Spontaneous Emission Characteristics Of Quantum Dot In Semiconductor Micro And Nano Structures

In recent years, with the rapid development of optical communication and optical electronics, the requirement of photoelectric device integration has become increasingly higher. Due to semiconductor nanomaterials’special properties, such as electric, light, stress, strain and tiny sizes, they have been extensively studied by scientists. Increasingly progress of semiconductor micro-nano manufacturing technology makes the applications of quantum dots, nanowires and photonic crystal become a reality. Nano-materials have distinctly different properties from macroscopic materials because of quantum confinement effect, size effect, quantum tunneling effect and surface effect. They offer more possibilities for a new generation of photonic information processing and micro-optical devices. The most important issue of the photonic communication to solve the single photon source problem. It is difficult for current sources to achieve ideal single photon emission because of the accuracy and complexity. Quantum dot single photon sources has high stability, high oscillator strength and narrow line width, etc, has a very important research value.This paper started from studying the quantum dot’s light-emitting mechanism, at first analyzed a kind of elliptical nanowire structure which can control the spontaneous emission’s polarization direction. Developing the surrounding electromagnetic environment of quantum dots can effectively control the spontaneous emission. This particular arrangement permits the photons emitted from the top only have a single direction of polarization. This paper analyzed the distribution of the electromagnetic field mode in a two-dimensional case, then established a three-dimensional model close to the actual situation. Theoretical calculations obtained the constituent of a single polarization mode in a wide frequency range reached as high as90%, even up to95%at960nm. This superior performance can replace a more complex photonic band gap material. Our study of the nanowire structure provides theoretical guidance of controlling photons’polarization direction, and is of great significance to realize single-photon source having a definite direction of polarization and high strength.Then we used the finite element method to analyze two-dimensional photonic crystal slabs which can control the direction of the spontaneous emission of quantum dots. The existence of the bandgap property makes the photons in the band gap cannot propagate in periodic dielectric region, effectively limited in the defect. The results showed that the photons in the plane of the TE mode substantially all coupled to guided mode, showed a high waveguide coupling efficiency. In the next step, we studied the influence of improving the optical coupling efficiency and reducing radiation modes through changing the width of the photonic crystal waveguide. Finally, we established a semi-waveguide model in which photons propagates in one direction. It proves photonic crystal’s reflection does not cause a great loss, and the transmission performance almost consists with the complete waveguide. Our simulation and study will provide important theoretical guidance for the design of single photon sources and new kinds of photonic devices.