Patent ID: 7319509

Claim:
An attenuator, comprising: a grating element having i) grating grooves that produce a grating period (p), and ii) a grating plane, wherein said grating period (p) is at least about 150 times greater than said used wavelength, wherein said grating element attenuates electromagnetic radiation of wavelengths unequal to said used wavelength, wherein said grating element is a binary grating and said grating grooves have a first height (H 1 ) and a second height (H 2 ) in a direction perpendicular to said binary grating, wherein said first height (H 1 ) and said second height (H 2 ) have a difference between them that defines a grating depth h, wherein said grating depth h is defined by the following equation: λ min 4 ⁢ ⁢ cos ⁢ ⁢ α < h < ( n + 1 2 ) ⁢ λ max 2 ⁢ ⁢ cos ⁢ ⁢ α , ⁢ and wherein λ min is a shortest wavelength of wavelengths to be attenuated by said attenuator, λ max is a longest wavelength of said wavelengths to be attenuated by said attenuator, α is an incidence angle of a ray relative to a normal line of a surface of said grating element, and n is an integer number ≧0.