Comparison of 850 nm VCSEL oxide aperture designs

We design, produce, characterize, and compare 850 nm vertical cavity surface emitting lasers (VCSELs) with one and two oxide aperture layers, and with cavity optical thicknesses of 0.5λ and 1.5λ. We process five VCSEL wafers side by side with varying oxide aperture diameters from about 4 to 16 m and perform on-wafer static and dynamic testing. From optical output power-current-voltage characteristics we extract and compare threshold currents, differential series resistances, and wall plug efficiencies. We measure the dynamic 2-port scattering parameters (S11 and S21) to determine the small signal modulation frequency response of the VCSEL and the combined VCSEL and photodetector optical link. By extracting and comparing the D-factor, modulation current efficiency factor, -3 dB bandwidth, and resistanceinductance- capacitance (RLC) circuit elements we find only a small difference in the static and dynamic performance characteristics of the five VCSEL designs, with slightly higher bandwidth for the half-lambda cavity VCSELs with two top oxide apertures.