EP-assisted wavelength tuning in a vertical-cavity surface-emitting laser

Vertical-cavity surface-emitting lasers (VCSELs) are appealing light sources for data communication, sensing, and LiDAR due to their small size, low power use, and high manufacturing yield. Wavelength tunability is essential for next-generation VCSELs to enable dense wavelength-division multiplexing (DWDM), portable spectroscopy, and biosensing platforms. Traditional tuning methods, including thermal, electrical, and mechanical techniques, face challenges with speed, limited tuning ranges, and reliability over time. In this work, we propose and demonstrate a method to control the wavelength of VCSELs electrically. This design uses laterally coupled cavities that operate near an exceptional point (EP). The system includes a gain cavity linked to a dissipative feedback cavity through a slow-light channel. Here, the longer photon lifetime and EP sensitivity result in a significant nonlinear response to wavelength changes. Coupled-mode theory suggests that a small change in cavity loss leads to a square-root relationship with the emission frequency, which allows for strong responsiveness. We also studied the impact of asymmetric detuning between the coupled cavities, which creates a trade-off: a smaller tuning range but greater output power and stability during operation. This EP-assisted, slow-light VCSEL platform provides a quick, compact, and energy-efficient option for tunable on-chip lasers. It presents new possibilities for DWDM optical interconnects, LiDAR, spectroscopy, and integrated biosensing technologies.