Igor O. Zolotovskii

High-repetition-rate pulse generation and compression in dispersion decreasing fibers

Optical pulse generation and compression have been numerically studied in anomalous dispersion decreasing fibers. We show that evolution of modulation instability (MI) observed with chirped wave packets in tapered fibers produces the mechanism for generation of ultrashort pulses with high repetition rates. The role of MI and Raman self-scattering has been also discussed. The simulations show that pulse chirping enhances self-Raman scattering at early stages of pulse propagation and improves compression of the generated pulses. It is also shown that the presence of amplitude and frequency modulation of the seed wave provide essential impact on the pulse train formation. The new method for increasing the pulse train repetition rate through frequency modulation of the seed wave has been proposed.

Optical amplifier with tailored dispersion for energy scaling of similaritons

We propose an optical amplifier composed of fibers with varying normal group velocity dispersion (GVD) for picosecond pulse amplification. The analytical analysis defines the optimal axial distribution of dispersion that results in shaping of the parabolic pulses with controllable chirp. The proposed cascaded all-fiber pulse amplifier employs fiber gain segments with exponential increase of normal dispersion separated by the passive fiber sections with decreasing normal GVD. The cascaded amplifier allows us to prevent an excessive broadening of the pulse spectrum and, therefore, offers an attractive potential for energy scaling of similariton pulses.

Formation of parabolic pulses in inhomogeneous fiber optical amplifiers

The conditions for forming pulses with parabolic envelope asymptotics in inhomogeneous fiber optical amplifiers are investigated. The profile of normal group-velocity dispersion, which ensures formation of parabolic pulses with a reduced rate of frequency modulation, is determined. It is shown by numerical simulation that the presence of chirp in the input pulse may cause narrowing of the spectrum at a certain energy.

Induced modulation instability of surface plasmon polaritons

We demonstrate the effect of the modulation instability of surface plasmon polariton waves in a layer structure of subwavelength thickness. The expressions describing the dispersion and nonlinear properties of this structure are derived. It is shown that the modulation instability effect could be used for the generation of ultrashort pulse trains and the localization of optical fields with a scale less than 1 micron.

Highly Nonlinear Dispersion Increasing Fiber for Femtosecond Pulse Generation

The optical pulse evolution in a highly nonlinear normal dispersion-increasing fiber has been considered, both experimentally and theoretically. It was found that large spectral broadening in tapered waveguides could occur without temporal instabilities and impose the linear frequency modulation, i.e., chirp, required for high-quality pulse compression. The pedestal-free pulses have been demonstrated after dechirping in a standard single-mode fiber.

A generator of far-infrared and terahertz radiation in nonlinear metamaterials exhibiting negative index of refraction

Laser oscillation conditions are analyzed in nonlinear composite metamaterials exhibiting a negative index of refraction. It is demonstrated that strong quadratic and cubic nonlinearities can be simultaneously realized in such structures. Based on the described composite material, a scheme of an optically pumped parametric generator of terahertz radiation is proposed.

Velocity of the maximum of the envelope of a frequency-modulated gaussian pulse in an amplifying nonlinear medium

The variation in the velocity of propagation of a narrowband frequency-modulated pulse in a nonlinear medium with dispersion of gain or absorption is studied. It is shown that the self-phase modulation caused by a cubic nonlinearity of the Kerr type can “accelerate” optical pulses of a Gaussian shape up to superluminal velocities even in the case where an initial frequency modulation (chirp) is absent.

Dynamics of radiation in optical fibers with a dispersive effective cross-section area of the mode

By using a graded-index optical fiber with a parabolic distribution of the refractive index as an example, it is shown that shock waves of envelopes can arise in optical fibers with a significantly dispersive (frequency-dependent) effective cross-section area of the mode. In principle, the shock wave caused by this dispersion can appear at the leading edge of the wave packet. The possibility of forming soliton pulses in media with a dispersive area of the mode is considered.

Surface plasmon polariton amplification in a single-walled carbon nanotube

The interaction of a surface plasmon polariton wave of the far-infrared regime propagating in a single-walled carbon nanotube with a drift current is theoretically investigated. It is shown that under the synchronism condition a surface plasmon polariton amplification mechanism is implemented due to the transfer of electromagnetic energy from a drift current wave into a terahertz surface wave propagating along the surface of a single-walled carbon nanotube. Numerical calculations show that for a typical carbon nanotube surface plasmon polariton amplification coefficient reaches huge values of the order of 106 сm-1, which makes it possible to create a carbon-nanotube-based spaser.

Analysis of steady bound soliton-state attributes in hybrid mode-locked fiber laser

We report on an analytical description of the bound states in soliton lasers combining active and passive mode locking. The perturbation theory has been applied to analyze the formation of bound states and to study the influence of cavity parameters on the characteristics of soliton groups generated through active phase modulation in the lasers. This analytical description is in agreement with the numerical simulation data. The theoretical approach demonstrated in this work could possibly be extended to other laser architectures.