Research On The Design And Characteristics Of Vertical Nanowire Lasers

Minimizing the size of semiconductor lasers is essential for realizing ultra-compact photonic integrated circuits.At present,most researches pay attention to nanowire lasers placed horizontally on the substrate and rarely to nanowire lasers standing vertically on the substrate.The vertical nanowire laser has a smaller footprint and therefore has outstanding advantages in many aspects,such as laser emission and large-scale integration.This thesis focuses on the theoretical research of vertical nanowire lasers,and the main contributions are as follows:(1)A Si-based vertical single GaAs nanowire laser with enhanced bottom reflection is designed,and the threshold gain characteristics of nanowire lasers with different reflection bottom mirrors are studied using the finite time domain difference method.The results show that by inserting SiO2 or air medium between the nanowire and the substrate,the bottom reflectivity is significantly improved,and the threshold of the laser with a diameter of 300 nm is reduced by 14 and 20 times,respectively.(2)This thesis theoretically studies the mode field characteristics of the vertical nanowire array.The research found that the periodically arranged vertical nanowire array have the characteristics of defect-free photonic crystals.There exists a surface-avoiding state like Dirichlet in the band-edge mode,and most of the photon energy is constrainted in the center of the array.The optical field leakage at the edge of the array is strongly suppressed.By optimizing the array parameters,when the lattice constant(ie,the distance between the center of the nanowires)is 3 times the diameter of the nanowire,the band gap effect of the photonic crystal is significant and the optical field limitation is the strongest.(3)A silicon-based vertical nanowire array laser is designed and simulated.And this thesis compares the threshold gain characteristics of the silicon-based vertical nanowire array laser and the vertical single nanowire laser.Benefiting from the optical localization effect of the photonic crystal,the cut-off diameter of the vertical nanowire array laser is 120 nm,which is only 3/4 of that of the vertical single nanowire laser;when the diameter is 160 nm,the threshold is reduced by 80%compared to the vertical single nanowire laser.