Coupling-induced Transparency Effect And Its Sensing Characteristics Based On Microrings

With the development of science and technology,the role of optical microstructure is becoming more and more important in the field of basic and applied research.Especially the microring resonator,because of its high quality factor and small volume,and the advantages of easy on-chip integration,so has extremely important research value in logic optics,optical sensing and other aspects.With the development of sensing applications and the requirements of integration,higher requirements are put forward for parameters such as device size and sensing range of sensors.In this thesis,a new structure coupled with grating and microring coupling is proposed to reduce the footprint of devices on the premise of ensuring quality factor and other parameters.In addition,the coupling-induced transparency effect found in silicon-based coupled microring resonators has gradually become a research hotspot.In a certain wavelength band,the coupling-induced transparency effect causes the light that should normally be transmitted at some wavelengths to be absorbed and even decrease to zero,making the substance transparent to the originally strongly absorbed detection light.Thus,the quality factor and other parameters of obtained sensing effect are improved compared with the ordinary Lorentzian line shape.Therefore,on the basis of the microring resonator theory,microring resonators based on silicon-on-insulator layer are designed in the thesis.By coupling with the grating,excellent line shapes with coupling-induced transparency are obtained,and the grating is set in the microring slit to reduce the size of the device.The main content of the thesis is as follows:(1)In this thesis,the structure of the basic through-download single microring is analyzed firstly,its transmission theory and analysis method are studied,and the research method of the improved microring is proposed accordingly.The mechanism of the coupling-induced transparency effect is studied,the different structures that produce the coupling-induced transparency are analyzed,and the method of optimizing the line shape is explored according to the method of evaluating the coupling-induced transparency.According to the research method,the microring is designed and optimized to achieve coupling-induced transparency.(2)According to the basic theory of microring and coupling-induced transparency effect,a grating-assisted slit microring resonator is proposed and theoretically analyzed.Based on the transmission results,optimization is carried out to achieve the coupling-induced transparency effect and improve the parameters of the device such as quality factor and transmission intensity.The slit structure is used to increase the contact area between the device and the object to be measured,thereby improving the sensitivity.Finally,the refractive index sensing effect of the sensor is verified and analyzed through simulation experiments.The results show that the transmission effect is excellent,and the proposed structure has a good coupling-induced transparent line shape under the condition of taking into account various parameters,which provides more options for the field of photonic devices.(3)Based on the grating-assisted slit microring resonator,an asymmetric grating-assisted slit microring sensor is designed.The structure is analyzed by the transmission matrix method,and the physical parameters such as the period,duty cycle,and radius of the microring of the asymmetric grating structure are optimized,so that the quality factor and sensitivity of the device are further improved,and part of the resonance peak is suppressed to obtain a high transmission effect in the free spectral range and expand the sensing range of the device.Compared with different microring structures proposed in recent years,the proposed device structure takes into account multiple parameters of sensitivity and quality factor at the same time,and the sensing effect is good.Finally,the refractive index sensing effect of the device is tested.The experimental results show that the free spectral range of the device has been greatly improved when multiple parameters are taken into account,which breaks through the limitation of the sensing detection range of the device.