| With the rapid development of information technology,sensing technology,as a comprehensive technology of many important disciplines,plays a vital role in many fields such as health care,aerospace,environmental monitoring,smart home,smart city and so on.Researchers have gradually begun to research optical sensors that are more resistant to electromagnetic interference for the purpose of achieving miniaturized,portable,low-cost,and highly sensitive sensor devices.Micro-ring resonator is a kind of micro optical device with high quality factor,narrow band width,compact structure,easy integration and resonant cavity,so it is widely used in temperature,humidity,biochemical solution,gas environment,refractive index and other different sensing fields.In this thesis,two optical devices based on micro-ring resonators are investigated in the context of sensing applications.One-dimensional photonic crystal micro-ring sensor is studied in order to meet the need for sensor to detect small changes in a physical quantity of a substance,and it takes advantage of the asymmetric and high slope properties of Fano spectrum to achieve highly sensitive detection;A micro-ring sensor with Bragg grating waveguide is proposed to solve the problem that that the sensitivity and detection range of the current micro-ring sensor cannot be achieved at the same time.The major works include the following:（1）The operating principles and transmission theories of all-pass and up-download micro-ring resonators are studied.Based on the coupling theory of the flat waveguide,these two conventional structures are analyzed using the transmission matrix method.And the resonance equations,extinction ratios,quality factors,and expressions for the half-height full-width and other performance indexes of the micro-ring are derived.（2）The solution process of Maxwell’s equations is investigated using FDTD.The electric field distribution and transmission spectrum of the micro-ring resonator are simulated.The slot waveguide’s local action on the optical wave is analyzed and verified,which provides a waveguide type capable of increasing sensitivity for the later design of refractive index sensor.Finally,the sensing mechanism of the micro-ring sensors are given,and the differences and application areas of spectral detection and intensity detection are presented.Performance indicators such as sensing sensitivity are investigated.（3）The transmission characteristics of one-dimensional photonic crystal slot micro-ring resonator are investigated,and asymmetric Fano resonance spectroscopy is achieved by exploiting the modulation properties of one-dimensional photonic crystal defects on light waves.The device was optimized and the tolerance analysis of the one-dimensional photonic crystal size was performed.A high extinction ratio,high Q-factor micro-ring resonator was achieved,the extinction ratio of 29.08 d B and Q-factor of 30950.The sensing performance was measured using the device as an optical sensor.The sensitivity S is 344 nm/RIU and the lower limit of refractive index detection LOD is 1.4×10-4 RIU when the spectral detection method is used.And the sensitivity was 2669.8/RIU when the intensity detection method was used.The designed sensor device can be applied to the trace substances to be measured with high sensitivity requirements.（4）A micro-ring resonant sensor with high sensitivity and wide detection range is proposed.The Bragg grating is embedded in the slotted ring waveguide slot.And the reflection of the grating makes the light waves on the inner and outer sidewalls have different light ranges and interfere with each other to produce an electromagnetically induced transparency effect with a high Q-factor and high slope.The wavelength-selective characteristic spectrum of Bragg grating is also given,which is used to broaden the free spectral range of the micro-ring resonator.Finally,the device is used as an optical sensor and the sensing performance is analyzed using spectral detection method.The sensitivity reaches 433.33 nm/RIU and the LOD is 8.26×10-4RIU.The designed sensor device can be applied to high sensitivity,wide detection range in the sensing field due to the unrestricted detection range. |
