Chaotic-cavity surface-emitting laser array for optical wireless communication and low-speckle illumination

Abstract

While highly coherent light has its advantages in certain applications, it also leads to some unwanted effects, such as the formation of speckles, negatively impacting imaging, lighting, and projection/display quality. This has prompted the development of edge-emitting semiconductor light sources with partial coherence, such as broadband lasers and superluminescent diodes (SLDs), which have found use in display applications, optical coherence tomography, and random bit generation. However, the edge-emission design of these sources complicates the fabrication of two-dimensional arrays, preventing their use in many applications. On the other hand, vertical-cavity surface-emitting lasers (VCSELs) have gained popularity in consumer electronics due to the unique benefits of surface emission. Yet, they face challenges related to high coherence. We demonstrate that by leveraging the distinctive properties of chaotic cavities, we can reduce the coherence of VCSELs without enlarging their emission area. This enables high-speed wireless communication with low-speckle illumination, as confirmed through comprehensive interference studies and high-speed testing. We show that the chaotic-cavity VCSELs can provide better illumination quality while maintaining high data rates (12.6 Gb/s over short distances and 6.5 Gb/s over 3 m). In addition, the use of a carefully designed AC signal for communication can further lower the speckle contrast, which improves the illumination performance. This paves the way for the potential use of chaoticcavity VCSELs as versatile light sources for illumination, imaging, projection, communication, and various other applications.