Methods and apparatus for etching a wafer. The wafer is positioned adjacent to a cathode within a vacuum chamber. The wafer includes a first layer stack, where the first layer stack includes a crystalline composition of a first element and a second element different from the first element. The crystalline composition may be BaTiO3 (BTO). A gas is received that includes a first partial gas and a second partial gas. The first and second partial gases may be HBr and Cl2, respectively. The gas is ionized, and the wafer is chemically etched by bombarding the layer stack with the ionized gas. The chemical etching includes reacting the first partial gas with the first element and reacting the second partial gas with the second element.

A optical device including: a substrate; an optical waveguide formed at the substrate; and a protective layer formed adjacent to the optical waveguide, wherein the optical waveguide includes multiple side surfaces that intersect the substrate, at least one side surface of the optical waveguide is provided with a rough surface. According to the optical device, the light propagation loss can be reduced.

Embodiments of the disclosure provide an optical antenna for a photonic integrated circuit (PIC). The optical antenna includes a semiconductor waveguide on a semiconductor layer. The semiconductor waveguide includes a first vertical sidewall over the semiconductor layer over the semiconductor layer. A plurality of grating protrusions extends horizontally from the first vertical sidewall of the semiconductor waveguide.

Examples described herein relate to an optical device with an integrated light-emitting structure to generate light and a waveguide integrated capacitor to monitor light. The light-emitting structure may emit light upon the application of electricity to the optical device. The waveguide integrated capacitor may be formed under the light-emitting structure to monitor the light emitted by the light-emitting structure. The waveguide integrated capacitor includes a waveguide region carrying at least a portion of the light. The waveguide region includes one or more photon absorption sites causing the generation of free charge carriers relative to an intensity of the light confined in the waveguide region resulting in a change in the conductance of the waveguide region.

A silicon-photonic optical modulator includes at least one optical input and at least one optical waveguide that is connected to the at least one optical input. The at least one optical waveguide is configured to propagate quasi-transverse-magnetic (quasi-TM) polarized light, where each of the at least one optical waveguide is configured as a rib waveguide that includes a rib arranged on a slab. The silicon-photonic optical modulator also includes at least one electrode configured to apply at least one electric field to the quasi-TM polarized light in the at least one optical waveguide. In some implementations, a height of the rib waveguide is greater than 0.85 λ/n, where A is a free-space wavelength of light and n is a refractive index of silicon in the silicon-photonic optical modulator, and a width of the rib waveguide is greater than a thickness of the slab.

Structures for a polarization rotator and methods of fabricating a structure for a polarization rotator. The structure includes a substrate, a first waveguide core over the substrate, and a second waveguide core over the substrate. The second waveguide core is positioned proximate to the section of the first waveguide core. The second waveguide core is comprised of a material having a refractive index that is reversibly variable in response to a stimulus.

Apparatus, sensor chips and techniques for optical sensing of substances by using optical sensors on sensor chips.

A disclosed optical device includes a first waveguide disposed between a branching portion and a multiplexing portion on a semiconductor substrate, and a second waveguide disposed between the branching portion and the multiplexing portion, the second waveguide being longer than the first waveguide. In the optical device, an optical confinement effect of the first waveguide is greater than an optical confinement effect of the second waveguide, the first waveguide has a curvature with a first curvature radius (Rs), the second waveguide has a curvature with a second curvature radius (Rl), and the first curvature radius is smaller than the second curvature radius.

Embodiments of the present disclosure provide etch-variation tolerant optical coupling components and processes for making the same. An etch-variation tolerant geometry is determined for at least one waveguide of an optical coupling component (e.g., a directional coupler). The geometry is optimized such that each fabricated instance of an optical component design with the etch-variation tolerant geometry has substantially the same coupling ratio at any etch depth between a shallow etch depth and a deep etch depth.

A single mode waveguide with a straight portion and a curved portion, the curved portion having the shape of an adiabatic bend. The single mode waveguide has a curved portion that is shaped according to an adiabatic bend, with a curvature that varies continuously, and that vanishes at a point at which the curved portion is contiguous with a straight portion of the waveguide. The absence of curvature discontinuities avoids the coupling, within the waveguide, of optical power from a fundamental mode into a higher order mode and the curvature of the curved portion results in attenuation of optical power, in higher order modes, that may be coupled into the waveguide at either end.