An optical multiplexer including a first and a second optical waveguides, and a multiplexing unit. The first and second optical waveguides have a first and a second mode coupling regions being proximate to each other with a predetermined gap width, the optical waveguides in the first and second mode coupling regions form the multiplexing unit. Light transfers between the optical waveguides in the first and second mode coupling regions, first light in the optical waveguide in the first mode coupling region and second light in the optical waveguide in the first or second mode coupling regions having the wavelength different from the first light are multiplexed to one of the waveguides in the first and second mode coupling regions, and the core cross-section of the optical waveguide at least in the first and second mode coupling regions in the first and second optical waveguides is asymmetric in the height direction.

An optical modulator that uses adiabatic tapers to change the width of the waveguides between multimode waveguides and single mode waveguides on a low-loss, e.g. thin-film lithium niobate, electro-optic platform. The architecture enables the utilization of the fundamental mode of multimode wide optical waveguides that have lower optical propagation loss without sacrificing the benefit of the signal integrity and ease of control of single mode operation.

First and second waveguide structures are coupled to a waveguide coupling structure, the first waveguide structure comprising a first guiding core structure formed on a first cladding structure, and a second cladding structure formed on the first guiding core structure. The first and second waveguide structures have respective guiding ridges. The second waveguide structure comprises a second guiding core structure formed on a third cladding structure, and a fourth cladding structure formed on the second guiding core structure. The waveguide coupling structure comprises a transition structure, a multimode interference structure between the transition structure and the second waveguide structure, and an electrode over at least a portion of the guiding ridge within the second cladding structure and over at least a portion of the transition structure.

A photonic coupler includes an input coupling section, an output coupling section, and a multimode interference (MMI) waveguide section. The input coupling section is adapted to receive an input optical signal along an input waveguide channel. The output coupling section is adapted to output a pair of output optical signals along output waveguide channels. The output optical signals having output optical powers split from the input optical signal. The MMI waveguide section is optically coupled between the input and output coupling sections. Notched waveguide sections may each be disposed between the MMI waveguide section and a corresponding one of the input or output coupling sections and/or the MMI waveguide section may include curvilinear sidewalls.

The present application discloses a polarization beam splitter (PBS). The PBS includes a silicon substrate and a planar structure formed thereon characterized by an isosceles trapezoid shape with a first parallel side and a second parallel side connected by two tapered sides. The first parallel side has longer width than the second parallel side, both of which is separated by a length no greater than 100 μm along a line of symmetry bisecting the pair of parallel sides. The PBS further includes a pair of input ports coupled to the first parallel side and a pair of output ports coupled to the second parallel side. The planar structure is configured to receive an input light wave of any wavelength in C-band via one input port and split to a TE-mode light wave and a TM-mode light wave respectively outputting to the pair of output ports.

Structures for an optical power splitter and methods of forming a structure for an optical power splitter. A first waveguide core includes a portion positioned over a multimode interference region, a second waveguide core includes a portion positioned over the multimode interference region, and a third waveguide core includes a portion positioned over the multimode interference region. The first waveguide core provides an input port to the optical power splitter. The second waveguide core provides a first output port from the optical power splitter, and the third waveguide core provides a second output port from the optical power splitter.

Structures with waveguide cores in multiple levels and methods of fabricating a structure that includes waveguide cores in multiple levels. The structure includes a first waveguide core and a second waveguide core positioned in a different level than the first waveguide core. The first waveguide core includes a longitudinal axis and a plurality of segments having a spaced arrangement along the longitudinal axis. The second waveguide core is aligned to extend across the plurality of segments of the first waveguide core.

A light polarizing element include: a first port waveguide; two second port waveguides; and a multi-mode interference waveguide optically connected to the first port waveguide and the two second port waveguides, the multi-mode interference waveguide having at least one slit formed therein, the at least one slit having a shape that enables the multi-mode interference wave guide to give different effective refractive indexes to respective mutually orthogonal polarized light waves input from the first port waveguide, thereby separating the mutually orthogonal polarized light waves, and that enables the separated mutually orthogonal polarized light waves to be output from the respective two second port waveguides.

An optical semiconductor device includes a first optical coupler including a first input port and a second input port, a first optical branching device including a first output port and a second output port, a second optical coupler including a third input port and a fourth input port, a second optical branching device including a third output port and an fourth output port, a first single mode waveguide configured to connect the second input port and the first output port, a second single mode waveguide configured to connect the second output port and the third input port, a third single mode waveguide configured to connect the fourth input port and the third output port, and a fourth single mode waveguide configured to connect the fourth output port and the first input port.

An optical modulator that uses adiabatic tapers to change the width of the waveguides between multimode waveguides and single mode waveguides on a low-loss, e.g. thin-film lithium niobate, electro-optic platform. The architecture enables the utilization of the fundamental mode of multimode wide optical waveguides that have lower optical propagation loss without sacrificing the benefit of the signal integrity and ease of control of single mode operation.