| Coupling plays an important role in optics such as coupling of optical field between waveguides in integraded-optics,evanescent field coupling between micro-fiber and light source.Besides,elementary excitation coupling is also applied in photon-material interaction,such as surface plasmon plariton-exciton coupling,exciton-phonon coupling and so on.In optics,coupling is used to enhance some specific effects.Utilizing evanescent field coupling and elementary excitation coupling,we explored how to realize wavelength-tunable nanolasers and ultra-sensitive stimulated Raman scattering(SRS)spectro-microscopy,respectively.The innovations are listed as follows:1.By evanescent field coupling,we realized reversibly wavelength-tunable nanolasers based on single bandgap-graded semiconductor nanowires.Optical hybrid structuring contributes to micro-nanodevice parameter modulating and optimizing through evanescent field coupling.Recently,lasing source on low dimentional micro-nanomaterials has been drawing a lot of attention.Becase of owning a sufficient gain,high refractive index,strong optical field confinement factor and evanescent field,as well as pretty low optical propagation loss,semiconductor micro-nanomaterials become a hit in material and optical science.Meanwhile,parameter modulating and optimizing enable them applied in more and more fields.Wavelength-tunable nanolasers play key roles in bioimaging,integraded optics,optical communications,environment sensing,etc.,which makes it attractive and important.It is hard to resolve the contradiction that is simultaneously to own the adequate Q-factor of nanoscale resonators and the continues-varying gain compositions.In the dissertation,we demonstrated a new approach where two nanowires touch each other vertically like a cross to generate FP-WGM micro-nanocavity coupling.FP-WGM micro-nanocavity coupling enhances the Q-factor of resonator successfully,contributing to lowering the lasing threshold.Combined with FP-WGM micro-nanocavity coupling,a bandgaps-graded semiconductor nanowire has been exploited to be a reversibly wavelength-tunable nanolaser,which can be operated electrically.A 42-nm wavelength tuning range and a 1.18-nm spectral resolution have been realized with excellent control,reversibility,stability and reproducibility.2.By elementary excitation coupling,we deveploed an ultra-sensitive SRS spectro-microscopy and revealed retinoid imaging in multi-level biosystems.Exciton-phonon coupling,a type of elementary excitation coupling,proves to enhance strongly Raman cross section.Modern spectro-microscopic imaging serves as a platform in exploring molecule-level function in biochemistry with high sensitivity and selectivity.Vibrational Raman scattering detects samples directly without probes,which is label-free and can be used widely.However,the low efficiency of Raman scattering limits its biological application even if the coherent Raman scattering improves the scattering efficientcy by sitmulating.Meanwhile,the surface enhanced Raman scattering can't be used in vivo due to the near-field metal micro-nanostructure.Recently,electrical resonance Raman scattering has been improved to electrical pre-resonance stimulated Raman scattering,which boosts the detect sensitivity.Retinoids play crucial roles in embryonic development,immunity,neural system,and their deficiency leads to a variety of human disorders.People merely detect them indirectly because a variety of tools can't provide high enough sensitivity.To address this problem,we developed a visible pre-resonance SRS microscopy based on exciton-longitude optical phonon coupling and excitation laser blue shifting.By VP-SRS,Raman cross section of retinol is improved by at least two orders of magnitude.We realized the detect limit of retinol solution as low as 34 ?M by VP-SRS.VP-SRS also reveals retinoid imaging and distribution in cancer cells,embryonic neurons,a mouse whole brain tissue and in vivo E.elegan and further explores retinoid functioning in chemo-resistance,neuron development,brian science and homeostasis.FP-WGM mico-nanocavity evanescent field coupling motivates the development of the wavelength-tunable nanolasers while the exciton-phonon coupling enhances SRS detect sensitivity.Collectively,coupling boosts optics and opens opportunities in optical science and technology,which can be applied in photoelectronics,optical communications,environment sensing,biological exploring,medical imaging and even cancer therapy,etc. |
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