This article explains the technology of Vertical Cavity Surface-emitting Lasers (VCSELs), a type of surface-emitting semiconductor laser. It covers the basic device structure, featuring a short monolithic resonator with distributed Bragg reflectors, and the resulting performance. The vertical-cavity surface-emitting laser (VCSEL / ˈvɪksəl /) is a type of semiconductor laser diode with laser beam emission perpendicular from the top surface, contrary to conventional edge-emitting semiconductor lasers (also called in-plane lasers) which emit from surfaces formed by cleaving. Vertical-cavity surface-emitting lasers (VCSELs) operating at 850 nm have emerged as the dominant solution for short-reach interconnects due to their inherent advantages in power efficiency, low latency, and cost-effectiveness. Here, we report our work on 850 nm multimode VCSELs to achieve high. Vertical Cavity Surface Emitting Laser (VCSEL) technology has become an indispensable element in optical communication systems and optoelectronics due to its many advantages, and the unique characteristics of VCSELs, including vertical emission, high-speed operation, and low power consumption, have. In this Letter, we present a comprehensive analysis of the high-speed performance of 940 nm oxide-confined AlGaAs vertical-cavity surface-emitting lasers (VCSELs) grown on Ge substrates.