The Research And Application Of High Quality Factor Resonant Dielectric Metasurface

In the past decade,metamaterials have attracted much attention in numerous fields,due to the excellent optical properties such as artificial magnetism and negative refractive index.Different from the traditional natural materials,the properties of metamaterials are mainly determined by the artificial unit cell which constitutes the structure.Therefore,metamaterials offer very high design freedom for researchers:the required properties could be obtained by changing the shape,material,cycle size or cycle number of the structural unit.Metasurface is a two-dimensional structure evolution from the three-dimensional metamaterials in order to get rid of the complex manufacturing process of metamaterial.The metasurface with simple fabrication process and perfect optical control.For example,the metal metasurface which is composed of noble metal unit cell,such as silver or gold,could control the polarization,phase and amplitude of incident light by different structural designs.However,as the research field gradually entered the near-infrared and visible light range,the intrinsic loss of metal became serious and could not be neglected.The dielectric metasurface could solve the problem of metal loss,the response to electromagnetic field of the dielectric metasurface derives from the Mie scattering and could be explained with Mie scattering theory.According to their function principles,dielectric metasurface could be classified into two categories.The first one is phase gradient metasurface,it could adjust and control the incident light wave front by introducing phase gradient,and the deflection property of the beam based on the generalized Snell law.The other one is the resonant metasurface,it could realize the light field enhancement by the resonant characteristic,with the help of small cavity mode volume,high-quality factor and collective coherent resonance,it could efficiently enhance the interaction between light and material and suppress the radiation loss.Aiming at the loss problem of metal metasurface and the improvement of quality factor(Q)of dielectric metasurface.In this dissertation,a series of simulation optimizations and experimental verifications are carried out around the design and fabrication of dielectric resonant metasurface with high-quality(high-Q)factor.The sample of dielectric metasurface with the high-quality factor was obtained in the experiments.Based on the high-quality factor of the fabricated device,the applications of the high-Q metasurface in sensing,enhancing the luminescence of two-dimesional thin film and silicon defects were explored.The specific research contents are as follows:(1)A dielectric metasurface with high-Q factor resonance based on the silicon nitride material is proposed.And then,the formation mechanism of the high-Q resonance and the influence of the parameters on Q factor is detailly analyzed.Finally,the sample fabrication and test are completed.The fabricated metasurface has a high-Q factor of 16670 and an extinction ratio of 12 dB.The Q factor and extinction ratio of the metasurface could be adjusted by the volume and period of the unit cell which lay the foundation for the subsequent experiments.(2)Based on the dielectric metasurface with high-Q factor,the metasurface with the property of narrow linewidth is used to detect the refractive index change of the environment.The position and extinction ratio of the resonance of the sample changed as the reflective index changed on the surface of the metasurface.And then,the results are compared with the resonance position and extinction ratio of the metasurface placed in the air.In consequence,the metasurface consist of hole with high-Q factor could be applied in the sensing filed with 367 sensing quality factor value.In addition,as the resonance position and extinction ratio changed at the same time,the metasurface possesses the potential in dual variable detection.The metasurface device with high-Q factor can be applied in the field of sensing.(3)Combining the high-Q resonant metasurface with two-dimensional thin film materials creatively to enhance its photoluminescence efficiency.The high-Q factor metasurface was fabricated on silicon nitride thin film which deposited on the glass substrate,and the resonant peaks of the metasurface shifted to visible band by adjusting the period of the metasurface.The MoS₂ and WSe₂ thin film materials is transferred on the metasurface,respectively.The photoluminescence enhancement of MoS₂ and WSe₂ thin film beyond 30times at the resonant peaks of the metasurface under continuous light pumping at room temperature.The metasurface device with high-Q factor can be applied in the field of the photoluminescence enhancement of the thin film materials.(4)An asymmetric hole metasurface with high-Q factor based on SOI material is proposed,the principle is that the perfect bound states in the continuum(BICs)mode could be transformed to quasi-BICs mode while maintaining high Q factor by breaking the symmetry of the metasurface elements.The Q factor could exceed 1×10⁸ in simulation,the theoretical analysis of the high-Q factor resonance introduced by the asymmetry is carried out.Finally,the metasurface sample is fabricated on 220 nm SOI,and the resonant wavelength is adjusted to the photoluminescence peak of the C-C pair defects(G-center).The G-centers could be introduced by the etching process and the photoluminescence peak is located at 1278 nm.Finally,the photoluminescence of the G-center could be enhanced by approximately 40 times using the asymmetric metasurface.Besides,the characteristics of linewidth narrowing and superlinear power dependence is similar to the non-threshold laser at low power pumping.The metasurface device with high-Q factor can effectively enhance the photoluminescence of G-centers,which has a potential application in the field of the silicon source.