Mode-locked Ytterbium-doped Fiber Laser Research Articles

Blue-enhanced supercontinuum generation pumped by a giant-chirped SESAM mode-locked fiber laser

We report a blue-enhanced supercontinuum generation pumped by a giant-chirped SESAM mode-locked ytterbium-doped fiber laser. An extremely wide optical spectrum spanning from 380 nm to 2400 nm with total power of 3 W is obtained.

Nanosecond pulse generation in a MoS2 mode-locked ytterbium-doped fiber laser

We demonstrate a mode locked nanosecond ytterbium-doped fiber laser using a multilayer MoS2 saturable absorber. The MoS2 is prepared by a simple hydrothermal method and made into a film structure by spin-coating. The laser directly produces nanosecond pulses with stable mode locking at a pump threshold of 110 mW with a slope efficiency of 41 %. Resultant output pulses have central wavelength, pulse duration, and repetition rate of 1063.25, 0.1 nm, 22.88 ns and 2.17 MHz, respectively. The average output power was measured to be 9.84 mW under the pump power of 220 mW, corresponding to single pulse energy of 4.53 nJ. The experimental results show that multilayer MoS2 is a promising material for ultrafast laser systems.

Mode-locked ytterbium-doped fiber laser based on tungsten disulphide

We demonstrated an all-normal-dispersion Yb-doped mode-locked fiber laser based on tungsten disulphide (WS2). The saturable absorbers (SA) were made by mixing WS2 solution with polyvinyl alcohol (PVA), and then evaporated on a substrate. The modulation depth of the WS2 film was 2.06% and the saturable optical intensity was 71.6 MW cm−2. When the WS2 film was inserted into the fiber laser, the mode-locked pulses with pulse width of 2.5 ns and repetition rate of 2.84 MHz were obtained. As the pump power increased to 350 mW, the maximum output power was measured to be 8.02 mW. To the best of our knowledge, this is the first time to realize mode-locked pulses based on WS2-SA at 1 μm waveband.

Fabrication of 16 W all-normal-dispersion mode-locked Yb-doped rod-type fiber laser with large-mode area**Project supported by the National Key Technology R&D Program of the Ministry of Science and Technology, China (Grant No. 2012BAC23B03), the National Basic Research Program of China (Grant No. 2013CB922401), and the National Natural Science Foundation of China (Grant No. 11474002).

A mode-locked ytterbium-doped rod-type fiber laser with 85 μm core diameter is developed based on the nonlinear polarization evolution in an all-normal-dispersion ring cavity, in which a uniaxial birefringent plate is used as the spectral filter. Average power up to 16 W is obtained at the repetition rate of 58 MHz, and the pulse duration is compressed to 182 fs with a grating-pair compressor. The output laser pulses show very good beam quality and power stability.

Optimization of spectral distortion in a ytterbium-doped mode-locked fiber laser system

A method for optimizing the spectral distortion of an ultrafast pulse in a polarization-maintaining picosecond linear-cavity fiber laser with a one-stage fiber amplifier is proposed and demonstrated. The mechanism of control of the spectral distortion in the fiber system has been investigated. The experimental and theoretical results illustrate that the filtering effect of a fiber Bragg grating can effectively decrease the spectral oscillatory distortion accumulated by self-phase modulation. Injected into a Nd:YAG regenerative amplifier, the ultrafast pulse could produce high pulse energy of 1.2 mJ at a repetition rate of 1 kHz.

High energy rectangular pulse generated in a low repetition rate all normal-dispersion Yb3+-doped fiber laser

With elongated cavity length, a 317 kHz low-repetition-rate rectangular pulse was demonstrated in an all-normal dispersion mode-locked (ML) ytterbium-doped fiber laser (YDFL) based on the nonlinear polarization evolution technique. As the pump power increased, the duration of the rectangular pulse broadened linearly without wave-breaking. At a maximum pump power of 240 mW, a rectangular pulse with a duration of 20.5 ns and highest pulse energy of 182 nJ was produced. Through an Yb3+-doped fiber amplifier with 4 W pump power, the energy of the rectangular pulse was further amplified up to 2.28 µJ. The duration of the rectangular pulse remained constant as the pump energy increased and revealed no pulse distortion under the maximum output energy.

Influences of pumping schemes on the properties of dissipative soliton in fiber lasers

Based on the extended scalar nonlinear Schrödinger equation, the influences of pumping schemes on the properties of dissipative soliton are investigated theoretically in passively mode-locked ytterbium-doped fiber laser with positive dispersion cavity. Results show that, under the conditions of the same initial total gain, the dissipative solitons obtained in the backward pumping fiber laser have the narrowest spectral width, shortest pulse duration and highest pulse peak power for the forward, backward and bidirectional pumping schemes, moreover, the linear fitting degree of pulse chirp is lowest. With the same gain saturation energy, the pulse energies of the dissipative solitons are equal for three pumping schemes, but the differences of output spectra and temporal waveforms increase as the gain saturation energy increases.

Trapping of Soliton Molecule in a Graphene-Based Mode-Locked Ytterbium-Doped Fiber Laser

We reported on the trapping of soliton molecule in a passively mode-locked ytterbium-doped fiber laser with a microfiber-based graphene saturable absorber (GSA). By virtue of the highly nonlinear effect of microfiber-based GSA, the multipulse formation, such as the soliton molecule, is greatly enhanced despite of the all-normal dispersion regime. Depending on the cavity parameter selections, it was found that the conventional multisoliton could be reconstructed and then evolve into the soliton molecule. The soliton molecule trapping of two polarization components with a 0.65-nm wavelength separation was observed, which propagated as a group-velocity locked vector soliton despite of the cavity birefringence. The obtained results provide an enhanced understanding of dynamics of the soliton molecule.

Tunable dual- and triple-wavelength mode-locked all-normal-dispersion Yb-doped fiber laser

A tunable dual- and triple-wavelength passively mode-locked ytterbium-doped fiber laser in the all-normal-dispersion regime is reported and demonstrated. Using a phase-shifted long-period fiber grating as an all-fiber format spectral filter in the laser cavity, a self-starting stabilized multi-wavelength mode-locking operation is achieved by nonlinear polarization evolution. The mode-locked multi-wavelength output can be tuned continuously and smoothly over a spectral range of 10 nm using the phase-shifted long-period fiber grating bandpass filter without re-adjusting any elements in the system. It opens a new possibility to achieve tunable and controllable multi-wavelength mode-locked high-energy laser output in the all-normal-dispersion cavity in an all-fiber format.

Flexible rectangular wave-breaking-free pulse generation in actively mode-locked ytterbium-doped fiber laser.

We demonstrate nanosecond scale rectangular wave-breaking-free pulse generation in an actively mode locked Yb-doped fiber laser based on a combined action of active periodic cavity loss modulation and nonlinear polarization rotation effect. The pulse width of the laser can be controlled in the range of 890 ps to above 124 ns instantaneously by adjusting the electrical signal applied on the modulator. As high as 19.8 nJ wave-breaking-free pulse is achieved with maximum available pump power. The output pulse temporal dynamics exhibit various distinct characteristics under different modulation and polarization control. The laser presents unusually flexible tunabilities in pulse width, pulse energy and pulse shape.

Mode-locked ytterbium-doped fiber laser based on topological insulator: Bi₂Se₃.

We demonstrated an all-normal-dispersion Yb-doped mode-locked fiber laser based on Bi₂Se₃ topological insulator (TI). Different from previous TI-mode-locked fiber lasers in which TIs were mixed with film-forming agent, we used a special way to paste a well-proportioned pure TI on a fiber end-facet. In this way, the effect of the film-forming agent could be removed, thus the heat deposition was relieved and damage threshold could be improved. The modulation depth of the Bi₂Se₃ film was measured to be 5.2%. When we used the Bi₂Se₃ film in the Yb-doped fiber laser, the mode locked pulses with pulse energy of 0.756 nJ, pulse width of 46 ps and the repetition rate of 44.6 MHz were obtained. The maximum average output power was 33.7 mW. When the pump power exceeded 270 mW, the laser can operate in multiple pulse state that six-pulse regime can be realized. This contribution indicates that Bi₂Se₃ has an attractive optoelectronic property at 1μm waveband.

Multi-pulses dynamic patterns in a topological insulator mode-locked ytterbium-doped fiber laser

Multi-pulse dynamic patterns have been experimentally observed in an Ytterbium-doped fiber laser passively mode locked by a topological insulator (TI) Bi2Te3 saturable absorber (SA). The fundamental mode-locking operation with a repetition rate of ~1.10MHz was achieved under a pump power of ~160mW with an appropriate setting of the polarization controller (PC). It was found that through either changing the pump power or rotating the orientation of intra-cavity PC, several characteristic modes have been experimentally observed, including disordered multi-pulses, bunch of pulses, and soliton rains. Simultaneously, quasi-square pulses have also been observed in the laser cavity. Our systematic study clearly demonstrated that TI could be developed as an effective SA for the generation of different pulse operation states in a passively mode-locked all-normal-dispersion Ytterbium-doped fiber laser.

Fiber optical parametric oscillator based on photonic crystal fiber pumped with all-normal-dispersion mode-locked Yb:fiber laser

We demonstrate a cost effective, linearly tunable fiber optical parametric oscillator based on a home-made photonic crystal fiber pumped with a mode-locked ytterbium-doped fiber laser, providing linely tuning ranges from 1018 nm to 1038 nm for the idler wavelength and from 1097 nm to 1117 nm for the signal wavelength by tuning the pump wavelength and the cavity length. In order to obtain the desired fiber with a zero dispersion wavelength around 1060 nm, eight samples of photonic crystal fibers with gradually changed structural parameters are fabricated for the reason that it is difficult to accurately customize the structural dimensions during fabrication. We verify the usability of the fabricated fiber experimentally via optical parametric generation and conclude a successful procedure of design, fabirication, and verification. A seed source of home-made all-normal-dispersion mode-locked ytterbium-doped fiber laser with 38.57 ps pulsewidth around the 1064 nm wavelength is used to pump the fiber optical parametric oscillator. The wide picosecond pulse pump laser enables a larger walk-off tolerance between the pump light and the oscillating light as well as a longer photonic crystal fiber of 20 m superior to the femtosecond pulse lasers, resulting in a larger parametric amplification and a lower threshold pump power of 15.8 dBm of the fiber optical parametric oscillator.

Bright and Dark Square Pulses Generated From a Graphene-Oxide Mode-Locked Ytterbium-Doped Fiber Laser

The observation of the bright pulses and dark square pulses in a graphene-oxide saturable absorber (GOSA) passively mode-locked ytterbium-doped fiber laser has been investigated experimentally. Bright pulses are achieved at a pump power of ~ 200 mW. However, the dark-square-pulse generation starts at a much higher pump power of ~ 450 mW. At the maximum pump power of 600 mW, the dark-square-pulse bunches and harmonic mode locking (HML) can be also obtained by tuning the polarization controller (PC) to different orientations. It is the first demonstration of the bunches and HML of dark square pulses in a GOSA passively mode-locked ytterbium-doped fiber laser with large normal dispersion cavity.

Observation of multipulse bunches in a graphene oxide passively mode-locked ytterbium-doped fiber laser with all-normal dispersion

We give a systematic experimental study of multipulse bunches in a graphene oxide saturable absorber (GOSA) passively mode-locked all-normal dispersion ytterbium-doped fiber laser (YDFL). Some special phenomena such as harmonic multipulse bunches, harmonic mode-locking, and chaotic multipulse states are also obtained. Our experiment reveals that the inserted 2.5-nm narrow bandwidth filter plays an important role in the formation of multipulse in all-normal dispersion fiber lasers. Because of the effective gain bandwidth depends on both the 2.5-nm narrow bandwidth filter and the artificial fiber birefringence filter, the multipulse operation states are sensitive to the polarization. It is the first demonstration of multipulse evolution in a GOSA passively mode-locked all-normal dispersion YDFL.

Experimental studies of multiple pulses in a passively ytterbium-doped fiber laser based on graphene-oxide saturable absorber

The different multiple pulse phenomena are experimentally studied in a passively mode-locked ytterbium-doped fiber laser based on graphene-oxide saturable absorber (GOSA) with net normal dispersion cavity. At the same pump power with different polarization orientations, we observe the multiple pulse phenomena, including harmonic mode-locking of rectangular pulses, dissipative solitons, quasi-harmonic mode-locking, periodical peak modulation, multipulse bunches, multipulse cluster, and chaotic multipulse. The inserted 2 nm narrow bandwidth filter is important for limiting the gain bandwidth and shaping pulses. Adjusting the polarization controller is equivalent to changing the gain in the laser cavity, which is the main reason for the formation of different multiple pulses states. This is the first time that different multiple pulses states have been observed in an-normal-dispersion Yb-doped fiber laser with graphene-oxide saturable absorber. These results could extend the understanding of multiple pulse dynamics in GOSA mode-locked fiber lasers.

Soliton rains in a graphene-oxide passively mode-locked ytterbium-doped fiber laser with all-normal dispersion

We experimentally investigated soliton rains in an ytterbium-doped fiber (YDF) laser with a net normal dispersion cavity using a graphene-oxide (GO) saturable absorber (SA). The 195 m-long-cavity, the fiber birefringence filter and the inserted 2.5 nm narrow bandwidth filter play important roles in the formation of the soliton rains. The soliton rain states can be changed by the effective gain bandwidth of the laser. The experimental results can be conducive to an understanding of dissipative soliton features and mode-locking dynamics in all-normal dispersion fiber lasers with GOSAs. To the best of our knowledge, this is the first demonstration of soliton rains in a GOSA passively mode-locked YDF laser with a net normal dispersion cavity.

Demonstration of optical parametric gain generation in the 1 μm regime based on a photonic crystal fiber pumped by a picosecond mode-locked ytterbium-doped fiber laser

We report the experimental demonstration of the optical parametric gain generation in the 1 μm regime based on a photonic crystal fiber (PCF) with a zero group velocity dispersion (GVD) wavelength of 1062 nm pumped by a homemade tunable picosecond mode-locked ytterbium-doped fiber laser. A broad parametric gain band is obtained by pumping the PCF in the anomalous GVD regime with a relatively low power. Two separated narrow parametric gain bands are observed by pumping the PCF in the normal GVD regime. The peak of the parametric gain profile can be tuned from 927 to 1038 nm and from 1099 to 1228 nm. This widely tunable parametric gain band can be used for a broad band optical parametric amplifier, large span wavelength conversion or a tunable optical parametric oscillator.

Low repetition rate, hybrid fiber/solid-state, 1064 nm picosecond master oscillator power amplifier laser system

We report on an investigation of a passively mode-locked picosecond ytterbium-doped fiber laser with a repetition rate close to 1 MHz. The mode-locking operation was induced by a butt-coupled semiconductor saturable absorber mirror (SESAM) and stabilized in the normal dispersion regime by means of spectral filtering of a narrow bandwidth (0.1 nm) fiber Bragg grating (FBG). A pulse duration of about 50 ps with maximum output power of 20 mW at 1064 nm were achieved after amplification in the double-pass fiber preamplifier. This compact and reliable all-fiber laser operating at 1064 nm is intended to seed bulk amplifiers in a hybrid fiber/solid-state configuration. Employing a two-stage Nd:YVO4 amplifier, we obtained 10 W average output power, which preserved both the quasi-diffraction limited beam quality and spectral purity of the seeder. Second harmonic generation (SHG) with 50% conversion efficiency was demonstrated in type-II potassium titanyl phosphate (KTP) and type-I angle phase matched lithium triborate (LBO) crystal. Furthermore, a space independent numerical model was developed in order to study the dependence of intracavity pulse energy on the main design parameters of the master oscillator (cavity length, FBG bandwidth, SESAM modulation depth) within the stability range (single pulse per round trip in CW mode-locking operation) of the fiber laser master oscillator.

Experimental and numerical studies of mode-locked fiber laser with large normal and anomalous dispersion

An ytterbium-doped mode-locked fiber laser was demonstrated with a chirped fiber Bragg grating for dispersion management. The cavity net dispersion could be changed from large normal dispersion (2.4 ps(2)) to large anomalous dispersion (-2.0 ps(2)), depending on the direction of the chirped Bragg grating in laser cavity. The proposed fiber lasers with large normal dispersion generated stable pulses with a pulse width of <1.1 ns and a pulse energy of 1.5 nJ. The laser with large anomalous dispersion generated wavelength-tunable soliton with a pulse width of 2.7 ps and pulse energy of 0.13 nJ. A theoretical model was established and used to verify the experimental observations.