Traveling Wave Analysis of Non-Thermal Far-Field Blooming in High-Power Broad-Area Lasers

Abstract

With rising current, the lateral far-field angle of high-power broad-area lasers widens (far-field blooming), which can be partly attributed to non-thermal effects due to carrier-induced refractive index and gain changes that become the dominant mechanism under pulsed operation. To analyze the non-thermal contribution to far-field blooming, we use a traveling wave-based model that properly describes the injection of the current into and the diffusion of the carriers within the active region. Although no pre-assumptions regarding the modal composition of the field is made and filamentation is automatically accounted for, the highly dynamic time-dependent optical field distribution can be very well represented by only a few modes of the corresponding stationary waveguide equation obtained by a temporal average of the carrier density and field intensity. The reduction of current spreading and spatial holeburning by selecting proper design parameters can substantially improve the beam quality of the laser.