Owing to its strong optical characteristics, graphene has emerged in the field of ultrafast lasers as a prominent saturable absorber. In this communication, we present a passively mode-locked Er:Yb doped double-clad fiber laser using a graphene deposited tapered fiber (GDTF). Averaging 20 μm of diameter with a length of 6 mm, the taper enables a strong light–graphene interaction owing to the evanescent field of the excited cladding mode. To create the saturable absorber device, graphene solution is carefully deposited via a micro syringe so that the waist of the taper is completely immersed into the aqueous solution. Then, a continuous wave laser with output power up to 95-mW centered at 1550 nm is injected into the taper. Deposition of graphene onto the taper by the optical tweezers effect started when the transmitted power dropped significantly. Afterwards, the GDTF is implemented in a fiber cavity to test its mode-locking performance. At the maximum available pump power, we obtain the 326th harmonic mode locking of soliton bunches with average output power of 520 mW.
Dissipative soliton resonance (DSR) is an efficient way to achieve high energetic pulses without wave breaking. In fiber laser, DSR operation manifests as square pulses emission. Based on this principle, we have experimentally demonstrated pulses in the micro joule range. Experiments have been conducted using double-clad Er:Yb-doped fiber lasers in different optical configurations. In particular, we demonstrate 10 μJ DSR emission in an optimized cavity and also the possibility to observe wave breaking in DSR regime. In the latter case, harmonic mode-locking of square pulses is demonstrated.
We present a widely adjustable high energy square pulse laser operating in DSR in a passively mode-locked F8L using dual Er:Yb co-doped double clad amplifiers. By manually controlling the power of each amplifier, the pulse width can be varied in a range of 360 ns without generating multi-pulsing instabilities. To ensure that DSR would dominate the modelocking mechanism, we use a 1.5 km standard single-mode fiber in the cavity. At a maximum pumping power, the laser generated square pulses with 416 ns duration and an average output power of about 1.33 W with a repetition frequency of 133 KHz corresponding to a record pulse energy of 10 μJ.
In this communication, we demonstrate a passive mode-locked Er:Yb co-doped double-clad fiber laser using a tapered microfiber topological insulator (Bi2Se3) saturable absorber (TISA). The topological insulator is drop-casted onto the tapered fiber and optically deposited by optical tweezer effect. We use a ring laser setup including the fabricated TISA. By carefully optimizing the cavity losses and output coupling ratio, the mode-locked laser can operate in L-band with a high average output power. At a maximum pump power of 5 W, we obtain the 91st harmonic mode-locking of soliton bunches with a 3dB spectral bandwidth of 1.06nm, a repetition rate of 640.9 MHz and an average output power of 308mW. As far as we know, this is the highest output power yet reported of a mode-locked fiber laser operating with a TISA.
We numerically analyze the square pulse emission from a passively mode-locked figure-of-eight microstructured optical fiber laser. Numerical simulations demonstrate that the high nonlinearity of the microstructured fiber plays a key role in the output pulse duration. A dual-stage erbium-doped fiber amplifier has been used in the cavity. The first amplifier, localized in the nonlinear amplifying loop mirror, allows control of the pulse width, while the second amplifier in the unidirectional ring allows variation of the amplitude without affecting the pulse width. Our results give some physical insight to the square pulse formation and the generation of high-energy pulses. Our numerical model provides a general approach to control the properties of a square pulse, and hence could be of great importance for the design of practical high-energy fiber laser systems.
The effect of an external continuous wave (cw) on the operating regime of a passively mode-locked double-clad fiber
laser, operating in the anomalous dispersion regime, is experimentally investigated. Starting from different soliton
distributions, we demonstrate that, under specific conditions, the cw signal forces the principal laser to operate in
harmonic mode-locking regime.
We investigate the soliton pattern formation in an erbium-doped figure-of-eight double-clad fiber laser. The mode-locking
is realized with a nonlinear amplifying loop mirror. Different soliton complexes have been obtained similar to
those obtained when the mode-locking is achieved through the nonlinear polarization rotation technique.
KEYWORDS: Solitons, Picosecond phenomena, Mode locking, Liquids, Crystals, Fiber lasers, Dispersion, Liquid crystals, High power fiber lasers, States of matter
Ordered and disordered pattern formation of solitons is experimentally investigated in the passively mode-locked doubleclad
erbium-doped fiber laser. Soliton complexes of about 500 pulses are obtained which organize in different patterns
analogous the states of the matter. We have identified a soliton gas, a supersonic soliton gas flow, a soliton liquid, a
soliton polycrystal and a crystal of solitons.
We report on the observation of bound state of some hundreds of solitons in a passively mode-locked Er:Yb-doped fiber
laser. A double-clad fiber is used in a unidirectional ring cavity where the mode-locking is obtained thanks to the
nonlinear polarization rotation. The phenomenon is described theoretically using a multiscale approach to the gain dynamics.
We investigate triplet bound-states with a new symmetry, called "cis", using the cubic-quintic CGL equation.
We show that the leading term of the functional J[ψ], which governs the evolution of the momentum of the
solution to the CGL equation, vanishes for the cis symmetry. Numerical investigation show that stable cis triplet
bound states are solutions of the CGL equation. Quasi-stable cis states are also found, and also a stable quasi-stationary
asymmetrical triple state. Then we show that it is possible to experimentally distinguish between the
trans and cis triplet states, using either the optical spectrum or the collinear autocorrelation trace.
KEYWORDS: Solitons, Dispersion, Phase velocity, Nonlinear optics, Wave propagation, Radio propagation, Physics, Optical solitons, Near field optics, Chemical species
Using Maxwell-Bloch equations, we analyze the response of a two-component medium of two-level atoms driven by a two-cycle
optical pulse beyond the traditional approach of slowly varying amplitudes and phases. We show that the notions of
carrier, envelope, phase and group velocities can be generalized to this situation, and that for optical pulses of a given
duration, the optical field can evolve into temporal few-cycle solitons.
The multiple pulse passive mode-locking with equidistantly arranged pulses in a laser cavity has been analyzed.
Mechanisms resulting in such type of passive mode-locking have been studied. Among of them there are the additional
weak active amplitude and phase modulations of the intracavity radiation, the additional inertial nonlinear refractive
index and darkening absorber. The transient period for the realization ofthe harmonic passive mode-locking due to these
mechanisms has been estimated.
The interaction of dissipative solitons in fiber laser with nonlinear losses due to nonlinear polarization rotation is studied
by numerical simulation. Technique control of spectrum and amplitude of pulse wings allows effective management of
the soliton interaction under long distance between pulses (considerably much more than pulse duration). The interaction
can be attractive or repulsive. Moreover the sign of the interaction may depend on distance between pulses.
We present the results of our theoretical investigation on passive mode-locking of fiber lasers. The mode-locking is achieved using the nonlinear polarization technique. The practical case of the ytterbium-doped fiber laser operating is analysed. A simple model is developed allowing to study several features observed in passively mode-locked fiber lasers such as bistability between the mode-lock and the continuous regime, multiple pulse operation, hysteresis phenomena, bound solitons. The dynamics of the number of pulses as a function of laser parameters is also reported. Pump power hysteresis is demonstrated.
We present an improved method to measure the third order nonlinearity of materials. The principle is based on a pump/probe experiment using a Mach-Zehnder interferometer coupled to a CCD camera. Experiments are performed with fluoride glasses (PZG) and chalcogenide glasses. A comparison with the nonlinear coefficients obtained with the Z-scan technique is done and has led us to improve the detailed analysis of the Z-scan technique.
We consider an Yb-doped double-clad fiber laser in a unidirectional ring cavity containing a polarizer placed between two half-wave plates. Depending on the orientation of the phase plates, the laser operates in continuous, Q-switch, mode-lock or unstable self-pulsing regime. An experimental study of the stability of the mode locking regime is realized versus the orientation of the half-wave plates. A model for the stability of self-mode locking and cw operation is developed. The model is reduced to a master equation in which the coefficients are explicitly dependent on the orientation angles of the phase plates.
We consider the output of a longitudinally pumped heavily doped Er:Yb:phosphate glass laser. We experimentally observe that the characteristic curve output-versus-input is not linear and exhibits bistability. A theoretical approach, based on a thermal lensing effect that is different depending on whether the laser is ON or OFF and on the overlapping mismatch between the pump and the laser spot sizes, provides an excellent description of the experimental results.
Far-Field non-gaussian fundamental transverse modes have been obtained in CW end-pumped Nd:YVO4 microchip laser for particular cavity lengths. Such profiles appear at threshold and are not distorted when pump power increases but they strongly depend on the pump to mode size ratio. An implemented theoretical model qualitatively reproduces these transverse profiles. It is based on the hypothesis of diffraction effects of the resonant intra-cavity field on a Gaussian gain profile. Dependence of the pump to mode size ratio on such profiles will be also theoretically explained.
We report on the different regimes observed in a bipolarized neodymium-doped fiber laser self Q-switched by a thin slice of a polymer-based saturable absorber. We demonstrate the interplay between the total losses and the loss anisotropy induced respectively by defocusing the saturable absorber and by tilting the cavity mirror. Starting from a global chaotic behavior for low-losses (i.e. good cavity) configuration, the system evolves toward n-periodic (n= 4,2 and 1) regime for increasing losses (bad cavity configuration). Stabilization of the regimes depends on the anisotropic losses introduced. These regimes have been identified as to be due to non-linear coupling through saturable absorber between two distinct polarized modes. These modes have been experimentally resolved. Simple model based on a bipolarized fiber laser reproduces such dynamics.
We present an experimental study of the Yb-doped double-clad fiber laser operating in the 1.08 micrometers wavelength. The fiber side-pumped with a high power laser diode using the v- groove technique. Various experimental configurations are performed from the linear cavity to an all-fiber tunable unidirectional ring cavity. Mode-locking of the Yb laser are investigated using the nonlinear polarization rotation.
We propose a new method for transforming an elliptic Gaussian beam, in the near-field, into a circular Gaussian beam in the far field using a very simple diffractive optical element which is a phase slit. We show that a circular Gaussian beam can be transformed into a flat-top profile, a doughnut profile or a ring-shaped profile.
Chalcogenide glasses in the [Ge-Se-S-As] system have been synthesized and studied with respect to their nonlinear optical properties from third and second order. Z-scan and Mach Zehnder interferometry measurements of the nonlinear refractive index (n2) and nonlinear absorption ((beta) ) have been performed at 1064 nm. Some z-scan measurements have been also realized at 1430 nm. The results have been correlated to the structures of the glasses and the figure of merit has been calculated with the purpose of a potential utilization of these glasses in the realization of ultra- fast all-optical switches. Nonlinearities as high as 850 times the nonlinearity of silica glass have been obtained and some glasses exhibit at 1430 nm nonlinear optical characteristics suitable for telecommunication applications. The all-optical poling of a chalcohalogenide glass has been realized with a Q-switch mode-locked Nd:YAG laser at 1064 nm emitting 45 ps pulses at a repetition rate of 10 Hz with frequency doubling at 532 nm. A nonlinear coefficient deff equals 2.8 10-17 m/V similar to that of the reference glass Schott SF 57 has been obtained. The thermal poling of a chalcogenide glass also has been realized and a transient second order nonlinear susceptibility (chi) (2) has been observed.
We present an experimental study of the Yb-doped double-clad fiber laser operating in the 1.08 micrometers wavelength. The fiber is side-pumped with a high power laser diode using the v-groove technique. Various experimental configurations are performed from the linear cavity to an all-fiber tunable unidirectional ring cavity.
We theoretically model the polarization properties of an optical fiber by the Jones matrix of an elliptical birefringent plate. The properties of this model are investigated and lead to develop experimental methods to extract the parameters of the model for a real fiber. A magneto-optical method that measures the beat length of the fiber is also presented and gives a more complete description of the fiber. Wavelength dependence of the parameters characterizing the fiber is finally experimentally investigated.
A linear stability analysis of the laser-Lorentz equations taking into account local field correction is presented. It is demonstrated that this correction lowers the instability threshold for negative detunings. In addition, we determine the criteria for which the instability occurs.
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