An optical device includes an optical waveguide and a plurality of reflective polarizers. The plurality of reflective polarizers include a first reflective polarizer and a second reflective polarizer disposed inside the optical waveguide so that the first reflective polarizer receives light propagating inside the optical waveguide, redirects a first portion of the light in a first direction, and transmits a second portion of the light in a second direction non-parallel to the first direction. The second reflective polarizer receives the second portion of the light from the first reflective polarizer, redirects a third portion of the light, and transmits a fourth portion of the light. A ratio between the first portion and the second portion of the light has a first value and a ratio between the third portion and the fourth portion of the light has a second value distinct from the first value.

Provided are a coherent optical receiver and a fabrication method thereof, the coherent optical receiver including a substrate, signal and local input waveguides extending in a first direction parallel to a top surface of the substrate and configured to receive an optical signal, a first optical circuit element including a first optical waveguide connected to the signal input waveguide and a trench provided in one side of the first optical waveguide in parallel to the first direction, a second optical circuit element including a second optical waveguide connected to the first optical waveguide, a slit crossing the second optical waveguide, and a wavelength plate inserted to the slit, and third optical circuit elements connected to the second optical circuit element, wherein the first to third optical circuit elements are monolithically integrated in the substrate.

Structures for a polarization splitter and methods of fabricating a structure for a polarization splitter. First and second waveguide cores of the polarization splitter are located adjacent to each other in a coupling region. A third waveguide core is located over the second waveguide core in the coupling region. The third waveguide core is composed of a material having a variable refractive index.

An apparatus and method for monitoring a change of a polarization state resulted from an optical link and optical receiver is provided. By combining zero-frequency response matrices and phase information on the received signal at two moments, a change matrix of the zero-frequency channel response matrices at the two moments is obtained, and a parameter characterizing a polarization state change induced by the optical link is determined according to the change matrix, which may dynamically monitor in real-time manner the polarization state change induced by the optical link, irrelevant to the polarization state of an input signal of the optical link. Due to the combination of the zero frequency response matrices and the phase information, response of the optical link may be completely reflected, for more accurate monitoring the polarization state. In addition, there is no need to add additional hardware and controls, thereby simplifying the structure and saving cost.

Example polarization splitter and rotator devices are described. In one example, an optical apparatus includes a splitter configured to split a light signal into a first signal having a first polarization and a second signal having a second polarization, a polarization rotator configured to rotate the second polarization of the second signal into a third polarization, and a polarization mode converter configured to convert the third polarization of the second signal into the first polarization. In certain aspects of the embodiments, the splitter can be a curved multi-mode inference (MMI) polarization splitter, and the polarization rotator comprises input and output ports, with the output port being wider than the input port. The polarization mode converter can be an asymmetrical waveguide taper mode converter. The devices described herein can overcome the deficiencies of conventional devices and provide low insertion loss, flat and/or wide wavelength response, high fabrication tolerance, and compact size.

Provided are a coherent optical receiver and a fabrication method thereof, the coherent optical receiver including a substrate, signal and local input waveguides extending in a first direction parallel to a top surface of the substrate and configured to receive an optical signal, a first optical circuit element including a first optical waveguide connected to the signal input waveguide and a trench provided in one side of the first optical waveguide in parallel to the first direction, a second optical circuit element including a second optical waveguide connected to the first optical waveguide, a slit crossing the second optical waveguide, and a wavelength plate inserted to the slit, and third optical circuit elements connected to the second optical circuit element, wherein the first to third optical circuit elements are monolithically integrated in the substrate.

An optical modulation device includes: a substrate which extends in one direction; an optical waveguide provided on the substrate in a longitudinal direction of the substrate; a half-wave plate; and a combining element which faces an end portion of the substrate and combines two types of linearly polarized light, which have vibration planes orthogonal to each other, to generate composite light, in which the optical waveguide modulates the linearly polarized light which propagates through an inside of the optical waveguide to generate first polarized light and second polarized light, which are linearly polarized light, the half-wave plate is provided at a position to which the second polarized light enters, the combining element includes a transparent base body, a first optical film provided on a first surface of the transparent base body, and a second optical film provided on a second surface which faces the first surface of the transparent base body, the first optical film transmits one of the first polarized light and the second polarized light, which is emitted through the half-wave plate, and reflects the other light, the second optical film reflects the one light, and the composite light is reflected in a direction intersecting the longitudinal direction.

One illustrative TE pass polarizer disclosed herein includes an input/output layer, a first buffer layer positioned above at least a portion of the input/output layer, a layer of epsilon-near-zero (ENZ) material positioned above at least a portion of the first buffer layer, and a metal-containing capping layer positioned above at least a portion of the layer of ENZ material.

One illustrative TE pass polarizer disclosed herein includes an input/output layer, a first buffer layer positioned above at least a portion of the input/output layer, a layer of epsilon-near-zero (ENZ) material positioned above at least a portion of the first buffer layer, and a metal-containing capping layer positioned above at least a portion of the layer of ENZ material.

An integrated optical polarizer for generating linear polarizing light may be formed in a photonic integrated circuit (PIC) for applications that require stable output state of polarization. The integrated polarizer may be built by using the same materials already present in the PIC without use of other additional layers and claddings, and without other additional structural modification to the waveguide profile. The integrated polarizer comprises a plurality of bending waveguides of a pre-determined radius that are connected to each other in sequence. The bending waveguide has a high birefringence and a loose confinement to conduct one polarization mode and attenuate the other polarization mode. The polarization discrimination is controlled with the degree of the mode confinement, the bending radius, and the number of the bending waveguides that are connected in series.