MICROCAVITY EFFECTS IN AN EXTERNAL-CAVITY SURFACE-EMITTING LASER

Microcavity-induced lasing threshold reduction and modulation of the s pontaneous emission coherence length with cavity length in an external -cavity resonant-periodic-gain, surface-emitting laser is reported, In contrast to comparing different epitaxial growths, external-cavity op eration allows changing the cavity length without affecting material p roperties as well as arbitrarily long resonator lengths. The transitio n to the macrocavity domain is observed by extending the cavity length beyond the spontaneous emission coherence length, The maximum change in the spontaneous emission rate induced by the cavity QED effect in t he presence of resonant periodic gain is calculated, As expected, for cavities longer than several wavelengths, microcavity Fabry-Perot reso nance effects dominate over cavity QED in determining the cavity-norma l spontaneous emission power and coherence length. A simple model of t he cavity-normal spontaneous emission coherence length and spontaneous emission power emitted from a Gaussian source placed in an ideal Fabr y-Perot cavity is consistent with our observations.