Optical device and method of manufacturing the same

Abstract

An optical device includes a relief structure formation layer, a first layer made of a first material having a refractive index different from that of a material of the relief structure formation layer, and a second layer made of a second material different from the first material and covering the first layer. A ratio of an amount of the second material at a position of the second region to an apparatus area of the second region is zero or smaller than a ratio of an amount of the second material at the position of the second sub-region to an apparatus area of the second sub-region.

What is claimed is: 
     
         1 . An optical device comprising:
 a relief structure formation layer including first and second regions adjacent to each other, the first region including first and second sub-regions, the first sub-region being adjacent to the second region and extending along a boundary between the first and second regions, the second sub-region being adjacent to the second region with the first sub-region interposed therebetween, the second region being provided with recesses or protrusions and having a ratio of surface area to apparent area greater than that of the first region;   a first layer made of a first material having a refractive index different from that of a material of the relief structure formation layer and covering at least the second sub-region, a portion of the first layer corresponding to the second sub-region having a surface profile corresponding to a surface profile of the second sub-region, a ratio of an amount of the first material at a position of the second region to an apparatus area of the second region being zero or smaller than a ratio of an amount of the first material at a position of the second sub-region to an apparatus area of the second sub-region; and   a second layer made of a second material different from the first material and covering the first layer, a ratio of an amount of the second material at a position of the second region to the apparatus area of the second region being zero or smaller than a ratio of an amount of the second material at the position of the second sub-region to the apparatus area of the second sub-region.   
     
     
         2 . The optical device according to  claim 1 , wherein the first region is provided with recesses or protrusions, the recesses or protrusions of the second region have an average values of ratios of depth to diameter or width of openings of the recesses or an average value of ratios of height to diameter or width of bottoms of the protrusions greater than that of the recesses or protrusions of the first region. 
     
     
         3 . The optical device according to  claim 2 , wherein the recesses or protrusions of the first region have the average value of the ratios of depth to diameter or width of the openings of the recesses or the average value of the ratios of height to diameter or width of the bottoms of the protrusions of 0.5 or less, and the recesses or protrusions of the second region have the average value of the ratios of depth to diameter or width of the openings of the recesses or the average value of the ratios of height to diameter or width of the bottoms of the protrusions falling within a range of 0.8 to 2.0. 
     
     
         4 . The optical device according to  claim 1 , wherein the recesses or protrusions of the second region are arranged two-dimensionally. 
     
     
         5 . The optical device according to  claim 1 , wherein a portion of the second layer corresponding to the second sub-region has an average thickness falling within a range of 0.3 nm to 200 nm. 
     
     
         6 . The optical device according to  claim 1 , wherein the second layer is a layer formed by a vapor deposition method. 
     
     
         7 . The optical device according to  claim 1 , wherein the first layer is provided only at a position corresponding to the second sub-region or a position corresponding to the first region. 
     
     
         8 . The optical device according to  claim 1 , wherein a first orthogonal projection of a contour of the first layer on the main surface entirely overlaps a second orthogonal projection of a contour of the second layer on the main surface, the first orthogonal projection has a shape similar to the second orthogonal projection and is surrounded by the second orthogonal projection, or a part of the first orthogonal projection overlaps a part of the second orthogonal projection and the remainder of the first orthogonal projection has a shape similar to the remainder of the second orthogonal projection and is surrounded by the second orthogonal projection. 
     
     
         9 . The optical device according to  claim 1 , wherein a maximum value of a shortest distance from a boundary between the first and second regions to the contour of the first layer is 20 μm or less. 
     
     
         10 . A method of manufacturing an optical device, comprising:
 forming a relief structure formation layer including first and second regions adjacent to each other, the second region being provided with recesses or protrusions and having a ratio of surface area to apparent area greater than that of the first region;   vapor-depositing a first material having a refractive index different from that of a material of the relief structure formation layer entirely on the first and second regions to form a reflective material layer, the reflective material layer having a surface profile corresponding to surface profiles of the first and second regions, or the reflective material layer having a surface profile corresponding to the surface profile of the first region at a portion corresponding to the first region and being partially opened correspondingly to an arrangement of the recesses or protrusions at a portion corresponding to the second region;   vapor-depositing a second material different from the first material on the reflective material layer to form a mask layer, the mask layer having a surface profile corresponding to the surface profiles of the first and second regions, or the mask layer having a surface profile corresponding to the surface profile of the first region at a portion corresponding to the first region and being partially opened correspondingly to the arrangement of the recesses or protrusions at a portion corresponding to the second region; and   exposing the mask layer to a reactive gas or liquid capable of causing a reaction with the first material to cause the reaction at least at a position of the second region, thereby obtaining a first layer made of the first material and a second layer made of the second material.   
     
     
         11 . The method according to  claim 10 , wherein the reflective material layer is partially removed by the reaction. 
     
     
         12 . The method according to  claim 11 , wherein the partial removal of the reflective material layer obtains the first layer as a layer covering only the first region of the first and second regions. 
     
     
         13 . The method according to  claim 10 , wherein the reaction changes a part of the reflective material layer into a layer made of a material different from the first material. 
     
     
         14 . The method according to  claim 10 , wherein the reflective material layer is formed to have an average thickness falling within a range of 5 nm to 500 nm at a portion corresponding to the first region, and the mask layer is formed to have an average thickness falling within a range of 0.3 nm to 200 nm at a portion corresponding to the first region. 
     
     
         15 . The method according to  claim 10 , wherein
 the main surface of the relief structure formation layer further includes a third region, the third region being provided with recesses or protrusions and having a ratio of surface area to apparent area greater than that of the first region,   the reflective material layer is formed by vapor-depositing the first material entirely on the first to third regions, and   the method further comprises forming a cover layer facing only the third region of the second and third regions prior to causing the reaction.