Optimizing waveguide array mode-locking for high-power fiber lasers

Abstract

A comprehensive theoretical treatment is given of the mode-locking dynamics produced by the intensity discrimination (saturable absorption) generated by the nonlinear mode-coupling in a waveguide array [1]. Emphasis is placed on the mode-locking stability as a function of the critical physical parameters in the laser cavity. The theoretical characterization of the laser cavity's stability and dynamics allows for a comprehensive optimization of the laser cavity parameters towards achieving high peak-power, high-energy pulses in both the anomalous and normal dispersion regimes. The technology and components to construct a mode-locked laser based upon a waveguide array are currently available [2]. An advantage of this technology is the short, nonlinear interaction region and robust intensity-discrimination (saturable absorption) provided by the waveguide array. The results here also suggest how the waveguide array spacing and waveguide array losses should be engineered so as to maximize the output intensity (peak power) and energy. The findings relate directly to the design and optimization of laser cavities. In the anomalous dispersion regime, solitonlike pulses can be formed as a result of the balance of anomalous dispersion and positive (i.e. self-focusing) nonlinearity. Typically mode-locked fiber lasers operating in the anomalous dispersion regime are limited in pulse energy by restrictions among the soliton parameters as demonstrated in Fig. 1. Further, our model predicts that mode-locking in the normal dispersion regime relies on non-soliton processes that have been shown experimentally to have stable high-chirped, high-energy pulse solutions.