Influence of Lateral Current Spreading on the Characteristics of High Fill Factor Mesa-Stripe Laser Diode Arrays

We have investigated the effect of mesa depth on the characteristics of high fill factor (typically the inter- element spacing is < ~20 μm and stripe width ~ 150 μm) laser diode arrays (LDAs). Measurements were carried out on different laser diode bars and it was observed that a shallow mesa not only increases the threshold current of these laser bars but it can prevent lasing condition for a combination of geometrical parameters of mesa. Minimum mesa depth required to achieve lasing in these laser diode arrays is calculated as a function of inter-element spacing considering the effect of lateral current spreading. The work reported here shows that in order to achieve lasing in laser diode arrays with small inter-element distance, the mesa should be deep enough to prevent electrical coupling between the neighboring stripes of LDAs.