinin, “Mode-locked ytterbium fiber laser tunable in the 980–1070-nm spectral range,” Opt. Lett. 28(17), 1522–1524 (2003). [CrossRef]
7. L. A. Gomes, L. Orsila, T. Jouhti, and O. G. Okhotnikov, “Picosecond SESAM-based ytterbium mode-locked fiber lasers,” IEEE J. Sel. Top. Quantum Electron. 10(1), 129–136 (2004). [CrossRef]
8. J. Lhermite, G. Machinet, C. Lecaplain, J. Boullet, N. Traynor, A. Hideur, and E. Cormier, “High-energy femtosecond fiber laser at 976 nm,” Opt. Lett. 35(20), 3459–3461 (2010). [CrossRef]
9. Y. Zhou, Y. Dai, J. Li, F. Yin, J. Dai, T. Zhang, and K. Xu, “Core-pumped mode-locked ytterbium-doped fiber laser operating around 980 nm,” Laser Phys. Lett. 15(7), 075107 (2018). [CrossRef]
10. P. Li, B. Liang, M. Zhang, Y. Yao, J. Chi, H. Hu, G. Zhang, C. Ma, and N. Su, “978 nm 1.24 ps ultra-short plused large mode area photonic crystal fiber laser,” Opt. Commun. 352, 19–24 (2015). [CrossRef]
11. J. Lhermite, C. Lecaplain, G. Machinet, R. Royon, A. Hideur, and E. Cormier, “Mode-locked 0.5 μJ fiber laser at 976 nm,” Opt. Lett. 36(19), 3819–3821 (2011). [CrossRef]
12. P. Li, Y. Yao, J. Chi, H. Hu, C. Yang, Z. Zhao, and G. Zhang, “980 nm all-fiber NPR mode-locking Yb-doped phosphate fiber oscillator and its amplifier,” Opt. Commun. 332, 187–191 (2014). [CrossRef]
13. S. S. Aleshkina, D. S. Lipatov, V. V. Velmiskin, V. Temyanko, and M. E. Likhachev, “Generation of chirped femtosecond pulses near 977 nm using a mode-locked all-fiber laser,” IEEE Photonics Technol. Lett. 32(13), 811–814 (2020). [CrossRef]
14. P.-X. Li, Y.-F. Yao, J.-J. Chi, H.-W. Hu, G.-J. Zhang, B.-X. Liang, M.-M. Zhang, C.-M. Ma, and N. Su, “980-nm all-fiber mode-locked Yb-doped phosphate fiber oscillator based on semiconductor saturable absorber mirror and its amplifier,” Chin. Phys. B 25(8), 084207 (2016). [CrossRef]
15. Y. Zhang, J. Zhu, P. Li, X. Wang, H. Yu, K. Xiao, C. Li, and G. Zhang, “All-fiber Yb-doped fiber laser passively mode-locking by monolayer MoS2 saturable absorber,” Opt. Commun. 413, 236–241 (2018). [CrossRef]
16. P. Li, X. Wang, C. Yao, and W. Xiong, “Layered structured binary alkaline metal phosphide of KP15 as saturable absorbers for ultrashort pulsed laser generation,” Laser Phys. Lett. 16(12), 125101 (2019). [CrossRef]
17. N. Su, P. Li, C. Yao, X. Wang, and W. Xiong, “Passively mode-locked Yb-doped all-fiber oscillator operating at 979 nm and 1032 nm with the single wall carbon nanotubes as SA,” Optik 198, 163282 (2019). [CrossRef]
18. S. Fu, L. Li, X. Zhu, R. A. Norwood, and N. Peyghambarian, “10-W level picosecond Yb3+-doped all-fiber laser source at 976 nm,” J. Lightwave Technol. 40(13), 4415–4419 (2022). [CrossRef]
19. S. Li, Z. Dong, G. Li, R. Chen, C. Gu, L. Xu, and P. Yao, “Chirp-adjustable square-wave pulse in a passively mode-locked fiber laser,” Opt. Express 26(18), 23926–23934 (2018). [CrossRef]
20. S. S. Aleshkina, A. Fedotov, D. Korobko, D. Stoliarov, D. S. Lipatov, V. V. Velmiskin, V. L. Temyanko, L. V. Kotov, R. Gumenyuk, and M. E. Likhachev, “All-fiber polarization-maintaining mode-locked laser operated at 980 nm,” Opt. Lett. 45(8), 2275–2278 (2020). [CrossRef]
21. J. Szczepanek, T. M. Kardaś, C. Radzewicz, and Y. Stepanenko, “Ultrafast laser mode-locked using nonlinear polarization evolution in polarization maintaining fibers,” Opt. Lett. 42(3), 575–578 (2017). [CrossRef]
22. L. Zhou, Y. Liu, G. Xie, W. Zhang, Z. Zhu, C. Ouyang, C. Gu, and W. Li, “Generation of stretched pulses from an all-polarization-maintaining Er-doped mode-locked fiber laser using nonlinear polarization evolution,” Appl. Phys. Express 12(5), 052017 (2019). [CrossRef]
23. J. Zhou, W. Pan, X. Gu, L. Zhang, and Y. Feng, “Dissipative-soliton generation with nonlinear-polarization-evolution in a polarization maintaining fiber,” Opt. Express 26(4), 4166–4171 (2018). [CrossRef]
24. Z. Wu, Q. Wei, P. Huang, S. Fu, D. Liu, and T. Huang, “Nonlinear polarization evolution mode-locked YDFL based on all-PM fiber cavity,” IEEE Photonics J. 12(2), 1–7 (2020). [CrossRef]
25. H. Zhao, G.-M. Ma, X.-Y. Li, T.-J. Li, H. Cui, M. Liu, A.-P. Luo, Z.-C. Luo, and W.-C. Xu, “Buildup dynamics in an all-polarization-maintaining Yb-doped fiber laser mode-locked by nonlinear polarization evolution,” Opt. Express 28(17), 24550–24559 (2020). [CrossRef]
26. P. Grelu and N. Akhmediev, “Dissipative solitons for mode-locked lasers,” Nat. Photonics 6(2), 84–92 (2012). [CrossRef]
27. A. Chong, W. H. Renninger, and F. W. Wise, “All-normal-dispersion femtosecond fiber laser with pulse energy above 20 nJ,” Opt. Lett. 32(16), 2408–2410 (2007). [CrossRef]
28. A. Chong, J. Buckley, W. Renninger, and F. Wise, “All-normal-dispersion femtosecond fiber laser,” Opt. Express 14(21), 10095–10100 (2006). [CrossRef]
29. S. Smirnov, S. Kobtsev, S. Kukarin, and A. Ivanenko, “Three key regimes of single pulse generation per round trip of all-normal-dispersion fiber lasers mode-locked with nonlinear polarization rotation,” Opt. Express 20(24), 27447 (2012). [CrossRef]
30. J. Zhao, J. Zhou, Y. Jiang, L. Li, D. Shen, A. Komarov, L. Su, D. Tang, M. Klimczak, and L. Zhao, “Nonlinear absorbing-loop mirror in a holmium-doped fiber laser,” J. Lightwave Technol. 38(21), 6069–6075 (2020). [CrossRef]
31. M. Michalska and J. Swiderski, “Noise-like pulse generation using polarization maintaining mode-locked thulium-doped fiber laser with nonlinear amplifying loop mirror,” IEEE Photonics J. 11(6), 1–10 (2019). [CrossRef]
