Structure Design,and Simulation Analysis Of Subwavelength ZnO Single Crystal Guided-mode Resonance Grating Filters

Guided mode resonance grating filter based on subwavelength structure has ideal characteristics such as high diffraction efficiency,low sideband,controllable bandwidth,be sensitive to the change of parameters.It is easy to integrate because of it's small size.It is a research hotspot in the field of forefront optical communication devices in recent years and can promote the future development of optical communication systems.The key to the fabrication of a guided mode resonant grating filter with excellent filtering performance is to select a grating dielectric material with low loss and good robustness.ZnO is a representative third-generation wide-bandgap semiconductor material with excellent physical-chemical and electro-optical properties.Compared with the second-generation semiconductor materials,devices made with ZnO single crystal have better performance,and have the potential to gradually replace the current mature Ga N and other semiconductor optoelectronic devices in the future.Therefore,this paper selects ZnO single crystal as the grating dielectric material,and uses the method of iterative optimization parameters to simulate the high-performance guided mode resonant grating filter.On this basis,the parameter analysis and tunable design are carried out.Firstly,the characteristics of ZnO and the growth mode of single crystal are introduced,then the research background of diffractive element is introduced,and the research status of design and preparation of guided mode resonant grating filter at home and abroad is illustrated with examples.Then,the rigorous coupled wave theory and the equivalent medium theory are described in detail,and the equivalent waveguide models of single-layer and multi-layer gratings are analyzed.The reflective grating filter with single and double-layer ZnO single crystal subwavelength structure at 1315 nm resonance wavelength is mainly designed.On this basis,the multilayer reflective grating filter and transmission grating filter are also designed.The calculated and simulated analysis of the designed grating filter using Mathematical and RSoft software shows that the ZnO single crystal gratings have good filtering characteristics such as high diffraction rate,low side bands on both sides and narrow bandwidth.What's more,their bandwidths are controllable.They have the potential to be widely used in micro-optics in the future.In addition,a suspended grating refractive index sensor structure and a separate air gap layer tunable grating structure are also designed.The influence of resonance conditions on the guided mode resonance effect is analyzed,and the tuneable design of the relative resonance peak position is carried out.The analysis results show that the modulation coefficient affects the coupling strength and thus the spectral line shape;when the duty cycle is 0.5 under weak modulation,the line width has the maximum value.It is emphasized that the duty cycle will only show high diffraction peaks when the duty cycle is greater than 0.8;the thickness of the grating and the thickness of the waveguide affect the side band and resonance wavelength,and the thickness of the cover layer has little effect on the resonance wavelength;changing the incident angle and grating period can accurately tune the resonance peak position.