Quantum Dots Emit Single Photons at High Temps

In the Feb. 23 issue of Applied Physics Letters, Richard P. Mirin of the National Institute of Standards and Technology in Boulder, Colo., presents the findings of his recent investigation into single-photon emission in optically stimulated quantum dots at various temperatures. His observations of such behavior at up to 120 K and photon antibunching at up to 135 K indicate that quantum dots may serve as the basis of single-photon sources for use in quantum cryptography and in low-light-level metrology.

In the work, Mirin excited samples of self-assembled InGaAs quantum dots at temperatures of 5 to 135 K with subpicosecond pulses of 850-nm radiation from a mode-locked Ti:sapphire laser. A microscope collected the infrared response, which was directed onto a monochromator and then to a CCD or to photon-counting avalanche photodiodes in a Hanbury Brown-Twiss interferometer. As the temperature increased, higher pump intensities were required to generate single photons.