Fabrication And Parameters Control Of Micro/Nano Light Emission Devices

Nano wires and nanobelts have attracted much attention for the small volume,high smoothness,strong optical confinement ability and so on.The coherent light sources with subwavelength scale have been realized by using nanowires or nanobelts.These nanoscale lasers have many important applications in the field of integrated photonic circuits,optical sensors with low power consumption and high resolution imaging,etc.The nanowire or nanobelt lasers with wavelength ranging from ultraviolet to near infrared have been demonstrated by employing different types of semiconductors which own various bandgaps.Many works about the parameters controlling or engineering,for example wavelength tuning,single mode emission,low threshold and polarization control,for nanowire or nanobelt lasers have been done to facilitate the nanoscale lasers to meet the requirements of practical applications.Though some progress have been made,the reports about mode and polarization controlling are few.Meanwhile,for these works,only one of these parameters was tailored in a single nanowire or nanobelt laser which is far away from the nanoscale lasers with several parameters controlling and excellent functionalities.Considering the research background,this thesis aimed at the work about the parameter controlling of nanowire/nanobelt lasers.Here,the polarized light sources based on graphene/nanobelt was proposed whose emission are uniformly TE polarized compared to the original nanobelt lasers with random emission polarization directions.To further improve the polarization ratio and realize multi-parameter controlling in a single laser,a new type of nanobelt with nanoscale bumps on the surface was designed and fabricated.The bumped nanobelt lasers were demonstrated and have shown excellent properties such as lateral emission,single mode,high polarization and low threshold.In the first chapter of the thesis,we summarized the development of nanowire/nanobelt lasers and introduced a series of semiconductor nanowire/nanobelt lasers.Moreover,the research about parameter control of nanowire/nanobelt lasers,especially on the wavelength tuning,mode tailoring and polarization,were reviewed.In the second chapter,the typical fabrication and characterization methods for nanowire/nanobelt lasers were introduced.The theory of Vapor Liquid Solid methods was described and the common methods and instruments used for structure characterization of nanowire/nanobelt were summarized as well as the optical measurements for single nanowire/nanobelt laser.In the third chapter,the polarized light source based on graphene/nanobelt hybrid structure were proposed by exploiting the differential absorption of graphene for TE modes and TM modes and the simulations were also carried out.The graphene was obtain by mechanical exfoliation method and the CdSe nanobelts were grown using VLS method.The hybrid structure light source was fabricated through micromanipulations.The fluorescence testing shows that the emission of the hybrid light sources were uniformly TE polarized both under the fluorescence state and lasing state.In the fourth chapter,to improve the polarization ratio and realize multi-parameter controlling in a single laser,a new type of nanobelt with wire-like or belt-like bumps on the surface was designed via analysis and simulations.By controlling the conditions of VLS method,the nanobelts with nanoscale bumps were synthesized.The bumped nanobelts emit light in the lateral direction and the emission are single mode and highly polarized with the polarization ratio as high as 0.91 which is the highest among the reported nanowire/nanobelt lasers.This new type of nanobelt lasers make the multi-parameter controlling realized in a single nanobelt laser which is significant for the applications of nanowire/nanobelt lasers.In the final chapter,the work introduced in this thesis were concluded and the limitations about these work were also pointed out.Meanwhile,the plan of the related work,in the future,were discussed.The parameter controlling is critical and significant for the practical applications of nanowire/nanobelt lasers and the research in the field will be further continued which will push the development of nanoscale lasers and pave the foundation for the integrated applications of micro-nano scale photonic devices.