A single photon source comprises a photon emitter (10), an excitation waveguide (30) arranged to direct excitation photons having a first polarisation direction into the photon emitter, and a collection waveguide (42) arranged to collect photons having a second polarisation direction from the photon emitter. The first polarisation direction is coupled to a first exciton state of the photon emitter and the second polarisation direction is non-parallel to the first polarisation direction and is coupled to a second exciton state of the photon emitter, and the first and second exciton states have substantially equal energies.

Disclosed is a compact on-chip polarization splitter-rotator based on a Bezier curve gradient waveguide. The Bezier curve gradient waveguide structure is a standard SOI-based wafer structure, comprising a substrate, of which the bottom layer is buried with oxide (SiO.sub.2), and the top is composed of silicon waveguides, including a common output waveguide and a specially-structured waveguide containing Bessel curve boundaries. The common waveguide structure is composed of a cuboid waveguide, and the specially-structured waveguide is composed of an input region, an output region, a width-gradient waveguide (Bezier curve gradient structure) and a coupling region, where a width of the gradient waveguide is determined by a third-order Bezier curve, and the coupling region is composed of two asymmetrical waveguide regions.

Disclosed is a compact on-chip polarization splitter-rotator based on a Bezier curve gradient waveguide. The Bezier curve gradient waveguide structure is a standard SOI-based wafer structure, comprising a substrate, of which the bottom layer is buried with oxide (SiO.sub.2), and the top is composed of silicon waveguides, including a common output waveguide and a specially-structured waveguide containing Bessel curve boundaries. The common waveguide structure is composed of a cuboid waveguide, and the specially-structured waveguide is composed of an input region, an output region, a width-gradient waveguide (Bezier curve gradient structure) and a coupling region, where a width of the gradient waveguide is determined by a third-order Bezier curve, and the coupling region is composed of two asymmetrical waveguide regions.

Structures for a polarization rotator and methods of fabricating a structure for a polarization rotator. The structure includes a substrate, a first waveguide core over the substrate, and a second waveguide core over the substrate. The second waveguide core is positioned proximate to the section of the first waveguide core. The second waveguide core is comprised of a material having a refractive index that is reversibly variable in response to a stimulus.

Structures for a polarization rotator and methods of fabricating a structure for a polarization rotator. The structure includes a substrate, a first waveguide core over the substrate, and a second waveguide core over the substrate. The second waveguide core is positioned proximate to the section of the first waveguide core. The second waveguide core is comprised of a material having a refractive index that is reversibly variable in response to a stimulus.

The invention relates to optical waveguide components, such as Faraday rotators and their manufacture Faraday rotators based on silicon waveguides are provided, where the waveguide has folded or wound sections that are parallel to an externally applied magnetic field.

In part, the disclosure relates to system. The system includes a polarization diversified wavelength demultiplexer (WDM). The polarization diversified wavelength demultiplexer includes a polarization beam splitter configured to output a first polarized signal and a second polarized signal based on an input signal; and a wavelength demultiplexer (WDM) having two inputs that are connected to the two outputs of the polarization beam splitter, and configured to output signals with a single set of outputs that carry signals of both polarizations, based on the first polarized signal from the first input and the second polarized signal from the second input.

An asymmetric adiabatic polarization beam splitter integrated with a waveband filtering splitter unit and a polarization filtering splitter unit is capable of being packaged to form an integrated optical waveguide filtering chip. The waveband filtering splitter unit utilizes an adiabatic optical waveguide structure and stimulated Raman adiabatic passage on an optical waveguide to split the energy of light sources of different bands to different spaces when the light energy is performed with an adiabatic process. The polarization filtering splitter unit utilizes the two orthogonal polarization modes of an optical waveguide with birefringence to achieve a polarization-dependent mode splitting effect based on an adiabatic theory. The asymmetric adiabatic polarization beam splitter realizes the characteristics of integration and high process tolerance, and improves the mass production feasibility.

An asymmetric adiabatic polarization beam splitter integrated with a waveband filtering splitter unit and a polarization filtering splitter unit is capable of being packaged to form an integrated optical waveguide filtering chip. The waveband filtering splitter unit utilizes an adiabatic optical waveguide structure and stimulated Raman adiabatic passage on an optical waveguide to split the energy of light sources of different bands to different spaces when the light energy is performed with an adiabatic process. The polarization filtering splitter unit utilizes the two orthogonal polarization modes of an optical waveguide with birefringence to achieve a polarization-dependent mode splitting effect based on an adiabatic theory. The asymmetric adiabatic polarization beam splitter realizes the characteristics of integration and high process tolerance, and improves the mass production feasibility.

An optical assembly for realizing horizontal and vertical spot-size conversion to couple light from a thin waveguide to a thick waveguide is disclosed. The assembly comprises at least one first thin waveguide with a first section having a first optical mode field and a horizontal spot-size expansion section providing spot-size conversion for a first horizontal dimension of said first optical mode field of a light beam propagating in said first waveguide, and at least one second thick waveguide with a second section having a second optical mode field and a horizontal spot-size reduction section providing spot-size conversion for a second horizontal dimension of said second optical mode field of a light beam propagating in said second waveguide. The expanded end of said first waveguide is aligned and rotated to interface with the reduced end of said second waveguide, so that the mode fields in said first and second waveguides are rotated 90 degrees with respect to each other, whereby the spot size of a light beam so coupled between the first and second waveguides is expanded or shrunk in both transverse dimensions, depending on the direction of the light beam.