A semiconductor photodetector comprising a closed loop configured to receive light from an external source adapted to trap light within said closed loop until absorption by the semiconductor.

A quantum-dot based avalanche photodiode (QD-APD) may include a silicon substrate and a waveguide on which a quantum dot (QD) stack of layers is formed having a QD light absorption layer, a charge multiplication layer (CML), and spacer layers. The QD stack may be formed within a p-n junction. The waveguide may include a mode converter to facilitate optical coupling and light transfer from the waveguide to the QD light absorption layer. The QD absorption layer and the CML layer may be combined or separate layers. The CML may generate electrical current from the absorbed light with more than 100% quantum efficiency when the p-n junction is reverse-biased.

Methods and structures for shielding optical waveguides are provided. A method includes forming a first optical waveguide core and forming a second optical waveguide core adjacent to the first optical waveguide core. The method also includes forming an insulator layer over the first optical waveguide core and the second optical waveguide core. The method further includes forming a shielding structure in the insulator layer between the first optical waveguide core and the second optical waveguide core.

A method for manufacturing a waveguide aperture to block stray light from a facet of an integrated optical device include obtaining a wafer with one or more integrated optical devices formed thereon and with a cleaved facet; positioning a mask in front of the cleaved facet, thereby masking at least a portion of the waveguide aperture of at least one the one or more integrated optical devices; and applying a light-blocking coating to the cleaved facet with the mask masking the portion of each of the one or more integrated optical devices.

In a photonic integrate circuit (PIC) architecture, non-guided stray light that is radiated from components, junctions, discontinuous and scattering points in an integrated optic device, may be received by an integrated waveguide structure in the path of the stray radiation. The integrated waveguide structure may comprise a plurality of collectors that are configured to collect the non-guided stray light from the radiating source. Each of the collectors may comprise an integrated waveguide with a front end that is tapered to increase the mode-field size and pointed toward the stray light source, and with a back end that is connected to a secondary waveguide. The collectors are placed in the path of the stray light and aligned in the propagation direction of the stray light. The collected stray light is guided to a light energy damper through the second waveguide for converting light energy into heat.

Two input waveguides are made of a semiconductor material. One output waveguide is made of a semiconductor material. A multi-mode-interference part is made of a semiconductor material. The multi-mode-interference part has an incoming end surface connected to the input waveguides, and an outgoing end surface opposite to the incoming end surface and connected to the output waveguide. The multi-mode-interference part has a waveguide width wider than the waveguide widths of the input waveguides and the waveguide width of the output waveguide. Two unwanted-light waveguides are made of a semiconductor material. The unwanted-light waveguides are connected to the outgoing end surface of the multi-mode-interference part so as to sandwich the output waveguide. The unwanted-light waveguides each satisfy a single-mode condition.

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.

Provided is a light receiving element with high light receiving sensitivity. The light receiving element comprises: a light absorbing layer that absorbs light to generate a carrier; and a diffraction element that converts the optical path of first polarized light, which is obliquely incident on a plane formed by the light absorbing layer, so that the first polarized light propagates in a first direction along the light absorbing layer, and that converts the optical path of second polarized light incident from the same direction as the first polarized light so that the second polarized light propagates in a second direction, opposite the first direction, along the light absorbing layer.

Narrow linewidth multi-wavelength (MW) light sources and related methods are disclosed. Such a light source includes gain chips coupled to a wavelength combiner and reflection chip that includes phase control sections (PCSs), a wavelength division multiplexer (WDM), and a micro-ring resonator (MRR) based reflector. The WDM combines light beams received from the gain chips, via the PCSs, into a combined light beam. The MRR based reflector receives the combined light beam and generates both a reflection MW light beam and a transmission MW light beam. The WDM receives the reflection MW light beam, separates it into different wavelengths, and provides each different wavelength of light via a respective one of the PCSs to a respective one of the gain chips to self seed an internal laser cavity thereof. The transmission MW light beam is, or is used to produce, the narrow linewidth MW light produced by the light source.

A low loss high extinction ratio on-chip polarizer. 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.