Anti-phase coating for mode control in single-mode oxide-confined vertical-cavity surface-emitting lasers

Abstract

The prevalence of Vertical-Cavity Surface-Emitting Lasers (VCSELs) in the technological landscape has increased substantially recently due to many inherent and beneficial device characteristics. For emerging application such as 3D-sensing in smart phones and automobiles, light detection and ranging (LiDAR), and 4-level pulse amplitude modulation (PAM4), VCSELs present solutions not possible otherwise with edge-emitting lasers (EELs) or light-emitting diodes (LEDs). VCSELs inherently exhibit a circular, low-noise and low-dispersing emission beam, operate with low threshold currents, and can be packaged into high-power 2D-arrays because of their unique geometry. Moreover, VCSELs that operate with only a single-fundamental mode in the transverse direction have improvements in these lasing characteristics. Therefore, control of the lasing modes of a VCSEL is essential to meeting the demands of the applications aforementioned.

Single-transverse fundamental-mode operation can be achieved many ways, most readily by use of a semiconductor anti-phase coating. By depositing and patterning the coating spatially across the top surface of a VCSEL into the shape of an annulus, the threshold modal gain in the outer region can be selectively increased while minimizing the gain in the center of the device. This coating therefore suppresses the higher order transverse modes and fundamental-mode operation can be achieved.

This work explores the development process of 850 nm oxide-confined VCSELs. By first simulating the device structure, the coating can be designed with the appropriate parameters. This is followed up with the fabrication of the VCSEL structure concluding with the characterization of the device for various performance metrics. Thus, the effects of the anti-phase coating are illustrated and single-mode high-power VCSEL operation is realized.