Longitudinal current profile modification for higher brightness in GaAs-based high-power diode lasers

The output power and the lateral far-field profiles (and hence the brightness) of broad-area lasers with asymmetric facet coatings degrade at high continuous-wave (CW) operation current due to non-uniformities in longitudinal photon density and temperature variation (LTV). Here, we change the longitudinal current profile (and hence Joule heating) using customized segmented-contact lasers to regulate LTV at high CW operation current. Diode lasers with 90 µm wide stripes and 6 mm long resonators have been fabricated with either 0.8% or 20% front facet reflectivity and 98% rear facet reflectivity to vary photon density profiles. Spontaneous emission results show that the LTV is reduced for the devices with 20% front facet reflectivity and eliminated for the devices with 0.8% front facet reflectivity when the operation current is low at the front and high at the back. As a result of this, the lasers with 20% front facet reflectivity show around 17% increased output power compared to conventional constant voltage operation, whilst around 26% narrower lateral far-field is seen in lasers with 0.8% front facet reflectivity, with thermal blooming of the far-field being strongly suppressed. The modified current profile must be selected carefully, as excessive currents at the rear facet lead to power loss.