Study On Filtering Characteristics Of Quantum Well Photonic Crystal

High-precision optical filters is an indispensable optical device with selection and extraction in the optical communication system for dense wavelength division multiplexing,image detection system for special band,and spectral analysis system for the high-precision division.Photonic crystals can block or allow the propagation of light in some bands.Photonic crystals have the advantages of high control accuracy and low optical loss,which is beneficial to the miniaturization and integration of photonic filter devices.The design of new structures,the exploration of new physical properties and the expansion of the application range of optical devices have always been the focus of photonic crystal research.Quantum well photonic crystals are the expansion and optimization of traditional photonic crystal structures.Quantum well photonic crystal offers more options for filtering channels and width of forbidden band due to the flexible tuning mode and large filtering range.In order to solve the problems existing in photonic crystal filter,such as non-linearity tuning filtering,narrow band gap of band-pass filter and unclear influence of film thickness disturbance on filtering performance,three kinds of quantum well photonic crystal structures are proposed in this paper.Multi-channel tuning filtering with high precision,band-pass filtering with wide band gap and band-stop filtering with stable center band can be realized,and the influence of disorder disturbance on photonic crystal filtering characteristics is evaluated.The?Si/SiO₂?⁶ photonic crystal samples were prepared by magnetron sputtering and compared with the simulation results.1.An ABA-type quantum well photonic crystal structure is proposed by inserting an air defect cavity into a mirror-symmetric photonic crystal of Si/SiO₂.By mechanically tuning the physical thickness of the air cavity,dual-channel and multi-channel tuning filtering with high-precision can be realized in the optical communication band,which can solve the problem of large volume,nonlinearity tuning and instability DWDM in the filter.The transmittance of multi-channel is up to 100%,while the full width at half maximum is less than 0.2nm,which is meeting the needs of dense wavelength division multiplexing filtering.Tuning filter range can be extended to communication bands of O,E,S,C,L,U?1260nm-1675nm?by combining air cavity thickness tuning and light incident angle tuning.The structure satisfies the requirements of real-time and high-precision filtering,and can improve the information processing rate and transmission capacity.2.Due to the narrow range in band-stop and a low transmittance in band-pass of the UV band-pass filter,an ABC-type quantum well photonic crystal structure of ZrO₂/MgF₂ is designed by using the principle of frequency domain superposition.By adjusting the structural parameters,it is found that the structure order and period of the central photonic crystal have a great influence on the filtering characteristics of the forbidden band.By optimizing the structural parameters,the filter can achieve efficient filtering in solar-blind UV band?240nm-280nm?,with an average transmittance of 64.524%.Simultaneously,a deep rejection of the band-stop appears in the near ultraviolet and visible region?300nm-700nm?and its average transmittance is below 0.309%.Based on the characteristics of UV band-pass filter and quantum dot photoluminescence,a spectral converter which can convert UV light into visible light directly is designed.This spectral converter breaks through the limitation of traditional imaging method of optical-electrical-optical and can be used in high-resolution solar-blind UV imaging systems.3.In order to study the influence of film thickness perturbation on the performance of nanophotonic devices during experimental preparation of photonic crystal multilayer film,a disordered quantum well photonic crystal model with film thickness perturbation was designed by introducing a pseudo-random error obeying Gaussian distribution in each layer of film thickness.By analyzing the influence of period number and disturbance error on defect state,a compensation scheme for a stable center position and width of forbidden band is proposed,that is,the film thickness deviation of the j-th layer can be compensated by adjusting the thickness of the j+1-th layer.This scheme can reduce the accumulation of thickness deviation and weaken the influence of film thickness disorder on the center position and width of the forbidden band,which provides a theoretical basis for reducing the deviation between experiment and theory.4.By adjusting the working parameters such as gas pressure and gas flow rate of magnetron sputtering coating machine,the film thickness error of single-layer film is controlled to be less than 20%,and?Si/SiO₂?⁶ photonic crystal is experimentally prepared.It was found by transmission spectrum characterization that a film thickness error within 20%will reduce the width of band gap to40.99%-49.73%of the theoretical perfect photonic crystal bandwidth.Further,comparing the experimental results with the theoretical simulation results of the film thickness deviation of 20%,the photon energy band of the experimental sample can be well fitted with the theoretical value.