Amplified spontaneous emission from organic film based on a Bragg reflection waveguide.

Electrically pumped organic edge-emitting lasers face a fundamental trade-off between optical confinement and electrical injection losses, hindered by the low refractive index contrast of organic layers and severe plasmonic absorption from metallic electrodes in conventional waveguides. Here, we demonstrate a single-sided Bragg reflection waveguide (BRW) architecture to overcome these constraints. By exploiting photonic bandgap confinement, this structure achieves efficient transverse resonance within a low-index organic film (CBP:BSBCz) independent of total internal reflection. The resulting device exhibits amplified spontaneous emission at 465.1 nm, featuring a low threshold of ∼4.45 µJ cm-2, a narrow FWHM of 2.30 nm, and dominant TE polarization. Comprehensive simulations and experiments confirm that the BRW mode provides enhanced mode confinement and lower propagation loss compared to conventional waveguide modes. Consequently, this architecture effectively isolates the optical mode from the top metal contact, establishing a robust design pathway for future electrically driven organic lasers.