Spontaneous-emission measurements in broad-area quantum well semiconductor lasers

摘要

Abstract: Spontaneous emission spectra have ben obtained from semiconductor quantum well lasers of varying epitaxial design. Initial measurements taken normal to the active region through the substrate and a transparent contact exhibited a modulated spectral profile dependent on the collection angle. An image model with the quantum well active region as the source and the p-side metallization as the image plane explains the observed modification and as such, presents an excellent example of a simple cavity quantum electrodynamics (QED) effect in a planar semiconductor laser. The phenomenon is made possible by the proximity of the quantum well active region to the p-side electrical contact of the device. Modification of the spontaneous emission rate and spectra can be substantial and must be accounted for if one hopes to correctly infer modal gain or carrier heating phenomena in a device using this geometry. Alternatively, to avoid the influence of the cavity QED effect, spontaneous emission can be obtained through the side wall of the device. Using this method for collection of spontaneous emission, the effect of quantum well dimensions on carrier heating in single quantum well InGaAs or GaAs active regions was also investigated. Incomplete pinning of the carrier density was observed above threshold in these samples with low duty cycle pumping.However, minimal distortion of the carrier distribution to higher energies was observed at room temperature up to current densities of 1.6 kA cm$+$MIN@2$/. Low temperature spontaneous emission spectra revealed gain suppression from carrier heating and possibly spectral hole burning in InGaAs deep and shallow quantum well lasers. !24