Absorptive wire-grid polarizer and optical apparatus

An optical apparatus comprising:

• a body of the apparatus;
• and
• an absorptive wire-grid polarizer housed in the body,
• wherein the absorptive wire-grid polarizer comprises:
• a dielectric substrate;
• and
• a periodic structure formed on a substrate surface of the dielectric substrate and constituted by a metal and one or more dielectric materials whose number is represented by i,
• wherein the periodic structure has a one-dimensional grating structure in which, in a sectional plane orthogonal to a normal to the substrate surface, grating portions of a metal grating formed of the metal and grating portions of dielectric gratings formed of the one or more dielectric materials are one-dimensionally arranged with a grating period P smaller than that of an entering light entering the polarizer, and
• wherein the following conditions are satisfied:
• nm≧1.0,km≧2.0
• 0.01≦FF≦0.25
• nb≧1.40
• h≧250 [nm]
• where h represents an entire height of the metal and dielectric gratings, nm represents a refractive index of a real part of a complex refractive index of the metal for a wavelength of the entering light, km represents an extinction coefficient of an imaginary part of the complex refractive index, nb represents an average refractive index of the dielectric grating, and FF represents an average filling factor of the metal grating to the grating period P, FF and Nb being expressed by the following expressions:
• F
• 
• 
• F
• =
• 1
• h
• 
• ∫
• 0
• h
• 
• W
• 
• (
• z
• )
• p
• 
• 
• z
• 
• 
• n
• b
• =
• 1
• h
• 
• ∫
• 0
• h
• 
• (
• ∑
• 1
• 
• ni
• 2
• ·
• Wi
• W
• 
• (
• z
• )
• )
• )
• 0.5
• 
• 
• z
• ,
• 
• W
• 
• (
• z
• )
• =
• ∑
• i
• 
• W
• i
• 
• (
• z
• )
• where W(z) represents a grating width of the grating portion of the metal grating occupying in the grating period P at a grating height z, and ni and Wi respectively represent a refractive index and a grating width of an i-th dielectric material.