Generation Of Soliton-like Pulses Research Articles

Generation of high-energy soliton-like pulses in 1.9–2.5 µm spectral domain

We experimentally demonstrate the generation of soliton-like pulses with 195–230 fs duration and energy up to 20 nJ in the spectral region of 1.9–2.5 µm directly from the Tm-doped all-fiber MOPA laser. The emerged Raman solitons generated directly in the fiber amplifier exhibit unusual dynamics and spectral properties forming a supercontinuum without conventional gaps between Stokes pulses. Namely, at the output powers above 2 W, in addition to conventional soliton spectral peaks beyond 2.3 μm, we observe high spectral density over an extended range of 1.95–2.23 μm corresponding to a coherent structure that to the best of our knowledge differs from any previously observed supercontinuum regimes. The average optical power of the fiber laser is at the 3-W level, whereas the estimated peak power reached the 80-kW level. Such a relatively simple laser system with high spectral density is a promising light source for various applications ranging from advanced comb spectroscopy to ultra-fast photonics.

Generation of high frequency trains of chirped soliton-like pulses in inhomogeneous and cascaded active fiber configurations

Abstract We present a theoretical formalism of description of soliton-like pulse generation in longitudinally inhomogeneous active optical fibers. Dynamics of the wave packet during the nonlinear stage of the modulation instability is described for fibers with distributed gain and group velocity dispersion profiles. Generation of pico- and sub-picosecond pulse trains operating in THz repetition range from quasi-continuous pump wave is simulated for fibers of different inhomogeneity and for cascade fiber configurations comprising homogeneous and inhomogeneous segments. Pulse train generation is shown to occur in resonant manner once the gain and GDV distributed fiber profiles are perfectly matched.

Mode-locked dark pulse Kerr combs in normal-dispersion microresonators

Kerr frequency combs from microresonators are now extensively investigated as a potentially portable technology for a variety of applications. Most studies employ anomalous dispersion microresonators that support modulational instability for comb initiation, and mode-locking transitions resulting in coherent bright soliton-like pulse generation have been reported. However, some experiments show comb generation in normal dispersion microresonators; simulations suggest the formation of dark pulse temporal profiles. Excitation of dark pulse solutions is difficult due to the lack of modulational instability in the effective blue-detuned pumping region; an excitation pathway has been demonstrated neither in experiment nor in simulation. Here we report experiments in which dark pulse combs are formed by mode-interaction-aided excitation; for the first time, a mode-locking transition is observed in the normal dispersion regime. The excitation pathway proposed is also supported by simulations.

Modulational instability and energy localization of twisted DNA with solvent interaction

We investigate the generation of soliton-like pulses along a DNA chain which takes into account both torsional and solvent interaction effects. Interactions between neighboring base pairs are described by a twist angle. Twisting is essential in the model to capture the importance of nonlinear effects for the thermodynamical properties. The nonlinear dynamics of the DNA is then modeled in the Hamiltonian approach by the generalized Dauxois–Peyrard–Bishop model (combination of several models). We introduce the generalized discrete nonlinear Schrödinger equation describing the dynamics of modulated wave through the twisted DNA with solvent interaction. The modulational instability is studied and we present an analytical expression for the MI gain to show the effects of twist angle on MI gain spectra as well as on stability diagram. With the increase of the twist angle the MI gain decreases then increases. Some interesting MI phenomena appear with an additional new MI region as the twist angle increases. The instability and stability diagrams are also affected. Numerical simulations are carried out to show the validity of the analytical approach. The result is that the initial wave breaks into a train of ultrashort pulses with repetition rates, which are trapped in some sites. The impact of the twist angle is investigated and we obtain that the twist angle affects the dynamics of stable patterns generated through the molecule. Thereafter, we study energy localization in the framework of twisted DNA with solvent interaction. While the twist angle leads to a stronger localization of energy, the solvent interaction delocalizes energy along the molecule.

325 MHz and near transform-limited pulse output directly from an Er:fiber ring laser

A compact Er:fiber ring laser operated at a fundamental repetition rate of 325 MHz is reported. Two gain fibers with opposite dispersion are employed to shorten the fiber laser cavity for high repetition rate and soliton-like pulse generation without losing gain and compactness. The spectral bandwidth of the output pulse is 24 nm and the direct pulse duration is 123 fs without extra-cavity compression, which are values near the transform-limited range.

Optical generation of solitonlike pulses in a single-component gas of neutral fermionic atoms

We analyze, the generation of soliton-like solutions in a single-component Fermi gas of neutral atoms at zero and finite temperatures with the phase imprinting method. By using both the numerical and analytical calculations, we find the conditions when the quasisolitons, which apparently resamble the properties of solitons in non-linear integrable equations, do exist in a non-interacting Fermi gas. We present the results for both spatially homogeneous and trapped cases, and emphasize the importance of the Fermi statistics and the absence of the interaction for the existence of such solutions.

Solitons of singly resonant optical parametric oscillators

Single resonant parametric oscillators including intracavity quadratic and cubic nonlinearities are described in the mean-field limit with a cubic and quintic complex Ginzburg-Landau equation. Following our model, simple design criteria are derived for the generation of solitonlike pulses and beams for singly resonant optical parametric oscillators.