Study On Splitting Performance Of Multiple Micro/Nano Structural Diffraction Gratings

With the rapid development of modern science and technology,electronic products presents a high-efficiency,high-integration development trend.The diffraction grating of micro-nano structure plays an indispensable role in optical industry with its high-integration and high-precision microstructures.In this paper,based on the modal method and rigorous coupled-wave analysis(RCWA)mainly on the following five different function use the micro-nano diffraction grating is studied.(1)This paper shows a novel reflective grating as one sort of high effective grating under Littrow appliance.A covering layer and a dielectric layer are employed in this structure to achieve higher efficiency and wider bandwidth.For the given wavelength of1550 nm,by using two-beam-interference theory for a modal method,a duty cycle and a period of grating can be calculated,and the modal method is well explained the physical essence of the-1st order.The other grating parameters are optimized by using RCWA.Compared with the reported surface-relief high-efficiency grating,the diffraction efficiencies of the proposed grating can be greatly improved.(2)This paper shows a transmission polarization beam splitter by a sandwiched grating with a connecting layer under Littrow mounting.The novel grating is analyzed and designed by modal method and RCWA.Compared to the reported surface-relief PBS gratings,the proposed grating extinction ratio,fabrication tolerance and incident spectrum band width can be improved greatly.(3)This paper shows a 50%-50% splitting ratio element by the covering-layer grating.The novel grating introduces a covering layer on the surface-relief grating,which can improve the performance of a beam splitter compared with the surface-relief grating.For different incident wavelengths and angles,the 50%-50% splitting ratio element exhibits wideband properties,which are useful compared with most beam splitters operated for certain incident wavelength or angle.(4)This paper shows a sandwiched polarizing beam splitter based on a three-layer dielectric and rectangular-groove structure under Littrow appliance.By using two-beam-interference theory for the modal method,three thicknesses of the three grating layers can be estimated with the chosen duty cycle of 0.3 and period of 500 nm.In order to obtain exact grating parameters,a RCWA can be employed to optimize grating parameters to seek the exact grating depths.At wavelength of 800 nm,high efficiencies can be obtainedfor TM polarization in the 0th order and TE polarization the-1st order,respectively.The novel highly-efficient(5)This paper shows an ultrabroadband two-layer hybrid grating for polarizing beam splitter(PBS).The efficiencies and extinction ratios of the two-layer polarizer were characterized for different grating geometrical parameters including periods,duty cycles and dielectric layer thicknesses.In order to obtain the most suitable geometric parameters of grating,the grating was numerically simulated by using RCWA in the near infrared regions.Based on the simulation results,polarization efficiencies of TE-polarized light reflection and TM-polarized transmission are larger than 96% can be obtained within the incident wavelength rang 1220-1940 nm and incident angle range of 4.2°-58.8°.Furthermore,the extinction ratio of the grating can retched to 64.69 dB.