A. E. Ismagulov

Four-wave-mixing-induced turbulent spectral broadening in a long Raman fiber laser

We present a detailed analytical self-consistent theory based on wave kinetic equations that describes generation spectrum and output power of a Raman fiber laser (RFL). It is shown both theoretically and experimentally that the quasi-degenerate four-wave mixing (FWM) between different longitudinal modes is the main broadening mechanism in the one-stage RFL at high powers. The shape and power dependence of the intracavity Stokes wave spectrum are in excellent quantitative agreement with predictions of the theory. FWM-induced stochasticity of the amplitude and the phase of each of the ∼106 longitudinal modes generated in the RFL cavity is an example of a light-wave turbulence in a fiber.

Spectral broadening in Raman fiber lasers

We present an analytical theory based on wave kinetic equations that describes a Raman fiber laser (RFL) generation spectrum. It is shown both theoretically and experimentally that the quasi-degenerate four-wave mixing between different longitudinal modes is the main broadening mechanism in the one-stage RFL at high powers. The shape and power dependence of the intracavity Stokes wave spectrum are in excellent quantitative agreement with predictions of the theory.

Turbulence-induced square-root broadening of the Raman fiber laser output spectrum

The output characteristics of the conventional one-stage Raman fiber laser (RFL) are described in an optical wave turbulence formalism. Simple analytical expressions describing RFL output power and its spectral shape are presented, and square-root law for the output spectrum broadening law has been discovered. The indications of the turbulent-like spectral broadening in other types of cw fiber lasers and propagation phenomena in fibers are also discussed.

Modulation instability at propagation of narrowband 100-ns pulses in optical fibers of various types

The instability of the propagation of narrowband 100-ns laser pulses in the transparency window of a single-mode fiber in the presence of continuous broadband noise is demonstrated. The modulation instability developed due to the nonlinearity and anomalous dispersion leads to a rapid decay of the narrowband component after passing through the fiber. The modulation-instability threshold is shown to be sensitive to the noise level in a spectral interval of about 100 GHz near a central wavelength of about 1.55 μm and is inversely proportional to the fiber length (varied from 1.6 to 21.0 km in the experiments). The effect is completely eliminated owing to the application of a dispersion-shifted fiber with normal dispersion.

All-fiber widely tunable Raman fiber laser with controlled output spectrum

In the present paper we report on the all-fiber widely tunable high efficient RFL with controlled output spectrum that is applicable for further frequency doubling.

Broadening of the intracavity and output spectra of a raman fiber laser with a low-Q cavity

Intracavity and output spectra broadened in a Raman fiber laser with a low-Q cavity are measured and theoretically described. It is demonstrated that the previously developed approach of optical-wave turbulence can be used to describe the spectral broadening owing to the multiple four-wave mixing processes that involves numerous longitudinal modes of the low-Q cavity. The theoretically calculated spectra are in good agreement with the experimental data for various output reflection coefficients of the fiber Bragg gratings across the entire power range.

Turbulent Square-Root Broadening of Fiber Lasers Output Spectrum

The conventional RFL output spectrum and power are analytically described by the optical wave turbulence approach. The turbulent broadening can be also important in other types of fiber lasers, propagation phenomena and CW supercontinuum generation.

Turbulent Broadening of a Raman Fiber Laser Spectrum

An analytical wave kinetic theory has been developed that describes a Raman fiber laser (RFL) generation spectrum. A four-wave mixing between RFL longitudinal modes in turbulent regime is shown to be the main broadening mechanism.

Mechanisms of spectral broadening in Raman fiber lasers

Raman gain at high powers is shown to be saturated homogeneously due to pump depletion. At the same time single-frequency RFL generation is not possible because of four-wave mixing, that is demonstrated experimentally and theoretically.