Reflection type diffraction grating
First Claim
1. In a diffraction grating having a groove period which is 0.1 to 10 times as large as a wavelength of incident light λ
- , a reflection type diffraction grating comprising(1) a laminate of a metal film as a first layer with reflectance not lower than 30%;
wherein said metal film has a refractive index not higher than 2.0 and an extinction coefficient not smaller than 6.0 with respect to the wavelength of the incident light; and
(2) a transparent dielectric film as a second layer, wherein the transparent dielectric film has an optical film thickness in a range of 0.20λ
to 0.80λ
, said first and second layers being laminated in order on a surface side of said diffraction grating, whereby incident light is reflected by said first layer through said second layer;
wherein said dielectric film has a refractive index in a range of from 1.30 to 1.65, both inclusively, with respect to the wavelength of the incident light.
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Abstract
A reflection type diffraction grating according to the present invention has a structure in which a metal film as a first layer with reflectance not lower than 30% with respect to the wavelength of incident light and a transparent dielectric film as a second layer are laminated successively on the surface of the reflection type diffraction grating. With respect to the wavelength of incident light, the metal film has a refractive index selected to be not higher than 1.5 and an extinction coefficient selected to be not smaller than 6.0. The transparent dielectric film has a refractive index selected to be in a range of from 1.30 to 1.46, both inclusively, with respect to the wavelength of incident light and has an optical film thickness selected to be in a range of from 0.20λ to 0.38λ, both inclusively, when λ is the wavelength of incident light.
41 Citations
6 Claims
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1. In a diffraction grating having a groove period which is 0.1 to 10 times as large as a wavelength of incident light λ
- , a reflection type diffraction grating comprising
(1) a laminate of a metal film as a first layer with reflectance not lower than 30%;
wherein said metal film has a refractive index not higher than 2.0 and an extinction coefficient not smaller than 6.0 with respect to the wavelength of the incident light; and
(2) a transparent dielectric film as a second layer, wherein the transparent dielectric film has an optical film thickness in a range of 0.20λ
to 0.80λ
, said first and second layers being laminated in order on a surface side of said diffraction grating, whereby incident light is reflected by said first layer through said second layer;
wherein said dielectric film has a refractive index in a range of from 1.30 to 1.65, both inclusively, with respect to the wavelength of the incident light. - View Dependent Claims (2, 3, 4, 5)
- , a reflection type diffraction grating comprising
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6. A diffraction grating comprising:
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(A) a substrate defining a fine roughness structure on a surface, said fine roughness structure being constructed by a large number of fine grooves arranged periodically;
(B) a transparent dielectric layer provided to said substrate as an exposed surface;
wherein the transparent dielectric film has an optical film thickness in a range of 0.20λ
to 0.80λ
; and
wherein a refractive index of said dielectric layer is in a range of from 1.30 to 1.65, both inclusively, with respect to the wavelength of the incident light;
(C) at least one metal layer provided to said substrate to be located between said dielectric layer and said fine roughness structure; and
reflectance of said metal layer is not lower than 30%; and
wherein a refractive index of said metal layer is not higher than 2.0 with respect to the wavelength of the incident light; and
wherein an extinction coefficient of said metal layer is not smaller than 6.0 with respect to the wavelength of the incident light.
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Specification