Vertical cavity surface emitting lasers (VCSEL's) lase in a single longitudin al mode, have a circularly symmetric output beam that can be very tightly focused, offer extremely high coupling efficiencies into optical fiber, and can be mas s produced in two-dimensional arrays relative to the conventional edge-emitting semi conductor laser. To obtain a high optical output power, besides enlarging of VCS EL's lasing area, the key points are proper number of quantum wells, homogeneous dist ribution of current density in the active layer and good thermal control. The dependenc e of VCSEL's performance on the number of quantum wells, the active diameter, th e thermal conductivity and the electric resistance of the material; and the dist ance between electri cal contacts are investigated. By optimizing the design parameters for a 980 nm In0.2Ga0.8As/GaAs VCSEL, a maximum continuous wave (cw) output power of 1.95 W at room temperature is obtained, which to our knowledge is the highest cw output power of any single VCSEL so far.