Research On Controlling Lasing Wavelength Over A Wide Range In Single Semiconductor Nanowires

Due to the high refractive index, unique optical and electrical properties, high aspect ratio and low surface roughness, chemically synthesized semiconductor nanowires may become improtant building blocks for future photonic and optoelectronic circuits. Semiconductor nanowires are suitable to achieve nanoscale lasers, because they can function as both gain materials and Fabry-Perot cavities simultaneously. To push nanowire lasers closer to practical applications, some important challenges, for instance, wavelength variability and mode selectivity, must be addressed. In this paper, we realized relatively precise control of lasing wavelength and mode in a bandgap-graded CdSSe nanowire laser.In the first chapter of this work, we briefly summarize the research background of semiconductor nanowires, and then introduce the research progress of semiconductor nanowire lasers and the methods for controlling lasing wavelength in a semiconductor nanowire laser.In the second chapter of this work, we describe the preparation of the bandgap-graded CdSSe nanowires and introduce the method of controlling lasing wavelength and mode in semiconductor nanowire lasers. We synthesize bandgap-graded CdSSe nanowires by using source-moving vapor-liquid-solid (VLS) approach. According to the localized photoluminescence spectra, we first demonstrate the ability to define lasing wavelengths over a wide range (up to119nm) based on an individual bandgap-graded CdSSe nanowire by forward cutting the nanowire from CdSe to CdS end. Furthermore, free spectral range and modes of the obtained nanowire lasers could be controlled by backward cutting the nanowire from CdS to CdSe end step-by-step. Interestingly, single-mode nanowire laser with predefined lasing wavelength is realized in short nanowires. Finally, the gain properties of the bandgap-graded nanowires are investigated.In the third chapter of this work, we simply describe a method to control the lasing wavelength by introducing a scattering point. We put another CdSSe nanoribbon on the top of the CdSSe nanowire and the crossed point is scattering point. When wide bandgap segment of the CdSSe nanowire is excited by355nm pulsed laser, lasing oscillation is established and the lasing wavelength is decided by the bandgap of gain materials near the crossed point.In the fourth chapter, we give a summary of our work and propose some follow-up study plans.