Enhancing the energy utilization efficiency of broadband emission from organic molecules using narrowband photonic-crystal nanocavity modes.

Nanocavities can enhance the luminescence of light-emitting materials via the Purcell effect. However, if the emitter spectrum is much broader than the cavity-mode spectrum, a large fraction of the energy used to excite the emitter can usually not be extracted by the cavity mode. Here, we demonstrate that energy-utilization efficiency enhancements are nevertheless possible due to improved radiation directionality, provided that the emitter spectrum is determined by population-conserving homogeneous broadening. Our best cavity can re-shape a 50-nm-broad emission spectrum from organic molecules to a spectrum with a 0.72-nm linewidth while increasing the detected integrated intensity by a factor of 2.1.