Coherent Radiation Generation and Amplification in Erbium Doped Systems

The erbium doped fiber systems results into important advantages for information processing and transmission like: possibility of easy integration, highly efficiency and gain, immunity to crosstalk, low noise and high saturation output power (Agrawal, 1995 & 1997; Desurvire, 1995; Sterian, 2006). During the last years, they have been published many studies carrying out the improving and optimization of the coherent optical systems by "computer experiments". Based on some computational models known in the literature, this chapter proposes to present the main author's results obtained by numerical simulation concerning some coherent optical amplifier and laser systems. Will be presented firstly the computational model which govern the amplification regime of an uniform doped optical fiber under the form of a system of the nonlinear transport coupled equations, respectively for the signal and for the pumping. This system was used for numerical simulation of the amplification phenomena by a Runge Kutta type method (Agrawal, 1995; Sterian, 2006; Press et al., 1992). The study continues with the computational model presentation used for numerical analyses of the laser system doped with Er3+ ions, both of the crystal type and of the optical fiber laser type (Pollnau et al., 1996; Maciuc et al., 2001; Sterian & Maciuc, 2003). The main problems studied by numerical simulation, using these models known in literature are: the amplification, the laser efficiency and threshold for different optical pumping wavelengths, the dependence of the output optical power on the levels life time, the influence of the host materials on the output power and the time dependent phenomena, stability and nonchaotic regime of operation (Maciuc et al., 2001; Pollnau et al., 1994). We realized the numerical simulation of the erbium doped fiber amplifier concerning the functional and constructive parameters. It was demonstrated that for the Er3+ doped fiber laser, the optimum operation condition are obtained for ┣ = 791 nm, when the upper laser level is directly pumped but in the presence of the „colaser“ process which improves two times the laser efficiency for ┣ = 3 μm. The Er3+ laser system functionment and optimization was studied for different host material, using 3D numerical simulation to take into account the characteristic parameters variations in the range of values resulting from experience; the material selection recommends as efficient materials LiY F8 and BaY F8.