Efficient Source of Single Photons: A Single Quantum Dot in a Micropost Microcavity

We have demonstrated efficient production of triggered single photons by coupling a single semiconductor quantum dot to a three-dimensionally confined optical mode in a micropost microcavity. The efficiency of emitting single photons into a single-mode traveling wave is approximately 38%, which is nearly 2 orders of magnitude higher than for a quantum dot in bulk semiconductor material. At the same time, the probability of having more than one photon in a given pulse is reduced by a factor of 7 as compared to light with Poissonian photon statistics.

Figure 1

(a) Scanning-electron microscope (SEM) image of a micropost microcavity with a top diameter of $0.6\mu \mathrm{m}$ and a height of $4.2\mu \mathrm{m}$. (b) Color-scale representation of the amplitude of the electric field for the fundamental mode of the micropost microcavity, as calculated by the finite-difference time-domain method. The profile of the modeled post matches the profile of the real posts as measured from SEM images.

Figure 2

(a) Measured autocorrelation for photons from a single quantum dot in a micropost microcavity, for an incident pump power of $10.9\mu \mathrm{W}$ and an integration time of 300 s (points), and corresponding fit (line). Because of the relatively low emission rate from the QD, adjacent peaks overlap. (b) Area of the central autocorrelation peak relative to the area of the side peaks as a function of pump power (points). The line is a guide for the eye.

Figure 3

External quantum efficiency of a single-photon source consisting of a single quantum dot in a micropost microcavity as a function of pump power (points), together with a saturation fit (line).