The back reflection in photodiodes is caused by an abrupt index contrast between the input waveguide and the composite waveguide/light absorbing material. In order to improve the back reflection, it is proposed to introduce an angle between the waveguide and the leading edge of the light absorbing material. The angle will result in gradually changing the effective index between the index of the waveguide and the index of the composite section, and consequently lower the amount of light reflecting back.

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.

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 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 integrated light absorber/deflector may be coupled to the outer waveguiding regions.

It is provided a circuit assembly, comprising at least one electronic circuit; at least one optical waveguide, wherein the core and the cladding of the optical waveguide are formed of an amorphous material; at least one carrier on which the optical waveguide is arranged; and at least one electro-optically active material layer electrically connected to the electronic circuit. The at least one electro-optically active material layer at least partially extends in the optical waveguide and the electrical connection between the electronic circuit and the at least one electro-optically active material layer is produced in that at least one electrical contact extends from the electronic circuit through at least one section of the cladding of the optical waveguide to the at least one electro-optically active material layer or is connected to a section of the electro-optically active material layer, which protrudes from the cladding of the optical waveguide.

A substrate type optical waveguide element includes a bent waveguide that guides a basic mode, that converts an unneeded mode other than the basic mode to a slab mode, and that is a rib type. Furthermore, the substrate type optical waveguide element includes a removing portion that is arranged at an outer circumferential portion of the bent waveguide, and that removes, from the bent waveguide, the slab mode converted in the bent waveguide.

The present disclosure provides an optical waveguide capable of enhancing the suppression of crosstalk. The optical waveguide includes: under claddings; cores for light propagation arranged in side-by-side relation on surfaces of the respective under claddings; over claddings covering the cores; and a light absorbing part provided between adjacent ones of the cores, the light absorbing part being in non-contacting relationship with the cores. The light absorbing part contains a light absorbing agent having an ability to absorb light propagating in the cores. The optical waveguide is produced on a surface of a substrate.

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.

The present disclosure provides an optical waveguide capable of enhancing the suppression of crosstalk. This optical waveguide includes: under claddings; cores for light propagation arranged in side-by-side relation on surfaces of the respective under claddings; over claddings covering the cores; and a light absorbing part provided between adjacent ones of the cores and adjacent to light exit member connecting portions for connection to light exit members, the light exit member connecting portions being disposed in first end portions of the adjacent cores, the light absorbing part being in non-contacting relationship with the cores. The light absorbing part contains a light absorbing agent having an ability to absorb light exiting the light exit members. The optical waveguide is produced on a surface of a substrate.

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.