Sol - Gel Preparation Of Tio <sub> 2 </ Sub> / Sio <sub> 2 </ Sub> Broadband Antireflection Film And The Polarizing Beam Splitter Research

In virtue of the thin film designing software Mass, broadband reflection reducing coating and polarizing beam splitter composed of TiO₂/SiO₂ multilayer films have been prepared according with the multilayer theory. Titanic oxide sol and silicon dioxide sol were obtained by hydrolysis and co-condensation reactions occurred in acid-catalyzed system by carefully controlling the sol-gel process of tetrabutylorthotitanate (Ti(OBu)₄) and tetraethoxysilane (TEOS). The samples were coated on glass slides by dipping method. The samples' characters, such as transmission spectrum, surface morphologies, thickness and extinction ratio were studied by double-beam ultraviolet-visible spectrophotometer, atomic force microscopy (AFM), ellipsometer and dual-channel power meter.The result of simulation shows that the transmission spectrum of the TiO₂/SiO₂ films for both surfaces is 99% at normal incidence. It's better than the films for one suface. Using the alternating coated method differing from the composite method, the broadband reflection reducing coating was prepared. The result of experimentation: from the transmission spectra of the samples we can see that for the case of vertical incidence, the average transmission of the slide sample increased 7% compared to the uncoated one in the spectra range from 400nm to 700nm, for 45°incidence the increase is 10%. The dependence of samples' transmittance on hoist speed and annealing temperature was investigated. It is best when hoist speed is 9cm/min and the film thickness is 255nm. Annealing treatment had great effect on transmittance. Through controlling annealing temperature and hoist speed, the transmittance at some wave band can be enhanced. The reflection reducing coating of 80℃annealed has smooth and even surface, its Root Mean Square (RMS) and Average Roughness (RA) are estimated to be 1.682 and 1.208 . To the film of 300℃annealed the RMS and RA are estimated to be 0.289 and 0.207 and to the film of 500℃annealed they are 0.167 and 0.108. The surface roughness decreasd with increasing of the annealing temperature and the transmission is high when the surface roughness is big, because the hydroxy was removed with increasing of temperature.Broadband polarizing beam splitters were designed. The transmittance and reflectivity of TiO₂/SiO₂ four-layer alternate films is approaching 50% in range from 430nm to 700nm. The reflectance of the S polarized light is 95% and the transmittance of the P polarized light is 90%, so the S polarized light and P polarized light were better detached. In the lab, the samples were prepared using sol-gel technology by dip-coating and the testing methods were designed. The results show that the transmittance of the P polarized light obeys the Malus law with the turning of analyzer, further more the minimum approach zero compare with maximum and the wave crests of transmitted light were symmetric. Those show that the polarize of the samples are batter. The extinction ratio of sample is 476:1. The transmittance of P polarized light is extend to more than 80% in the spectra range from 400nm to 700nm,and its extinction ratio is insensitive to the change of incident angle.