More power! VCSELs near 1 million amps per square centimeter

While time-of-flight applications have led to VCSEL arrays operating at currents measured in the amperes and producing very high aggregate powers, the current through each individual VCSEL aperture is not substantially higher than in many other applications. Driving a single VCSEL emitter of moderate size to extremely high currents requires specialized circuits and operation in a regime where thermal effects will not destroy it, meaning low duty cycles and pulse on-times measured in single-digit nanoseconds. In that regime traditional VCSEL performance and geometry scaling rules no longer apply and surprising behaviors emerge. We describe results for small area single-emitter 850-nm VCSELs designed for high power extraction operating at peak currents of several amperes. The electrooptical behaviors observed afford opportunities for VCSELs in nontraditional areas, but they may also indicate some previously unsuspected limitations.