Research On 900nm Single Photon Sources By Molecular Beam Epitaxy

Quantum information technology is one of the focal points of scientific research in the21^st century.In the computer field,random number generators,quantum computing,and quantum storage are all core technologies for future development.In the field of communication,quantum key encryption and quantum teleportation are also areas of competition for scientific research.At present,the research team led by Academician Pan Jianwei of the University of Science and Technology of China has made remarkable achievements in quantum key encryption and quantum teleportation.However,these technologies are inseparable from the support of high-quality single-photon sources.This thesis mainly studies the semiconductor quantum dot single photon source with scalability and high potential for development,including the use of III-V materials to grow a high-quality 900 nm band single photon source and how to effectively propagate in the optical fiber.The specific work is as follows:First of all,the difference between single photon source,ordinary thermal radiation source and laser source is briefly described.The classification of single photon sources is explained,and some main test equipment and their principles are introduced.Two design structures of a single photon source in the 900nm band are proposed:(1)direct growth method;(2)growth corrosion layer peeling method.The growth conditions of the Al_0.9Ga_0.1As,Al_0.4Ga_0.6As,and Al As materials used in the two design structures were optimized.The surface roughness of various materials under different conditions was measured by atomic force microscopy,and the best optimal growth conditions of materials were summarized.In addition,the optical fiber needs to be coupled with a low-density single-photon source to meet its propagation requirements in the optical fiber.Therefore,the low-density single-photon source is grown by the spot burning method and the gradient growth method during the growth process.Secondly,considering that the planar multilayer nanostructured material is confirmed to have a Purcell effect on spontaneous emission,a Distributed Bragg Reflector(DBR)grown with Al_0.9Ga_0.1As and Ga As alternately was designed to form an upper 15 pairs and a lower25 pairs of planar multilayer structures to enhance the single photon intensity.The final result showed that it has a significant enhancement to the single photon intensity.It is worth noting that during the research process,a thickness calibration scheme based on DBR growth was proposed to solve the problem of reflection wavelength shift caused by uneven thickness of DBR growth.Finally,two process schemes for device of two different growth structures are designed.(1)directly etching of the micro-pillars;(2)backside gold plating.The device of the single photon source was finally achieved by directly etching of the micro-pillars,and the light output of the single photon source was finally tested through fiber coupling and low temperature testing,and the quality factor Q of 1800 was obtained.The photon count rate at the fiber output end was 4.73M/s.Through the HBT(Hanbury-Brown-Twiss)experiment,the second-order autocorrelation coefficient g²(0)was measured to reach 0.08,which verified that the single-photon source has high intensity and single-photon properties.Backside gold plating mainly focused on how to replace the traditionally grown Bragg reflector with gold plating on the back of the device.