Analysis of polarization characteristics of liquid crystal Lieb lattice diffraction

Lieb lattice is one of the most studied complete lattice structures with flat band properties. In this paper , the Lieb lattice is prepared based on the liquid crystal light orientation technology. By changing the polarization direction of exposure , the LC Lieb lattice structure is constructed with the liquid crystal 90 degrees twisted (TN ) orientation inside the lattice site and uniform (PA ) orientation outside the pattern. The diffraction characteristics of liquid crystal Lieb lattice with different incidence schemes are measured under different applied electric field. The polarization characteristics of multiple diffraction orders under different applied electric fields are measured by polarization tester. The experiments show that the order of diffraction spots increases when voltage is added. As the voltage increases to about 2.5 V PP , the diffraction effect of liquid crystal Lieb lattice structure becomes worse , and the intensity of diffraction spots is the weakest except for zero -order diffraction spots. When the voltage increases to 4 V PP , the intensity of the diffraction spots is gradually enhanced , and the diffraction pattern is gradually clear. In the process of changing the voltage , the polarization state of the diffracted light of different orders in various incident cases also gradually changes , and the first -order diffracted light has special polarization states such as +45 degrees linear polarized light , -45 degrees linear polarized light , right -handed circularly polarized light , and left -handed circularly polarized light between 1 V PP and 3 V PP . The liquid crystal Lieb lattice proposed in this paper has the characteristics of easy regulation and preparation. By regulating the voltage applied on the liquid crystal , the dynamic regulation of the diffraction order polarization state can be realized , which provides a new way for the light field regulation.