Study On Optical Properties Of Plasmon Coupled Nanocavity

With the development of nanotechnology,the demand for device,such as laser,urgently needs to be miniaturized.However,when the cavity size of the traditional nanolaser is reduced to near the diffraction limit,the photonic mode size is much larger than the cavity size,resulting in poor optical gain and heavy cavity loss.Surface plasmon stimulated radiation amplification（SPASER）provides a breakthrough for solving the above problems.Since the first experimental realization of plasmonic nanolasers with three kinds of optical confinement in 2009,various high-performance plasmonic nanolasers have been realized successively,and become essential unit devices in optical interconnection,sensors,far-field,biological fields and so on.As human beings step into the nanochip era,light from metal plasmonic nanocavity coupling to SOI（Silicon on insulator）waveguide could provide a way for Silicon photonics to integrate laser sources.At present,the fabrication process of metal plasmonic nanocavity is complicated and the volume of effective mode is large,which makes it impossible to break through the diffraction limit.Therefore,it is necessary to find metal plasmonic nanocavity with simple preparation and small mode volume.Firstly,we deeply investigate the gain and loss in optimized ZnO/Al₂O₃/Ag structure,which proposed the quantitative models of the gain and loss.In order to reduce the mode loss and mirror loss in the plasmonic nanolaser,the core-shell plasmonic nanocavity with three dimensional optical confinement realized the plasmonic laser behavior,which the thickness of the metal was optimized by calculating the transparency gain of the HE₁₁mode in the nanocavity,and the feasibility of the laser behavior under the thickness was verified experimentally.This research proposed plasmonic laser can be used for optical interconnection on a chip.Subsequently,in order to achieve a nanocavity with high optical confinement and more compatible with on-chip integration,we constructed semishell ZnO-（SiO₂/Al）plasmonic structure（with the insulator layer）,which realized the HE₁₁mode with small effective mode area in the nanocavity.The feasibility of high performances laser behavior was proved theoretically and experimentally.The results are helpful to explore the electrically-pumped based on Metal-Insulator-Semiconductor nanocavity design.The specific content mainly includes:1.we quantitatively investigate plasmonic lasing dynamics using carrier density in theory and experiment.According to Drude model and rate equation,the quantitatively dependency between carrier density and refractive index in plasmonic nanolaser is used to optimize laser performance and verify the SP-exciton coupling mechanism.Particularly,the laser mode blueshift of the plasmonic nanolaser with the increase of power density is explained by the free carrier effect which can confirm gain and loss coefficient in the theory and experiment.What’s more,different from photonic nanolaser,high carrier recombination rate in plasmonic nanolaser could provide the means to deliver energy to the nanoscale on short time,thereby achieving extremely high gain in the near field.2.we designed a semiconductor/metal（ZnO/Al）core-shell nanocavity without insulator spacer and fabricated by a simple magnetron sputtering.The theoretical and experimental investigation presented the plasmonic lasing behavior and SP-exciton coupling dynamics.The simulation demonstrated the three-dimensional optical confinement of the light field in the core-shell structure,while the experiments revealed a lower threshold of the optimized ZnO/Al core-shell nanolaser than that of the same-sized ZnO photonic nanolaser.More importantly,the blue shift lasing mode demonstrated the SP-exciton coupling in the ZnO/Al core-shell nanocavity,which was also confirmed by low-temperature photoluminescence（PL）spectra.The analysis of Purcell factor and PL decay time revealed that SP-exciton coupling accelerated the exciton recombination rate and enhanced the spontaneous radiation converting into the stimulated radiation.3.we designed a semishell ZnO plasmonic nanolaser with metal/insulator/semiconductor configuration that flat Al and insulator SiO2 layers were semishell to ZnO nanorod using sample magnetron sputtering method to realize ultra-strong optical confinement.The simulation indicated an optimized thickness of insulator layer for higher Purcell factor（Fp）with the higher effective index and smaller effective mode area.Meanwhile,the experiment demonstrated high performance of the plasmonic nanolaser with lower threshold and higher quality factor.The coupling process between SP-exciton in the semishell nanocavity was revealed by exploring the distinct lasing mode shift,high spontaneous radiation coupling factor and shorter PL decay life.SP-exciton coupling reduces the dependency of temperature and PL decay life in the semishell nanocavity and further accelerates the temporal response under direct laser modulation.