PLANE FRESNEL LENS AND ITS PRODUCTION,申请号JP19850021144-传众专利搜索

PLANE FRESNEL LENS AND ITS PRODUCTION

申请公布号：JPS61180205(A)

申请号：JP19850021144

申请日期：1985.02.06

申请公布日期：1986.08.12

申请人：

NEC CORP

发明人：TAKADO NOBUKAZU

分类号：G02B6/122;G02B3/08;G02B6/124

主分类号：G02B6/122

摘要：PURPOSE:To obtain a lens having a large aperture and high diffraction efficiency by providing a step to the boundary between a high refractive index optical waveguide part and plane optical waveguide and making the layer thickness of the high refractive index optical waveguide part larger than the layer thickness of the plane waveguide. CONSTITUTION:A titanium film is formed on the surface of a lithium niobate substrate 11 and the titanium is thermally diffused to form the optical waveguide 12. The surface of the waveguide 12 is dug in except the lens part 13 to increase the titanium concn. in the lens part 13 and to make the refractive index in said part higher than the refractive index of the periphery. The thickness of the optical waveguide is made smaller than the thickness of the lens part in addition to a difference in the refractive index owing to a difference in the titanium concn. between the lens part 13 and the waveguide 12. The difference in the equiv. refractive index between the light beams propagating in the lens part 13 and the waveguide 12 is therefore made larger than in the case such as the conventional embodiment in which the difference is larger by as much as the difference in the titanium concn. alone. The decrease in the lens thickness is thus made possible and the plane lens having the large aperture diameter and high diffraction efficiency is thus obtd.