Revital Shechter

Compact beam expander with linear gratings

Novel compact beam expanders that could be useful for applications such as providing light to flat panel displays are presented. They are based on a planar configuration in which three spatially linear gratings are recorded on one transparent substrate, so as to expand a narrow incoming beam in two dimensions. We present the design and recording procedures along with results, showing a relatively uniform intensity of the wide output beam. Such expanders can serve for illuminating flat panel displays.

Achromatic phase retarder by slanted illumination of a dielectric grating with period comparable with the wavelength

We discuss some properties of dielectric gratings with period comparable with the illuminating wavelength for slanted illumination (this illumination geometry is often referred to as concical mounting). We demonstrate the usefulness of such an illuminating geometry. We show that the threshold period (under which only the zeroth transmission and reflection orders are nonevanescent) can be significantly higher, thereby easing fabrication constraints, and that this illumination setup makes it possible to design achromatic phase retarders. Such a design, for an achromatic quarter-wave plate with lambda/60 uniformity of the retardation phase in the 0.47-0.63-mum wavelength interval, is demonstrated.

Planar holographic elements with uniform diffraction efficiency

A planar holographic lens is investigated for imaging applications. The design and recording of the holographic lens are based on a transference of wavefronts method, where a desired grating function, with low aberrations, is transferred from a thin hologram to one recorded in thick recording materials. The resulting thick planar holographic lens fulfills the Bragg condition over a relatively large field of view. Experimental results, presented for planar holographic lenses recorded in photopolymers and dichromated gelatin materials, show that a high diffraction efficiency greater than 50% and uniform over a field of view of 16° can be obtained.

Concentration of diffuse light at the thermodynamic limit with an aplanatic curved diffractive element

A novel configuration for concentrating diffuse, based on a reflective curved diffractive element, is proposed and demonstrated. Such an aplanatic element satisfies the Abbe sine condition, and hence can achieve diffuse light concentration close to the thermodynamic limit. In our experiments, a thin, cylindrically shaped diffractive element with a numerical aperture of 0.86 yielded a one-dimensional concentration ratio that was 80% of the thermodynamic limit.

Compact red-green-blue beam illuminator and expander

A compact multicolor beam illuminator and a compact multicolor beam expander are presented. The illuminator performs the dual task of demultiplexing a narrow red-green-blue (RGB) input beam into three separate beams, each of a different color, and expanding them to yield three separate magnified plane waves. The beam expander expands a narrow RGB input beam into a single magnified RGB plane wave. The design and recording procedures, along with experimental results for a beam illuminator and a beam expander with a magnification of approximately 3, are presented.

Planar Diffractive Elements for Compact Optics

Research in planar optics aims to develop a technology for designing and constructing compact optical systems. The basic planar multi-grating configuration is composed of cascaded gratings recorded on a single substrate. The first grating diffracts the incident light from the source so that it will be trapped inside the substrate by total internal reflection, while the last grating in the cascade diffracts the light out of the substrate to a detector (or into the eye of a viewer). The planar optical configurations are usually much more compact, more mechanically stable, less sensitive to illumination wavelength and more suitable for mass production than systems using free space optics. An example illustrating a planar optics configuration for head mounted display is presented.

Planar holographic configuration for efficient imaging

Abstract A planar holographic configuration that can be exploited for imaging with high light throughput efficiency is presented. The configuration is comprised of two elements — a linear grating and a corrected holographic lens. The design and recording of the holographic lens are based on a technique, where a desired-grating function, with low aberrations, is transferred from a thin hologram to on recorded in thick recording materials, so the Bragg condition is fulfilled over a broad range of incidence angles. As a result, it is possible to get a halographic lens having low aberrations and uniform high diffraction efficiency over a relatively large field of view. When combined with the linear grating, the overall planar optics configuration can be exploited for imaging information displayed with quasi monochromatic light source, as in a visor display application. Such a configuration was designed, recorded and evaluated experimentally, demonstrating a uniform, and relatively high diffraction efficiency over a field of view of 16 degrees.

Hybrid polymer-on-glass integrated optical diffractive structures for wavelength discrimination

Abstract We present novel compact planar configurations for wavelength discrimination. These configurations include multiple diffractive optical elements (DOEs) that are recorded in very thick photopolymer layers that are coated on one planar transparent substrate. The design, material parameters, recording procedures and experimental results for configurations are presented. For a configuration that was designed to discriminate three closely separated wavelengths, the results reveal that the wavelength separation could be as low as 3 nm at an operating wavelength of 1567 nm, for 80 μm thick photopolymer layers. The crosstalk between adjacent wavelengths was less than 2% for one DOE that is comprised of three sub-DOEs, each designed for a different wavelength.

Compact wavelength division multiplexers and demultiplexers

Novel compact devices for wavelength division multiplexing and demultiplexing are presented. These devices are based on planar optics configurations. A method for designing and recording such planar devices is described. Experimental procedures and results for devices that can handle three closely separated wavelengths in the visible as well as near infrared radiation are presented.

Planar diffractive elements as Bragg volume holograms versus surface relief gratings

A method for designing and fabricating optical systems based on planar holographic optics is presented. The planar optical system is usually composed of two (or more) holographic optical elements which are fabricated onto the same substrate. This paper compares and contrasts the two principal fabrication methods of holographic elements as Bragg volume holograms or as surface relief gratings. Various examples of planar holographic optical systems are presented, and their advantages over regular optical systems are illustrated.