Study On The Performance Of Beam Splitters With Various Sub-wavelength Grating Structures

With the rapid development of economy,the demand of high integrated optoelectronic devices and the maturity of semiconductor processing technology,the sub-wavelength grating based on miniaturization and high integration has attracted more and more attention of researchers.In such a background,it is of great practical significance to study many kinds of grating beam splitters based on subwavelength structure.Therefore,based on the modal theory and the rigorous coupled-wave analysis(RCWA),this paper studies and analyzes a variety of grating beam splitters based on sub-wavelength structure.The main research results are as follows:1.In this paper,a sandwich polarization selective beam splitting grating based on metal mirror is designed.According to the phase difference of TE and TM polarized plane,the period of grating is 1181 nm.Then,the depth of groove and the thickness of connecting layer of grating are 1.25 ?m and 1.75 ?m,respectively.The grating device can diffract the TE-polarized plane light only in the-1st diffractive order with high reflection efficiency of 97.91%.Meanwhile,for the TM-polarized plane light,the diffraction efficiencies in the 0th order and the-1st order corresponding to 48.67% and 48.68% are obtained,respectively.In addition,the incident wavelength bandwidth of grating is 14 nm.2.In this paper,a dual-functional transmissive sandwich polarization selective beam splitting grating with a connecting layer is designed.The grating device diffracts TE polarized light only by-1st order,and the diffraction efficiency is as high as 98.36%.At the same time,for the transverse magnetic polarized light,the diffraction efficiencies of the 0th order and-1st order emitted light are 49.34% and 49.29%,respectively.3.In this paper,a dual-functional sandwich type three-layer polarization selective beam splitting grating is designed.Under the condition of litero incidence,the diffraction efficiency of-1st order TE polarized light is 97.04%,and the diffraction efficiency of 0th order and-1st order TM polarized light is 49.64% and 49.80%,respectively.In addition,this new type of grating also has an incident spectral width of 20 nm.4.In this paper,a three-port sandwich beam splitter with a connection layer under normal incidence is designed.The diffraction efficiency of TE polarized light in the 0th,-1st and 1st orders is 32.30%,32.38% and 32.38%,and the diffraction efficiency of TM polarized light is32.3%,32.26% and 32.26%,respectively.The incident wavelength has a working bandwidth of 22 nm.5.In this paper,a three-port sandwich grating is designed under the condition of the second Bragg angle incidence.Strictly coupled wave analysis method was used to design and study this kind of sandwich reflection grating,which improved diffraction efficiency and incident angle bandwidth.The total efficiency of TE polarized light can reach 98.07%.The beam splitting effect of TM polarized light is better and more uniform.The efficiency ratio of0 th order and-2nd order can reach 1.0003,and the efficiency ratio of 0th order and-1st order can reach 1.001.6.In this paper,a three-port sandwich grating with a connecting layer under the condition of the second Bragg angle incidence is designed.The grating can be used as a beam splitter to divide the polarized light into three orders of 0th order,-1st order and-2nd order.In particular,the beam splitting effect of the TM polarization grating is more consistent,the energy ratio between the 0th order and the-1st order is 1.01,and the diffraction energy of the-1st order and the-2nd order are equal.7.This paper has designed a double-layer reflective three-port grating under the condition of the second Bragg angle incidence.TE polarization grating can divide TE polarized light into three diffraction orders of 0th order,-1st order and-2nd order,and the diffraction efficiency of each order is the diffraction efficiency of three orders can reach 32.89%,32.90%and 32.97%,and the sum of the reflection efficiencies of the three orders exceeds 98%.8.This paper designs a three-layer high-efficiency polarization selective dielectric transmission grating.The diffraction characteristics of the new type grating were analyzed by modal analysis method,and the grating parameters were evaluated.Based on the parameters obtained by the modal method,more appropriate grating parameters are obtained by numerical analysis.By optimizing the grating profile,a new type of grating is obtained that makes TE polarized light have a-1 order efficiency of 96.88% and TM polarized light has 0th order efficiency of 96.93%.This new type of grating has the advantages of high efficiency and wide spectral angle bandwidth,and can meet the requirements of various optoelectronic devices.