Extended Data Fig. 6. The j-dependent spectra of edge-emitted EL of  the BRW device measured with a TE polarizer.

Owing to a ‘lossy’ character of TM modes (strongly attenuated by the silver electrode), ASE occurs because of low-loss TE modes. The spontaneous emission does not exhibit preferred polarization. Therefore, the use of a TE polarizer allows us to emphasize narrowband ASE features over broadband spontaneous emission. As a result, the EL spectra measured at high current densities (j > 200 A cm⁻²) are dominated by narrow 1S and 1P ASE peaks. The marked difference of these spectra from those of the reference devices (Fig. 1f and Extended Data Fig. 1a) is yet another confirmation of the ASE effect realized in our BRW devices. a.u., arbitrary units.