Automatic Measurement Of Second-order Susceptibilities For Nanowires

Second harmonic generation (SHG) is the first nonlinear optical effect observed in the experiment. Recently, the study on SHG has been extended to nano materials. Nano materials have important applications in single electron transistor, nano laser, etc. The one-dimension (ID) nanowires can be used to fabricate field-effect transistor (FET), gas sensors and nano resonator.The SHG in ID nano materials is very different from the bulk materials. Many research groups have developed various methods to determine the second-order susceptibility of them. In this thesis, ZnO nanowires and CdS nanowires are studied. Both of them have wide direct bandgaps, which have important applications in the photoelectric devices.The previous methods to measure the second-order susceptibility of nanowires have several limitations. Firstly, the methods based on the measurement of thin film composed by nanowires ignore the characteristics of single nanowire. Secondly, previous methods usually use the back-irradiated signal, which has a short coherence length. In this thesis, based on the theory of SHG in a single nanowire, I design an automatic measurement system including the optical part and electrical part.This thesis is organized in 5 chapters. Chapter 1 presents a general introduction of nonlinear optical theory and the background information of nanowires; Chapter 2.describes the hardware of the measurement system, including optical part and electrical part; Chapter 3 introduces the software based on LabView which can automatically performs the data measuring, data monitor and data stores; Chapter 4 shows the results of the experiments about ZnO and CdS nanowires; Chapter 5 present a brief summary and future outlook.