Visible-NIR Graded Refractive Index Antireflection Coatings Assembled With Znse Hollow Nanospheres

Zinc selenide(ZnSe)has a wide transmission band in the infrared region and lower absorption coefficient.However,its transmittance is only 70 % because of its high refractive index.So it is necessary to construct antireflection coatings to improve its transmittance.Compared to single-refractive-index coatings,graded-refractiveindex antireflection coatings can achieve high transmission with larger incident angles and in wider optical bands,however,studies on graded-refractive-index antireflection coatings for ZnSe substrates have been seldom reported.Therefore,the research on visible-NIR graded refractive index antireflection coatings on ZnSe has both theoretical significance and application value.In this thesis,a large number of ZnSe hollow nanospheres with good crystallinity were synthesized by laser ablation in liquid and hot-injection methods,based on the nanoscale Kirkendall effect.Then double-layer graded-refractive-index antireflection coatings were prepared on ZnSe substrates by spin-coating and a template method.The results showed that regulating the porosity of coatings could effectively control the coatings refractive index.And the refractive index of graded index coatings was close to the theoretical model.The refractive index of high-refractive-index coatings reached 1.75,and the low-refractive-index coatings could reach 1.35.The high and low-refractive-index coatings were superposed together to form double-layer gradedrefractive-index antireflection coatings that has good antireflection properties in the visible-NIR range and also good mechanical stability.High transmittance could be achieved,up to 91.5%,with incident angles ranging from 0°-30°.In addition,compared to the single-refractive-index antireflection coatings,the double-layer graded-refractive-index coatings had a much wider optical band for high transmittance.