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Subwavelength metallic and dielectric diffraction gratings which rotate the linear polarization of incident light by 90[degrees] are examined. Using rigorous diffraction theory in total-internal-reflection configuration, it is shown that full conversion from incident transverse electric field to transverse magnetic zero-order field can be achieved with both dielectric and metallic elements, but dielectric gratings provide higher efficiency and are thus preferable. The fabrication aspects and constraints are discussed in detail and the behavior of the gratings over broad wavelength bands is presented. OCIS codes: 230.1950, 260.2110, 260.5430.

Radial diffractive gratings are used to couple light of a white LED into a light guide. Theoretical coupling efficiencies are evaluated with rigorous diffraction theory in a pure conical mounting. It is shown that when the refractive index of the grating increases from 1.46 to 2.05 the incoupling efficiency increases from 42% to 63%. Also, with the increasing refractive index the incoupling efficiency is shown to become more nearly uniform over the visible spectrum. Experimental results for the incoupled efficiencies and the color coordinates of the incoupled spectra are introduced for refractive indices n = 1.46 and n = 1.56. OCIS codes: 230.0230, 230.1950, 230.7400, 050.1970.

Ring-shaped and radial diffractive gratings are designed with rigorous diffraction theory to couple light of a nearly monochromatic LED into a thin planar light guide on the bottom side. The theoretical coupling efficiencies for ring-shaped and radial gratings are 41% and 66%, respectively. Optimized diffractive elements are manufactured with direct electron-beam lithography and reactive-ion-etching into Si[O.sub.2] substrates. Good agreement between experimental and theoretical results for selected radial gratings is reached. Furthermore, the mass production tests using injection molding are carried out with good replicability. OCIS codes: 050.1970, 230.1950, 230.7400.

Subwavelength dielectric gratings are examined in total-internal-reflection configuration. It is demonstrated experimentally that such elements, fabricated in TiO2, can perform full polarization conversion from incident TE to TM with nearly 100% efficiency. The dependence of the polarization conversion on the angle of incidence is analyzed. Rigorous diffraction theory is used to cross check the experimental results.

A LCD backlighting device that uses a diffractive light extractor has been developed for applications in which pointlike light sources are employed. The novel system eliminates the images of light sources, which appear as bright lines emanating from each source in the conventional diffractive approach. In addition, the system illuminates the LCD uniformly: Modulation of the diffractive structure as a function of position is used to control the output field of this extended planar light source. [C] 2001 Optical Society of America OCIS codes: 050.1970, 220.4000, 230.7390.

Asymmetric transmission gratings operating in the resonance domain are designed by modeling of the dose-controlled electron-beam lithography process with Gaussian convolution. We aim to exceed some efficiency limit [[Eta].sub.s] over a specified spectral range and to maximize [[Eta].sub.s]. The resultant continuous-profile gratings are fabricated by electron-beam lithography and proportional reactive-ion etching into Si[O.sub.2]. We demonstrate gratings with good signal-to-noise ratio and a diffraction efficiency greater than 40% for wavelengths from 400 to 750 nm. OCIS codes: 090.1970, 050.1950, 220.3740.

We report a physical mechanism leading to high phase retardation in slanted photonic nanostructures. The phenomenon is based on the waveguiding of the transverse electric polarization component inside the slanted pillars, while the transverse magnetic component is not guided. Such a mechanism leads to very high phase retardation even with shallow structures that are suitable also for lithographical mass production. We present physical principle, numerical analysis of the phenomenon and designs for half-wave retarders. As an experimental result, a slanted grating producing 177 degrees retardation and 95.5% efficiency is presented.