Tailored polarization-switchable VCSEL arrays for photonic Ising computing

Photonic Ising computing based on vertical-cavity surface-emitting lasers (VCSELs) offers a promising approach to solving combinatorial optimization problems at the speed of light, where encoding bits or qubits into orthogonal lasing polarization states has been proposed. However, challenges remain due to the inherent polarization preference and limited switchability of VCSELs, which hinder the polarization encoding and increase the injection power required to achieve polarization locking, which serves as the physical mechanism for mapping Ising interactions. To address these challenges, we design and fabricate VCSEL arrays with tailored oxidation apertures to compensate for the inherent anisotropy. Experimental results reveal controllable polarization switching and relatively narrow wavelength distributions across multiple array types, both of which are desirable for polarization-encoded computing. In particular, switchable VCSELs are found to require lower injection power for polarization locking compared to non-switchable ones. Finally, we numerically extend our study to a mutually injection-locked VCSEL Ising system, revealing the expected polarization dynamics.