Spaser Based On Mesoporous-silica-coated Noble Metal Structure

Similar to the development of electronic components,the integration and miniaturization of optical components can significantly improve the performance of optical systems and open up many new application areas.Among them,the miniaturized laser is key factor in accelerating the development of integrated photonic devices.The integrated optical communications and data processing on the chip have huge application potential,which may make data transmission rates exceed existing integrated electronic circuits.Therefore,as an important light source equipment,the prospect of laser miniaturization is particularly special and extremely challenging.The traditional laser cannot break the diffraction limit due to the use of an optical cavity,so the physical volume cannot be compressed below half a wavelength.A feasible solution is the Surface Plasmon Amplification by Stimulated Emission of Radiation(SPASER).Compared with traditional lasers,in a SPASER system,the photons of stimulated radiation are replaced by surface plasmons,and the optical resonator is replaced by metal structures that support the plasmonic mode.Because surface plasmon has the properties of sub-wavelength propagation and local field enhancement,SPASER can break the diffraction limit in size,providing a new solution for the miniaturization and integration of laser.A SPASER usually consist of metal,dielectric gap layer and gain medium.Among them,the metal is usually precious metals such as gold and silver.The dielectric gap layer usually uses low refractive index materials such as silica and magnesium fluoride.The gain medium is usually semiconductors.According to the type of plasmon generated by the metal structure,it can be divided into two types.One is based on the propagation surface plasmon,that is,the metal structure is larger than the wavelength order,and is mainly used in the field of on-chip integration.Another one is based on the local surface plasmons,that is,the metal structure is smaller than the wavelength order,which is mainly used in the field of high-resolution probes.In this thesis,the SPASER is realized based on the propagation surface plasmon and local surface plasmon,respectively.The noble metal/mesoporous silica structure combined with the gain medium is used to achieve lasing.The research contents of this thesis are as follows:1.The development history of laser miniaturization is reviewed;the optical properties of precious metal materials are summarized;the basic concepts of the plasmon on the propagation surface of the precious metal thin film and the local surface plasmon of the precious metal nanoparticle are introduced respectively.2.The basic principles of surface plasmon nanolaser are summarized.The research progress of propagation surface plasmon laser and local surface plasmon laser is reviewed,and the design principles of two types of surface plasmon laser are summarized respectively.3.Designed and fabricated a SPASER based on the propagating surface plasmon,which has a structure of quantum dots/mesoporous silica films/gold films.We use mesoporous silica film as the dielectric gap layer,and the pore structure can reduce the loss caused by the dielectric gap layer.A core-shell structure Cd S/Zn S quantum dots was used as the gain medium.Two-photon excitation at room temperature was achieved with an 800 nm femtosecond laser pump,and the output wavelength was 451 nm.We also observed the enhancement of two-photon up-conversion fluorescence by surface plasmons and explored the enhancement mechanism using finite-difference time-domain(FDTD)simulations.This study confirms that mesoporous silica thin film is an effective dielectric gap layer and provides a reference for the preparation of quantum dot-based plasmon devices.The device has many potential applications in optical integrated circuits,medical imaging and sensing.4.Designed and prepared a SPASER based on local surface plasmon,which has a silver nanocube/silica/mesoporous silica·perovskite multi-layer core-shell structure.A silver nanocube is used as a metal resonant cavity,silicon dioxide is used as a dielectric gap layer,and mesoporous silicon dioxide doped with MAPb Br3 perovskite is used as a gain medium.The discrete dipole approximation method(DDA)was used to investigate the influence of morphology and particle size on the local surface plasmon resonance of silver nanoparticles.Based on the results,it was determined that silver nanocubes with a particle size of 80 nm were used as the metal resonant cavity.Silver nanocubes with the desired particle size were synthesized by an improved polyol method.With 800 nm femtosecond laser pumping,two-photon excitation at room temperature is achieved with an output wavelength of 546 nm.We also found that this structure has good stability in the air environment due to the combination of mesoporous materials and MAPb Br3.This device has potential application prospects in integrated light source and probe detection.