Structures for a coupler and methods of forming a structure for a coupler. A structure for a directional coupler may include a first waveguide core having one or more first airgaps and a second waveguide core including one or more second airgaps. The one or more second airgaps are positioned in the second waveguide core adjacent to the one or more first airgaps in the first waveguide core. A structure for an edge coupler is also provided in which the waveguide core of the edge coupler includes one or more airgaps.

A three-dimensional photonic integrated structure includes a first semiconductor substrate and a second semiconductor substrate. The first substrate incorporates a first waveguide and the second semiconductor substrate incorporates a second waveguide. An intermediate region located between the two substrates is formed by a one dielectric layer. The second substrate further includes an optical coupler configured for receiving a light signal. The first substrate and dielectric layer form a reflective element located below and opposite the grating coupler in order to reflect at least one part of the light signal.

In some implementations, a Mach-Zehnder interferometer (MZI) includes a delay line arm formed in a chip and a mirrored facet formed in the chip. The delay line arm may be configured to propagate light to the mirrored facet. The mirrored facet may be configured to reflect, to the delay line arm, a percentage of the light propagated to the mirrored facet by the delay line arm.

One example system comprises a plurality of substrates disposed in an overlapping arrangement. The plurality of substrates includes at least a first substrate and a second substrate. The system also comprises a first waveguide disposed on the first substrate to define a first optical path on the first substrate. The first waveguide is configured to guide light along the first optical path and to transmit, at an output section of the first waveguide, the light out of the first waveguide toward the second substrate. The system also comprises a second waveguide disposed on the second substrate to define a second optical path on the second substrate. An input section of the second waveguide is aligned with the output section of the first waveguide to receive the light transmitted by the first waveguide. The second waveguide is configured to guide the light along the second optical path.

A digital measuring device implemented on a photonic integrated circuit, the digital measuring device including a laser source implemented on the photonic integrated circuit configured to provide light, a first waveguide structure implemented on the photonic integrated circuit configured to direct a first portion of light from the laser source at a moving object and receive light reflected from the moving object, a second waveguide structure implemented on the photonic integrated circuit configured to combine a second portion of light from the laser source with the light reflected from the moving object to produce a measurement beam, a first multiplexer implemented on the photonic integrated circuit configured to split the measurement beam into a plurality of channels, and a plurality of detectors implemented on the photonic integrated circuit configured to detect an intensity value of each channel to measure a distance between the digital measuring device and the moving object.

The present disclosure provides for periscope optical assemblies within interposers that include a bulk material having a first side and a second side opposite to the first side; a first optic defined in the bulk material at a first height in the bulk material along an axis extending between the first second sides; a second optic defined in the bulk material at a second height in the bulk material, different than the first height, along the axis; a first waveguide defined in the bulk material, extending from the first side to the first optic; a second waveguide defined in the bulk material, extending from the second optic to the second side; and a third waveguide defined in the bulk material, extending from the first optic to the second optic.

An optical device includes a first substrate having a first surface, a second substrate having a second surface, at least one optical waveguide, and a plurality of spacers, disposed on at least either the first surface or the second surface, that include a first portion and a second portion. The first portion of the plurality of elastic spacers is at least one elastic spacer located in a region between the first substrate and the second substrate in which the first substrate and the second substrate overlap each other as seen from an angle parallel with a direction perpendicular to the first surface. The second portion of the plurality of elastic spacers is at least one elastic spacer located in a region in which the first substrate and the second substrate do not overlap each other as seen from an angle parallel with the direction perpendicular to the first surface.

Disclosed is a method for fabricating a spherical concave mirror in an optical waveguide based on ultraviolet (UV) grayscale lithography. A key component is a specially designed mask pattern composed of a rectangle as well as a semicircle adjacent to the rectangle, where a rectangular area has no grayscale distribution, and UV light penetrating through different portions of the rectangular area has the same intensity; a semicircular area has the grayscale distribution, and the UV light penetrating through the semicircular area with the grayscale distribution is changed in intensity from the center of a circle in the radius direction according to a special function distribution law; an interlayer photoresist in the rectangular area is irradiated by the UV light penetrating through a mask plate and is developed to form an optical waveguide core.

Various embodiments of a photodetector having a reflector are described. The photodetector includes a waveguide layer disposed on top of a substrate, an avalanche multiplication detection region disposed on top of the waveguide layer, and a reflector disposed adjacent to a rear surface of the waveguide layer. The waveguide layer includes a narrower input section and a wider detection section concatenated with the input section. The waveguide layer may also include a tapering section having a changing width that follows the detection section. The reflector may be a one-dimensional photonic crystal, a two-dimensional photonic crystal, or a bulk material. A careful design of the reflector and the waveguide layer of the photodetector is helpful in achieving a high responsivity and a high operation speed at the same time.

Integrated-optics systems are presented in which an active-material stack is disposed on a coupling layer in a first region to collectively define an OA waveguide that supports an optical mode of a light signal. The coupling layer is patterned to define a coupling waveguide and a passive waveguide, which are formed as two abutting, optically coupled segments of the coupling layer. The lateral dimensions of the active-material stack are configured to control the shape and vertical position of the optical mode at any location along the length of the OA waveguide. The active-material stack includes a taper that narrows along its length such that the optical mode is located completely in the coupling waveguide where the coupling waveguide abuts the passive waveguide. In some embodiments, the passive layer is optically coupled with the OA waveguide and a silicon waveguide, thereby enabling light to propagate between them.