Design of monolithic microcavities for enhancing organic quantum emitters

Single organic molecules, such as dibenzoterrylene (DBT) embedded in crystalline hosts, are promising candidates for high-quality single-photon generation. However, their emission spectra are often dominated by red-shifted phonon sidebands and vibrational peaks, which reduce the fraction of photons emitted into the desired narrowband zero-phonon line (00ZPL). While optical microcavities can suppress this unwanted emission through the Purcell effect, integrating organic materials into monolithic structures has historically been hindered by the incompatibility of organic crystals with standard clean-room nanofabrication processes.

The authors present three monolithic microcavity designs—Fabry–Perot, micropillar, and circular Bragg grating (CBG) cavities—tailored for organic emitters. The design process utilized Bayesian optimization and the adaptive Antoulas–Anderson (AAA) algorithm to navigate complex parameter spaces and reconstruct spectra from scattering simulations. The primary goal was to achieve a Purcell enhancement (FP) greater than 20, which is sufficient to ensure that approximately 90% of emitted photons originate from the 00ZPL, while simultaneously maximizing collection efficiency into a single, well-defined optical mode.

The optimized Fabry–Perot design, featuring a concave top mirror, demonstrates a Purcell enhancement of approximately 160 and a collection efficiency of 98% within a numerical aperture of 0.75. The micropillar design provides a robust alternative for integrating DBT-doped anthracene nanocrystals. These structures are designed to be compatible with existing preparation techniques, such as channel filling or drop-casting, allowing for the realization of stable, mechanically rigid, and efficient single-photon sources that do not require active stabilization.