Study On Optical Device Design And Sensing Characteristics Of Silica-based Micro-nano Materials

With the continuous development of micro-nano optics,micro-nano optical devices as a kind of important modern detection device have been widely used in industrial production.The micro-nano optical devices can achieve light wave control and can be used to develop sensors.The optical devices have a broad application prospect in chemical analysis,biological detection,environmental monitoring and other fields.In this paper,three silica-based micro-nano optical devices are designed and optimized,and the principle of light wave control and sensing performance are analyzed.The detail contents are as follows:1.In order to realize the enhancement in the near field and unidirectional radiation in the far field,the multipole resonance mode of the nanoantenna and the scattering characteristics of light wave are studied by finite element method.The relationship between the multimode interaction of nanoantennas and the directivity of far-field scattering are discussed.A full dielectric nancolumnar array is proposed.TD,MD and MQ are excited by changing the direction of the electric dipoles.It is found that the resonance peak of the multipole decomposition scattering spectrum is affected by the inner diameter,outer diameter and height of the nancolumnar.A high dielectric silicon hollow nanoblock structure nanoantenna that can support multiple resonant modes is proposed.By optimizing the geometry of the nanoblock,the far-field scattering is unidirectional and the directivity of the far field is up to 44.6d B.At the same time,the first Kerker condition can be satisfied at a specific wavelength.2.The surface plasmon resonance（SPR）effect based on evanescent wave excitation is studied.By designing periodic photonic crystal fiber（PCF）structure based on silicon dioxide material and coating plasma material,the special light wave can be absorbed.Using the relation between the spectrum and the outer medium,three kinds of PCF-SPR refractive index sensors are designed.Firstly,a simple PCF-SPR sensor with large air holes is designed.The maximum wavelength sensitivity and amplitude sensitivity of the sensor are 35000 nm/RIU and 1120.73 RIU^-1 respectively in the range of 1.26～1.38.The wavelength and amplitude resolutions are 2.86×10^-6 RIU and 8.92×10^-6 RIU respectively.In order to improve the performance of the sensor,a dual-core quasi-D-type PQF-SPR refractive index sensor is designed using Penrose photonic quasi-crystal（PQF）structure.The structure effectively enhances the coupling between the core mode and the SPP mode,improves the sensing sensitivity.Meanwhile the mechanical strength of the fiber is maintained.In the range of1.40～1.44,the maximum wavelength sensitivity and average wavelength sensitivity reach62000 nm/RIU and 26500 nm/RIU,respectively.Finally,the methane sensor is designed based on SPR effect,and Cryptophane E is used as methane sensitive material.The PQF-SPR sensor adopts six-fold photonic quasi-crystal structure,the method of double-sided polishing can enhance the SPR effect and improve the performance of the sensor.The maximum sensitivity of the sensor is 8nm/%and the average sensitivity is 6.643 nm/%as the methane concentration is in the range of 0～3.5%.3.The spectral characteristics of tilted fiber Bragg grating（TFBG）based on silicon dioxide material with periodic refractive index modulation are studied.The influences of grating spacing,grating length,refractive index modulation depth and tilt angle on transmission spectrum are simulated and analyzed.The results show that the core mode resonance peak of the transmission spectrum is sensitive to the temperature and strain,and the cladding mode resonance peaks are sensitive to the ambient refractive index.The temperature,strain and refractive index can be measured by TFBG.The TFBG with an inclination angle of3.5°and a length of 12 mm is used to measure the temperature and refractive index in the experiment.Meanwhile the TFBG is used to measure liquid level using its sensitivity to the refractive index.The transmission spectra of 60%-80%glycerol solution at different liquid levels are tested respectively,the relationship between the envelope area of the transmission spectrum and the liquid level was established.The experimental results show the sensitivity of measuring liquid level increase with increasing solution concentration,the method can achieve accurate measurement of liquid level.