The invention relates to a beam polarization rotator, which comprises: (a) a waveguide having an input facet, an output facet, and four side facets; (b) a core material of the waveguide having a first refractive index; (c) a coating material of the side facets having a refractive index lower than said refractive index of the core material; wherein the waveguide has a cuboid-twisted shape, such that a distal portion of an originally cuboid body is twisted at an angle α about a longitudinal-central axis of the waveguides body, while a proximal portion of the body remains fixed relative to said axis, resulting in said output facet be at an offset orientation angle α relative to the orientation of said input facet.

An optical device includes a light source configured to provide illumination light and a waveguide. The waveguide has an input surface, an output surface distinct from and non-parallel to the input surface, and an output coupler. The waveguide is configured to receive, at the input surface, the illumination light provided by the light source and propagate the illumination light via total internal reflection. The waveguide is also configured to redirect, by the output coupler, the illumination light so that the illumination light is output from the output surface for illuminating a spatial light modulator.

Various example embodiments relate to active optical fibers and devices using active optical fibers. An active optical fiber may comprise a central part surrounded by an annular active core. The fiber may have a tapered longitudinal profile such that the fiber comprises a single-mode portion and a multimode portion. The annular core may have low birefringence, obtained for example by rotating (spinning) the fiber preform during manufacture of the fiber. Refractive index of the annular core may be higher than the refractive indices of the central part and cladding layer(s) surrounding the annular core. The active optical fiber enables selective generation or amplification of light modes with orbital angular momentum (OAM). Furthermore, the fiber has a large mode field diameter (MFD) and it is not sensitive to internal heating or environmental influences.

A single-ended output circulator includes a three-core optical fiber head having first, second, and third optical fiber cores; a walk-off crystal having a first surface facing towards the second end of the three-core optical fiber head tube and a second surface facing away from the second end of the three-core optical fiber head tube; a plurality of half-wave plates each having a first surface coupled to the second surface of the walk-off crystal and a second surface facing away from the second surface of the walk-off crystal; a collimating lens having a first end and a second end; a reflection mirror configured to reflect light beams from the collimating lens; an optical prism between the collimating lens and the reflection mirror and configured to transmit a light beam along a propagation direction according to a polarization direction of the light beam; and a polarization rotator.

A light-receiving device includes: a light guide plate that is a transparent member having, as main surfaces, a first surface and a second surface facing each other and has an emission end formed on at least one end portion of the light guide plate; a wave plate that is disposed on the first surface of the light guide plate and converts an optical signal of circularly polarized light into linearly polarized light; a hologram layer that is disposed on the second surface of the light guide plate and guides a traveling direction of the optical signal converted into the linearly polarized light toward the emission end of the light guide plate; and a light receiver that receives the optical signal emitted from the emission end of the light guide plate and converts the received optical signal into an electrical signal.

An optical device for providing illumination light includes an optical waveguide and a plurality of polarization selective elements. The plurality of polarization selective elements is disposed adjacent to the optical waveguide so that a respective polarization selective element receives light in a first direction, and redirects a first portion of the light in a second direction. A second portion, distinct from the first portion, of the light undergoes total internal reflection, thereby continuing to propagate inside the optical waveguide.

A lightguide optical element (LOE) configured for polarization scrambling is provided. The LOE includes a transparent substrate having a first refractive index, the substrate having a pair of parallel external surfaces configured to propagate light within the LOE through total internal reflection (TIR), and a plurality of mutually parallel partially reflective internal surfaces, those being non-parallel to the pair of parallel external surfaces and configured to couple out said light to a viewer. The LOE further includes a first coating on at least one external surface of the substrate, the first coating being of a coating material having a second refractive index higher than the first refractive index; The LOE further includes an antireflective (AR) coating on at least one external surface of the substrate over the first coating.

A photonic integrated circuit (PIC) in which some optical waveguides have laterally tilted waveguide cores used to implement passive polarization-handling circuit elements, e.g., suitable for processing polarization-division-multiplexed optical communication signals. Different sections of such waveguide cores may have continuously varying or fixed lateral tilt angles. Different polarization-handling circuit elements can be realized, e.g., using different combinations of end-connected untilted and laterally tilted waveguide-core sections. In some embodiments, laterally tilted waveguide cores may incorporate multiple-quantum-well structures and be used to implement active circuit elements. At least some embodiments beneficially lend themselves to highly reproducible fabrication processes, which can advantageously be used to achieve a relatively high yield of the corresponding PICs during manufacture.

A terahertz polarization beam splitter based on a two-core negative curvature fiber is provided, which relates to the technical field of optical fiber communication. The polarization beam splitter includes: a base circular tube and core separation structures. Multiple large cladding tubes are internally tangent and connected to an inner wall of the base circular tube and arranged at equal intervals along a circumference of the inner wall of the base circular tube, and the multiple large cladding tubes are symmetrically distributed on the inner wall of the base circular tube. Embedded circular tubes are internally tangent and connected to inner walls of the multiple large cladding tubes respectively. The core separation structures are two in number.

An image sensor for recording incident radiation may include a first layer for filtering the incident radiation by attenuating incident radiation with a frequency below a cutoff frequency and a second light-sensitive layer for absorbing radiation passing through the first layer. The first layer may precede the second light-sensitive layer in a direction of propagation of the incident radiation and the first layer includes at least one aperture passing through the first layer to the second light-sensitive layer for propagating radiation therethrough. The cross sectional size of the at least one aperture may be configured to provide a cutoff frequency so that incident radiation with a frequency below the cutoff frequency is attenuated inside the at least one aperture and incident radiation with a frequency above the cutoff frequency propagates through the at least one aperture.