We demonstrate that spectral peak power of negatively chirped optical pulses can acquire a blueshift after amplification by a semiconductor optical amplifier. The central wavelength of a transform limited optical pulse translates over 20 nm towards a shorter wavelength after propagation in a single-mode fiber and semiconductor optical amplifier. A chirped Gaussian pulse with full width at half maximum 1 ps and dimensionless chirp parameter C = − 20 can be blueshifted by 5 THz.

We examine spectral properties of radiation in the pulsed fiber lasers using the semiconductor optical amplifier (SOA) as the gain medium. The complex light dynamics that result from the interplay between the fiber propagation effects in the cavity, the nonlinear effects in the SOA and spectral filtering, shift the generated radiation from the central wavelength of the filter. The resulting wavelength of the output radiation depends on the SOA pump power and the bandwidth of the intracavity filter. This offers the possibility of a spectral tunability of the generated pulses through nonlinear dynamics rather than the conventional use of a tunable filter.

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Выполнено математическое моделирование волоконного лазера с синхронизацией мод на основе эффекта нелинейного вращения поляризации. Проведена оптимизация лазера с использованием генетического алгоритма. В результате были определены параметры лазерного резонатора, при которых достигается наибольшая энергия выходного импульса Purpose. The article addresses optimization of mode-locked fiber laser based on nonlinear polarization rotation. Determination of the resonator parameters corresponding to the single-pulse with the highest energy has been performed using the genetic algorithm. Metodology. Mathematical modelling has been carried out with the help of two models, namely, scalar and hybrid. Scalar model describes signal propagation by generalized nonlinear Schr¨odinger equation. Hybrid model describes section of DCF by pair of generalized nonlinear Schrodinger equations. Numerical simulation has been performed by the split-step Fourier method. Genetic algorithm has been implemented as SteadyState method by GALib library. The value of the fitness function is equal to the energy value for the single-pulse and otherwise zero. Findings. The genetic algorithm has been implemented for solving optimization problem of fiber lasers and modifying the algorithm to reduce the calculation time. The parameters of the laser for the scalar model are determined and agreement with the results obtained by the enumeration method is presented. For the hybrid model, a stable pulse with three times the energy was found. Conclusions. In this work, a determination of the optimal parameters for mode-locked fiber lasers based on nonlinear polarization rotation was presented. The problem was solved using a genetic algorithm. This is the first step towards creating a “smart” self-tuning laser

We demonstrated both through numerical modeling and experimentally that optical pulses with appropriate initial chirp can undergo a nonlinear spectral blueshift, opposite to the Raman-induced redshift, when they are amplified by the SOA.