An efficient single-photon source based on low-density InGaAs quantum dots in a photonic-crystal nanocavity is demonstrated. The single-photon source features the effects of a photonic band gap, yielding a single-mode spontaneous emission coupling efficiency as high as beta = 92% and a linear polarization degree up to p = 95%. This appealing performance makes it well suited for practical implementation of polarization-encoded schemes in quantum cryptography.

We propose a novel technique to fabricate a free-standing three-dimensional colloidal crystal by self-assembling the colloidal microspheres with controllable thickness from the air–liquid interface. Highly ordered three-dimensional colloidal crystals are formed by polymethylmethacrylate or polystyrene monodisperse microspheres. We also demonstrate the fabrication technique of the free-standing inversed opals by removing the microspheres using calcination. The free-standing colloidal crystal structures can be used for nano-photonic circuits, white-light LEDs or as a photocatalyst.

This work demonstrates single photon emissions from a site-controlled quantum dot ͑QD͒ grown on a self-constructed nanoplane. The size of the nanoplane on the micron-sized multifacet structure is accurately controlled by a low surface reducing rate ͑ϳ16 nm/ min͒. Single QD spectral lines were resolved and identified. The antibunching behavior reveals that single photons are emitted from the positioned QD.

Photoluminescence investigations on stacked Ge/Si dots with different spacer thicknesses are presented. According to the emission energy shift in the Ge dots, we found that a thinner spacer layer will lead to remarkable Ge–Si intermixing during the stacking of the Ge/Si dots. Such material intermixing not only shallows the dot potential depth, but also softens the sharpness of the dot/spacer interface. In addition, the temperature of photoluminescence quenching also varies with the spacer thickness. Finally, we point out some important factors that are relevant to the room-temperature luminescence efficiency of stacked Ge/Si quantum dots.

Wafer-scale production of single InGaN quantum disks (QD) ina-nanorod array with small rod diameter (> 9 nm) and low rod-density (< 10 8 cm −2 ) has been achieved without extensive processing steps. Excitation power-dependent µPL spectrum of single QD reveals multi-excitonic peak with 0.75 meV blue-shift for 3 orders of magnitude increasing power, indicating the present system is spectrally stable and nearly free of quantum-confined Stark effects, due possibly to the strain relaxation induced by free surface of small rod diameters. The fully polarized emissions, a high working temperature (180 K), low rod density and good alignment, render this system promising as a potential quantum photon source.