Microcavity resonance is demonstrated in nanocrystal quantum dot fluorescence in a one-dimensional (1D) chiral photonic bandgap cholesteric-liquid crystal host under cw excitation. The resonance demonstrates coupling between quantum dot fluorescence and the cholesteric microcavity. Observed at a band edge of a photonic stop band, this resonance has circular polarization due to microcavity chirality with 4.9 times intensity enhancement in comparison with polarization of the opposite handedness. The circular-polarization dissymmetry factor g(e) of this resonance is ~1.3. We also demonstrate photon antibunching of a single quantum dot in a similar glassy cholesteric microcavity. These results are important in cholesteric-laser research, in which so far only dyes were used, as well as for room-temperature single-photon source applications.
Nanocrystal quantum dot (NQD) fluorescence in 1-D glassy cholesteric liquid crystal host is investigated: (1) Microcavity resonance is obtained under cw-excitation demonstrating coupling between NQD fluorescence and a cholesteric microcavity. Observedat a band edge of a photonic stopband, this resonance has circular polarization due to microcavity chirality with 4.9 times intensity enhancement in comparison with polarization of the opposite handedness. (2) Photon antibunching of a single NQD in a similar microcavity was observed. (3) Fluorescence decay time constants were measured at different excitation powers. These results are important in developing cholesteric lasers and single-photon sources for secure quantum communication.
We study the quality factor of single-mode optical whispering gallery mode resonators using finite element method simulations, with a particular focus on the photonic belt resonator geometry. We experimentally observe a large difference between the quality factors of TM and TE modes in such resonators. Examining radiative losses, we conclude that the TM fundamental mode of single-mode resonators can have geometry related radiative losses caused by mode hybridization and coupling that limits their achievable quality factor. However, TE modes are free from mode hybridization radiative losses. This leads to much higher achievable Q factors for TE modes, only limited by fabrication and material quality. We experimentally observed photonic belt resonator quality factors on the order of one billion for TE modes, higher than in any other single mode optical resonator of similar dimensions.
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