Patent ID: 8238025

Claim:
A polarizing mirror device comprising: an optical substrate of refractive index real part n s ; a dielectric multilayer mirror composed of layers of high and low refractive index n h and n l ,; and a grating layer arranged at the side of a cover medium and defining a corrugated grating of local period Λ, wherein said local period Λ is selected such that upon substantially normal incidence of an incident wave, at a wavelength λ in the laser range, from the cover medium there is no diffraction order other than the 0 th reflected order in this cover medium, such that the field of the +1 st and −1 st orders diffracted into the layers of said multilayer and into the optical substrate have a non-evanescent propagating character, and such that the respective angles θ 1h and θ 1l , under which the +1 st and −1 st orders propagate in any layer of said multilayer have an absolute value, arc sin(λ/n l ·Λ) in the layers of low index and arc sin(λ/n h ·Λ) in the layers of high index, which is larger than or equal to the angle corresponding to the angular band edge of the central TM reflection band and, if a central TE reflexion band of finite angular width exists, smaller than the angle corresponding to the angular band edge of this central TE reflection band in the angular reflexion spectrum of the multilayer at the wavelength λ.