A tunable optical device comprising an optical ring cavity and one or more pairs of electrodes for capacitive actuation of the optical tuning. Applying a potential difference to the electrodes applies a capacitive force to the optical ring cavity which changes the optical resonance frequency. The device can be used as a binary optical switch.

A polarization splitter-rotator (PSR) is described. The PSR having a silicon nitride based waveguide to split and rotate an optical beam. The silicon nitride based waveguide having a first silicon nitride segment including a first layer and a second layer coupled with the first layer.

An electrically controlled depolarizer based on a crossed-slit waveguide (3) includes a horizontal-slit waveguide (1), a 45-degree polarization rotation waveguide (2), a pair of modulation electrodes (4) and the crossed-slit waveguide (3). Broad-spectrum TM (transverse magnetic) polarized light is inputted from one end of the horizontal-slit waveguide (1), and then a part of the broad-spectrum TM polarized light is converted into broad-spectrum TE (transverse electric) polarized light through the 45-degree polarization rotation waveguide (2), and then the broad-spectrum TE polarized light and the remaining broad-spectrum TM polarized light enter an input end of the crossed-slit waveguide (3); the board-spectrum TE polarized light is transmitted in a vertical slit of the crossed-slit waveguide (3); the remaining broad-spectrum TM polarized light is transmitted in a horizontal slit of the crossed-slit waveguide (3); and the broad-spectrum TE polarized light and the remaining broad-spectrum TM polarized light form depolarized light at an output end of the crossed-slit waveguide (3). The pair of modulation electrodes (4) realize the precise adjustment of the rotation angle of the 45-degree polarization rotation waveguide (2) by electronic control, such that the TE polarized light and the TM polarized light at the output end of the crossed-slit waveguide (3) have equal energy, thereby overcoming uneven light splitting caused by loss of the polarization rotation waveguide and TE and TM waveguide transmission loss.

A variable optical attenuator (VOA) may include an input collimator with an input fiber connected on one side and an output collimator with an output fiber connected on one side, where the collimators are on a same surface of a VOA enclosure. A retroreflector may receive a light beam from the input collimator and reflect the light beam to the output collimator. The VOA may include an attenuation element positioned between the input collimator and the retroreflector and/or another attenuation element positioned between the retroreflector and the output collimator to provide variable attenuation to the light beam. The attenuation elements may be moved to set an attenuation level by one or more adjustment elements such as a miniature motor. The attenuation element may include a gradient index (GRIN) element, a polarizer, a neutral density filter, or a wavelength tunable filter.

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.

Various polarization rotator splitter (PRS) configurations are disclosed. In an example embodiment, a system includes a PRS that includes a silicon nitride (SiN) rib waveguide core that includes a rib and a ridge that extends vertically above the rib, the SiN rib waveguide core having a total height h.sub.SiN from a bottom of the rib to a top of the ridge, a rib height h.sub.rib from the bottom of the rib to a top of the rib, a rib width w.sub.rib, and a top width w.sub.SiN of the ridge. The rib width w.sub.rib varies along at least a portion of a length of the SiN rib waveguide core.

Provided are a dual coupler device configured to receive lights of different polarization components, a spectrometer including the dual coupler device, and a non-invasive biometric sensor including the spectrometer. The dual coupler device may include, for example, a first coupler layer configured to receive a light of a first polarization component among incident lights. and a second coupler layer configured to receive a light of a second polarization component among the incident lights, wherein a polarization direction of the light of the first polarization component is perpendicular to a polarization direction of the light of the second polarization component. The first coupler layer and the second coupler layer may be spaced apart from each other and extended along a direction in which the light propagates in the first coupler layer and the second coupler layer.

An integrated polarization splitter and rotator (PSR) employs the TE0 and TE1 modes of propagating light, rather than the TE0 and TM0 modes used in conventional prior art PSR. The integrated PSR exhibits appreciably flatter wavelength response because it does not require a directional coupler to de-multiplex incoming polarizations. The PSR allows tuning of the TM0 loss to reduce polarization dependent loss (PDL). This integrated polarization splitter and rotator is applicable to all integrated platforms including Silicon-on-Insulator (SOI) and III-V semiconductor compound systems. The PSR may be very compact (122 m.sup.2), and provides low loss (<0.3 dB across the C-band) and ultra-broadband operation. The PSR also affords better control of polarization dependent losses.

A surface grating coupler for polarization splitting or diverse includes a planar layer and an array of scattering elements arranged in the planar layer at intersections of a first set of concentric elliptical curves crossing with a second set of concentric elliptical curves rotated proximately 90 or 180 degrees to form a two-dimensional (2D) grating. Additionally, the grating coupler includes a first waveguide in double-taper shape and a second waveguide in double-taper shape respectively for split or diverse an incident light into the 2D grating into two output light to two output ports with a same (either TE or TM) polarization mode or one output port with TE polarization mode and another output port with TM polarization mode. The polarization diverse grating coupler is required to test multiple polarization sensitive photonics components and can be used with other single polarization grating coupler via a fiber array to perform wafer-level testing.

The invention relates to a method for producing an optical waveguide (1), the surface of which is at least partly coated with a coating material. The coating material contained in a target (4) is removed using laser radiation (6) of a processing laser or converted into another aggregate state. The coating material is then deposited on the surface of the waveguide (1) and forms a coating thereon, said coating modifying the light guidance. It is the object of the present invention to provide an improved method for producing optical waveguides, in which guidance of undesired electromagnetic radiation and/or guidance of radiation in undesired areas of the waveguide is avoided. To this effect, the present invention proposes that the laser radiation (7) reflected from the target (4) or transmitted through the target heats-up the waveguide (1), said laser radiation (6) being polarized and impinging the target (4) at a specified angle () between 10 and 80 relative to the surface normal.