Research Of Three-port Beam Splitter Based On High Density Grating

The beam splitter is an important element, which are widely used in numerous optical systems. The beam splitter is an element in optical systems, which can separate an incident wave into several with equal energies. The three-port beam splitter is a kind of beam splitter, which can separate the incident wave into three beams, which have been reported in reflection and transmission. Fused silica is an ideal high-density optical material. It is possible to product the high-density beam splitter grating with low cost and good performance by the development of micro-fabrication technology.The typical research work about the transmission three-port beam splitter is based on the single-layer fused-silica grating, which was first reported in 2008. The parameters of the grating structure are optimized by using rigorous coupled-wave analysis (RCWA) for both TE and TM polarizations, the three-port beam splitter grating can have high efficiency and good uniformity. Now, by changing the reported grating structure and designing new structure of high-density-based grating has become the new direction of grating research. In this paper, five kinds of three-port beam splitter of structure high-density-based grating with polarization-independent have been researched. The main content of this paper include:(1) A new structure of sandwiched single-layer grating for a transmission three-port beam splitter for TE and TM polarizations has been designed in this paper, which is based on the single-layer grating structure. High efficiencies of 32.54% and 32.29% can be obtained in the ±st and the 0th orders for TE polarization and efficiencies of 33.08% and 32.28% for TM polarization for the incident wavelength of 800nm under normal incidence. The aspect ratio of the grating depth to the ridge width is 1.72, which is far below the reported 4.85.(2) A new structure of single-layer grating for a reflection three-port beam splitter for TE and TM polarizations has been designed in this paper, which is based on the single-layer grating structure. High efficiencies of 32.28% and 32.37% can be obtained in the±1st and the 0th orders for TE polarization and efficiencies of 32.35% and 32.52% for TM polarization for the incident wavelength of 1550nm under normal incidence.(3) A new structure of sandwiched single-layer grating for a reflection three-port beam splitter for TE and TM polarizations has been designed in this paper, which is based on the single-layer reflection grating structure. High efficiencies of 32.36% and 32.79% can be obtained in the±st and the Oth orders for TE polarization and efficiencies of 32.18% and 32.52% for TM polarization for the incident wavelength of 1550nm under normal incidence.(4) A new structure of sandwiched two-layer grating for a transmission three-port beam splitter for TE and TM polarizations has been designed in this paper, which is based on the sandwiched single-layer transmission grating structure. High efficiencies of 32.42% and 32.93% can be obtained in the±st and the 0th orders for TE polarization and efficiencies of 33.09% and 32.81% for TM polarization for the incident wavelength of 800nm under normal incidence. The duty cycle range of grating structure is 0.492-0.520.(5) A new structure of sandwiched two-layer grating for a reflection three-port beam splitter for TE and TM polarizations has been designed in this paper, which is based on the single-layer reflection grating structure. High efficiencies of 31.03% and 31.08% can be obtained in the±st and the 0th orders for TE polarization and efficiencies of 31.21% and 31.17% for TM polarization for the incident wavelength of 1550nm under normal incidence.