Numerical Modeling of Multi-Core Fiber Laser (original) (raw)
2006, 2006 International Workshop on Laser and Fiber-Optical Networks Modeling
The problem of phase locking is of importance in the development of multi-core fiber lasers. To treat correctly the limit of strong coupling one needs to employ methods of direct numerical simulations of wave field propagation in a compound structure. Numerical modeling of a laser amplifier is difficult problem because of non-linear dependence of gain and index on the wave field intensity. Specific trouble of a fiber amplifier lies in non-reflection boundary conditions at the computational region boundary. We present two numerical codes for wave propagation and results of its implementation to simulations of 7-core hexagonal fiber structure of evanescent coupled cores. The 3D diffraction code developed earlier [1] for the scalar parabolic equation is the implementation of split-step Fast Fourier Transform technique [2] with the absorbing boundary conditions . At present we have developed another propagation code realizing the second-order implicit finite difference scheme which incorporates the perfect-matched layer boundary conditions [4] at the computational region boundary. The supplementing numerical code was developed for calculation of the fiber modes in the passive assembly (without gain and non-linear refraction). The shift-and-invert Arnoldi method was used for such a problem. Our propagation codes were tested by comparison with analytical solutions for the single-core fiber and with solutions for the passive assembly obtained by shift-and-invert Arnoldi method. Mechanism underlying experimentally observed convergence of the wave field in the laser to the in-phase mode was identified as spatial filtering by gain. Earlier discussed mechanism associated with the resonant index non-linearity plays secondary role.
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