The invention relates to photonic circuits, in particular to photonic circuits where light is escalated transferred between optical waveguides which are coupled to photonic devices. A first waveguide on a silicon substrate is provided having a first thickness and a first refractive index. A tapered second waveguide having a second thickness less than the first thickness and a second refractive index higher than said first refractive index is deposited on the first waveguide. At least one layer of an optically active material comprising a photonic device is deposited on the first waveguide adjacent to the second waveguide. The photonic device is interfaced with the wide end of the tapered second waveguide to provide an optical coupling, and the opposite narrow end of the tapered second waveguide is interfaced on top of the first waveguide to provide adiabatic light transfer between said first and second waveguides.

A low loss high extinction ratio on-chip polarizer is disclosed. The polarizer includes an input waveguide taper having an outer waveguiding region that widens in the direction of light propagation along at least a portion of the taper length, and a core waveguiding region that narrows in the direction of light propagation along at least a portion of the taper length, so as to selectively squeeze out light of undesired modes into the outer regions while preserving light of a desired mode in the waveguide core. An output filter section is provided to prevent light from reentering the output waveguide after being squeezed out. An integrated light absorber/deflector may be coupled to the outer waveguiding regions.

Structures for an edge coupler and methods of fabricating such structures. The structure includes a back-end-of-line stack located over a substrate. The back-end-of-line stack includes a waveguide core having a longitudinal axis and a tapered section with a width that varies with position along the longitudinal axis based on a non-linear function.

A photonic integrated circuit (PIC) includes photonic components fabricated on the PIC. One of the photonic components includes an optical coupler configured to optically couple to an optical component. The optical coupler includes waveguide elements arranged in a 2-Dimensional array that is configured to provide a first mode having a first shape chosen to match a second shape of a second mode of the optical component.

A compact silicon waveguide mode converter, a dielectric meta-surface structure based on periodical oblique subwavelength perturbations, including a top silicon structure with oblique subwavelength perturbations etched in certain periods with period length of Λ, a duty cycle and an oblique angle θ on the SOI substrate. The invention adopts an all-dielectric meta-surface structure with oblique subwavelength perturbation, which can achieve a compact mode conversion from fundamental mode to arbitrary high-order mode of silicon waveguide, and can improve the optical communication capacity greatly.

Structures for an edge coupler and methods of fabricating such structures. The structure includes a back-end-of-line stack located over a substrate. The back-end-of-line stack includes a waveguide core having a longitudinal axis and a tapered section with a width that varies with position along the longitudinal axis based on a non-linear function.

A 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 and at least one of the modal gain control structures. The second element comprises a passive waveguide structure supporting a second optical mode. The third element, at least partly butt-coupled to the first element, comprises an intermediate waveguide structure supporting intermediate optical modes. 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 facilitate efficient adiabatic transformation between the second optical mode and one of the intermediate optical modes. No adiabatic transformation occurs between any of the intermediate optical modes and the first optical mode. Mutual alignments of the first, second and third elements are defined using lithographic alignment marks.

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

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.

A device includes a grating coupler with a grating constant, two light sources, and a planar waveguide, which are configured to couple light with two different wavelengths λ.sub.1, λ.sub.2 into the waveguide. The waveguide has a waveguiding layer disposed adjacent to a substrate layer and a cover layer. The waveguiding layer has a thickness d and effective refractive indices of N(λ.sub.k, j.sub.k), wherein λ.sub.k is one of the wavelengths and j.sub.k is an order of a waveguide mode, wherein the coupled light of the wavelength λ.sub.k has a coupling angle α.sub.k into the waveguide, and wherein an amount of difference between the coupling angles is a divergence angle Δα. Guiding of waveguide modes of the order j.sub.k>0 is possible for a wavelength of the coupled light. The waveguiding layer is arranged to couple the light via the grating coupler under a divergence angle of Δα<6.