The development of a usable single-photon source (SPS) with photons exhibiting antibunching has recently been of significant interest for its applications in quantum cryptography and quantum communication. A desirable feature for a SPS is deterministic photon polarization, so that losses are not introduced by using polarizers to encode information. Meanwhile, colloidal quantum-dot (QD) based devices are promising because QD fluorescence has higher photostability at room temperature than conventional dyes, and relatively high quantum yield. To increase spontaneous emission of QDs, microcavities including photonic crystals can be used. In this paper, we report experimental results of a novel SPS on demand based on a single CdSe QD suspended in a liquid crystal host self-assembled in a 1-D chiral photonic bandgap structure. This structure provides not only spontaneous emission enhancement and a diminishing of the fluorescence lifetime, but also circular polarization of definite handedness even for emitters without a dipole moment. 1-D chiral photonic bandgap structures possess an advantage over conventional 1-D photonic bandgap technologies. Because the refractive index n varies gradually in chiral structures rather than abruptly, there are no losses into the waveguide modes, which arise from total internal reflection at the border between two consecutive layers with different n. We report here for the first time fluorescence antibunching of a QD doped in a liquid crystal photonic bandgap material. Earlier we reported both fluorescence antibunching and deterministic polarization of dye fluorescence in aligned liquid crystal hosts [1-2].
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