A diffractive optical waveguide and a display apparatus are disclosed. A coupling-out grating includes a first grating having a first, second, and third grating vectors, directions of the second and third grating vectors, being respectively towards both sides of a direction of first grating vector, form acute angles with it, a cross-section profile of an optical unit structure of the first grating has a first, second, third, and fourth vertices, a straight line passing through the first and second vertices and a straight line passing through the third and fourth vertices are perpendicular to the direction, a straight line passing through the first and fourth vertices and a straight line passing through the second and third vertices respectively form angles ?.sub.1 and ?.sub.2 having a same sign with the direction, wherein 15??|?.sub.1|?45? and 15??|?.sub.2|?45?.

A semiconductor structure includes a substrate, a grating coupler structure over the substrate, a multi-layers film structure over the grating coupler structure. The multi-layers film structure include a first layer including a first refractive index, a second layer over the first layer and including a second refractive index and a third layer over the second layer and including a third refractive index. The second refractive index is greater than the first refractive index and is greater than the third refractive index of the third layer, and a thickness of each layer of the multi-layers film structure is within a range from /4 to 2, is a wavelength of light.

A semiconductor structure includes a substrate, a grating coupler structure over the substrate, a multi-layers film structure over the grating coupler structure. The multi-layers film structure include a first layer including a first refractive index, a second layer over the first layer and including a second refractive index and a third layer over the second layer and including a third refractive index. The second refractive index is greater than the first refractive index and is greater than the third refractive index of the third layer, and a thickness of each layer of the multi-layers film structure is within a range from /4 to 2, is a wavelength of light.

An optical coupling device includes a first waveguide layer, including a first semiconductor material, which is disposed over a dielectric substrate layer. A dielectric intermediate layer overlies the first waveguide layer. A second waveguide layer, which includes a different, second semiconductor material, is disposed over the dielectric intermediate layer and is patterned to define a waveguide. A first grating in the second waveguide layer diffracts light of a given wavelength from the waveguide into a specified diffraction order at a given coupling angle, whereby a first fraction of the light propagates out of the device while a second fraction of the light is diffracted into the intermediate dielectric layer in a conjugate diffraction order. A second grating in the first waveguide layer diffracts the second fraction of the light into a second diffraction order, propagating out of the device at the given coupling angle.

A structure includes a dielectric waveguide, and at least one grating coupler adjacent the dielectric waveguide. Each grating coupler includes a set of parallel optofluidic grating channels oriented orthogonally to the dielectric waveguide. The structure may also include a radiation source operatively coupled to the dielectric waveguide, and an optical receiver such as a photosensor adjacent the grating coupler(s). The structure may be used as part of an optofluidic sensor system for, for example, biochemical applications.

There is provided an exit pupil expander (EPE) for use in a diffractive display, the EPE comprising a plurality of diffractive zones on a waveguide and a plurality of non-diffractive zones between at least some of the diffractive zones.

There is provided an exit pupil expander (EPE) for use in a diffractive display, the EPE comprising a plurality of diffractive zones on a waveguide and a plurality of non-diffractive zones between at least some of the diffractive zones.

With a wavelength conversion device based on a nonlinear optical effect, when arrayed waveguides including an intended nonlinear waveguide are fabricated, unwanted slab waveguides are inevitably formed. The slab waveguides can cause an erroneous measurement in the selection of a waveguide having desired characteristics from the arrayed waveguides. The erroneous measurement can lead to redoing steps for fabricating the wavelength conversion device and a decrease in the yield and inhibit the evaluation of the characteristics in selection of the waveguide and the subsequent fabrication of the wavelength conversion device from being efficiently performed. A wavelength conversion device according to the present invention includes a plurality of waveguides formed on a substrate, and a plurality of slab waveguides that are arranged substantially in parallel with and spaced apart from the plurality of waveguides, and each of the slab waveguides has a grating structure that reflects light of a particular wavelength.

Provided is an optical densitometer for measuring a density of a gas or liquid of interest, the optical densitometer comprising: a light source capable of introducing light into a core layer; a detector capable of receiving the light that has propagated through the core layer; and an optical waveguide, the optical waveguide comprising: a substrate; and the core layer comprising a light propagation portion capable of propagating the light in an extending direction of the light propagation portion, and a diffraction grating portion, the diffraction grating portion comprising a diffraction grating region and an extension region connected to the diffraction grating region, and a first optical coupling region included in the extension region and a second optical coupling region included in the light propagation portion being optically coupled with respect to the light propagating through the core layer.

Provided is an optical densitometer for measuring a density of a gas or liquid of interest, the optical densitometer comprising: a light source capable of introducing light into a core layer; a detector capable of receiving the light that has propagated through the core layer; and an optical waveguide, the optical waveguide comprising: a substrate; and the core layer comprising a light propagation portion capable of propagating the light in an extending direction of the light propagation portion, and a diffraction grating portion, the diffraction grating portion comprising a diffraction grating region and an extension region connected to the diffraction grating region, and a first optical coupling region included in the extension region and a second optical coupling region included in the light propagation portion being optically coupled with respect to the light propagating through the core layer.