Improvement to the Lateral Mode Stability in High-Power Laser Diodes by Multistripe-Gain Distribution

Wide-stripe design for high-power laser diodes (LDs) permits multilateral-mode optical field distribution and the formation of an unstable filament pattern within the active waveguide. This is a serious drawback leading to a decrease in the emitted beam quality. The filaments cause spatial and time fluctuations in the LDs near- and far-field (FF) characteristics due to their random nature. The multimode optical field induces a widening of the FF pattern (known as FF blooming effects) as the drive current increases due to an increasing number of lateral modes. In this paper, the gain shaping in the LDs active region by ion implantation is proposed as a way to induce beam stability improvement. The optical resonator of the presented LDs consists of a series of interlaced narrow high- and low-gain stripes. The low-gain stripes are pumped only by spreading the current from neighboring stripes. The calculations show that under such conditions, one of the higher lateral modes can be excited at laser threshold due to the best spatial fit to the stripe’s periodicity. This should restrict the FF blooming effect. The predictions are confirmed by measurements of the LDs based on the multistripe design. A reduction of the optical field intensity fluctuations has also been observed.