7-Methoxy-13-dehydroxypaxilline: New indole diterpenoid from an endophytic fungus Penicillium sp. Nb 19

ABSTACTA chemical investigation of the endophyte Penicillium sp. Nb 19, isolated from leaves of the traditionally medical plant Baphicacanthus cusia (Nees) Bremek., yielded one new indole diterpenoid, 7-methoxy-13-dehydroxypaxilline (1) together with seven known metabolites (2-8). The obtained structure of compound 1 was elucidated by its spectroscopic data. In addition, the absolute configuration of compound 6 was confirmed by ECD for the first time. Compounds 1-6 were evaluated for antitumor activity against MCF-7, HepG2, and HCCC-9810 cell lines.

Collision between soliton and polarization domain walls in fiber lasers

We report on the experimental observation of coexistence of solitons and polarization domains, as well as features of soliton collision with polarization domain walls (or kink solitons) in a single mode fiber laser. Depending on the sign of cavity dispersion, either bright or dark solitons have been formed in our fiber laser. Under suitable laser operation conditions, they could even coexist with polarization domains and collide with the domain walls. We show experimental evidence of both the elastic and inelastic soliton collisions with the domain wall solitons. Some interesting features of soliton interaction with polarization domains in a fiber laser are also firstly revealed.

Dark-bright soliton trapping in a fiber laser

We report, to the best of our knowledge, the first experimental observation of coexistence of scalar dark and bright solitons in a fiber laser operating in the near zero-dispersion regime. We show that because of the incoherent cross coupling, under suitable conditions a bright soliton formed in the net anomalous cavity dispersion regime could bind with a dark soliton formed in the net normal cavity dispersion regime in a fiber laser. The properties of the dark and bright solitons, as well as their bound states, are experimentally investigated. The numerical simulations based on the coupled Ginzburg-Landau equations have reproduced the experimental results well.

Coherently coupled vector black solitons in a quasi-isotropic cavity fiber laser

We report the first experimental observation of coherently coupled black-black solitons in a quasi-isotropic cavity fiber laser with normal cavity dispersion. The properties of the vector solitons accord well with the theoretical predictions based on the coherently coupled nonlinear Schrödinger equations. Numerical studies and experimental results clearly confirmed the existence of the highly robust vector black solitons in the fiber laser system.

[Application and safety evaluation of plant growth regulators in traditional Chinese medicine]

Plant growth regulator is a kind of synthetic pesticide with similar physiological activity to plant hormones. It has been widely used in grain, vegetables, fruits, flowers and other crops, and become an important technical guarantee for high yield, stable yield, high quality and efficient production of crops. In recent years, plant growth regulator is widely used in Chinese herbal medicine production for regulating the growth and development and increasing production of traditional. However the crop is different from general Chinese medicinal materials, the use of plant growth regulator should not only consider the effect of Chinese herbal medicine production, and also pay special attention to the influence of Chinese traditional medicine efficacy and safety. This paper reviewed the application of plant growth regulator in the traditional Chinese medicine, the impact on the quality and safety of Chinese medicinal materials, as well as plant growth regulator of residue limits standards and testing technology, so as to the scientific use of plant growth regulator, to promote Chinese standardization planting, provide the scientific basis to protect the safety of herbal medicine. At present, the indiscriminate use and abuse of plant growth regulators such as Zhuanggenling and bulking element are common in the production of Chinese crude drugs, which has led to a significant decline in the quality of some Chinese crude drugs, and resulted in the dual residual harm to the Chinese crude drugs and the cultivation environment, causing serious safety risks to human health. In the future, it is necessary to strengthen the registration management, use norms and limit standards of plant growth regulators in traditional Chinese medicinal materials, and strengthen the supervision and regulations on the use of fertilizer instead of medicine to avoid pesticide registration and other disorders, so as to provide a basis for the quality and safety monitoring of traditional Chinese medicinal materials. Simultaneously, it is encouraged to reduction or non-application of plant growth regulators in the production of Chinese medicinal materials, especially for traditional Chinese medicine which contains a variety of active ingredients. Therefore, it is actively advocated to cultivate Chinese medicinal materials through organic or ecological method.

Observation of incoherently coupled dark-bright vector solitons in single-mode fibers

We report experimental observation of incoherently coupled dark-bright vector solitons in single-mode fibers. Properties of the vector solitons accord well with those predicted by the respective systems of incoherently coupled nonlinear Schrödinger equations. To our knowledge, this is the first experimental observation of temporal incoherently coupled dark-bright solitons in single-mode fibers.

Observation of dark-bright vector solitons in fiber lasers

We report the experimental observation of coherently coupled dark-bright vector solitons in single mode fiber lasers with either normal or anomalous cavity dispersion. The properties of these vector solitons were found to agree well with theoretical predictions based on the coherently coupled nonlinear Schrödinger equations. The experimental results clearly confirmed the existence of a fundamentally new form of optical solitons in coupled nonlinear systems.

Coexistence and interaction of vector and bound vector solitons in a dispersion-managed fiber laser mode locked by graphene

We report on the experimental observation of vector and bound vector solitons in a fiber laser passively mode locked by graphene. Localized interactions between vector solitons, vector soliton with bound vector solitons, and vector soliton with a bunch of vector solitons are experimentally investigated. We show that depending on the soliton interactions, various stable and dynamic multiple vector soliton states could be formed.

Broadband nonlinear optical response in multi-layer black phosphorus: an emerging infrared and mid-infrared optical material

Black phosphorous (BP), the most thermodynamically stable allotrope of phosphorus, is a high-mobility layered semiconductor with direct band-gap determined by the number of layers from 0.3 eV (bulk) to 2.0 eV (single layer). Therefore, BP is considered as a natural candidate for broadband optical applications, particularly in the infrared (IR) and mid-IR part of the spectrum. The strong light-matter interaction, narrow direct band-gap, and wide range of tunable optical response make BP as a promising nonlinear optical material, particularly with great potentials for infrared and mid-infrared opto-electronics. Herein, we experimentally verified its broadband and enhanced saturable absorption of multi-layer BP (with a thickness of ~10 nm) by wide-band Z-scan measurement technique, and anticipated that multi-layer BPs could be developed as another new type of two-dimensional saturable absorber with operation bandwidth ranging from the visible (400 nm) towards mid-IR (at least 1930 nm). Our results might suggest that ultra-thin multi-layer BP films could be potentially developed as broadband ultra-fast photonics devices, such as passive Q-switcher, mode-locker, optical switcher etc.

Initial conditions for dark soliton generation in normal-dispersion fiber lasers

We report results of numerical simulations on the various initial conditions for dark soliton generation in an all-normal-dispersion fiber laser. All the dark solitons generated are odd dark solitons. Differently from the dark soliton generation in fibers, where an arbitrary dip could evolve into a dark soliton, it is found that the dark soliton can originate only from an initial dip with a certain parameter requirement. A bright pulse with either a hyperbolic secant square, Gaussian, or Lorentz profile can be developed into a dark soliton, provided that the parameters of the initial bright pulse are selected. Dark solitons can be generated in fiber lasers only if there is a phase jump, and this phase jump can be maintained and evolve to π during the pulse evolution.

280 GHz dark soliton fiber laser

We report on an ultrahigh repetition rate dark soliton fiber laser. We show both numerically and experimentally that by taking advantage of the cavity self-induced modulation instability and the dark soliton formation in a net normal dispersion cavity fiber laser, stable ultrahigh repetition rate dark soliton trains can be formed in a dispersion-managed cavity fiber laser. Stable dark soliton trains with a repetition rate as high as ∼280  GHz have been generated in our experiment. Numerical simulations have shown that the effective gain bandwidth limitation plays an important role on the stabilization of the formed dark solitons in the laser.

Molybdenum disulfide (MoS₂) as a broadband saturable absorber for ultra-fast photonics

The nonlinear optical property of few-layered MoS₂ nanoplatelets synthesized by the hydrothermal exfoliation method was investigated from the visible to the near-infrared band using lasers. Both open-aperture Z-scan and balanced-detector measurement techniques were used to demonstrate the broadband saturable absorption property of few-layered MoS₂. To explore its potential applications in ultrafast photonics, we fabricated a passive mode locker for ytterbium-doped fibre laser by depositing few-layered MoS₂ onto the end facet of optical fiber by means of an optical trapping approach. Our laser experiment shows that few-layer MoS₂-based mode locker allows for the generation of stable mode-locked laser pulse, centered at 1054.3 nm, with a 3-dB spectral bandwidth of 2.7 nm and a pulse duration of 800 ps. Our finding suggests that few-layered MoS₂ nanoplatelets can be useful nonlinear optical material for laser photonics devices, such as passive laser mode locker, Q-switcher, optical limiter, optical switcher and so on.

Graphene mode-locked femtosecond laser at 2 μm wavelength

We experimentally demonstrated a passively mode-locked femtosecond laser by using a graphene-based saturable absorber mirror (graphene SAM) in the spectral region of 2 μm. The graphene SAM was fabricated by transferring chemical-vapor-deposited, high-quality, and large-area graphene on a highly reflective plane mirror. Stable mode-locked laser pulses as short as 729 fs were obtained with a repetition rate of 98.7 MHz and an average output power of 60.2 mW at 2018 nm.

Highly efficient 2 μm Tm:YAG ceramic laser

We have experimentally demonstrated a highly efficient diode-pumped Tm:YAG ceramic laser operating at 2 μm wavelength. The maximum output power of 6.05 W was realized with a slope efficiency as high as 65%. As far as we know, it is the highest slope efficiency reported for Tm:YAG ceramic laser. The wavelength tuning experiment of Tm:YAG ceramic laser was carried out and the results suggest that Tm:YAG ceramic laser could operate simultaneously at multiple wavelengths in a wide range of 1884-2017 nm.

[Research of seedling quality grading of Dendrobium nobile]

OBJECTIVE

To establish the seedling quality grading standard of Dendrobium nobile.

METHODS

Height, stem thickness and stem nodes of seedlings (test-tube seedling and cutting seedling) from Chishui city Guizhou province were tested. Through statistical analysis, the key indicators for seedling quality grading were defined.

RESULTS

Height and the number of cluster were the primary indicator of test-tube seedling; Height and the number of buds were the primary indicator of cutting seedling.

CONCLUSION

The grade test-tube seedling quality of each grade should reach the following requirements: for the first grade seedlings height > or = 17cm, the numbers of cluster > or = 3; For the second seedling height 11 -17cm, the numbers of cluster > or =2. The grade cutting seedling requires the first grade seedlings height > or = 12cm, the numbers of buds > or = 3; The second grade seedling height 6 - 12cm, the numbers of cluster > or = 2. Seedlings those can hot reach the second grade requirements are defined as unqualified seedlings.

High-power polycrystalline Er:YAG ceramic laser at 1617 nm

We report on the efficient operation of a high-power erbium-doped polycrystalline Er:YAG ceramic laser at 1617 nm resonantly pumped by a high-power 1532 nm Er,Yb fiber laser. Lasing characteristics of Er:YAG ceramics with different Er3+ concentrations are evaluated and compared. With an output coupler of 15% transmission and 0.5 at. % Er3+-doped YAG ceramic as the gain media, the laser generates 14 W of output power at 1617 nm for 28.8 W of incident pump power at 1532 nm, corresponding to a slope efficiency with respect to incident pump power of 51.7%.

Diode-pumped femtosecond Yb:CaNb2O6 laser

We report to our knowledge a diode-pumped passively mode-locked Yb:CaNb(2)O(6) (Yb:CN) laser for the first time. Both CW and passive mode-locking operation of the laser are experimentally investigated. A maximum CW output power of 1.4 W with a slope efficiency of 20% is obtained on a 7 mm long 1.5 at.% Yb:CN crystal, while stable passive mode-locking with a commercial semiconductor saturable absorption mirror (SESAM) was achieved on a 3 mm long 3 at.% Yb:CN crystal. The mode-locked pulses have pulse width of 251 fs and an average output power of 44 mW at 1038 nm.

Evidence of dissipative solitons in Yb³⁺:CaYAlO₄

Operation of an end-pumped Yb³⁺:CaYAlO₄ laser operating in the positive dispersion regime is experimentally investigated. The laser emitted strongly chirped pulses with extremely steep spectral edges, resembling the characteristics of dissipative solitons observed in fiber lasers. The results show that dissipative soliton emission constitutes another operating regime for mode locked Yb³⁺-doped solid state lasers, which can be explored for the generation of stable large energy femtosecond pulses.

Direct laser writing of near-IR step-index buried channel waveguides in rare earth doped YAG

A new (to our knowledge) ultrashort laser pulse irradiation regime that allows us to directly modify and increase the refractive index of rare earth doped YAG polycrystalline ceramics has been identified. Single-mode buried channel waveguides in both Ho:YAG and Er:YAG ceramics at the near-IR wavelengths of 1.55 μm and 1.95 μm are demonstrated by fabricating positive square step-index cores. Minimum propagation losses of 1.5 dB cm(-1) at a 1.51 μm wavelength have been preliminarily obtained. Confocal microluminescence mapping reveals that the increased refractive index regions retain the near-IR spectral properties of Er3+ ions in the YAG crystalline matrix.

Femtosecond and continuous-wave laser performance of a diode-pumped Yb3+:CaYAlO4 laser

The cw and femtosecond laser operations of Yb(3+):CaYAlO(4) (Yb:CYA) are demonstrated. The laser emitted a maximum cw power of 1.94 W with a slope efficiency (η(slope)) of 71% and an optical-to-optical efficiency (η(opt)) of 51%. Under mode-locking operation, the laser emitted near transform-limited pulses with 156 fs pulse width, 8.1 nJ pulse energy and 0.74 W average power. The η(slope) and η(opt) of the mode-locked laser were 37% and 20%, respectively.

Dissipative soliton operation of an ytterbium-doped fiber laser mode locked with atomic multilayer graphene

Mode locking of an ytterbium-doped fiber laser with atomic multilayer graphene is, to the best of our knowledge, experimentally demonstrated for the first time. Dissipative solitons with duration of 580 ps at 1069.8 nm were generated. Since graphene can also be used to mode lock erbium-doped fiber lasers, our result shows that graphene indeed has wavelength-independent saturable absorption, which could be exploited to mode lock fiber lasers with various operating wavelengths.

Dissipative soliton trapping in normal dispersion-fiber lasers

We report on the dissipative soliton (DS) trapping in a fiber ring laser mode locked with a semiconductor saturable absorber mirror and operated in normal dispersion regime. It was shown that despite the fact that a DS is strongly frequency chirped, two DSs formed along the two orthogonal polarization directions of a birefringent cavity fiber laser can incoherently couple and travel with the same group velocity in the laser. Numerical simulations have well confirmed the experimental observations.

Vector dark domain wall solitons in a fiber ring laser

We observe a novel type of vector dark soliton in a fiber ring laser. The vector dark soliton consists of stable localized structures separating the two orthogonal linear polarization eigenstates of the laser emission and is visible only when the total laser emission is measured. Numerical simulations based on the coupled complex Ginzburg-Landau equations have well reproduced the results of the experimental observation.

Coexistence of polarization-locked and polarization-rotating vector solitons in a fiber laser with SESAM

We report the experimental observation of the coexistence of polarization-locked vector solitons (PLVSs) and polarization-rotating vector solitons (PRVSs) in a fiber laser mode locked with a semiconductor saturable absorber mirror. It was found experimentally that interaction between the PLVSs in a fiber laser could lead to formation of bound states of PRVSs. Moreover, the bound PRVSs as a unit have the same group velocity as that of the PLVSs in the cavity.

Large energy mode locking of an erbium-doped fiber laser with atomic layer graphene

We report on large energy pulse generation in an erbium-doped fiber laser passively mode-locked with atomic layer graphene. Stable mode locked pulses with single pulse energy up to 7.3 nJ and pulse width of 415 fs have been directly generated from the laser. Our results show that atomic layer graphene could be a promising saturable absorber for large energy mode locking.

Gain dispersion for dissipative soliton generation in all-normal-dispersion fiber lasers

Properties of dissipative solitons generated in all-normal-dispersion fiber lasers through the gain dispersion effect are numerically studied by using a pulse-tracing technique that considers interaction between gain saturation, gain dispersion, cavity dispersion, fiber Kerr nonlinearity, and cavity boundary conditions. The numerical results qualitatively match with experimental observations and show that the finite gain bandwidth, together with the pump power, determines the properties of the generated dissipative solitons, which further dictates the performance of the pulse compression.

Multi-wavelength dissipative soliton operation of an erbium-doped fiber laser

We report on the generation of multi-wavelength dissipative soliton (DS) in an all normal dispersion fiber laser passively mode-locked with a semiconductor saturable absorber mirror (SESAM). We show that depending on the strength of the cavity birefringence, stable single-, dual- and triple-wavelength DSs can be formed in the laser. The multi-wavelength soliton operation of the laser was experimentally investigated, and the formation mechanisms of the multi-wavelength DSs are discussed.

Bunch of restless vector solitons in a fiber laser with SESAM

We report on the experimental observation of a novel form of vector soliton interaction in a fiber laser mode-locked with SESAM. Several vector solitons bunch in the cavity and move as a unit with the cavity repetition rate. However, inside the bunch the vector solitons make repeatedly contractive and repulsive motions, resembling the contraction and extension of a spring. The number of vector solitons in the bunch is controllable by changing the pump power. In addition, polarization rotation locking and period doubling bifurcation of the vector soliton bunch are also experimentally observed.

Dissipative soliton resonance in an all-normal-dispersion erbium-doped fiber laser

We report on the generation of 281.2 nJ mode locked pulses directly from an erbium-doped fiber laser mode-locked with the nonlinear polarization rotation technique. We show that apart from the conventional dissipative soliton operation, an all-normal-dispersion fiber laser can also emit square-profile dissipative solitons whose energy could increase to a very large value without pulse breaking.

Observation of spectral enhancement in a soliton fiber laser with fiber Bragg grating

We demonstrate that soliton generation in a fiber laser containing a fiber Bragg grating exhibits spectral enhancement near the Bragg resonance wavelength. The Bragg grating leads to a spectral hole on the soliton spectrum while the observed enhancement is always located at the long wavelength side of the Bragg resonance.

Dissipative vector solitons in a dispersionmanaged cavity fiber laser with net positive cavity dispersion

We report on the experimental observation of gain-guided vector solitons (GGVSs) in a dispersion-managed fiber laser mode-locked with a semiconductor saturable absorber mirror (SESAM). Both the frequency-locked and phase-locked GGVS were observed. In addition, formation of multiple GGVSs and GGVS harmonic mode-locking were also experimentally revealed. Numerical simulations confirmed the GGVS formation in the fiber lasers.

Subpicosecond pulse generation from a Nd:CLNGG disordered crystal laser

We report on a diode-pumped passively mode-locked subpicosecond Nd:CLNGG disordered crystal laser for the first time to our knowledge. Owing to the large inhomogeneous broadening and spectrum splitting of the disordered crystal, the Nd:CLNGG laser generated 900 fs mode-locked pulses with a repetition rate of approximately 88 MHz at 1061 nm wavelength. With a single-emitter laser diode pumping, a maximum average output power of 486 mW was achieved with a slope efficiency of 26%. Our experimental results show that the four-level Nd:CLNGG disordered crystal could be an excellent alternative for subpicosecond pulse generation.

Induced solitons formed by cross-polarization coupling in a birefringent cavity fiber laser

We report on the experimental observation of induced solitons in a passively mode-locked fiber ring laser with a birefringence cavity. Owing to the cross coupling between the two orthogonal polarization components of the laser, it was found that if a soliton was formed along one cavity polarization axis, a weak soliton was also induced along the orthogonal polarization axis, and depending on the net cavity birefringence, the induced soliton could have either the same or different center wavelengths to that of the inducing soliton. Moreover, the induced soliton always had the same group velocity as that of the inducing soliton. They formed a vector soliton in the cavity. Numerical simulations confirmed the experimental observations.

Observation of high-order polarization-locked vector solitons in a fiber laser

We report on the experimental observation of a new type of polarization-locked vector soliton in a passively mode-locked fiber laser. The vector soliton is characterized by the fact that not only are the two orthogonally polarized soliton components phase-locked, but also one of the components has a double-humped intensity profile. Multiple phase-locked high-order vector solitons with identical soliton parameters and harmonic mode locking of the vector solitons were also obtained in the laser. Numerical simulations confirmed the existence of stable high-order vector solitons in the fiber laser.

Coherent energy exchange between components of a vector soliton in fiber lasers

We report on the experimental evidence of four wave mixing (FWM) between the two polarization components of a vector soliton formed in a passively mode-locked fiber laser. Extra spectral sidebands with out-of-phase intensity variation between the polarization resolved soliton spectra was firstly observed, which was identified to be caused by the energy exchange between the two soliton polarization components. Other features of the FWM spectral sidebands and the soliton internal FWM were also experimentally investigated and numerically confirmed.

Dual-wavelength synchronously mode-locked Nd:CNGG laser

We have experimentally demonstrated a dual-wavelength synchronously mode-locked Nd:CNGG laser based on the semiconductor saturable absorber mirror technique. Mode locking was achieved simultaneously on two gain bands of the crystal that have a central wavelength separation of 2.4 nm. The fundamental mode-locked pulse train has a repetition rate of 88 MHz and pulse duration of 5 ps, with an average output power of approximately 90 mW. Autocorrelation measurements show that each of the synchronously mode-locked pulses consists of a train of quasi-periodic beat pulses with a 660 fs pulse width and a 0.63 THz repetition rate.

Pulse breaking recovery in fiber lasers

Pulse breaking recovery is numerically demonstrated in dispersion-managed fiber lasers designed for generating high peak power ultrashort optical pulses. It is shown that due to the cavity boundary condition, local pulse breaking can be absorbed by the pulse propagation in erbium-doped fiber with normal dispersion. Consequently, high peak power transform-limited pulses beyond the gain-bandwidth limitation could be generated.

Polarization rotation locking of vector solitons in a fiber ring laser

Polarization rotation of vector solitons in a fiber ring laser was experimentally studied. It was observed that the period of vector soliton polarization rotation could be locked to the cavity roundtrip time or multiple of it. We further show that multiple vector solitons can be formed in a fiber laser, and all the vector solitons have the same group velocity in cavity, however, their instantaneous polarization ellipse orientations could be orthogonal.

Soliton trapping in fiber lasers

We report on the soliton trapping in a fiber ring laser modelocked with a SESAM. It was observed that solitons along the two orthogonal polarization directions of the cavity with fairly large difference in central frequency and energy could be coupled together to form a group velocity locked vector soliton. In particular, due to that each of the coupled solitons forms its own soliton sidebands, two sets of soliton sidebands could be observed on the vector soliton spectrum. Numerical simulations have well confirmed the experimental observations.

Efficient operation of a diode-pumped Yb:NaY(WO(4))(2) laser

An efficient diode-pumped Yb:NaY(WO(4))(2) (Yb:NYW) disordered crystal laser has been experimentally demonstrated for the fist time. The Yb:NYW crystal has a peak absorption cross section of 1.09 x 10(-20) cm(2) at 972 nm and emission cross section of 1.24 x 10(-20) cm(2) at 1010 nm. Under an absorbed pump power of 11.7 W, the Yb:NYW laser generated an average output power as high as 4.1 W, with a slope efficiency of 45%. It was found that the laser always operated in a self-pulsing mode, and the laser spectrum showed random jumps with time. The mechanism of self-pulsing in the laser was also investigated.

Bound states of gain-guided solitons in a passively mode-locked fiber laser

We report on the observation of bound states of gain-guided solitary pulses (GGSPs) in a dispersion-managed erbium-doped fiber laser. Despite the fact that the GGSP is a chirped pulse and there is strong pulse stretching and compression along the cavity in the laser, the bound GGSPs observed have a fixed pulse separation, which is invariant to the pump strength change. Numerical simulation confirmed the experimental observations and further showed that not only the pulse separation but also the relative phase difference between the bound GGSPs remained fixed along the cavity.

High-power self-mode-locked Yb:Y(2)O(3) ceramic laser

We have experimentally demonstrated a high-power self-mode-locked Yb:Y(2)O(3) ceramic laser. Without any additional active or passive element in the cavity, self-started cw mode-locking was achieved. The maximum output power was as high as 2.7 W with a pulse duration of 1.1 ps. Numerical studies show that the diffraction loss induced by thermal lens aberration, in combination with the Kerr self-focusing effect in the gain medium, results in the mode locking of the laser. To our knowledge, this is the first self-mode-locked ceramic laser.

Bound states of dispersion-managed solitons in a fiber laser at near zero dispersion

We report on the observation of various bound states of dispersion-managed (DM) solitons in a passively mode-locked erbium-doped fiber ring laser at near zero net cavity group velocity dispersion (GVD). The generated DM solitons are characterized by their Gaussian-like spectral profile with no sidebands, which is distinct from those of the conventional solitons generated in fiber lasers with large net negative cavity GVD, of the parabolic pulses generated in fiber lasers with positive cavity GVD and negligible gain saturation and bandwidth limiting, and of the gain-guided solitons generated in fiber lasers with large positive cavity GVD. Furthermore, bound states of DM solitons with fixed soliton separations are also observed. We show that these bound solitons can function as a unit to form bound states themselves. Numerical simulations verified our experimental observations.

Dynamics of gain-guided solitons in an all-normal-dispersion fiber laser

We report experimental and numerical results on the dynamics of gain-guided solitons in a passively mode-locked erbium-doped fiber laser made of purely normal dispersion fibers. We show that formation of the soliton in the laser is a result of mutual interaction and balance among the cavity transmission, fiber Kerr nonlinearity, gain saturation, and filtering over one cavity round trip.

Generation of multiple gain-guided solitons in a fiber laser

We report the experimental observation of multiple gain-guided solitons in an erbium-doped fiber laser made of all normal-dispersion fibers. Numerical simulations show that, in the case of a narrow gain bandwidth, under the action of the cavity pulse peak clamping effect multiple gain-guided solitons can indeed be formed in a laser.

Noise-like pulse in a gain-guided soliton fiber laser

We report on the operation of a passively mode-locked fiber ring laser made of purely positive dispersion fibers and mode-locked by using the nonlinear polarization rotation technique. It was experimentally found that apart from the gain-guided soliton operation the laser can also emit a kind of noise-like pulse. We show numerically that the noise-like pulse emission is caused by the peak power clamping effect of the laser cavity on the gain-guided soliton.

High-efficiency 1040 and 1078 nm laser emission of a Yb:Y2O3 ceramic laser with 976 nm diode pumping

We report a high-efficiency diode-end-pumped polycrystalline Yb:Y2O3 ceramic laser. Pumped by a 976 nm laser diode bar and with an absorbed pump power of 2.8 W, cw output power of 1.74 W at 1078 nm, and 0.73 W at 1040 nm were obtained. The slope efficiency was measured to be 82.4% for the 1078 nm laser emission and 57.1% for the 1040 nm laser emission.

Generation of 47-fs pulses directly from an erbium-doped fiber laser

We show both numerically and experimentally that through appropriately selecting the output coupling position and strength in a mode-locked fiber laser, one can effectively manage the nonlinearity of the cavity. By implementing the technique together with cavity dispersion management in an erbium-doped fiber laser, we have achieved stable mode-locked pulses with a single-pulse energy of 2.08 nJ and pulse width of 46.2 fs directly from the laser.

Gain-guided solitons in dispersion-managed fiber lasers with large net cavity dispersion

Gain-guided solitons are experimentally observed in dispersion-managed fiber lasers with large net positive group-velocity dispersion. It is shown that formation of the soliton is a robust feature of the lasers. Numerical simulations also confirmed the experimental results.

Soliton polarization dynamics in fiber lasers passively mode-locked by the nonlinear polarization rotation technique

By numerically solving the coupled laser Ginzburg-Landau equations and using the pulse tracing technique to incorporate the cavity effect in the simulation, we have explicitly calculated the soliton polarization ellipses throughout the cavity of a fiber-ring laser mode-locked by the nonlinear polarization rotation technique, and investigated the soliton polarization dynamics in laser cavities. It was found that in a conventional stable soliton operation state, although the soliton polarization varies as the pulse propagates, at a fixed position inside the laser cavity the soliton polarization is invariant with time. However, in the presence of laser dynamics, at a fixed location within the cavity the soliton could either have multiple alternating fixed polarization states or no fixed polarization state at all, depending on the soliton dynamics.