A vertical-cavity surface-emitting laser (VCSEL) is provided. The VCSEL includes a mesa structure disposed on a substrate. The mesa structure has a first reflector, a second reflector, and an active cavity material structure disposed between the first and second reflectors. The mesa structure defines an optical window through which the VCSEL is configured to emit light. The mesa structure further includes a passivation layer disposed at least within the optical window. The passivation layer is designed to seal the mesa structure to reduce the humidity sensitivity of the VCSEL and to protect the VCSEL from contaminants. The passivation layer also provides an improvement in overshoot control, broader modulation bandwidth, and faster pulsing of the VCSEL such that the VCSEL may provide a high speed, high bandwidth signal with controlled overshoot and dumping behavior.