Research Of Fast-and Slow-light Characteristics And Nonlinear Switch Based On Micro-ring Resonator System

With the rapid development of the communication network technology,the material civilization and spiritual civilization of human society have been highly improved,the demand for information and the speed of the transmission have higher requirements.It is imperative to the development of all-optical-network,all-optical-network do not need optical-to-electronic conversion,exchange and transmission of all information are carried out in the optical domain,the transmission efficiency are greatly improved,and the electronic bottleneck problem is solved.Due to its series of features such as small size,simple structure and stable performance,the micro-ring resonator is used as the basic optical device for the realization of all-optical-network.Micro-ring resonator is widely used in the field of optical switch,filter,buffer and sensing,and become a research hotspot.In this paper,we study the fast-and slow-light characteristics and nonlinear switching effects of single-ring and double-ring resonators based on the grating,the main research works and results are as follows:Firstly,this paper introduces the working principle of the optical fiber coupler.The theoretical part includes coupled mode theory and the transfer matrix equation that derived from the coupled mode theory.The model of the coupler is an important part of the micro-ring resonator,and then we describe the structure and working principle of the micro-ring resonator,and we focus on single-ring resonator and cascaded double-ring resonator.According to the coupling principle of the coupler and the the transfer matrix equation,the transmission characteristics of the signal in the micro-ring resonator are analyzed.Through the calculation and simulation by using the theoretical formula,the time delay,phase shift and transmission coefficient of the output signal in single-ring resonator and double-ring resonator are studied respectively.By comparing the transmission characteristics of single-ring and cascade double-ring resonator,we also analyze the influence of the the number of micro-ring resonator on the transmission characteristics of the micro-ring resonator system.Secondly,basing on the micro-ring resonator we study the the transmission characteristics of single-ring resonator and double-ring resonator containing the grating,the transmission characteristics includes time delay,phase shift and transmission coefficients.The signal is added at one end of the straight waveguide,the single-ring resonator without grating has two output ports,and produces slow light at the resonance point.With the addition of the grating,the output port increases,the position of the resonance point changes,there are fast-light and slow-light coexistence in the output port of the straight waveguide,and the time delay of the slow-light decreases in the single-ring resonator system.Due to the transmission and reflection characteristicsof the grating,all ports of the single-ring resonator produce light,and the output light performs as slow-light.The time delay of all output ports changes by the exist of the grating,and the amplitude of the phase also change.The theoretical model of the double-ring resonator containing the grating is formed on the basis of a single-ring resonator containing the grating by cascading a same ring.Compared to the double-ring resonator without grating,the output port in the straight waveguide also produces fast-light and slow-light in the double-ring resonator containing the grating,and the time delay of the slow-light decreases in the double-ring resonator system containing the grating.And all ports produce light and the time delay changes,the amplitude of the phase decreases.In addition,we also study the effect of the coupling coefficient on transmission characteristics,and we make a conclusion: with the increase of the cross-coupling coefficients,the time delay of the Through port increases and time delay of other two Drop port decreases in the double-ring resonator containing the grating.The transmission coefficient of the Through port decreases and the transmission coefficient of the two Drop port increases by increasing the cross-coupling coefficient.We also find that the effect of the cross-coupling coefficient on the phase of the output signal is negligible.Lastly,this paper introduces the model of optical modulator based on single-ring resonator and the switching characteristics of the micro-ring resonator.For weak signal light,the signal outputs from the Drop port in the single-ring resonator without adding pump on the same coupling coefficient of the two couplers.With the addition of the pump power,the Through port also produces light.Transmission power and transmission coefficient of Drop port will decrease with the increase of pump power.On the contrary,transmission power and transmission coefficient of the Through port will increase with the increase of pump power.By changing the pump power transferring between Through port and Drop port,and we can realize optical modulator.The critical power of the output changes by the increase of the coupling coefficient of the micro-ring resonator.Then we analyze the switching characteristics of the single-ring resonator system.In the double coupler resonator system,the signal outputs completely from the Drop port when the reflectivitys of the two couplers are the same.And when the reflectivitys of the two couplers completely are close to 1 and are not equal,then the signal output completely from the Through port.So we can realize the optical switch by changing the reflectivity of the upper and lower coupler.