D. A. Korobko

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.

Multistage fiber preamplifier employing spectral compression for generation of high-energy laser pulses

We report the main features of spectral compression (SC) of parabolic pulses in nonlinear optical fibers. It is shown that variational analysis correctly describes evolution of pulse parameters during SC. The model of a cascade amplifier system that employs SC is developed to achieve superior spectral densities. The proposed configuration is promising as an optical pulse preamplifier for operation in high-energy pulse laser systems.

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.

Long-range soliton interactions through gain-absorption depletion and recovery.

We report the interpulse dynamics in fiber soliton laser because of depletion and relaxation of gain and absorption. The soliton interaction range is shown to depend largely on the relaxation time of dissipative parameters while the compensation of the dynamical gain and absorption depletion leads to the formation of stationary soliton groups with unequal interpulse distances.

Broadband infrared continuum generation in dispersion shifted tapered fiber

Experimental and theoretical studies of supercontinuum generation in the telecom spectral window are reported for fibers with shifted decreasing anomalous dispersion. Numerical analysis highlights the high average power of the emitted dispersive waves and the good spectral flatness achieved within the control spectral band for the supercontinuum generated in optical fiber tapers. Reduction of the third-order dispersion in optical fiber tapers is shown to cause spectral broadening, which is extended by hundreds of nanometers in comparison with the supercontinuum generated in uniform fibers, even when subpicosecond pulses of moderate powers are used.

Modulation instability of pulsed radiation in an optical waveguide in the presence of the traveling refractive index wave

The conditions for the onset of modulation instability of wave packets in an optical waveguide in the presence of the traveling refractive index wave are investigated. An expression governing the growth rate of a small harmonic perturbation at the early development stage of the modulation instability is obtained. Based on numerical analysis, the behavior of the wave packet at the developed modulation instability stage is studied for different parameters of the waveguide and the refractive index wave.

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.

Infiltrated bunch of solitons in Bi-doped frequency-shifted feedback fibre laser operated at 1450 nm

Mode-locked fibre laser as a dissipative system is characterized by rich forms of soliton interaction, which take place via internal energy exchange through noisy background in the presence of dispersion and nonlinearity. The result of soliton interaction was either stationary-localized or chaotically-oscillated soliton complexes, which have been shown before as stand-alone in the cavity. Here we report on a new form of solitons complex observed in Bi-doped mode-locked fibre laser operated at 1450 nm. The solitons are arranged in two different group types contemporizing in the cavity: one pulse group propagates as bound solitons with fixed phase relation and interpulse position eventuated in 30 dB spectrum modulation depth; while the other pulses form a bunch with continuously and chaotically moving solitons. The article describes both experimental and theoretical considerations of this effect.