Temporal and spectral properties of an all-fiber APM laser with two-coupled cavities of different lengths

EMANUEL PAULUCCI; ENRIQUE SICRE; NÉLIDA RUSSO; RICARDO DUCHOWICZ

Pasaje Dardo Rocha. La Plata. Buenos Aires Argentina

Congreso; HK 2010 - Humboldt Kolleg - International Conference of Physics; 2011

UNLP

p { margin-bottom: 0.21cm; } Some properties of a two coupled cavities all-fiber laser as a function of the ratio between their optical lengths are analyzed in this work. The operation of this additive-pulse mode-locking (APM) laser is based on the coherent addition of pulses that interact on a central reflective element which is a common component for both cavities. The developed model derive the non-linear Schrödinger equation to resolve the propagation of fields through the Split-Step method, together with the T-matrix method for obtaining the reflectivity and transmittance characteristics of the fiber Bragg gratings (FBG´s) employed as feedback elements of the system. This is composed of an active primary cavity generated by an erbium-doped fiber and two fiber Bragg gratings (FBG1 and FBG2), and a passive cavity made with an appropriate length of standard optical fiber, delimited by FBG2 and the end of the fiber (4% reflectivity). The main parameters taken into account for defining the output of the laser are: the group velocity dispersion, the self-phase modulation, the gain factor that includes the effects of self- and cross- saturation, fiber losses and dispersion of the FBG. The emission generated, is analyzed in time and/or frequency domains, for different ratios between both cavities lengths. Numerical results for the pulse width and the peak power of the output, obtained from the application of the analytical model, are compared with experimental values measured by varying the length of the auxiliary cavity. These results show a decrease in the temporal width with a corresponding increase in the repetition frequency of the pulses, when the auxiliary cavity length is reduced with respect to the main cavity length. The experimental results are in good agreement with those obtained with the simulations.