Application Of Parity-time Symmetric Structures On Design Of Sensors

As basic components of modern information systems,sensors perform as the interfaces between systems and external environment,and play an important role in modern information and intelligence systems.In recent years,with the development of all optical networks,optical sensors have got wide attention.Various photonic crystal sensors have been developed.In the field of optical device designing,many achievements have been made in PT symmetric structures due to its extraordinary optical properties.In this thesis,the PT symmetric structure and one-dimensional photonic crystal are combined,and a unique sensing mechanism is discovered.On this basis,three theoretical models of optical sensors are presented.At the same time,the sensing mechanism has also been changed to improve the performance of traditional sensors.The thesis firstly presents a theoretical model of temperature sensor based on PT symmetric structure.The model combines the PT symmetric structure and thermal-optical material,and realizes the high sensitivity temperature sensing.Besides,the performance of the sensor can be controlled by adjusting the structural parameter.The sensor can achieve ultra-high sensitivity in a small temperature range,or widen the sensing range by decreasing the sensitivity,reasonably.Through the numerical calculation,the maximum sensitivity and sensing range can reach over40dB/K and 58K,respectively.Besides temperature sensor,the thesis also presents a theoretical model for gas sensing.By optimizing the structural parameters,the transmission character of the model is sensitive to tiny variation of refractive index in the structure.The sensor can be used to measure the concentration of a certain foreign gas mixed in the air.The numerical calculation results show that the sensor has the best performance when the concentration of the foreign gas is low.1%change in the concentration of foreign gas will lead to at most 28%change in transmittance peak value.Besides,this thesis also compares the sensitivities with different sensing principles.Finally,the thesis investigates the properties of a periodic PT symmetric structure.Combing with electro-optical material,a model of electric field sensor has been designed.The theoretical analysis shows that the structure has two special properties.One is band edge mode,the other is unidirectional reflection.The peak value and its position of transmittance depend on the intensity of external electric field,which can be used for the measurement of the field intensity.Besides,the tendency of such property is affected by the direction of external electric field,which can be used for the judgment of the field direction.The sensitivity reaches about±5nm~2/V.The direction of the electric field will influence the sensitivity of the sensor.