Study On Transmission Enhancementt Characteristics Of Optical Micro/Nano Sensors Based On Parity-Time Symmetry

Since its birth,optical sensors have been widely studied and applied due to their low cost,low loss,and simple fabrication.With the emergence and gradual development of nanotechnology,optical micro/nano sensing technology has developed rapidly.In the research of optical sensors,efforts have been made to improve their sensing performance.There are two main directions for improving the performance of optical sensors: increasing the resonance peak to peak and reducing the full width at half peak.Due to the limitations of traditional sensors,the improvement of peak value is limited,until the appearance of the Parity-Time(PT)symmetry principle.The main research contents of this article include:Firstly,the PT symmetry principle in the optical field is studied.We studied the initial definition of PT symmetry principle in quantum mechanics,as well as the definition and application in optical systems after the introduction of optical systems.By designing an optical structure that meets the PT symmetry principle,and designing an optical system with gain and loss,it can break the time reversal symmetry of the system,generate transmission enhancement effects,and improve sensing performance by increasing the peak value.Secondly,a transmission enhancement mechanism for photonic crystal coupled resonator structures based on the PT symmetry principle is proposed.This structure is based on one-dimensional periodic photonic crystals,and a defect layer is added.At the same time,in order to make the photon localization effect stronger,a circular resonator is introduced,resulting in a resonance peak with a transmittance much greater than 1 in the photonic band gap,which is called the transmission enhancement effect.Unlike traditional sensors,which use the change in resonance wavelength position as the sensing detection amount,the structure that produces the transmission enhancement effect uses the change in transmittance as the sensing detection amount.Compared with traditional sensors,the sensing performance of the proposed structure is greatly improved.Finally,a transmission enhancement mechanism of photonic crystal coupled groove type sub-wavelength grating structure based on the PT symmetry principle is proposed.Based on the sub-wavelength grating,this structure introduces a groove structure to enhance the interaction between the grating and light,making the Fano resonance generated by the grating sharper.At the same time,the method of increasing the resonance peak and reducing the full width at half peak is used.After coupling a groove type sub-wavelength grating with a PT symmetric photonic crystal structure,the transmission enhancement effect deforms the resulting Fano resonance curve,greatly increasing the peak transmittance,far exceeding the transmission peak of ordinary sensors.Based on this,the angle modulation mechanism of the structure is studied.Based on the PT symmetry principle,a groove type sub-wavelength grating is coupled to a photonic crystal.The angle modulation mechanism based on incident light greatly increases the peak value compared to traditional angle modulation sensors,thereby greatly improving the transmission and sensing performance of the structure.In summary,the principle of PT symmetry has been elaborated in detail,and sensor structures that combine the principle of PT symmetry with more optical micro/nano structures have been studied.This has changed the sensing principle of traditional sensors and improved their sensing performance.Moreover,the structure proposed based on the PT symmetry principle provides more possibilities for the combination of the PT symmetry principle and optical micro/nano structures,and provides ideas for the subsequent application of the PT symmetry principle.