The working principle of an optical isolator made of two corrugated dielectric gratings is introduced. One grating acts as a polarizer, and the other acts as a quarter-wave plate used in conical incidence converting linearly polarized light into circularly polarized light. Global maxima of diffraction efficiency for surface-corrugated gratings with binary, sinusoidal, and pyramidal ridge shapes with dependence on the material index are identified. Regarding technological feasibility for use in the visible wavelength range, high-frequency gratings with a binary shape were realized. With these gratings, an extinction ratio of more than 40 dB for the polarizer is theoretically possible, and more than 20 dB was experimentally achieved. A good correlation between theoretically calculated efficiencies and birefringences based on rigorous methods and the experimental results is demonstrated.
© 2002 Optical Society of America
(050.0050) Diffraction and gratings : Diffraction and gratings
(050.1950) Diffraction and gratings : Diffraction gratings
(230.1360) Optical devices : Beam splitters
(260.1440) Physical optics : Birefringence
(260.5430) Physical optics : Polarization
Tilman Glaser, Siegmund Schröter, Hartmut Bartelt, Hans-Jörg Fuchs, and Ernst-Bernhard Kley, "Diffractive Optical Isolator made of High-Efficiency Dielectric Gratings Only," Appl. Opt. 41, 3558-3566 (2002)