Photonic Nanojet And Super-resolution Imaging By Microlenses Research

Optical microscopes are widely used in the fields of biology,medical and industrial,but their imaging resolution is limited by the diffraction limit.The lateral resolution of the microscope can only reach one-half of the wavelength of visible light(200 nm).Generally,the imaging resolution is increased by increasing the numerical aperture,but this also produces a certain aberration.Therefore,the development of classical optical microscopes has reached the stage of bottlenecks.With micro-lenses-assisted optical microscopy imaging,the imaging resolution can be increased,allowing us to observe images with fine structure information of the object.The photonic nanojet field generated by electromagnetic waves irradiated to the micro-lenses is considered to be one of the factors that achieve high resolution microscopic imaging of the micro-lenses.The photonic nanojet effect is a powerful photon focusing and scattering field formed near the surface of the micro-lenses,which can increase the probability of real-time observation of viruses or bio-molecules.At present,how to achieve high-resolution imaging is a hot issue in the industry.The main research work of this paper is as follows:1.The scattering simulation calculation process of the numerical algorithm of Discrete Dipole Approximation(DDA)and the accuracy of the subdivision are introduced in detail.DDA is a numerical algorithm that calculates the electromagnetic scattering and absorption properties of an arbitrary beam interacting with particles of any shape.The ADDA software is a light scattering simulation simulator for the DDA numerical algorithm.With ADDA,the field distributions of microsphere lenses with different diameters incident on plane waves at different unit wavelength dipoles are calculated and compared with the Mie theoretical analysis algorithm.The relative error of maximum intensity and maximum intensity position of the microsphere lenses are analyzed.The results show that the forward scattering intensity of microsphere lenses is basically the same under the comparison of DDA numerical algorithm and Mie theoretical analytical algorithm.And for the electromagnetic simulation in this paper,it is determined that the optimal number of dipoles per unit wavelength is 20.2.Based on the DDA numerical algorithm,scattering characteristics of the internal and near-field distributions of micro-sphere lenses,micro-ellipsoid lenses,multiple micro-sphere lenses and multiple micro-ellipsoid lenses under the plane wave,the Gaussian beam are simulated and analyzed.The photonic nanojet characteristics of micro-lenses are mainly studied.When calculating the distribution of electric field under the Gaussian beam incidence,the internal and near-field distributions of Gaussian beams with different beam centers and beam waists acting on the micro-lenses and the photonic nanojet characteristics are discussed.The numerical results show that the Gaussian beam incident micro-lenses is equivalent to the plane wave incident micro-lenses as the beam waist radius increases.For the electric field simulation calculation of the array micro-lenses,the photonic nanojet region formed on the surface of the micro-lenses can act as a new beam on the rear micro-lenses.Electromagnetic calculations are also performed on micro-lenses of other typical shapes.In this paper,three types of micro-lenses are selected,which are a truncated micro-lenses,a conical micro-lenses,and a pot micro-lenses.The field distribution acting on the three shape micro-lenses under the plane wave is calculated and studied.The results show that the micro-lenses has a converging effect on the beam.Factors such as the refractive index and the size of the micro-lenses,and the wavelength of the incident light,and the refractive index of the external medium have a certain degree of influence on the photonic nanojet region of the micro-lenses.3.In the process of constructing the microscopic imaging experimental platform,the imaging operation flow and the selection of samples to be tested are described in detail.The process of microscopic imaging is divided into three parts,namely sample preparation,microscopic imaging,and data acquisition.The sample to be tested is selected as a Blu-ray disc.The micro-lenses selects a silica microsphere lenses having a focusing characteristic and a low refractive index.The surface-treated Blu-ray discs are microscopically imaged using an optical microscope and a silica microsphere lenses with diameters of 3 mm and 5 mm,respectively,and the microscopic imaging of the Blu-ray disc was observed and verified.The experimental results show that the smaller the diameter of the silica microsphere lenses,the higher the resolution of the microscopic imaging of the Blu-ray disc.Based on the above experimental data results,compared with the theoretical magnification,it shows that the experimental imaging magnification of the silica microsphere lenses is higher than the theoretical imaging magnification.