Structures for a wavelength division multiplexing filter and methods of fabricating a structure for a wavelength division multiplexing filter. The structure includes a first waveguide core having a first section and a second section. The first section and the second section have a first notched sidewall and a second notched sidewall opposite to the first notched sidewall. The structure further includes a second waveguide core positioned with a first offset in a first direction relative to the first section and the second section of the first waveguide core and with a second offset in a second direction relative to the first section and the second section of the first waveguide core. The second direction is transverse to the first direction.

Disclosed is a plasmonic device (10), comprising: a substrate (11); and a dielectric layer (13) arranged between a base metal layer (12) and a structured metal layer (14) which form with respect to the substrate (11) a vertical stack of layers, wherein the structured metal layer (14) includes arranged in a horizontal direction an input structure (141) for enabling an input section (21), a waveguide structure (142) for enabling a plasmonic waveguide (22), and an output structure (143) for enabling an output section (23), wherein the input section (21) is configured to receive an optical input signal (31) and transmit input power (41) to the plasmonic waveguide (22), wherein the plasmonic waveguide (22) is configured to receive input power (41) from the input section (21) and transmit output power (43) to the output section (23), and wherein the output section (23) is configured to receive output power (43) from the plasmonic waveguide (22) and transmit an optical output signal (33).

Disclosed is a plasmonic device (10), comprising: a substrate (11); and a dielectric layer (13) arranged between a base metal layer (12) and a structured metal layer (14) which form with respect to the substrate (11) a vertical stack of layers, wherein the structured metal layer (14) includes arranged in a horizontal direction an input structure (141) for enabling an input section (21), a waveguide structure (142) for enabling a plasmonic waveguide (22), and an output structure (143) for enabling an output section (23), wherein the input section (21) is configured to receive an optical input signal (31) and transmit input power (41) to the plasmonic waveguide (22), wherein the plasmonic waveguide (22) is configured to receive input power (41) from the input section (21) and transmit output power (43) to the output section (23), and wherein the output section (23) is configured to receive output power (43) from the plasmonic waveguide (22) and transmit an optical output signal (33).

Disclosed are apparatus and methods for optical coupling in optical communications. In one embodiment, an apparatus for optical coupling is disclosed. The apparatus includes: a planar layer; an array of scattering elements arranged in the planar layer at a plurality of intersections of a first set of concentric elliptical curves crossing with a second set of concentric elliptical curves rotated proximately 90 degrees to form a two-dimensional (2D) grating; a first taper structure formed in the planar layer connecting a first convex side of the 2D grating to a first waveguide; and a second taper structure formed in the planar layer connecting a second convex side of the 2D grating to a second waveguide. Each scattering element is a pillar into the planar layer. The pillar has a top surface whose shape is a concave polygon having at least 6 corners.

An optical circuit inspection probe includes a piezoelectric element and a gel-like medium layer provided at an end of the piezoelectric element to absorb light and convert the light into a sound wave. The piezoelectric element may be formed of piezoelectric ceramics such as Pb (Zr.Math.Ti)O.sub.3 (PZT). The piezoelectric element has, for example, a cylindrical shape. The medium layer is formed of a hydrogel. The hydrogel may include, for example, polydimethylsiloxane (PDMS). Further, the medium layer may contain carbon.

An apparatus comprises: a photonic integrated circuit comprising an optical phased array, a first focusing element at a fixed position relative to the optical phased array and configured to couple an optical beam to or from the optical phased array, and a second focusing element at a fixed position relative to the first focusing element and configured to couple the optical beam to or from the first focusing element. At least one of the first or second focusing element is externally coupled to the photonic integrated circuit, and the first and second focusing elements have different effective focal lengths.

An apparatus comprises: a photonic integrated circuit comprising an optical phased array, a first focusing element at a fixed position relative to the optical phased array and configured to couple an optical beam to or from the optical phased array, and a second focusing element at a fixed position relative to the first focusing element and configured to couple the optical beam to or from the first focusing element. At least one of the first or second focusing element is externally coupled to the photonic integrated circuit, and the first and second focusing elements have different effective focal lengths.

Embodiments of the present disclosure describe waveguides having device structures with multiple portions and methods of forming the waveguide having multiportion device structures. The plurality of device structures are formed having two or more portions. The materials of the plurality of portions are chosen such that impedance matching is enabled between the portions to reduce reflection of light from the optical device.

A method for forming a device structure is disclosed. The method of forming a device structure includes forming a variable-depth structure in a device material layer using a laser ablation. A plurality of device structures is formed in the variable-depth structure to define slanted device structures therein. The variable-depth structure and the slanted device structures are formed using an etch process.

An optical structure includes a grating coupler and a microlens. The grating coupler is configured to receive a laser light. The microlens is above the grating coupler, in which a metal shielding covers the microlens and has an opening to allow the laser light entering an effective coupling region of the grating coupler.