【作者】 王飞；

【导师】 张俊喜；

【作者基本信息】 合肥工业大学 ， 仪器仪表工程（专业学位）， 2021， 硕士

【摘要】 不同于传统激光需要依靠镜面谐振腔反射来实现激射,随机激光仅依靠增益介质多重散射实现激射,它具有制备简单、成本低、尺寸小等优势而受到关注。然而,随机激光因没有谐振腔使得控制其发射波长面临挑战,这限制其在生物传感和医学治疗等方面的应用。目前人们在液晶、聚合物、光纤光栅、金属纳米颗粒等体系中研究了随机激光发射波长的调控,但发射波长调控范围较小、激光阈值较高。表面等离激元纳米共振腔因模式体积小和非常强的局域电场能增强光与物质的相互作用。本论文研究了银纳米棒阵列纳米共振腔的表面等离激元模式,通过增益介质与纳米共振腔耦合实现低阈值宽波段的可调谐随机激光,为其在生物传感和医学治疗等方面的应用提供原理和技术支持。具体研究内容和结果如下:(1)制备周期性银纳米棒阵列共振腔。采用二次阳极氧化法控制制备阳极氧化铝(AAO)模板。采用电沉积法在AAO模板中组装周期性银纳米棒阵列,通过控制电沉积时间和模板孔径实现对银纳米棒长度和直径的调控。发展银纳米棒阵列的金膜衬底去除方法成功制备银纳米棒阵列共振腔。(2)研究银纳米棒阵列共振腔的表面等离激元模式。反射光谱测量显示,随着银纳米棒长度增加,纳米共振腔在短波长出现纵向高阶表面等离激元模式,同一阶模式峰位显示红移,通过改变纳米棒尺寸实现了对表面等离激元高阶模式的调控。采用有限时域差分法(FDTD)对银纳米棒阵列纳米共振腔表面等离激元模式进行仿真,仿真结果与实验结果基本一致。进一步仿真显示纳米共振腔具有强的局域电场,且呈现驻波谐波的半波模式,这源于周期性纳米棒阵列耦合界面纳米棒之间的近场耦合。(3)研究基于尼罗红增益介质与银纳米棒阵列共振腔耦合的可调谐表面等离激元随机激光。制备尼罗红/聚甲基丙烯酸甲酯(PMMA)与银纳米棒阵列纳米共振腔的耦合结构。采用532 nm激光泵浦耦合结构产生多模振荡的随机激光,阈值可达49.2μJ,这是由纳米共振腔的强局域电场增强了增益介质的荧光发射、从增益介质到纳米共振腔的能量转移以及纳米棒阵列表面缺陷引起的多重散射共同作用所致的。进一步控制纳米共振腔的表面等离激元高阶谐波模式实现对随机激光发射波长从623 nm到654 nm的宽范围调控。更多还原

【Abstract】 Different from the traditional laser which relies on the reflection of the mirror cavity to realize lasing,random laser only dependent on multiple random scattering of gain medium can be generated.The random laser has attracted much attention due to their advantages of simple preparation,low cost and small size.However,controlling the emission wavelengths is challenging because of the absence of a resonant cavity in the random laser,which limits its applications in biosensing and medical treatments.At present,people have explored the modulation of emission wavelength of the random laser in liquid crystals,polymers,fiber gratings,metal nanoparticles etc.,but the modulation range of emission wavelength is small and the laser threshold is high.Plasmonic nanocavity can enhance the interaction between light and matter because of the small mode volume and the very strong local electric fields.In this thesis,the surface plasmon modes of the nanocavities of the silver nanorod arrays have been studied.A low threshold and a tunable broadband random laser have been realized by coupling the gain medium with the nanocavity,which provides the principle and technical support for its applications in biosensors and medical treatments.The specific research contents and results are as follows:(1)Cavities based on periodic silver nanorod arrays were fabricated.Anodic aluminum oxide(AAO)templates were prepared by a two-step anodization method,and the periodic silver nanorod arrays were assembled in AAO template by an electrodeposition approach,the length and diameter of the silver nanorods were controlled by changing the electrodeposition time and the nanochannel size of the AAO templates.A method for removal of the gold film substrate of silver nanorod arrays was developed to prepare the cavities based on the silver nanorod arrays successfully.(2)The plasmonic resonance modes of the cavities of the silver nanorod arrays were studied.The results of reflection spectrum measurements show that the resonance peaks of the same order modes shows red shifts with increasing of length of the silver nanorods,and the high-order modes of the surface plasmon resonance can be tuned by changing the nanorod size(e.g.,length,diameter).Moreover,the plasmonic resonance modes of the silver nanorod array nanocavity were simulated by a finite difference time domain(FDTD)method.The simulation shows that the nanocavities have strong localized electric fields and presents standing wave harmonics with half-wave modes,which is resulted from the near-field coupling between the adjacent nanorods at the coupling interface of periodic nanorod arrays.(3)A tunable plasmonic random laser based on the coupling between the gain medium Nile red and the silver nanorod array cavities is studied.The coupling structures based on the Nile red/polymethyl methacrylate(PMMA)and the silver nanorod array nanocavities were prepared.A low threshold random laser with multi-mode oscillations is generated in the coupling structures by using a 532 nm laser pump,and the threshold can reach 49.2 μJ,which results from the fluorescence emission of the gain medium is enhanced by the strong localized electric fields of the nanocavities,and the energy transfer from the gain medium to the nanocavities,as well as the multiple scattering caused by the surface defects of the nanorod arrays.Additionally,the random laser emission wavelengths in a wide range from 623 nm to 654 nm can be modulated by the high-order harmonic modes of the plasmonic nanocavities are controlled to achieve.更多还原