A polarization splitter-rotator (PSR) is described. The PSR having a silicon nitride based waveguide to split and rotate an optical beam. The silicon nitride based waveguide having a first silicon nitride segment including a first layer and a second layer coupled with the first layer.

A photonic integrated chip is configured as a transmitter-receiver chip. The photonic integrated chip includes a light emitter, a light detector, a multi-mode interference coupler, and a mode-filed adapter. The light emitted by the light emitter is guided to a core layer formed below the multi-mode interference coupler, and further to the mode-filed adapter for transmission of light to an optical fiber coupled with the photonic integrated chip. Similarly, light received by the mode-filed adapter from the optical fiber propagates to the core layer, and is guided by the multi-mode interference coupler into the light detector. The photonic integrated chip is utilized to realize a single-unit transmitter-receiver module for a fiber optic gyroscope circuit based on monolithic integration of photonics components via wafer fabrication on a substrate. The photonic integrated chip has a low fabrication cost, low size, and is robust.

An integrated mode converter and multiplexer (/demultiplexer) is disclosed, which combines a multimode interference coupler (100), at least one phase-shifter (200) and a symmetrical Y-junction (300). The dispersion of the multimode interference coupler (100) is engineered through subwavelength structures in order to achieve a very wide bandwidth. Several phase-shifter (200) topologies for further bandwidth enhancement are disclosed, as well as architectures for multiplexing a greater number of optical modes.

Aspects described herein include a mode multiplexer comprising a first optical waveguide extending between a first port and a second port. A first input mode of an optical signal entering the first port is propagated through the first optical waveguide to the second port. The mode multiplexer further comprises a second optical waveguide configured to evanescently couple with a coupling section of the first optical waveguide. A second input mode of the optical signal entering the first port is propagated through the second optical waveguide to a third port. The first optical waveguide further defines a filtering section between the coupling section and the second port, the filtering section configured to filter the second input mode.

An optical mode-size converter is presented, which includes a guiding portion, wherein at least a portion of the guiding portion extends between a first end and a second end along a first path, a first strip with a first refractive index, and a second strip with a second refractive index. The first strip and the second strip are embedded within the guiding portion extending along the first path such that a first optical mode received at the first end reaches the first strip before the second strip and such that the second strip extends to the second end. The first refractive index and the second refractive index are higher than a refractive index of the guiding portion, and a section of the first strip and a section of the second strip overlap to form an evanescent coupling region, such that converter is responsive to a first optical mode received at the first end to convert the first optical mode into a second optical mode with a smaller mode size along the first path towards the second end.

An in-plane photonic device is provided for transmission of an optical signal across a gap, in particular an in-plane photonic device for use in a photonic integrated circuit with one or more in-plane crossings of electrical connections and photonic waveguides. One embodiment relates to an in-plane photonic device for use in a photonic integrated circuit with in-plane crossings of electrical connections and photonic waveguides, including: at least one input optical waveguide; and at least one output optical waveguide; wherein the at least one input optical waveguide and the at least one output optical waveguides are positioned such that a gap between them separates the input and the output optical waveguide(s), and wherein the input and the output optical waveguides are configured for optical mode matching across the gap, such that an optical signal can be transmitted from the input optical waveguide to the output optical waveguide across the gap.

An optical circuit element formed on a substrate, the optical circuit element includes a first waveguide and a second waveguide, the second waveguide having a shape in a width direction, the shape being asymmetrical to the first waveguide. The first waveguide includes a first segment and a second segment, the first segment having a width that changes along a light propagation direction, the second segment continuous with the first segment. The second waveguide includes a coupled waveguide adjacent to the second segment of the first waveguide. At least one of the second segment and the coupled waveguide has a shape with a width that changes along the light propagation direction.

A photonic integrated chip is configured as a transmitter-receiver chip. The photonic integrated chip includes a light emitter, a light detector, a multi-mode interference coupler, and a mode-filed adapter. The light emitted by the light emitter is guided to a core layer formed below the multi-mode interference coupler, and further to the mode-filed adapter for transmission of light to an optical fiber coupled with the photonic integrated chip. Similarly, light received by the mode-filed adapter from the optical fiber propagates to the core layer, and is guided by the multi-mode interference coupler into the light detector. The photonic integrated chip is utilized to realize a single-unit transmitter-receiver module for a fiber optic gyroscope circuit based on monolithic integration of photonics components via wafer fabrication on a substrate. The photonic integrated chip has a low fabrication cost, low size, and is robust.

An optical device comprises first, second and third elements fabricated on a common substrate. The first element comprises an active waveguide structure supporting a first optical mode, the second element, fabricated on a planarized top surface of the first element, comprises a passive waveguide structure supporting a second optical mode, and the third element, at least partly butt-coupled to the first element, comprises an intermediate waveguide structure, positioned such that a top surface of the intermediate structure underlies a bottom surface of the passive waveguide structure. If the first optical mode differs from the second optical mode by more than a predetermined amount, a tapered waveguide structure in at least one of the second and third elements facilitates efficient adiabatic transformation between the first optical mode and the second optical mode. Mutual alignments of the first, second and third elements are defined using lithographic alignment marks.

A device coupon for use in a hybrid integration process with a silicon platform. The device coupon comprises: an input waveguide, including an input facet; an active waveguide, coupled to the input waveguide, the active waveguide including a III-V semiconductor based electro-optical device; and an output waveguide, configured to couple light between the active waveguide and an output facet. The input waveguide and output waveguide are passive waveguides.