Hai-Zhi Song

Promotion on Acetone Sensing of Single SnO2 Nanobelt by Eu Doping

SnO2 nanobelts (NBs) have unique structural and functional properties which attract great attention in gas detecting. In this work, Eu doping is adopted to improve the gas sensitivity of pure SnO2, especially to enhance the response to one single gas. The Eu-doped SnO2 NBs, pure-SnO2 NBs, and their single NB devices are fabricated by simple techniques. The sensing properties of the two sensors have been experimentally investigated. It is found that the two sensors possess long-term stability with rapid response performance, and Eu doping improves the electronic performance and the gas-sensing response, particularly to acetone. In addition, the effects aroused by Eu have been theoretically calculated, which indicates that Eu doping enhances the sensing performance of SnO2. Consequently, Eu-doped SnO2 NBs show great potential applications in the detection of acetone.

InGaAsP/InP Micropillar Cavities for 1.55 μm Quantum-Dot Single Photon Sources

Micropillar cavities containing 1.55 μm quantum dots are required for silica-fiber based quantum information processing. The straight way is to construct micropillars consisting of InGaAsP/InP distributed Bragg reflectors. We perform a systematic study mainly on optical properties correlated to the micropillar diameter. As expected, the mode wavelength increases with extending micropillar diameter and tends to saturate at 1.55 μm for the diameter larger than 2.0 μm. Able to be as high as 104, the quality factor, however, is almost independent of pillar diameter, which may be the result of the small refractive index contrast. The Purcell factor reaches highest ( >130) at pillar diameter of ~0.6 μm, suggesting that these cavities could serve as efficient 1.55 μm single photon sources. The output efficiency increases with extending diameter, and is acceptably good at small diameters. Although not easy in fabrication technique, this cavity provides monolithic scheme for constructing 1.55 μm single photon sources.

InGaAsP/InP-air-aperture microcavities for single-photon sources at 1.55-μm telecommunication band

InGaAsP/InP-air-aperture micropillar cavities are proposed to serve as 1.55-μm single photon sources, which are indispensable in silica-fiber based quantum information processing. Owing to air-apertures introduced to InP layers, and adiabatically tapered distributed Bragg-reflector structures used in the central cavity layers, the pillar diameters can be less than 1 μm, achieving mode volume as small as ~(λ/n)3, and the quality factors are more than 104 - 105, sufficient to increase the quantum dot emission rate for 100 times and create strong coupling between the optical mode and the 1.55- μm InAs/InP quantum dot emitter. The mode wavelengths and quality factors are found weakly changing with the cavity size and the deviation from the ideal shape, indicating the robustness against the imperfection of the fabrication technique. The fabrication, simply epitaxial growth, dry and chemical etching, is a damage-free and monolithic process, which is advantageous over previous hybrid cavities. The above properties satisfy the requirements of efficient, photonindistinguishable and coherent 1.55-μm quantum dot single photon sources, so the proposed InGaAsP/InP-air-aperture micropillar cavities are prospective candidates for quantum information devices at telecommunication band.

InP/InGaAsP-Si/SiO 2 Hybrid Micropillar Cavity for 1.55-μm Quantum Communication

Fiber-based quantum communication requires effective single photon sources. We designed a micropillar cavity with high quality factor (~105), small mode volume and sufficiently thick quantum-dot containing active layer.