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.

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.

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.

In the present invention a new atomic clock is proposed comprising: at least one light source adapted to provide an optical beam, at least one photo detector and a vapor cell comprising a first optical window, said optical beam being directed through said vapor cell for providing an optical frequency reference signal, said photo detector being adapted to detect said optical frequency reference signal and to generate at least one reference signal, whereinsaid atomic clock comprises a first optical waveguide arranged to said first optical window, said first optical waveguide being arranged to incouple at least a portion of said optical beam, said first optical waveguide being sized and shaped so that said first guided light beam is expanded, a first outcoupler is arranged to outcouple at least a portion of said guided light beam to said vapor cell, the thickness t of the atomic clock is smaller than 15 nm.

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.

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.

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.

To reduce or eliminate crosstalk between adjacent integrated optical waveguides, an embodiment of an integrated structure includes, between the optical waveguides, a metal isolation region configured to redirect a signal leaking from one waveguide away from the other waveguide, to absorb the leaking signal, or both to redirect and absorb respective portions of the leaking signal. For example, such an integrated structure includes a cladding, first and second optical cores, and a metal isolation region. The optical cores are disposed in the cladding, and the isolation region is disposed in the cladding between, and separate from, the cores. Including a metal isolation region between adjacent optical waveguides can reduce crosstalk between the waveguides more than coating the waveguides with a metal because the metal coating typically is not thick enough to redirect or absorb enough of a leakage signal to reduce crosstalk to a suitable level.

There is provided an optical waveguide device including: a substrate; an optical waveguide formed on the substrate; and a working electrode that controls a light wave propagating through the optical waveguide, in which the working electrode includes a first base layer made of a first material, a first conductive layer on the first base layer, a second base layer made of a second material different from the first material, which is on the first conductive layer, and a second conductive layer on the second base layer, and an edge of the second base layer is covered with the second conductive layer, in a cross-section perpendicular to an extending direction of the optical waveguide.

A self-fit optical filter includes a dual fiber collimator, a diffraction grating for spatially dispersing the input light beam into a plurality of sub-beams, a cylindrical lens for focusing each of the sub-beams at a saturable absorber which becomes saturated dependent on intensity of light, and a reflector for reflecting the sub-beams back along their optical paths. A method of filtering includes: demultiplexing an input beam into a plurality of sub-beams having distinct center wavelengths, at least partially absorbing one or more of the sub-beams by using a saturable absorber while allowing other sub-beams to pass through, substantially unattenuated, and multiplexing the sub-beams into an output optical signal.