The Design Of Polarized Light-emitting Diodes

With the continuous improvement of production processes and the decline in the cost, light-emitting diodes have become the ideal lighting source of the 21 st century. As the expansion of the application area of light emitting diodes and improvement of application requirements, the requirement of polarization degree is increasing. The twodimensional photonic crystal polarization layer, which is integrated onto a LED, has become an important solution to this problem, benefit from its high light efficiency, compact structure, process compatibility, tunable, etc.2D photonic crystal layer integrated onto LED surface was based on the traditional photonic crystal polarizer, and had been improved by applying the characteristics of the LED. The principle was that photonic crystals have different light transmission characteristics for different models. Through a reasonable set of photonic crystal structural parameters, such as the duty cycle, the lattice structure, medium pore shape, etc., separation mode could be achieved. A possibility to manufacture LEDs with high optical efficiency, high polarization degree may be provided. The changes in the refractive index of nematic liquid crystal during the reconstruction process, could also be used in the tunable photonic crystal polarization layer.Based on the excellent properties of two-dimensional photonic crystal polarization layer, its structural design and parameters were optimized. The numerical simulation algorithm was the plane wave expansion method. In order to overcome common design software’s restrictions on the photonic crystal structure, the paper designed a discrete numerical simulation algorithm which can be used with any cell shape and prepared the corresponding program. On this basis, various parameters of photonic crystals are individually optimized. The non-linear relationship between the bandwidth and the duty cycle was obtained. Different lattice structure was selected and compared. The relationship between the band gap and m, the number of its topological charge, was studied. An optimal infrastructure was given based on these experiences and a large number of analog data.Based on the above structure, the paper analyzed the advantages and disadvantages of conventional liquid crystal doped photonic crystal polarizers, which use the forbidden band edge mobile solutions to achieve tuned characteristic. The photonic crystal defect states polarization was proposed. Simulation results showed that the model can create a 2nm wide window area in the blue spectrum. The above model has greatly improved the traditional method for designing an integrated photonic crystal layer on the LED, and provides a new way, as a theoretical basis for further practical research.