A method for fabricating an integrated structure, using a fabrication system having a CMOS line and a photonics line, includes the steps of: in the photonics line, fabricating a first photonics component in a silicon wafer; transferring the wafer from the photonics line to the CMOS line; and in the CMOS line, fabricating a CMOS component in the silicon wafer. Additionally, a monolithic integrated structure includes a silicon wafer with a waveguide and a CMOS component formed therein, wherein the waveguide structure includes a ridge extending away from the upper surface of the silicon wafer. A monolithic integrated structure is also provided which has a photonics component and a CMOS component formed therein, the photonics component including a waveguide having a width of 0.5 m to 13 m.

A spot-size converter having a waveguiding structure. The first part of the waveguiding structure receives light from or transmits light to a first waveguide in a first propagation mode. The first part of the waveguiding structure has a longitudinally varying effective refractive index that decreases away from the first waveguide. The second part of the waveguiding structure transmits light to or receives light from a second waveguide in a second propagation mode. The second part of the waveguiding structure has a number of high-index elements arranged in a single plane, extending along a longitudinal waveguiding axis and at least partially overlapping the first part of the waveguiding structure. The first propagation mode of the first waveguide progressively transforms into the second propagation mode of the second waveguide along the longitudinal waveguiding axis through an overlap region between the first part and the second part of the waveguiding structure.

A system for detecting the installation of an optical tap on an optical fiber link. The system comprises a spatial mode de-multiplexer optically coupled to the optical fiber link. The spatial mode de-multiplexer is configured to isolate an optical signal in a first spatial mode of the optical fiber link. The spatial mode de-multiplexer is configured to isolate light in a second spatial mode of the optical fiber link 14. The system comprises an optical sensor optically coupled to the spatial mode de-multiplexer for measuring the optical power of the light in the second spatial mode of the optical fiber link. Also disclosed herein are methods for detecting installation of an optical tap and methods for securing an optical signal in an optical fiber.

An optical waveguide structure includes a substrate and a core structure disposed on the substrate. The substrate includes a first waveguide region, a second waveguide region, and a transition region between the first waveguide region and the second waveguide region. The core structure includes first core segments arranged in a first direction and a second direction crossing the first direction on the transition region. The core structure includes second core segments arranged in the first direction and the second direction on the second waveguide region. The first direction and the second direction are parallel to a top surface of the substrate.

A bent taper is provided that includes one or more waveguide bends, at least one of which has a tapering waveguide width along at least a portion thereof. In one embodiment, the bent taper is an S-shaped bent taper that is configured as a TE0-TE1 mode convertor. Such a bent taper can be combined with a linear bi-layer taper configured as a TM0-TE1 mode converter to form a TM0-TE0 polarization rotator.

A waveguide mode expander couples a smaller optical mode in a semiconductor waveguide to a larger optical mode in an optical fiber. The waveguide mode expander comprises a shoulder and a ridge. In some embodiments, the ridge of the waveguide mode expander has a plurality of stages, the plurality of stages having different widths at a given cross section.

An optical device and a method of manufacturing an optical device, including a ridge waveguide second, and a strip-loaded ridge waveguide section, comprises applying two different protective layers and two separate etches at two different depths. The protective layers overlap to protect the same section of the optical device, and to limit the surfaces of optical device to exposure to multiple etches, except at edges where the protective layers overlap.

A functional optical device is disclosed. The functional optical device integrates a coupling unit, a waveguide photodiode (PD) and an optical waveguide on a semiconductor substrate. The coupling unit extracts an optical signal by performing interference of signal light with local light. The optical waveguide carries the optical signal from the coupling unit to the waveguide PD. The semiconductor substrate provides a heavily doped conducting layer and a buffer layer that is un-doped or lightly doped with n-type impurities by density smaller than density of impurities in the heavily doped conducting layer. The conducting layer and the buffer layer continuously and evenly extend from the optical waveguide to the waveguide PD.

A SOI bent taper structure is used as a mode convertor. By tuning the widths of the bent taper and the bend angles, almost lossless mode conversion is realized between TE0 and TE1 in a silicon waveguide. The simulated loss is <0.05 dB across C-band. This bent taper can be combined with bi-layer TM0-TE1 rotator to reach very high efficient TM0-TE0 polarization rotator. An ultra-compact (9 m) bi-layer TM0-TE1 taper based on particle swarm optimization is demonstrated. The entire TM0-TE0 rotator has a loss <0.25 dB and polarization extinction ratio >25 dB, worst-case across the C-band.

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.