Figure 46.

(a) Current-density-dependent spectra of edge-emitted EL of the BRW device (Figure 45a) exhibit the transition from broad-band spontaneous emission (green line) to ASE (blue, red, and black lines), which manifests as two sharp peaks at the positions of the 1S and 1P transitions. (b) Intensities of the 1S spontaneous emission (black) and ASE (red) EL bands as a function of current density (top) and the dependence of the 1S emission FWHM on j (bottom). These data indicate the ASE threshold of 13 A cm^–2, after which the ASE peak shows accelerated growth accompanied by line narrowing. (c) Polarization characteristics of edge-emitted EL of the BRW device measured at j = 650 A cm^–2. The broader spontaneous-emission band at 1.98 eV does not exhibit preferred polarization. In contrast, the narrower 1S (1.93 eV) and 1P (2.11 eV) peaks are TE polarized. This type of polarization is expected for ASE as its development requires low-loss light propagation in a waveguided which is not possible for strongly damped TM modes. Indeed, neither of the sharp peaks is present in the TM polarized EL spectrum. Reproduced with permission from ref (63) (CC-BY 4.0).