A new technique for sensing optical cavity mode mismatch using a mode converter formed from a cylindrical lens mode converting telescope, radio frequency quadrant photodiodes (RFQPDs), and a heterodyne detection scheme. The telescope allows the conversion of the Laguerre-Gauss basis to the Hermite-Gauss (HG) basis, which can be measured with quadrant photodiodes. Conversion to the HG basis is performed optically, measurement of mode mismatched signals is performed with the RFQPDs, and a feedback error signal is obtained with heterodyne detection.

A display may have an array of display pixels that generate an image. A coherent fiber bundle may be mounted on the display pixels. The coherent fiber bundle may have a first surface that is adjacent to the display pixels and a second surface that is visible to a viewer. The coherent fiber bundle may contain fibers that carry light from the first surface to the second surface. The second surface may be planar or may have a central planar region and curved edge regions that run along opposing sides of the central planar region. The fibers may have cross-sectional surface areas with a first aspect ratio on the first surface and a second aspect ratio that is greater than the first aspect ratio on the second surface.

A new technique for sensing optical cavity mode mismatch using a mode converter formed from a cylindrical lens mode converting telescope, radio frequency quadrant photodiodes (RFQPDs), and a heterodyne detection scheme. The telescope allows the conversion of the Laguerre-Gauss basis to the Hermite-Gauss (HG) basis, which can be measured with quadrant photodiodes. Conversion to the HG basis is performed optically, measurement of mode mismatched signals is performed with the RFQPDs, and a feedback error signal is obtained with heterodyne detection.

A photonic platform based polarization controller providing a fixed target polarization is disclosed. The polarization controller has a polarization rotator splitter splitting the beam into first and second feeds corresponding to first and second orthogonal polarization components. A first Mach-Zehnder interferometer (MZI) stage provides a first phase delay between the first and second feeds based on a first control signal, and a first mixer mixes the first and second feeds to provide third and fourth feeds. A second MZI stage provides a second phase delay between the third and fourth feeds based on a second control signal, and a second mixer mixes the third and fourth feeds to provide fifth and sixth feeds. A third MZI stage provides a third phase delay between the fifth and sixth feeds based on a third control signal, and a third mixer mixes the fifth and sixth feeds to provide the fixed target polarization. An optical tap splits a portion of the beam.

Disclosed is a polarimetric-analysis-type dual liquid crystal (LC) wavelength filter module capable of miniaturization or optical integration in the form of a package. The polarimetric-analysis-type dual liquid crystal (LC) wavelength filter module includes a beam displacer disposed on a propagation path of light of an unpolarized light source for emitting unpolarized light and configured to generate two orthogonal polarization components corresponding to two polarization axes from the light of the unpolarized light source such that the polarization components are separated at a predetermined angle, a half-wavelength retarder disposed apart at a rear end of the beam displacer along the light propagation path, and a dual LC wavelength-tunable filter having two LC wavelength-tunable filters that overlap with a gap therebetween to detect light intensities of first polarized light of a Transverse Electric (TE) mode that is directly delivered from the beam displacer and second polarized light of the TE mode that is transmitted through or via the half-wavelength retarder and then converted.

A switch based on a phase-change material including: a region made of said phase-change material coupling first and second conduction electrodes of the switch; and a rotator of the polarization of a laser signal for activating the switch, located in front of a surface of the region made of said phase-change material.

Provided are polarization-mode controlled nonreciprocal optical waveguide devices, which are used in optical isolator and optical circulator devices. These devices offer a solution to the issues associated with traditional planar optical waveguide-based optical isolators, which are specific to a single polarization mode and result in significant optical loss. The new devices implement polarization-insensitive operation with minimal optical loss. They feature a magneto-optic (MO) film clad on one side and utilize waveguide mode converters or polarization-mode converters to guide the input light signals' mode or polarization. This reduces optical loss as the light passes through the interface between the non-MO clad region and the MO clad region and maximizes the MO effect within the MO clad region by ensuring proper polarization mode.

A core layer of an optical element includes a second conversion portion that converts a polarization mode of light from a TE1 mode to a TE0 mode. The second conversion portion includes: a splitting portion that splits the light in the TE1 mode incident from the first conversion portion into first split light in the TE0 mode and second split light in the TE0 mode which are in opposite phases; a coupling portion that couples the first split light that has propagated through a first branch waveguide and the second split light that has propagated through a second branch waveguide to emit the light in the TE0 mode; and a phase adjustment unit that adjusts a phase difference between the first split light and the second split light. The first branch waveguide and the second branch waveguide are arranged in a second direction.

A polarization controller based on on-chip mode conversion is provided. An input end-face coupler is connected to an input end of an input polarization-dependent mode converter through an input phase shifter. An output end of the input polarization-dependent mode converter is connected to an input end of a multi-mode 11 Mach-Zehnder interferometer (MZI), and an output end of the multi-mode 11 MZI is connected to an input end of an output polarization-dependent mode converter. An output end of the output polarization-dependent mode converter is connected to an output end-face coupler through an output phase shifter. The input end and the output end of the multi-mode 11 MZI are respectively connected to the input polarization-dependent mode converter and the output polarization-dependent mode converter to form a polarization insensitive beam splitting structure. The polarization controller can convert any two arbitrary polarization states, and has a compact structure and a large bandwidth.

Embodiments disclosed herein include photonics systems with a dual polarization module. In an embodiment, a photonics patch comprises a patch substrate, and a photonics die over a first surface of the patch substrate. In an embodiment, a multiplexer is over a second surface of the patch substrate. In an embodiment, a first optical path from the photonics die to the multiplexer is provided for propagating a first optical signal, and a second optical path from the photonics die to the multiplexer is provided for propagating a second optical signal. In an embodiment, a Faraday rotator is provided along the second optical path to convert the second optical signal from a first mode to a second mode before reaching the multiplexer.