Research On Second-order Nonlinear Optical Properties Of Semiconductor Nanowires Based On Femtosecond Lasers

Semiconductor nanowires are the basic building blocks in nanophotonics. Since itcombines both the local field enhancement effect of nanostructures and therecombination luminescence of semiconductor materials, the nonlinear coefficientwould be greatly enhanced under excitement of intense incident electromagnetic field,which leads to a superior nonlinear optical properties compared with bulk semi-conductor materials. The researchers focus on it with huge interests and imagination,and have made many breakthroughs in the nanowire-related fields such as nanolasers,frequency-mixers, solar cells, optoelectronic curcuits, and biosensing devices.This thesis reviews the optical properties of semiconductor nanowires under thestructure of nanophotonics. The nonlinear resonance and nonresonance effects areintroduced, and physical mechanism of second-order nonlinear effect of nanowires isdiscussed.The work within this thesis mainly consists of the experimental and theoreticalresearches of two kinds of second–order nonlinear optical properties of defects-freeblende GaAs nanowires. The numerical simulation with FEM demonstrated the exis-tence of local field enhancement effect within the nanowire structures, and simulatedthe SHG in a single nanowire. We experimentally demonstrated that the nanowirescould generate SHG within a broadband of1300nm-1600nm, and also a exacttunable SHG signal in the NIR of800nm-1800nm. The SHG in-tensity is highlydependent on the polarization of incedent field with a wave vectior perpendicular tothe nanowire axis. The SFG experiment demonstrates that we could acquire a tunableSFG signal on the nanowires by overlapping two pulses from a1040nm fs laser andan OPO (1416nm to1770nm). The relatively weak polarization dependency isexplained by calculation results based on nonlinear optical coefficient tensor ofcrystals. It is also shown that they can work for pulse-width measurement offemtosecond lasers.The works above adequately shows that GaAs nanowire, born with the excellentdoubling and sum frequency properties, is a potential candidate in the field ofnano-optoelectronics and other field of nanophotonics.