The Study Of Broadband Polarization Beam Splitter Based On Wave-Structure Multilayer Film

Wave-structure multilayer film is a kind of two-dimensional photonic crystals. Since the difference of band structures, The TE mode and TM mode are separated along different directions when the electromagnetic wave propagations in the structure, and it can work as a polarization beam splitter. The polarization beam splitter (PBS) based on wave-structure has attracted many researchers’attention, because it is compact, easy-integration and it can generates axisymmetric polarization. Until now, most of the PBSs based on wave-structure work at the infrared area. But at the visible area, the bandwidth of PBS is just100nm. Due to the complexity of band structure, there was no detailed analysis and optimization process in previous studies. And the bandgap is discontinuous which is not fully extended. A broadband polarization beam splitter based on wave-structure multilayer film is composed by the two different thickness periodic film stacks is proposed in this essay. Besides, wave-structure multilayer film can be fabricated by ion beam sputtering.The polarization beam splitter based on wave-structure multilayer film has a broadband at visible area, and the TiO2and SiO2are chosen to form the wave-structure multilayer film as the high and low refractive index of the dielectric material respectively. A method to broaden the bandwidth of polarization beam splitter which is composed by the two different thickness periodic film stacks is proposed.Combined with the evaluation function of polarization splitting characteristic, particle swarm optimization method is employed to design the optimal structural parameters,a broadband and compact polarization beam splitter is acquired, the center wavelength is565nm and the working range has achieved220nm with the average extinction ratio over30dB. This paper also analyze the substrate period and the size of wavy-structure, and based on these analysis, we can move the working wavelength range at infrared region and ultraviolet region. In addition, the angle sensitivity of the structure is investigated in detail. And we also study the electromagnetic field in wavy-structureIn addition, we fabricate wave-structure multilayer film on the silicon substrate by autocloning technique. Combining UV nano-imprint lithography and inductively coupled plasma (ICP) to prepare the silicon grating. Ion beam sputter is used to fabricate the multilayer on the substrate. The primary ion source is used to sputter and the assisted ion source is used to etch, at the same time, quartz crystal monitor is chosen to control the film thickness, and then fabricate wave-structure multilayer film that alternating high and low refractive index of the dielectric material. Experiment proved that dual-ion source ion beam sputter can be used to fabricate wave-structure multilayer film on the silicon substrate.