Nonlinear Dynamics in Semiconductor Lasers - Abstract
Zeghuzi, Anissa
For numerous applications of high-power broad-area lasers (BALs) a small lateral far-field divergence is vital. However, at high injection currents a broadening of the far-field is observable which is commonly attributed to the thermal lensing effect. Recently, several groups have proposed that carrier dependent effects also play an important role in this mechanism (non-thermal far-field blooming) [1]. Due to their non-stationary behavior [2, 3], the electro-optical characteristics of BALs have to be simulated on the basis of a time and space dependent model. For this purpose we use an improved version of the software kit BALaser [4] based on the traveling wave model, that properly describes the injection of the current into and the diffusion of the carriers within the active region. It allows a precise simulation of the dynamics of BALs in the absence of thermal effects (under pulsed operation). No ad-hoc assumptions of modes or stationary are made and filamentation effects are automatically accounted for. It turns out, that the time-dependent optical field distribution at a fixed longitudinal position and a given instantaneous time can be very well represented by only few modes of the corresponding stationary waveguide equation, obtained by a temporal average of the carrier density and field intensity. We have found that enhanced current spreading and spatial hole burning lead to excitation of higher order lateral modes thus increasing the far field divergence and reducing the beam quality. [1] M. Winterfeldt et al., IEEE Photonics Technol. Lett., 27(17), 1809(2015). [2] I. Fischer et al., Europhys. Lett., 35(8), 579(1996). [3] A. Klehr et al., Proc. SPIE 10553, 105530K(2018). [4] BALaser, A software tool for simulation of dynamics in broad area semiconductor lasers. http://www.wias-berlin.de/software/balaser/.