Evgenii Podivilov

Recent advances in fundamentals and applications of random fiber lasers

Random fiber lasers blend together attractive features of traditional random lasers, such as low cost and simplicity of fabrication, with high-performance characteristics of conventional fiber lasers, such as good directionality and high efficiency. Low coherence of random lasers is important for speckle-free imaging applications. The random fiber laser with distributed feedback proposed in 2010 led to a quickly developing class of light sources that utilize inherent optical fiber disorder in the form of the Rayleigh scattering and distributed Raman gain. The random fiber laser is an interesting and practically important example of a photonic device based on exploitation of optical medium disorder. We provide an overview of recent advances in this field, including high-power and high-efficiency generation, spectral and statistical properties of random fiber lasers, nonlinear kinetic theory of such systems, and emerging applications in telecommunications and distributed sensing.

Highly chirped dissipative solitons as a one-parameter family of stable solutions of the cubic–quintic Ginzburg–Landau equation

In this paper, the stability of the analytical solutions of the cubic–quintic Ginzburg–Landau equation (CQGLE) in the high-chirp approximation has been studied numerically. The existence domain for the stable solution in the CQGLE parameter set has been found. A temporal and spectral shape of the stable solution as dependent of the cavity parameters has been analyzed. Direct comparison of the spectra with numerical calculations has been performed, demonstrating 10−2–10−4 accuracy of the analytical solution for chirp parameter f>10. The stable solutions represent the dissipative soliton family with only one composite parameter. Inside this family, the pulse shape in the time domain evolves from the conventional soliton shape, sech−2, to a rectangular one in the opposite limit with a parabolic shape as an intermediate one. The obtained theoretical results make it possible to classify experimentally observed highly chirped pulses and to optimize experimental schemes with an all-normal-dispersion cavity.

NONPERTURBATIVE ZERO MODES IN THE KRAICHNAN MODEL FOR TURBULENT ADVECTION

The anomalous scaling behavior of the n-th order correlation functions

Negative light pressure force between two metal bodies separated by a subwavelength slit

{\cal F}_n

Spectral broadening in ultra-long raman fibre lasers by Optical wave turbulence

of the Kraichnan model of turbulent passive scalar advection is believed to be dominated by the homogeneous solutions (zero-modes) of the Kraichnan equation

Mode-locked fiber laser with cascaded generation of coherent Raman dissipative solitons

\hat{\cal B}_n {\cal F}_n=0

Statistical properties of partially coherent CW fiber lasers

. Previous analysis found zero-modes in perturbation theory in a small parameter. We present non-perturbative analysis of the simplest (non-trivial) case of n=3 and compare the results with the perturbative predictions.

Modelling of Femtosecond Inscription in Fused Silica

An explicit analytical expression of a light-induced attractive force between two macroscopic metal bodies or films separated by a subwavelength slit has been derived. The analytical expression obtained agrees well with the numerical calculations for the main TM mode. This force, which acts as a force with negative light pressure, arises by the interaction of plasmon-polaritons excited at the surface of metal when light propagates through the subwavelength slit. Estimations of this light-induced attractive force show that the force is sufficient to enable measurements and practical applications.

Random distributed feedback fibre lasers

Intra-cavity spectra of ultra-long (up to 84 km cavity length) Raman lasers have been measured and simulated. The results demonstrate FWM-induced turbulent-like (involving up to 108 modes) broadening of the spectrum with clear exponential tails.

Improved shell model of turbulence

We experimentally demonstrate a cascaded generation of a conventional dissipative soliton (DS) at 1020 nm and Raman dissipative solitons (RDS) of the first (1065 nm) and second (1115 nm) orders inside a common fiber laser cavity. The generated high-energy pulses are shown to be linearly-chirped and compressible to 200-300 fs durations for all wavelengths. Moreover, the pulses are mutually coherent that has been confirmed by efficient coherent combining exhibiting ~75 fs and <40 fs interference fringes within the combined pulse envelope of a DS with the first-order RDS and the second-order RDS respectively. The numerical simulation was performed with sinusoidal (soft) and step-like (hard) spectral filters and took into account the discreetness of the laser elements. Shown that even higher degree of coherence and shorter pulses could be achieved with hard spectral filtering. This approach opens the door towards cascaded generation of multiple coherent dissipative solitons in a broad spectral range (so-called dissipative soliton comb). The demonstrated source of coherent dissipative solitons can improve numerous areas such as frequency comb generation, pulse synthesis, biomedical imaging and the generation of coherent mid-infrared supercontinuum.