  Combining resonant excitation with Purcell-enhanced single quantum dots (QDs)
stands out as a prominent strategy for realizing high performance solid-state
single photon sources. However, optimizing photon efficiency requires
addressing challenges associated with effectively separating the excitation
laser from QDs' emission. Traditionally, this involves polarization filtering,
which limits the achievable polarization directions and the scalability of
photonic states. In this study, we have successfully tackled this challenge by
employing spatially-orthogonal resonant excitation of QDs, deterministically
coupled to monolithic Fabry-Perot microcavities. Leveraging the membrane cavity
structures, we have achieved filter-free single photon resonant fluorescence.
The resulting source produces single photons with a simultaneous high
extraction efficiency of 0.87, purity of 0.9045(4), and indistinguishability of
0.963(4).
