Strongly pumped fiber lasers

Modeling and optimization of high-power Nd/sup 3+/-Yb/sup 3+/ codoped fiber lasers

“…We note that there is a good agreement between the quasi-analytical solution and the exact solution over the entire range of fiber lengths and scattering loss (α). The dependence of the slope efficiency on the fiber length is in qualitative agreement with results obtained for the conversion efficiency (η c ≡ P + out /P p ) of typical strongly pumped fiber lasers [10]. That is, the slope efficiency increases with the fiber length until it saturates.…”

“…Bending losses can be applied to discriminate the fundamental LP 01 mode from higher order modes so that the laser output becomes practically single mode [9]. Previous works that model high-power rare-earth-doped fiber lasers have been limited to single-ion systems, such as Nd 3+ or Yb 3+ [10] or other codoped systems, e.g., Er 3+ -Yb 3+ [11]. Our goal here is to extend these works and to demonstrate models of NYDFLs based on numerical calculations of detailed coupled rate-propagation equations.…”

“…We note the existence of (2), (3), (8), and (9), for pumping at z = 0 or at z = L, respectively. The circles represent the approximate quasi-analytical solution obtained from (10) and (A12).…”

“…We find that it is sufficient to assume reflectivity boundary conditions only for a single central wavelength λ s of the DBR gratings [10], so that the power P ± s (z) = P ± (z, λ s )∆λ s at the lasing wavelength λ s represents an average over the many resonances within a bandwidth ∆λ s . The integration of the rate-propagation equations is carried iteratively along the forward and backward propagation direction, until all the ASE power densities converge to a steady-state value [10].…”

“…The integration of the rate-propagation equations is carried iteratively along the forward and backward propagation direction, until all the ASE power densities converge to a steady-state value [10]. On each integration step, the populations of homogeneous and clustered ions are found analytically by reducing (2) and (3) emission band with the Nd 3+ absorption band, the calculated backward energy transfer from Yb 3+ to Nd 3+ is considerably weaker than the forward energy transfer, and can safely be neglected.…”