Room-temperature single photon sources with definite circular and linear polarizations

Optics and Spectroscopy (Impact Factor: 0.56). 01/2010; 108(3):417-424. DOI: 10.1134/S0030400X10030161

ABSTRACT We report experimental results of two room-temperature single photon sources with definite polarization based on emitters
embedded in either cholesteric or nematic liquid crystal hosts. In the first case, a cholesteric 1-D photonic bandgap microcavity
provides circular polarization of definite handedness of single photons from single colloidal semiconductor quantum dots (nanocrystals).
In these experiments, the spectral position of the quantum dot fluorescence maximum is at the bandedge of a photonic bandgap
structure. The host does not destroy fluorescence antibunching of single emitters. In the second case, photons with definite
linear polarization are obtained from single dye molecules doped in a planar-aligned nematic liquid crystal host. The combination
of sources with definite linear and circular polarization states of single photons can be used in a practical implementation
of the BB84 quantum key distribution protocol.

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    ABSTRACT: Microcavity resonance is demonstrated in nanocrystal quantum dot fluorescence in a 1-D chiral photonic bandgap cholesteric liquid crystal host. The resonance demonstrates coupling between quantum dot fluorescence and the cholesteric microcavity. Observed at 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. The circular polarization dissymmetry factor ge 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 under pulsed excitation were used, as well as for room-temperature single-photon source applications.
    Proc SPIE 03/2013;
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    ABSTRACT: Definite circular and linear polarizations of room-temperature single-photon sources, which can serve as polarization bases for quantum key distribution, are produced by doping planar-aligned liquid crystal hosts with single fluorescence emitters. Chiral 1-D photonic bandgap microcavities for a single handedness of circularly polarized light were prepared from both monomeric and oligomeric cholesteric liquid crystals. Fluorescent emitters, such as nanocrystal quantum dots, nitrogen vacancy color centers in nanodiamonds, and rare-earth ions in nanocrystals, were doped into these microcavity structures and used to produce circularly polarized fluorescence of definite handedness. Additionally, we observed circularly polarized resonances in the spectrum of nanocrystal quantum dot fluorescence at the edge of the cholesteric microcavity's photonic stopband. For this polarization we obtained a ~4.9 enhancement of intensity compared to the polarization of the opposite handedness that propagates without photonic bandgap microcavity effects. Such a resonance is indicative of coupling of quantum dot fluorescence to the cholesteric microcavity mode. We have also used planar-aligned nematic liquid crystal hosts to align DiI dye molecules doped into the host, thereby providing a single-photon source of linear polarization of definite direction. Antibunching is demonstrated for fluorescence of nanocrystal quantum dots, nitrogen vacancy color centers, and dye molecules in these liquid crystal structures.
    Journal of Physics Conference Series 02/2013; 414(1):2006-.
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    ABSTRACT: High-damage threshold liquid crystal optical elements are used for high-power laser applications as mirrors, waveplates and optical power limiters. Several nonlinear optical effects under high-power, nanosecond laser irradiation of liquid crystals will be outlined: (1) athermal helical pitch dilation and unwinding of cholesteric mirrors by the field of a light wave (in free space and in a laser resonator); (2) dependence of nonlinear refraction of liquid crystal on the laser beam diameter in presence of two-photon absorption; (3) cumulative effects in nonlinear absorption and refraction at low repetition rate (5-10 Hz); (4) feedback-free kaleidoscope of patterns in dye-doped liquid crystals (hexagons/stripes).
    Proc SPIE 03/2013;

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