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 various embodiments, the beam parameter product and/or numerical aperture of a laser beam is adjusted utilizing a step-clad optical fiber having a central core, a first cladding, an annular core, and a second cladding.

After a step of etching a core layer, a lower cladding layer, and a substrate so that a recessed opening including one end of an optical waveguide is formed relative to a multilayer board and a step of forming mask layers on a top surface of the substrate including the opening, in a step, crystal is grown with respect to the mask layers in the opening, and a tilt surface to be used as the monolithic mirror is formed. An upper cladding layer is formed covering the core layer at the same time. Then, formation of an optical waveguide pattern, formation of the optical waveguide and an end surface of the optical waveguide, formation of a dielectric film for preventing reflection, and formation of a metal film on a surface of the tilt surface are executed.

A photonic structure can include in one aspect one or more waveguides formed by patterning of waveguiding material adapted to propagate light energy. Such waveguiding material may include one or more of silicon (single-, poly-, or non-crystalline) and silicon nitride.

An optical circuit includes one or more input waveguides, a plurality of output waveguides, and a reflector structure. At least a portion of the reflector structure forms an interface with the one or more input waveguides. The portion of the reflector structure has a smaller refractive index than the one or more input waveguides. An electrical circuit is electrically coupled to the optical circuit. The electrical circuit generates and sends different electrical signals to the reflector structure. In response to the reflector structure receiving the different electrical signals, a carrier concentration level at or near the interface or a temperature at or near the interface changes, such that incident radiation received from the one or more input waveguides is tunably reflected by the reflector structure into a targeted output waveguide of the plurality of output waveguides.

Embodiments may include or relate to an optical coupler. The optical coupler may include a silicon nitride (SiN) waveguide. The waveguide may be formed by placing SiN on an epitaxially grown silicon structure that is then removed subsequent to placement of the SiN. Other embodiments may be described and/or claimed.

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 technology is described for a Photonic Integrated Circuit (PIC) radio frequency (RF) oscillator. The PIC RF oscillator can comprise an optical gain media coupled to a first mirror and configured to be coupled to the PIC. The PIC can comprise a first optical cavity located within the PIC, a tunable mirror to form a first optical path between the first mirror in the gain media and the first tunable mirror, and a frequency tunable intra-cavity dual tone resonator positioned within the first optical cavity to constrain the first optical cavity having a common optical path to produce tow primary laser tones with a tunable frequency spacing. A photo detector is optically coupled to the PIC and configured to mix the two primary laser tones to form an RF output signal with a frequency selected by the tunable frequency spacing of the two primary tones.

Optical beam forming at the inputs/outputs of a photonic chip and to the spectral broadening of the light coupled to the chip. The photonic chip comprises an optical waveguide layer supported on a substrate. The chip includes an optical waveguide structure made of silicon and a coupling surface grating. The photonic chip has a front face on the side facing the coupling surface grating and a rear face on the side facing the substrate. A reflecting collimation structure is integrated in the rear face to modify the mode size of an incident light beam. The coupling surface grating is designed to receive light from the optical waveguide structure and to form a light beam directed to the reflecting collimation structure. The invention further relates to the method for producing such a chip.

One example system comprises a light source configured to emit light. The system also comprises a waveguide configured to guide the emitted light from a first end of the waveguide toward a second end of the waveguide. The waveguide has an output surface between the first end and the second end. The system also comprises a plurality of mirrors including a first mirror and a second mirror. The first mirror reflects a first portion of the light toward the output surface. The second mirror reflects a second portion of the light toward the output surface. The first portion propagates out of the output surface toward a scene as a first transmitted light beam. The second portion propagates out of the output surface toward the scene as a second transmitted light beam.