Study On Mode Characteristics For Nanowire Optical Microcavity And Squre Optical Microcavity

Optical microcavities have attracted great attention due to their unique properties, and they are suitable for the fabrication of optical communication devices, such as lasers, optical filters, optical demultiplexers, optical switches, optical modulaters and nonlinear optical frequency converters, etc. This dissertation mainly studies the mode properties of nanowire optical microcavity and square optical microcavity through theoretical analysis and numeric simulation because of their special optical properties. This part contains the following contents:Firstly, we introduce the developments of the optical microcavities in these years, research background and the applications in detail.Secondly, we introduce the Finite-Difference in Time-Domain method (FDTD) in detail, including the deduce of the difference format, the usage of the Mur and Perfect Matched Layer (PML) boundary absorbing conditions, the selection of the exciting source and numeric stability, etc. For the information from FDTD is in time domain, we must transfer it in frequency domain to obtain the frequency information. So we introduce an analysis method for frequency spectrum: Padéapproximation based on Bakers algorithm.What's more, we introduce the FDTD with Mur's absorbing boundary condition in the cylindrical coordinates. Then, we transform the three-dimensional (3-D) problem to two-dimensional (2-D) one based on the azimuthal symmetry of the nanowires to simulate the free-standing nanowire microcavity and nanowire microcavity with sapphire substrate at different size. Then the time variation of a selected field component in some points inside the nanowire microcavity is recorded as FDTD output, and the Padéapproximation based on Baker's algorithm is used to calculate the field spectrum for obtaining the Q-factor and the modes frequencies by fitting the Lorentzian curve. At last, we calculate the mode reflectivities for different nanowire cavity from the mode Q-factor and the group refractive index. The results show that HE11 mode has much larger Q-factor than that of TE01 and TM01 modes as...