Two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays can be manufactured by defining multiple apertures. Through the sharing of field via the evanescent fields of each aperture, the multiple array elements are able to coherently couple together. The coherently coupling locks the laser array into a coherent array supermode, which is characterized by an interference pattern that appears in the far field. The in-phase supermode, with an on-axis maximum, is the desired mode to have operate, since it has a centralized peak and low divergence. Moreover, by creating separated contacts, it is possible to direct the in-phase mode in different directions to realize coherent, controllable beam steering.
The goal of this project is to create two-dimensional coherent VCSEL arrays that operate in only the in-phase mode. This is accomplished by using a hybrid structure incorporating implant apertures and an etch photonic crystal. Preliminary results have shown 2x2, single-mode, in-phase arrays with low divergence. Additionally, these 2x2 devices have been demonstrated to be continuously steerable. Further development of this work is focused on increasing array size and improving the steering limits and resolutions.
A coherently coupled 2x2 VCSEL array
An in-phase far-field radiation pattern