Experimental Study On Non-bragg Antisymmetry Model

Defects in the perfect periodic structure can change the band structure and control the propagation of waves within the structure.It plays a very important role in the fields of electronic information industry and photonic crystal applications.The defects in the non-Bragg forbidden band can be used to make more precise optical switches,optical sensors and optical filters,etc.due to their complex resonance mechanism and rich intension of physical,which provides a new application for the application of defect modes.This direction has very important research significance.In this paper,the Bragg and non-Bragg structures with defects are studied theoretically and experimentally.The generation and properties of the defect mode in the non-Bragg structure are discussed.The main research contents of this paper include the following aspects:1.The generation and conversion of the wave surface band in the water surface of the periodic side wall trough are studied.The conclusion shows that the periodic structure of the water trough will produce a forbidden band on the transmission spectrum band,and the phase difference between the two side walls of the periodic side wall sink.changes the resonant form of the water surface wave.There is only a complete Bragg resonance when there is no phase difference between the two sidewalls;and the sidewalls are completely staggered,i.e.there is only a complete non-Brad resonance when the phase difference is ?.Bragg and non-Bragg resonances exist simultaneously when the phase difference is between the two.2.The influence of the length of the side wall of the trough and the depth of the undulation on the forbidden band is studied.Through theoretical calculations,we find that the center frequency and the width of the forbidden band change with the periodic wave number of the water trough and are confirmed by numerical simulation and experiment.At the same time,we also studied the variation of sidewall undulation ? and forbidden band width,and found that the increase of sidewall undulation depth will greatly change the width and depth of the forbidden band.Finally,we measured the energy distribution at the bottom of the forbidden band,the band gap and the passband,the energy distribution on the central axis of the trough,and found that there is a periodic energy distribution in the entire trough.And when the frequency is in the forbidden band,the energy propagates in the waveguide about half of the distance is completely attenuated,while the attenuation effect is not obvious in the pass band.3.The characteristic of the defect mode in the periodic structure is studied.We have found through numerical simulation and experiments that the transmission peak will appear in the forbidden band after the defect is introduced into the perfect periodic structure.After that we adjusted the length of the defect and found that the center frequency of the transmission peak and the position and width of the forbidden band will change.When the length of the defect increases over an integer number of periods,the transmission peak shifts toward the low frequency and the center frequency of the forbidden band also shifts red.When the defect length is close to an integer multiple of the period length,the transmission peak will be incorporated into the forbidden band edge,and the width of the forbidden band is minimized at this time.Then we analyzed the energy distribution at the center frequency of the transmission peak through experiments and found that the energy was localized at the defect,resulting in a transmission peak.Through time domain analysis,we also learned that the generation of localization is gradually accumulated over time.Finally,we use numerical simulation to analyze the energy distribution in the whole water tank when the defect is found.It is found that the energy distribution with phase in the non-Prague structure is symmetric about the center of the defect,and the structure is antisymmetric about the center of the defect.In summary,we have studied the properties of the defect modes in the Bragg and nonBragg forbidden bands and the forbidden band from the theoretical and numerical simulations and conducted experimental verification through an intuitive trough experiment to study the light waves in the defective non-Bragg optical waveguide.Medium transmission provides an important reference.