Bound-soliton fiber laser

Abstract

Experimental study of the soliton dynamics of a passively mode-locked fiber ring laser revealed a state of bound-soliton operation in the laser, where two solitons bind together tightly with fixed pulse separation. We further report on the properties of the bound-soliton emission of the laser. In particular, we demonstrate both experimentally and numerically that, like the single-pulse soliton operation of the laser, the bound soliton emission is another intrinsic feature of the laser. DOI: 10.1103/PhysRevA.66.033806 PACS number͑s͒: 42.55.Wd, 42.81.Dp, 42.60.Fc, 42.65.Sf Self-started, passively mode-locked fiber lasers as a potential source of ultrashort optical pulses have been intensively investigated ͓1-7͔. A generic feature of the lasers found is that under suitable operation conditions, they can emit the so-called soliton pulses-optical pulses that are sech-form shaped and have nearly transform-limited bandwidth-duration product. Under a soliton operation, not only the output pulses of the lasers become ultrashort, but also the pulse-to-pulse energy and peak power become ultrastable, which was found to be quantum noise limited ͓8͔.Soliton emission of the lasers is a natural consequence of the nonlinear pulse propagation in the fiber cavity, where due to the balanced action between the fiber-optical Kerr effect and the cavity dispersion on a pulse, the shape and duration remain unchanged with the propagation. Although in a passively mode-locked fiber laser, apart from the optical fiber other optical components such as the gain medium and output coupler coexist in the cavity, which affect the detailed dynamics of the formed pulses. It is nevertheless demonstrated that under weak influence of them, the average dynamics of the solitons could be well described by the nonlinear Schrödinger equation ͓9͔. In this paper we report on the states of bound-soliton emission and their properties in a passively mode-locked fiber ring laser. We show both experimentally and numerically that apart from the single-pulse soliton emission, the laser can also emit stable, closely spaced soliton pairs. In particular, when operating in the regime, the bound-soliton pair is the only stable structure of the solitary wave in the laser, as a unit, it has exactly the same features as those of a single-pulse soliton. For this reason, we refer the fiber laser as a bound-soliton fiber laser.Bound states of solitons have recently been predicted in the coupled nonlinear Schrödinger equations ͓10͔ and the quintic complex Ginzburg-Landau equation ͓11,12͔. Formation of bound solitons was explained as a result of direct soliton interaction. Solitons formed in these systems have an oscillating tail; when they interact, their effective interaction potential has spatial local minima, which give rise to stable, bound solitons. Bound solitons thus formed are characterized as having fixed, discrete pulse separations independent of soliton propagation. For a passively mode-locked fiber laser, when the influences of laser gain and cavity losses ͑and...

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

“…͞4, quarter-wave plate; ͞2, halfwave plate; PI, polarization dependent isolator; P, polarizer; WDM, wavelength-division multiplexer; EDF, erbium-doped fiber. ventional soliton operation of the fiber lasers [7][8][9] and the parabolic pulse operation in the positive net cavity dispersion regime [13], bound states of the DM solitons are also observed. In particular, depending on the detailed laser operation condition, we have observed bound solitons with various soliton number and soliton pulse separations.…”

“…We used exactly the same model and simulation techniques as described in [8] for the simulations. To be comparable with the experimental results, we used the following parameters for the current simulations: ␥ ϭ 3 W Ϫ1 km…”

Observation of soliton molecules with independently evolving phase in a mode-locked fiber laser

“…Theoretically, a few kinds of stable scalar soliton molecules have been discovered in mode-locked fiber lasers, namely, molecules with an invariant phase [1,2], or molecules which are slightly vibrating or shaking around a stationary state [2,3], and molecules with an independently evolving phase [4][5][6][7] and such with a flipping phase [6]. Experimentally, only soliton molecules with an invariant phase [5,[8][9][10], with a rotating phase [5], and vibrating molecules [11] have been reported to date. This may be attributed to practical difficulties in the measurement of minor changes in molecule parameters or of the complex internal dynamics like periodic or chaotic evolution of the phase difference between the pulses.…”

Observation of two-color pulses in a passively mode-locked erbium-doped fiber ring laser

“…1,2 Also, it is well known that there are several different operation states in a given passively mode-locked fiber laser, which are mainly determined by the polarizations and the cavity parameters: 3 normal solitons, bound solitons, 4 and noiselike pulse states. 5 In addition, another operation mode-the so-called two-color pulse mode-has been theoretically predicted and experimentally demonstrated.…”