Sampled-Grating DBR Lasers: Calibrated 3D Simulation of Tuning Characteristics

We present a calibrated full-3D simulation of a widely-tunable sampled-grating distributed Bragg reflector (SGDBR) laser showing the characteristic quasi-continuous tuning map. The SGDBR laser is a longitudinally integrated device consisting of five waveguide sections: a front and rear mirror section together with a phase section allow for quasi-continuous tuning over a wavelength range of 100nm, while an active section provides the optical gain for the laser operation. For real world applications the tuning behavior needs to be well understood in order to guarantee stable operation for each wavelength channel. Due to the strong inhomogeneities both in the transverse and longitudinal dimensions a 3D simulation model is necessary to cover the full complexity of such devices. In our physics-based approach, we solve the fully coupled semiconductor drift-diffusion equations for electrons and holes, taking into account longitudinal current flux in full 3D. Gain calculation and the photon rate equation are included self-consistently in an iterative Newton scheme. The optical field is composed of several transverse mode patterns combined with the longitudinal field distribution as obtained by a transfer matrix formalism. By means of a Gummel-type iteration scheme a self-consistent solution of the optics and elec-tronics is found. We show that this approach succeeds even in the numerically most challenging case of discrete wavelength jumps as observed in typical tuning maps of SGDBR lasers. Our simulations are in good agreement with measurements and prove the suitability of the simulator for the design and optimization of state-of-the-art tunable lasers