Microwave determination of electron-hole recombination dynamics from spontaneous to stimulated emission in a quantum-well microcavity laser

By studying the optical microwave frequency response of a microcavity quantum-well vertical cavity surface-emitting laser (VCSEL) in the transition, over a low (a spread-out) mode density, from spontaneous to coherent operation, we resolve the dynamics (spontaneous to stimulated) of electron-hole recombination and reveal the existence of “fast” spontaneous recombination $(τBspon<159ps)$ in a carrier population generally characterized by a large average lifetime of $∼1ns$ $(Δn/τav=Δn1/τfast+(Δn−Δn1)/τslow,τfast<τslow)$⁠. The measured average spontaneous lifetime is not a constant but is altered by the device size, geometry, and boundary conditions (e. g., cavity and current input-output boundary conditions).