Research On Refractive Index Sensors Based On Micro-nano Photonic Structures

As the compact structure and the size close to light wavelength,micro-nano photonic structures are extremely sensitive to the surrounding environment and have high detection performance.They can also be used in photon integration and micro-fluidic control system to construct “lab on a chip”,and realize the miniaturization,intellectualization and family of biochemical detection.In recent years,with the improvement of micro-nano processing technology,various micro-nano photonic structures have been realized which provides technical support for the design of higher performance refractive index sensors.Many research institutes have focused on the design of biochemical sensors on the development of new photonic structures and improving the performance of micro-nano photonic devices.However,there are still some inadequacies in the design,fabrication or application environment of the proposed micro-nano photonic structure sensors,so there is still great potential to improve sensing performance.In view of this,the refractive index sensors with high performance are designed using dielectric structure,metal structure and microstructured optical fibers at working bands of about 1500 nm,below 1000 nm and about 2000 nm respectively.This dissertation focuses on the research of the optical properties,detection principles,sensing properties and fabrication methods of several micro-and nano-photon structures.The specific works are as follow:To solve the problem that photonic crystal sensors need to design defect modes artificially,a 10-fold photonic quasicrystal refractive index sensor is designed based on the natural defect mode of photonic quasicrystal,and different structures of10-fold photonic quasicrystals are successfully developed experimentally.Firstly,a two-dimensional 10-fold photonic quasicrystal structure is designed using the umbrella-shaped five-beams interference model.Different photonic quasicrystal structures are obtained by changing the exposure threshold of the beam.On this basis,a liquid refractive index sensor is constructed by defect mode spectrum monitoringmethod.The sensitivity of this sensor is optimized by adjusting the radius of dielectric cylinder and the size of the sensing unit.Finally,a sensor structure is designed with sensitivity of 221 nm/RIU,quality factor of 1478 and sensing unit of18?m×4?m.An interferometer of multi-beam common-path top-cut pentaprism was constructed experimentally.By changing beam intensity,exposure time and beam uniformity ten-fold photonic quasicrystals with different structures were fabricated.Using the local surface plasmon resonance(LSPR)effect of metal micro-nanostructures,a gold nanoring array LSPR refractive index sensor is constructed.In order to overcome the shortcomings of randomly distributed gold nanorings which are easy to be missing and stacked,a gold nanoring array sensor is proposed based on the mechanism of metal particle dimer enhancing LSPR.The electromagnetic field distribution and extinction spectrum of the structure are analyzed by finite element method and the influences of the structure parameters of gold nanorings on extinction efficiency are studied.The local surface plasma electric field distribution of a single gold nanoring is similar to that of a pair of electric dipoles,and the gold nanoring array can effectively enhance the electric field intensity due to the dimer effect,thus improving the quality factor of the sensor.This plasma resonance sensor has great potential in identifying biomolecule binding events.In view of the measuring advantages of optical fiber sensors in narrow environment,two PCF SPR refractive index sensors are designed near 2000 nm.Firstly,in order to further enhance the resonance intensity of SPR,a D-shaped high birefringence(Hi-Bi)photonic crystal fiber SPR sensor is designed based on the sensitivity of SPR to polarization direction.The effects of the aperture ratio of air holes in X and Y directions of the core,the thickness of gold film and the refractive index of optical fiber materials on resonance are analyzed.It is found that the high birefringence structure can effectively enhance the SPR intensity,and the sensitivity of the sensor can be improved using the low refractive index optical fiber material,which can enhance the sensitivity and improve the quality factor of the sensor at the same time.Secondly,to solve the contradiction between large area mode and low confinement loss and improve the fiber plasma resonance,a D-shaped dual-corephotonic crystal fiber SPR sensor is proposed.The dual-core structure effectively enlarges the mode area and ensures the lower confinement loss and single-mode characteristics,thus improving the detection stability and expanding the measurement range.In experiments,PCFs with different structures are fabricated by stacking hollow glass tubes,melting of prefabricated rods and drawing at high temperatures.Their cross-sectional micro-nanostructures,bending losses,cut-off wavelength and other optical properties are measured.