An optical assembly for realizing horizontal and vertical spot-size conversion to couple light from a thin waveguide to a thick waveguide is disclosed. The assembly comprises at least one first thin waveguide with a first section having a first optical mode field and a horizontal spot-size expansion section providing spot-size conversion for a first horizontal dimension of said first optical mode field of a light beam propagating in said first waveguide, and at least one second thick waveguide with a second section having a second optical mode field and a horizontal spot-size reduction section providing spot-size conversion for a second horizontal dimension of said second optical mode field of a light beam propagating in said second waveguide. The expanded end of said first waveguide is aligned and rotated to interface with the reduced end of said second waveguide, so that the mode fields in said first and second waveguides are rotated 90 degrees with respect to each other, whereby the spot size of a light beam so coupled between the first and second waveguides is expanded or shrunk in both transverse dimensions, depending on the direction of the light beam.

A photonic polarization splitter rotator (PSR) includes a substrate, a first optical waveguide disposed in the substrate on a first layer, the first optical waveguide having a curved portion between a first end of the first optical waveguide and a second end of the first optical waveguide, and a second optical waveguide disposed in the substrate on a second layer, above the first layer, the second optical waveguide having a substantially rectangular shape and longitudinally arranged between the first end of the first optical waveguide and the second end of the first optical waveguide.

A photonic polarization splitter rotator (PSR) includes a substrate, a first optical waveguide disposed in the substrate on a first layer, the first optical waveguide having a curved portion between a first end of the first optical waveguide and a second end of the first optical waveguide, and a second optical waveguide disposed in the substrate on a second layer, above the first layer, the second optical waveguide having a substantially rectangular shape and longitudinally arranged between the first end of the first optical waveguide and the second end of the first optical waveguide.

A photonic integrated circuit (PIC) in which some optical waveguides have laterally tilted waveguide cores used to implement passive polarization-handling circuit elements, e.g., suitable for processing polarization-division-multiplexed optical communication signals. Different sections of such waveguide cores may have continuously varying or fixed lateral tilt angles. Different polarization-handling circuit elements can be realized, e.g., using different combinations of end-connected untilted and laterally tilted waveguide-core sections. In some embodiments, laterally tilted waveguide cores may incorporate multiple-quantum-well structures and be used to implement active circuit elements. At least some embodiments beneficially lend themselves to highly reproducible fabrication processes, which can advantageously be used to achieve a relatively high yield of the corresponding PICs during manufacture.

A photonic integrated circuit (PIC) in which some optical waveguides have laterally tilted waveguide cores used to implement passive polarization-handling circuit elements, e.g., suitable for processing polarization-division-multiplexed optical communication signals. Different sections of such waveguide cores may have continuously varying or fixed lateral tilt angles. Different polarization-handling circuit elements can be realized, e.g., using different combinations of end-connected untilted and laterally tilted waveguide-core sections. In some embodiments, laterally tilted waveguide cores may incorporate multiple-quantum-well structures and be used to implement active circuit elements. At least some embodiments beneficially lend themselves to highly reproducible fabrication processes, which can advantageously be used to achieve a relatively high yield of the corresponding PICs during manufacture.

Structures for managing light polarization on a photonics chip and methods of forming a structure for managing light polarization on a photonics chip. A single-mode waveguiding structure is formed that includes a first waveguide core region and a second waveguide core region positioned above the first waveguide core region. The second waveguide core region includes a first section, a second section connected to the first section, and a third section connected to the second section. The second section has a first width at an intersection with the first section and a second width at an intersection with the third section. The second width is greater than the first width. The first and second waveguide core regions contain materials of different composition.

Structures for managing light polarization on a photonics chip and methods of forming a structure for managing light polarization on a photonics chip. A single-mode waveguiding structure is formed that includes a first waveguide core region and a second waveguide core region positioned above the first waveguide core region. The second waveguide core region includes a first section, a second section connected to the first section, and a third section connected to the second section. The second section has a first width at an intersection with the first section and a second width at an intersection with the third section. The second width is greater than the first width. The first and second waveguide core regions contain materials of different composition.

A splitter. In some embodiments, the splitter includes an input waveguide; a first output waveguide; a second output waveguide; a first internal waveguide, connected to the input waveguide and to the first output waveguide, and a second internal waveguide, coupled to the first internal waveguide and connected to the second output waveguide. The splitter may be configured, when fed, at the input waveguide, power in a fundamental mode of the input waveguide or power in a first order spatial mode of the input waveguide: to transmit at least 80% of the power in the fundamental mode to the first output waveguide, and to transmit at least 80% of the power in the first order spatial mode to the second output waveguide.

A splitter. In some embodiments, the splitter includes an input waveguide; a first output waveguide; a second output waveguide; a first internal waveguide, connected to the input waveguide and to the first output waveguide, and a second internal waveguide, coupled to the first internal waveguide and connected to the second output waveguide. The splitter may be configured, when fed, at the input waveguide, power in a fundamental mode of the input waveguide or power in a first order spatial mode of the input waveguide: to transmit at least 80% of the power in the fundamental mode to the first output waveguide, and to transmit at least 80% of the power in the first order spatial mode to the second output waveguide.

Example polarization processing optical devices, methods, and systems are disclosed. A polarization processing optical device includes a polarization beam splitter (PBS), a polarization rotator (PR), a coupler, and a phase tuner (PT), where one port of the PBS is configured to input a continuous light source, and the other two ports of the PBS are respectively connected to the PR and one port of the coupler, the PR is connected to another port of the coupler, the PT is disposed on a connection between the PBS and the coupler or a connection between the PR and the coupler, at least one port of the coupler is configured to output single-polarization light, and the PT is configured to control output optical power of the coupler.