An optical waveguide (100) is disclosed, for guiding light in a photonic circuit comprising a layer of phase change material (101) for modulating the phase of the guided light. The phase change material (101) is switchable between at least a stable crystalline state and a stable amorphous state each with different refractive indexes. The phase change material (101) exhibits an extinction coefficient of less than 0.1 in both states for wavelengths greater than 1000 nm.

A lightguide optical element (LOE) configured for polarization scrambling is provided. The LOE includes a transparent substrate having a first refractive index, the substrate having a pair of parallel external surfaces configured to propagate light within the LOE through total internal reflection (TIR), and a plurality of mutually parallel partially reflective internal surfaces, those being non-parallel to the pair of parallel external surfaces and configured to couple out said light to a viewer. The LOE further includes a first coating on at least one external surface of the substrate, the first coating being of a coating material having a second refractive index higher than the first refractive index; The LOE further includes an antireflective (AR) coating on at least one external surface of the substrate over the first coating.

A bricked sub-wavelength periodic waveguide and a modal adapter, power divider and polarization splitter that use the waveguide. The waveguide includes blocks disposed periodically with a period “L.sub.z” on a substrate and which alternate with a covering material. The first blocks have a width “a.sub.x” and the second blocks have a width “b.sub.x”, alternating on the substrate according to a period “L.sub.x”, the second blocks being shifted a distance “d.sub.z” the first blocks in the direction of propagation. A modal adapter, a power divider and a polarization splitter all use the periodic waveguide and can operate with larger wave periods without leaving the sub-wavelength regime.

A thin-profile light source capable of providing polychromatic collimated light is disclosed. A waveguide propagates light along an optical path in the waveguide core. A top cladding of the waveguide is thinned so as to have a tail of the light mode propagating in the waveguide reach the end of the top cladding. A light extracting element is coupled to the top cladding. Light leaks out of the top cladding evanescently at an angle defined by a ratio of the refractive index of the light extracting element to an effective refractive index for the light mode propagating in the waveguide.

A lightguide optical element (LOE) configured for polarization scrambling is provided. The LOE includes a transparent substrate having a first refractive index, the substrate having a pair of parallel external surfaces configured to propagate light within the LOE through total internal reflection (TIR), and a plurality of mutually parallel partially reflective internal surfaces, those being non-parallel to the pair of parallel external surfaces and configured to couple out said light to a viewer. The LOE further includes a first coating on at least one external surface of the substrate, the first coating being of a coating material having a second refractive index higher than the first refractive index; The LOE further includes an antireflective (AR) coating on at least one external surface of the substrate over the first coating.

A polarization rotator structure includes: a first core structure formed at a first layer, extending from the first end to a second end, and a second core structure formed at a second layer that is at a different depth than the first layer and formed in proximity to the first core structure. The first core structure and the second core structure provide mode hybridization between at least two orthogonally polarized waveguide modes of the PRS. An optical splitter structure is optically coupled at a first end to the second end of the PRS, and optically coupled at a second end to at least two optical waveguides, and includes: a first core structure that is contiguous with at least one of the first or second core structures of the PRS, and a second core structure that is separate from both of the first and second core structures of the PRS.

A polarization rotator structure includes: a first core structure formed at a first layer, extending from the first end to a second end, and a second core structure formed at a second layer that is at a different depth than the first layer and formed in proximity to the first core structure. The first core structure and the second core structure provide mode hybridization between at least two orthogonally polarized waveguide modes of the PRS. An optical splitter structure is optically coupled at a first end to the second end of the PRS, and optically coupled at a second end to at least two optical waveguides, and includes: a first core structure that is contiguous with at least one of the first or second core structures of the PRS, and a second core structure that is separate from both of the first and second core structures of the PRS.

A polarization rotator structure includes: a first core structure formed at a first layer, extending from the first end to a second end, and a second core structure formed at a second layer that is at a different depth than the first layer and formed in proximity to the first core structure. The first core structure and the second core structure provide mode hybridization between at least two orthogonally polarized waveguide modes of the PRS. An optical splitter structure is optically coupled at a first end to the second end of the PRS, and optically coupled at a second end to at least two optical waveguides, and includes: a first core structure that is contiguous with at least one of the first or second core structures of the PRS, and a second core structure that is separate from both of the first and second core structures of the PRS.

Structures for a polarizer and methods of fabricating a structure for a polarizer. A first waveguide core includes a section and a taper connected to the section. A second waveguide core is laterally positioned adjacent to the taper of the first waveguide core. An absorber is connected to the section of the first waveguide core. The absorber is composed of germanium.

Structures for a polarizer and methods of fabricating a structure for a polarizer. A first waveguide core includes a section and a taper connected to the section. A second waveguide core is laterally positioned adjacent to the taper of the first waveguide core. An absorber is connected to the section of the first waveguide core. The absorber is composed of germanium.