EP0059304A2
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EP
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A method of manufacturing a curved diffraction grating structure
Assignee: NTT Inc
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Filing: 1979-07-16
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Granted: —
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Expires: 1999-07-16
Abstract
Abstract A method of manufacturing a curved diffraction grating is disclosed. The grating is made of a single crystalline silicon substrate, one major plane thereof being provided with a plurality of asymmetric triangular grooves, each having a wall inclined by an angle 8 with respect to the major surface so as to satisfy an equation where 0 represents the blaze angle, P the grating constant of the groove, λ B the blazing wavelength, and m the order of diffraction. The walls of each groove receiving incident light are covered with a metal coat. The diffraction grating is prepared by using an {hkl} plane (where h = k) inclined by 0 with respect to the {111} plane of the single crystalline silicon as a major surface, and then anisotropic etching the major surface through an etching mask having stripes of sufficiently smaller width than the constant. The planar diffraction grating thus obtained is mounted on a curved surface of a supporting member and, by applying pressure, curved to conform with the curved surface. Preferably, following the anisotropic etching, isotropic etching is performed for the major surface.
Inventors
- 👤 Yohji Fujii
- 👤 Junichiro Minowa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 00:36
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/18; G02B5/1847; G02B5/1857; G02B5/1861; H; H10; H10P; H10P50/00; H10P50/60; H10P50/64; H10P50/642; H10P50/644; Y; Y10; Y10S; Y10S438/00; Y10S438/978; Y10T; Y10T156/00; Y10T156/10; Y10T156/1002; Y10T156/1028
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
260 words
A method of manufacturing a curved diffraction grating structure in which a major surface of a single crystalline silicon substrate is provided with a plurality of triangular grooves at a predetermined grating constant or pitch, each groove having an asymmetric cross-sectional shape and a wall inclined by a blaze angle with respect to the major surface and wherein when the plurality of triangular grooves are projected on a plane, a pattern is formed in which the projections of the grooves are arrayed in parallel at the predetermined constant, characterised in that the method comprises the steps of: using an thkl) plane (where h = k) inclined by the blaze angle with respect to the {111} plane of the single crystalline silicon as parallel opposing first and second major surfaces; applying an etching mask onto the first major surface; anisotropic etching the single crystalline silicon through the etching mask with an etching solution having different etching speeds for different crystallographic directions of the single crystalline silicon, thus forming a planar diffraction grating, which forms a plurality of triangular grooves similar to the first mentioned triangular grooves when the planar diffraction grating is curved with the first major surface inward; mounting the planar diffraction grating on a supporting member with the second major surface in contact with a curved surface of the supporting member, the curved surface being provided with recesses containing an adhesive and evacuation openings; applying a negative pressure to the second major surface through the evacuation openings thereby curving the planar diffraction grating to conform with the curved surface.
Claim 2
Independent Claim
260 words
A method of manufacturing a curved diffraction grating structure in which a major surface of a single crystalline silicon substrate is provided with a plurality of triangular grooves at a predetermined grating constant or pitch, each groove having an asymmetric cross-sectional shape and a wall inclined by a blaze angle with respect to the major surface and wherein when the plurality of triangular grooves are projected on a plane, a pattern is formed in which the projections of the grooves are arrayed in parallel at the predetermined constant, characterised in that the method comprises the steps of: using an thkl) plane (where h = k) inclined by the blaze angle with respect to the {111} plane of the single crystalline silicon as parallel opposing first and second major surfaces; applying an etching mask onto the first major surface; anisotropic etching the single crystalline silicon through the etching mask with an etching solution having different etching speeds for different crystallographic directions of the single crystalline silicon, thus forming a planar diffraction grating, which forms a plurality of triangular grooves similar to the first mentioned triangular grooves when the planar diffraction grating is curved with the first major surface inward; mounting the planar diffraction grating on a supporting member with the second major surface in contact with a curved surface of the supporting member, the curved surface being provided with recesses containing an adhesive and evacuation openings; applying a negative pressure to the second major surface through the evacuation openings thereby curving the planar diffraction grating to conform with the curved surface.
Claim 3
Dependent Claim
28 words
A method according to claim 1, characterised in that metal coats having a uniform thickness are applied onto the walls of the triangular grooves upon which light impinges.
Claim 4
Dependent Claim
18 words
A method according to claim 1 or 2, characterised in that isotropic-etching is performed succeeding the anisotropic etching.
Claim 5
Independent Claim
35 words
A method according to any one of claims 1 to 3, characterised in that the etching mask includes a plurality of spaced apart parallel stripes each having a width substantially smaller than the grating constant.
Claim 6
Independent Claim
25 words
A method according to any one of claims 1 to 4, characterised in that the etching mask comprises a plurality of stripes at unequal pitch.
Claim 7
Independent Claim
24 words
A method according to any one of claims 1 to 4, characterised in that the etching mask comprises a plurality of equally spaced stripes.
Claim 8
Dependent Claim
34 words
A method according to claim 1 or 3, characterised in that the etching solution used for the anisotropic etching comprises a member selected from the group consisting of amine pyrocatecol water, alkalines, and amines.
Claim 9
Dependent Claim
20 words
A method according to claim 3, characterised in that the etching solution used for the isotropic etching comprises hydrofluoric acid.
Claim 10
Dependent Claim
26 words
A method according to claim 3, characterised in that the etching solution used for the isotropic etching comprises a mixture of nitric acid and hydrofluoric acid.
Claim 11
Dependent Claim
17 words
A method according to claim 2, characterised in that the metal coat comprises a plurality of layers.
Claim 12
Dependent Claim
26 words
A method according to claim 2, characterised in that each of the metal coats comprises a first layer of gold and a second layer of nichrome.
References Cited (Backward Citations)
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