An easy-to-fabricate and highly efficient single-mode optical fiber-to-single-mode optical waveguide coupler having relatively large horizontal and vertical alignment tolerances between the fiber and the waveguide coupler. The waveguide coupler also features ease of end-facet cleaving. The waveguide coupler can be used in ultra-broadband high coupling efficiency applications or other suitable applications. Single-mode on-chip waveguides incorporating such coupler(s) are also provided, as are methods of manufacturing the waveguide coupler and on-chip waveguide.

A method and system for optimizing structural parameters of an electromagnetic device is described that includes performing operations. The operations include performing a time-forward simulation of a field response in a simulated environment describing the electromagnetic device and extracting decomposition components from the field response to compute a loss value. The operations further include backpropagating the loss value backwards in time using the decomposition components to determine an influence of changes in the structural parameters of the electromagnetic device on the loss value. The operations further include generating a revised description of the electromagnetic device by updating the structural parameters to reduce the loss value.

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for tuning photonic device performance. In one aspect, a method includes receiving an initial photonic device configuration including multiple coupling structures and multiple photonic components. A first amount of light coupling between a first photonic component and a second photonic component of the multiple photonic components is received, which depends upon a subset of the coupling structures that are located between the first photonic component and the second photonic component. One or more coupling structures of the subset of coupling structures located between the first photonic component and the second photonic component are determined to be removed to cause the light coupling between the first photonic component and the second photonic component to change from the first amount of coupling to a target amount of coupling.

A method and system for optimizing structural parameters of an electromagnetic device is described that includes performing operations. The operations include performing a time-forward simulation of a field response in a simulated environment describing the electromagnetic device and extracting decomposition components from the field response to compute a loss value. The operations further include backpropagating the loss value backwards in time using the decomposition components to determine an influence of changes in the structural parameters of the electromagnetic device on the loss value. The operations further include generating a revised description of the electromagnetic device by updating the structural parameters to reduce the loss value.

A waveguide Bragg grating includes a silicon substrate defining a length, a width and a depth and a silicon dioxide (SiO.sub.2) cladding over the silicon substrate and encasing a silicon nitride (Si.sub.3Ni.sub.4) core extending along the length of the silicon substrate and defining a variable width and thickness; wherein the silicon nitride (Si.sub.3Ni.sub.4) core is configured as and functions as a complex Bragg grating waveguide. The waveguide Bragg grating is designed by determining a grating profile of the silicon nitride (Si.sub.3Ni.sub.4) core from a Layer Peeling algorithm and a Layer Adding algorithm; and mapping the grating profile to a 1-layer waveguide structure with varying width dimensions. The method further relates the grating profile to an effective index variation and maps the range of the effective index variation to the structure. The width corresponds to a single specific effective index. A method of manufacturing is also disclosed.

A delay line interferometer comprising an optical waveguide having a distributed Bragg reflector, e.g. Bragg grating, fabricated therein. The distributed Bragg reflector has a refractive index modulation with a period variation (z) along its length z that is arranged to output in transmission an output optical signal f.sub.out(t) in response to a input optical signal f.sub.in(t), wherein the output optical signal f.sub.out(t) is the result of temporal interference between one or more time-delayed replicas of the input optical signal f.sub.in(t). In other words, the distributed Bragg reflector is operable to generate and permit temporal interference between two or more time-delayed replicas of the input optical signal f.sub.in(t). The invention may thus mimic the behaviour of one or more MZIs.