Study Of The Interaction Between Surface Plasmon Polaritons And Quantum Light Sources

Photon is a kind of special particle in modern physics.The speed of photons is not only the fastest in physical sense,but also a constant in every reference system.There are a lot of physical properties of photons,such as wavelength,polarization,spin angular momentum and orbital angular momentum,and so on.All of these make pho-ton becomes a very effective information carrier,and thus created a series of light-based quantum correlation researches such as quantum optics,quantum communication,quan-tum simulation and quantum computing.However,there are still many problems in re-searches of photons,such as diffraction limit,nanostructures beyond the diffraction limit cannot be effective for photons processing.Another example is that photons are easy to interact with other substances,as they will interact with a variety of gas molecules in the air and scatter.So integrated optical research which means use nanostructure to limit and manipulate the photons came into being.We all know that the integrated circuit is electronic devices which could miniaturize of the entire circuit system and integrate in a small semiconductor substrate,so integrated optical research means miniaturize the optical system and integrate in an optical chip as the same.We can use the inte-grated optical chip to do experiments like quantum simulation and quantum computing research.A classic optical system usually contains light source,optical path,signal collection system and other parts.Among them,the study of integrated light source is a very important direction.In quantum optical experiments and quantum computing experiments,we usually require the light source to have a "single photon source" char-acteristic,which means,only one photon at the same time.This limits the availability of most luminescent materials in integrated optics.At the same time,the fluorescence intensity of single photon source is very low due to the requirement of single photon e-mission,which is not favorable to integrated optical experiment.The emission of single photon source is often isotropic,which not only makes the signal intensity further re-duce,but also makes the signal collection process more complex.So the modulation of single photon source has become an important research direction.In recent years,due to the continuous develop,ment of quantum optics research and micro-nano machining technology,people began to understand some unknown physical phenomena,such as surface plasmon polaritons.The surface plasmon polaritons is a free electron collector at metal surface whose size is sub-wavelength and therefore has very high localized energy.At the same time,surface plasmon polaritons can interact with photons,which allows the researchers to break the diffraction limit in integrated optical chip to further reduce the structural size and increase the density of the information.At the same time,due to the various advantages described above,it has become a viable solution to modu-late single photon sources,and several new experimental schemes and techniques have emerged.The main content of this paper is the interaction between surface plasmon polari-tons and quantum light sources.This paper introduces the following several experimen-tal studies and results that we have completed:1.The fluorescence intensity of quantum light source has always been one of the problems in integrated optical experiments,while Surface Plasmon can effectively en-hance the fluorescence of the quantum light source.This enhancement is directly related to the intensity of excited Surface Plasmon at the metal surface,so we can investigate the effect of fluorescence enhancement on quantum light source under different exci-tation conditions.The We experimentally measured the fluorescence intensity and the lifetime of quantum dots coupled with a silver nanowire with the change of exciting laser' s polarization.If the incident light is from positive side,we found that when the polarization of the exciting light is parallel to the nanowire direction,the nanowire will block the propagation of the exciting light,so the fluorescence intensity of the quan-tum dot is lower and its lifetime is higher.When the polarization of the exciting light is perpendicular to the direction of the nanowire,it can effectively excite the quantum dot and excite the local surface plasmaon polaritons on the nanowires.Therefore,the fluorescence intensity of the quantum dots is higher and its lifetime is lower.If the incident light is from back side,when the polarization of the exciting light is parallel to the nanowire direction,it cannot effectively stimulate the surface plasmon polaritons on the nanowire,but it can effectively stimulate the fluorescence of the quantum dots.Therefore,the fluorescence intensity of quantum dot and its lifetime is relatively high.Otherwise,when the polarization of the exciting light is perpendicular to the direction of the nanowire,the quantum dot fluorescence intensity and lifetime are relatively low.We also found that the lifetime of quantum dots is related to its polarization direction,and this relation is cyclical.The lifetime of quantum is just opposite when the incident light are in positive side or back side.This find allows us to more effectively stimulate quantum light sources which are interacted with metal nanostructures.2.For the quantum light source in integrated optics,there are not only require-ments of strength,sometimes directional emission are required too.In this regard,the most likely use is surface plasmon nano-antenna,but the production of the antenna is relatively hard,and good results need for a specific location of light source in the nano-antenna.Therefore,we decided to use a relatively simple structure with the relatively low coupling requirement,such as grating structure to obtain directional emission of fluorescence.We fabricated a metal grating structure that allows us to obtain enhanced fluorescence with multi-directional emission through the interaction of surface plasmon polaritons and quantum dot.The emission direction of the fluorescence is determined by grating period and the fluorescence wavelength.Due to the effect of localized surface plasmon polaritons,the radiation rate of quantum dot increases and the fluorescence is improved.3.In experiments of integrated optics,photons can not only be used as the carri-er of energy,but also can be the carrier of information,then we must be able to load the information into the carrier.In the physical properties of photons,the spin angu-lar momentum and orbital angular momentum are often used to encode information.We propose an experimental method of using a helical structure on a metal thin film and an coupled electric dipole whose polarization direction is vertical to produce e-mission photons with both orbital angular momentum and spin angular momentum.In the experiment,we use the radially polarized beam to selectively stimulate the quantum dot.We present the data for theoretical analysis,numerical simulation and experimental measurements.4.Two-dimensional materials are one of the hottest materials available,and many two-dimensional materials have good optical properties that can be used as quantum light sources and quantum single photon sources in integrated optical chips.Mono-layer molybdenum disulfide is a stable quantum light source,but because of its weak fluorescence intensity,it needs fluorescence enhancement.We demonstrate that met-al nano-particles have fluorescence enhancement effect with monolayer molybdenum disulfide and the fluorescence enhancement effect can be further increased when the excitation light is changed from linearly polarized beam to radially polarized beam.We compared the gold particles of different diameters to prove that when the diameter of the gold particle is less than the diameter of the excitation light spot,the use of larger diameter gold particles can get better fluorescence enhancement effect,and the effect of using radially polarized beam will be,better.We use a single gold particle to char-acterize the mechanism and effect of this fluorescence enhancement effect.If we use gold particle array,the effect should be much better.Our experiment shows that even without changing the structure of the sample,the enhancement of the fluorescence can be further better.