Design and fabrication of vertical-cavity surface-emitting laser with small divergence

In this paper, dramatic improvements in vertical cavity surface emitting laser (VCSEL) performance have been obtained due to the advanced fabrication techniques and electrical confinement, as well as the structural design and growth of Bragg mirrors. A numerical simulation of current density distribution in the active of a large aperture single device and an array element were constructed. It is found that the current density at the perimeter of the oxide aperture is higher than at the center of the active region. The highe order transverse modes were excited due to the current crowding at the perimeter of the oxide aperture, which lea-ding to large divergence angle. And it is suppressed by optimizing the p-contact diameter in a single device and suppressed by using an extra Au layer. The far-field angle of a single device with a 600 μm oxide aperture decreased from 30°to 15° when the p-contact diameter is optimized from 650 μm to 580 μm, and there is a slight increase in output power due to the optimization. By using an extra Au layer, the output aperture of a 4×4 two dimension array element is decreased to 180 μm, and the far-field angle of the array device is suppressed to 10°. There is a slight drop in output power due to the introduction of the extra Au layer.