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A multi-switchable generation between dissipative solitons (DSs) and noise-like pulses (NLPs) in a fiber laser is demonstrated. A 45° tilted fiber grating is applied as an effective in-line all-fiber polarizer to realize the nonlinear polarization rotation (NPR) mechanism. With the fixed orientations of polarization controllers, the operation regimes of the fiber laser can be alternatively switched between DS and NLP by monotonically increasing pump power only. We observed five switching stages between DS/NLP regimes with the pump power elevating from 200 to 660 mW. Remarkably, the whole procedure could be precisely controlled forwardly and backwardly. This multi-shuttle behavior between the two distinct types of output pulse can be attributed to the transmission of NPR mechanism together with the gain filtering effect. To the best of our knowledge, this is the first report on the multi-shuttle behavior between DS and NLP in a fiber laser under monotonic change of pump power. Our findings may contribute to in-depth understanding of nonlinear dynamics and laser physics.

We present a passively mode-locked Erbium-doped fiber laser with tunable parameters including central wavelength, 3-dB bandwidth, and pulse duration. The mode-locking mechanism of the laser is realized by using single-walled carbon nanotubes (SWCNTs) polyvinyl alcohol composite film as a saturable absorber. The tunable operation is implemented via a fiber birefringence filter consisting of a polarization maintaining (PM) fiber and a Brewster fiber grating. The laser achieves a maximum spectral tuning range of 36 nm with 8-cm PM fiber. The maximum spectral width variation of 5.19 nm is acquired when the PM fiber is 12 cm. Simultaneously, the spectral widths of pulses at different central wavelengths are also adjustable. Furthermore, the total cavity length is 8.28 m, which is the shortest cavity length to obtain such wide tuning range in an Erbium-doped fiber laser based on SWCNTs.

We systematically study the impact of average cavity dispersion and pulse spectral bandwidth on harmonic mode locking in the long-wavelength band from an Er-doped fiber laser using carbon nanotubes polyvinyl alcohol (CNTs-PVA) film mode locker. By carrying out pulse energy management through optimizing the average cavity dispersion and optical spectral bandwidth, 2.08 GHz repetition rate corresponding to 201 st harmonic with 36.5 dB side mode suppression ratio (SMSR) can be realized under 205 mW pump power at 1597.53 nm. Furthermore, we systematically investigate the characteristics of the harmonically mode locked ultrashort optical pulses with different spectral bandwidths versus pump power under fixed cavity dispersion first. Key laser parameters have been studied including pumping efficiency, duration, energy, SMSR, and time bandwidth product. Enlightened by the experimental results, a simple law on preliminary and fast judgment of pulses frequency under fixed pump power is proposed, namely, by monitoring the pulse spectral bandwidth. The laser source featuring high repetition rate and L-band operation is greatly sought-after in some specific applications such as modern optical communication system etc.

Via using an L-band optimized in-fiber polarizing grating device, a GHz L-band femtosecond passively harmonic mode-locked Er-doped fiber laser based on nonlinear polarization rotation is first demonstrated. In total, 4.22 GHz pulses with the duration of 810 fs and super-mode suppression ratio (SMSR) of 32 dB are obtained under the pump power of 712 mW corresponding to 215th harmonic order. The central wavelength of 4.22 GHz pulses is 1581.7 nm with 10.1 nm 3 dB bandwidth. Furthermore, under this fixed pump power, higher harmonic orders can also be attained by rotating the polarization controllers properly. The highest repetition rate we obtained is 7.41 GHz with the SMSR of 20.7 dB.

Passively Q-switched pulses generation from Erbium-doped fiber laser based on PbS quantum dots (QDs) with microfiber as saturable absorber (SA) is demonstrated in this work. We successfully fabricate the microfiber with the diameter of ∼5.86 μm and the PbS QDs with an obvious absorption at 1550 nm. The passively Q-switched operation is realized using the interaction between the QDs and the evanescent field. The maximum output power of 14.9 mW and maximum single pulse energy of 121.2 nJ are realized at the pump power of 457 mW. To the best of our knowledge, this is the first demonstration of passively Q-switched generation using PbS QDs on microfiber as SA.

We have systematically studied the 45° tilted fiber grating (45TFG) as a functional device for erbium-doped fiber laser (EDFL) mode locking. A number of 45TFGs with different polarization-dependent loss (PDL) have been fabricated. Mode-locked (EDFL) using these devices have been characterized in terms of threshold, pulse duration, signal-to-noise ratio, and spectral width. Our results show that a 45TFG with higher PDL could achieve better laser results. By using a 45TFG with 24 dB PDL, the mode-locked laser has 8.1% conversion efficiency and a threshold of 200 mW.

We report on an in-fiber Brewster device with a 45° tilted fiber grating (TFG) directly written by a plane-by-plane femtosecond laser inscription method. Up to 10 dB polarization-dependent loss was achieved, proving effective polarizing functionality. Furthermore, we employ it as an in-line polarizer to successfully mode lock a fiber laser through the nonlinear polarization rotation technique. A stable soliton pulse train has been generated at 1563.64 nm with a pulse width of 624 fs and pulse energy of 0.42 nJ. With proper polarization adjustment, the laser also can operate in a noise-like regime. The parameters of this kind of 45°-TFG can be flexibly customized owing to the high flexibility and controllability of the femtosecond laser-inscription approach. In particular, such in-fiber polarizing devices inscribed by femtosecond laser inscription without removing the fiber coating are extremely robust for fiber lasers working at a broad wavelength region including the mid-infrared.

We demonstrated a wavelength-tunable passively mode-locked erbium-doped fiber laser based on carbon nanotube and intermodal interference of the microfiber. Continuously tuning range from 1569.6 nm to 1561.57 nm is achieved under single pulse operation.

We demonstrate a 1.4 GHz-range frequency-tunable Er-doped passively harmonic mode locked fiber laser based on nonlinear polarization rotation. Under fixed pump power, harmonic orders can be tuned continuously by merely adjusting polarization controllers.

In addition to some regular pulses such as conventional soliton (CS) and dissipative soliton (DS), passively mode-locked fiber lasers can also generate another type of distinctive pulse, i.e. the so-called noise-like pulse (NLP) [1]. Generally speaking, in NLP fiber lasers, NLP can be switched from CS or DS by increasing the pump power or adjusting the polarization controller (PC) [2]. However, as far as we know, multiple switchable generation between NLP and DS or CS have never been reported. We here show the multiple switchable phenomenon between NLP and DS from an Er-doped fiber laser (EDFL) based on nonlinear polarization rotation (NPR) for the first time. This kind of fiber laser not only facilitates the deep understanding of the properties and mechanisms of NLP but also paves a new way for the design of multi-functional light source.

We demonstrated a continuously wavelength-tunable bidirectional passively Q -switched fiber laser based on a single-walled carbon nanotube saturable absorber and a bandpass filter (BPF). By tuning the commercial BPF, the Q -switched pulse can be obtained in the same cavity at the same pump power in clockwise (CW) and counter-clockwise (CCW) directions. The central wavelength can be continuously tuned from 1520.88 to 1568.56 nm in the CW direction, and from 1520.96 to 1568.64 nm in the CCW direction. A wide tuning range of 48 nm is achieved for two directions in the passively Q -switched fiber laser. During the tuning process of the fiber laser, the output pulses with the same central lasing wavelength can be obtained in both oscillation directions owing to the BPF. By increasing the pump power from 130 to 350 mW, the cavity delivers a Q -switched pulse with the central wavelength of 1560 nm whose repetition rate changes from 9.64 to 59.18 kHz for the CW direction. In the CCW direction, the repetition rate of the Q -switched pulse changes from 10.26 to 61.03 kHz. To the best of our knowledge, it is the first time that continuous wavelength-tunable passively Q -switched pulses have been achieved in a bidirectional erbium-doped fiber laser.

A single/dual-wavelength switchable bidirectional Q-switched fiber laser using a bidirectional fiber polarizer is demonstrated. A 45° tilted fiber grating is used as a bidirectional fiber polarizer to induce a bidirectional intracavity birefringence filter in both clockwise (CW) and counter-clockwise (CCW) directions. A carbon nanotube saturable absorber is employed to produce Q-switched pulses. Through adjusting polarization states, switchable single/dual-wavelength lasing at 1551 and 1560 nm can be achieved in both CW and CCW directions. To the best of our knowledge, this is the first demonstration of a wavelength switchable bidirectional passively Q-switched fiber laser.

We report on the generation of noise-like pulses from a passively mode-locked erbium-doped fiber laser based on 45° titled fiber grating for the first time. The 3-dB spectral bandwidth of the noise-like pulses is about 21 nm.

We have demonstrated a 1.92 GHz L-band passively harmonic mode-locked Er-doped fiber laser based on nonlinear polarization rotation using a 45° tilted fiber grating for the first time.

A passively harmonic mode-locked Er-doped fiber laser based on carbon nanotubes film is demonstrated. The 42nd order of harmonic mode-locking corresponding to 1.15 GHz with 39.17 dB super-mode suppression ratio is obtained for the first time.

A passively mode-locked fiber laser using femtosecond laser inscribed plane-by-plane 45°-tilted fiber grating is experimentally demonstrated. The generated solitons center at 1561.8 nm with bandwidth reaching 7.14 nm and pulse width of 1.1 ps.

We demonstrate an all-fiber dissipative soliton Er-doped laser in L-band region using a 45° titled fiber grating for the first time. 697fs dissipative soliton with 30.19 nm spectral bandwidth at 1596.12 nm is realized.

Passively harmonic mode locking in a fiber laser based on single wall carbon nanotubes polyvinyl alcohol film is experimentally implemented. 916MHz pulses at the 34thharmonic with 41 dB super-mode suppression ratio can be generated.

PbS quantum dots (QDs)deposited on microfiber as a new type of saturable absorber is demonstrated in an erbium doped fiber laser. Successfully mode locked pulses with 51.56 dB signal to noise ratio was achieved.

A wavelength-tunable all-fiber Erbium-doped mode-locked fiber laser based on carbon nanotubes and 45° tilted fiber grating (TFG) is demonstrated. We investigated the effect of PDL of 45TFG in the tuning range of a mode locked laser. The central wavelength of the laser can be tuned continuously from 1559.85 nm to 1564.46 nm with a tuning range of 4.6 nm using a weak 45TFG and from 1553.37 nm to 1568.63 nm with a tuning range of 15.26 nm using a strong 45TFG. The laser maintains high signal to noise ratio >50 dB across all the wavelength tuning range.

A carbon nanotube mode-locked fiber laser based on an all-fiber birefringent filter consisting of 45° tilted fiber grating and polarization maintaining fiber is demonstrated with a 30 nm tuning range.

We demonstrate a L-band passively all-fiber mode locked erbium-doped laser based on a single 45° titled fiber grating and the center wavelength of the fiber laser is 1598.5 nm.

We demonstrate a wavelength tunable bidirectional Q-switched fiber laser based on carbon nanotube and a tunable bandpass filter with tuning range 51.43nm from 1515.43nm to 1566.86nm in clockwise and counter-clockwise direction for the first time.

We have demonstrated a passively harmonic mode-locked Er-doped fiber laser operating at L band based on carbon nanotubes film. 456.76 MHz pulses at 49th harmonics centered at 1595.98nm with 45dB super-mode suppression ratio can be realized.

A wavelength switchable bidirectional Q-switched fiber laser based on carbon nanotube saturable absorber and 45° tilted fiber grating induced nonlinear polarization rotating filtering effect is demonstrated for the first time.

We demonstrate a dispersion-managed Er-doped all-fiber laser based on nonlinear polarization rotation using a 45°-titled fiber grating. Ultrawide spectrum with full-width half-maximum of 96.41nm at 108MHz repetition rates can be generated directly.

We have demonstrated an all-fiber Erbium doped ultrafast laser by inserting a 45° tilted fiber grating. After optimizing the balance between intra-cavity nonlinearity and dispersion, an ultrashort pulse with sub-70 fs pulse duration can be achieved.

We have demonstrated a passively mode-locked erbium-doped fiber laser using colloidal PbS quantum dots (QDs) thin film as saturable absorbers (SAs). As the pump power up to 34.1 mW, we can observe the mode-locked pulse with the duration of2.86 ns.

We demonstrate a dispersion managed Erbium doped all-fiber laser with 101.75MHz repetition rate using 45°TFG to realize mode locking based on nonlinear polarization rotation technique. In our experiment, stable dual-pulse tightly bound states were observed under the pump power of 505mW.

A wavelength-tunable Erbium-doped fiber laser with birefringence-enhanced cavity is proposed. A 45° tiled fiber grating (45°TFG) and a section of polarization maintaining (PM) fiber are placed between two two polarization controllers (PCs). Two PCs and PM fiber are employed to enhance the birefringence effect. The 45° TFG plays the role of an in-fiber polarizer. The fiber laser is mode-locked by single walled carbon nanotube polyvinyl alcohol (SWCNTs-PVA) composite film. Central wavelength of the fiber laser can be tuned from 1552.52nm to 1575.28nm with a tuning range of 22.76nm. The demonstrated laser provided the widest tuning range in a high repetition rate all-fiber Erbium doped laser based on SWCNT.

We demonstrate a continuous tunable mode locked Erbium fiber laser using a tilted fiber grating based birefringent filter and carbon nanotube based saturable absorber. The central wavelength can be tuned from 1558 nm to 1564 nm while maintaining ultrashort pulse emission.

We fabricated three SWCNT-PVA composite films containing more metallic carbon nanotubes by CoMoCAT for the first time and influence of these composite films on performance of an Erbium-doped mode locked fiber laser is also studied.

Passively harmonic mode-locking (HML) of an Erbium-doped fiber laser using carbon nanotubes polyvinyl alcohol (CNTs-PVA) film is presented. The 20th harmonic mode-locking pulses at 500MHz repetition rate with 42dB super-mode suppression ratio (SMSR) are achieved.

Via careful choice of Er-doped fiber length in the cavity, a widely wavelength-tunable L-band dissipative soliton all-fiber Er-doped laser incorporating a L-band optimized polarizing fiber grating device is experimentally demonstrated. The laser delivers 15.38 ps dissipative soliton pulses centered at 1597.34 nm with 3 dB bandwidth of 34.6 nm under 622 mW pump power. The pulse repetition rate is 23 MHz. After using single mode fiber at external cavity, the pulse duration is compressed to 772 fs. With nonlinear polarization rotation-based intracavity comb filter, the central wavelength of the generated dissipative soliton can be tuned from 1567 nm to 1606 nm with a spectral tuning range of 39 nm, which, to the best of our knowledge, is the widest tuning range yet reported for a dissipative soliton fiber laser working in communication band.

We experimentally investigate the alternative generation of dissipative solitons (DSs) or noise-like pulses (NLPs) from a passively mode-locked Er-doped all-fiber laser with a 45° tilted fiber grating (45° TFG). The 45° TFG serves as an in-fiber polarizer for mode locking in the all-fiber laser cavity. Under the fixed orientations of the polarization controllers, flexible generation between DSs and NLPs can be precisely controlled by adjusting the pump power only. To the best of our knowledge, the total cavity length 4.92 m of our fiber laser is the shortest one among all NLP fiber lasers. We obtain the DS with 3 dB bandwidth of 20.4 nm centered at 1577 nm and the NLP with 3 dB bandwidth of 25.2 nm centered at 1574 nm. The fundamental repetition rate of the mode-locked pulses is 42.3 MHz. This DS-NLP switchable Er-doped fiber laser can be regarded as a multifunctional optical source for diverse practical and potential applications.

We demonstrate a passively harmonic mode-locked (PHML) fiber laser operating at the L-band using carbon nanotubes polyvinyl alcohol (CNTs-PVA) film. Under suitable pump power and an appropriate setting of the polarization controller (PC), the 54th harmonic pulses at the L-band are generated with the side mode suppression ratio (SMSR) better than 44 dB and a repetition frequency of 503.37 MHz. Further increasing the pump power leads to a higher frequency of 550 MHz with compromised stability of 38.5 dB SMSR. To the best of our knowledge, this is the first demonstration on the generation of L-band PHML pulses from an Er-doped fiber laser based on CNTs.

We demonstrated a passively Q-switched erbium-doped fiber laser (EDFL) using PbS quantum dots in polystyrene films (QDPFs) as saturable absorbers (SAs). Compared to other SAs, PbS QDPFs have advantages of broad absorption range, high quantum yield, low cost, and facile preparation. We have successfully generated stable Q-switched pulses with an average output power of 40.19 mW, a single pulse energy of 586.1 nJ, a repetition rate of 68.04 kHz, a pulse width of 3.9 μs, and a signal-to-noise ratio of 50.5 dB under 660 mW pump power. The output of the EDFL has been monitored for 5 consecutive hours under laboratory conditions to show stable operation of the laser system.