We report on the demonstration of dielectric amplified spontaneous emission (ASE) from the gallium nitride (GaN) nanorod dimer, in which localized optical modes arise from strong coupling across a nanoscale air gap. The nanorod dimer forms a self-aligned cavity that supports spatially confined resonant modes, enabling ASE under continuous-wave excitation at room temperature. The system achieves a narrow emission line width of approximately 3 nm and a low ASE threshold of ∼26.98 kW/cm2. Photoluminescence (PL) measurements reveal distinct spectral narrowing and polarization-dependent emission as the injection power increases. Time-resolved PL and quality factor analysis confirm enhanced photon confinement and coherence in the dimer configuration, with the Q-factor increasing by nearly 8-fold compared to single nanorods. Finite-difference time-domain (3D-FDTD) simulations support these observations by showing electric field localization within the dimer cavity and modal selectivity between TE and TM modes. Furthermore, the air-gap cavity exhibits characteristics of a leaky-mode resonance, facilitating directional emission and improved gain accumulation. These findings highlight a fabrication-compatible route toward compact, low-threshold nanophotonic light sources based on the dielectric confinement in semiconductor nanostructures.
Kim et al. (2025) studied this question.