Lateral Separate Confinements of Carriers and Optical Fields to Improve the Beam Quality

A step-ridge structure is investigated to achieve lateral confinements of carriers and optical fields. Compared with the standard ridge laser structure, this structure can effectively diminish the carrier accumulation effect and reduce the lateral carrier leakage. Meanwhile, a smaller net modal gain of higher-order modes can be obtained by reducing the injection width, which helps improve lateral beam quality. The step-ridge lasers with different injection widths were fabricated. Benefiting from the lateral separation confinements of the step-ridge structure, M ² of the laser with an injection width of $30 ~\mu \text{m}$ is reduced from 13.7 to 6 and the lateral beam quality is improved by 56.2% at 6 A under the continuous wave condition, compared with the laser with an injection width of $90 ~\mu \text{m}$ . Furthermore, among all devices, the separate-confinement structure helps the device with a $30 ~\mu \text{m}$ injection width achieves the maximum power under the quasi-continuous wave operation.