| 摘要 |
A single-photon generator for generating a single photon with high efficiency at a constant frequency. A CW semiconductor laser ( 1 ) emits a laser beam of wavelength 780 nm. A photon of wavelength 780 nm is divided into two photons of wavelengths 1550 and 1570 nm by means of a non-degenerate waveguide PPLN ( 2 ). A dichroic mirror ( 6 ) separates the two photons. A gate-operation single-photon detector ( 4 ) detects one of the photons and generates a detection signal. An LN polarization modulator is operated with the detection signal. An optical switch ( 5 ) composed of the LN polarization modulator and a polarized beam splitter rotates the polarization of the other photon by 90° and outputs the photon in a given direction. With this, only one photon can be taken out in the direction of the travel at a frequency of several hundreds of kilohertz. Two photons of different wavelengths are produced by spontaneous parametric down-conversion by a non-degenerate waveguide PPLN, the photons are separated by a dichroic mirror, one of the photons is detected by a gate-operation single-photon detector, and the output of the other photon is controlled by a high-speed LN polarization modulator. Therefore, a single photon can be efficiently produced at a constant frequency.
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