Large-Scale Proton-Implant-Defined VCSEL Arrays With Narrow Beamwidth

In-phase coherently coupled proton-implant-defined vertical cavity surface emitting laser (VCSEL) arrays face difficulties in current spreading, resulting in small array scale, low output power, and broad beamwidth. Although patterned metal grids can improve the current spreading, the undesirable out-of-phase mode tends to be dominant in the array. In this letter, by means of engineering the implantation and array parameters, in-phase mode is obtained in large-scale proton-implant-defined arrays with metal grids. Experimental results show that these arrays are operating in in-phase mode with a nominal interelement spacing of 8 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and an implantation depth of 2.22 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>. By using these parameters, a <inline-formula> <tex-math notation="LaTeX">$5\times 5$ </tex-math></inline-formula> in-phase array with a narrow beamwidth (far-field full width at half maximum) of 1.61° is realized. Besides, a <inline-formula> <tex-math notation="LaTeX">$10\times 10$ </tex-math></inline-formula> in-phase array with a beamwidth of 1.89° and an output power of 10.25 mW for the in-phase mode is achieved. The calculation of far fields is performed to confirm the in-phase operation measured results. Such a simple and low-cost technology provides a promising method for preparing large-scale in-phase coherently coupled VCSEL arrays.