Research On Beam Splitting Micro-nano Optical Elements

With the continuous development of the integration of optical,mechanical and electrical,micro/nano optical devices have been developed rapidly to meet the requirements of miniaturization and integration of optical systems.micro/nano optical devices realize wavefront control of light in different ways and play an important role in many fields.As a kind of Micro/nano optical device,diffractive optical element can control light wave by changing the phase distribution,which has a very wide application.Diffractive optical elements are mostly designed based on scalar diffraction theory,which cannot be applied to the design of optical devices with subwavelength characteristic size,and cannot meet the requirements of increasingly integrated and high-precision devices.The sub-wavelength scale artificial micro/nano structures can control the phase,amplitude and polarization of light,which provides an effective scheme for the realization of ideal wavefront shaping.The inverse design method combined with the vector diffraction theory can optimize the design of multiple parameters of the artificial micronano optical element and obtain the micro-nano optical device that meets the design requirements.The design and simulation of beam split-diffraction optical element using scalar diffraction theory and phase recovery algorithm are carried out,but the effect obtained based on scalar theory is not very ideal.Then,a meta-surface with beam splitting function is designed by using the GS algorithm and the geometric phase principle of the metasurface,and the lattice with higher energy can be obtained in space.The process of inverse design of subwavelength grating is realized based on adjoint method.The adjoint method can be used to obtain the sensitivity information of the diffraction efficiency of the subwavelength grating about the material distribution parameters.Combined with the topology optimization method,the continuous parameter distribution obtained by the projection is gradually binarized.Finally,the approximately binary structure is binarized to obtain the binary structure subwavelength grating.The designed subwavelength grating can diffract most of the energy of incident TE polarized light to order(+1,0)and order(-1,0).The diffraction efficiency of the obtained subwavelength grating is 40.99%for order(+1,0)and 34.45% for order(-1,0).The total diffraction efficiency of subwavelength grating target order(+1,0)and(-1,0)is more than 90%,and the uniformity error is only 8.6%.