Plasmonic-Enhanced Photoluminescence of Spatially Extended Quantum Emitters

The spontaneous emission rate of a light source depends on its environment, in particular on the local photonic density of states. Quantum dots coupled to the optical cavities exhibit strongly enhanced photoluminescence opening a prospect of single photon sources [1]. Similarly, fluorescence of organic dyes can be enhanced by coupling to plasmonic antennas [2]. In both cases, the emitter can be treated as a point-like dipole source owing to its small dimensions in comparison with the dimensions of the optical resonator. In less frequently studied case of quantum dots coupled to plasmonic antennas [3], the dimensions of the emitter are comparable to the plasmon field decay lengths and the point-like representation of the emitter is no longer justified.

In our numerical study we discuss the plasmon-enhanced photoluminescence of quantum dots in view of finite size of the emitter. We consider two combinations of the dot/barrier material: InAs/GaAs with a spatially direct exciton and InAs/GaAsSb with an indirect exciton [4]. Exciton wave functions are calculated with eight-band k.p theory with the strain and piezoelectric fields taken into account. The effect of spherical and crescent-shaped gold antennas is simulated with boundary element method. The size, shape, and position of the antennas is optimized for a large emission enhancement. We show that although hindered by the finite size of the emitter, the plasmonic enhancement of the photoluminescence is still possible.

[1] D. Englund et al., Phys. Rev. Lett. 95, 013904 (2005).
[2] A. Kinkhabwala et al., Nat. Photon. 3, 654 (2009).
[3] M. Pfeiffer et al., Nano Lett. 10, 4555 (2010).
[4] P. Klenovský et al., Appl. Phys. Lett. 97, 203107 (2010).

vlastimil.krapek@ceitec.vutbr.cz