79results about How to "High Polarization Extinction Ratio" patented technology

The invention provides an on-chip integrated polarization beam splitter and a polarization beam splitting method thereof. The on-chip integrated polarization beam splitter comprises a hybrid plasma waveguide, a coupling waveguide, an S-bend waveguide and an output silicon waveguide, wherein the coupling waveguide, the S-bend waveguide and the output silicon waveguide are located on the same side of the hybrid plasma waveguide, are sequentially connected in series and are equal in thickness. The hybrid plasma waveguide is divided into a metal coverage layer, an upper silicon dioxide layer, a silicon nitride waveguide layer, a lower silicon dioxide layer and a silicon waveguide layer from top to bottom. The coupling waveguide, the S-bend waveguide and the output silicon waveguide are equal to the silicon waveguide layer in thickness. The coupling waveguide is a silicon waveguide. After input signals including transverse electric modes and transverse magnetic modes enter a coupling zone, transverse electric mode light signals are coupled to the taper-type coupling waveguide and then are output through the S-bend waveguide and the output silicon waveguide, and the transverse magnetic mode light signals are directly transmitted along the hybrid plasma waveguide and are directly output, and waveguide coupling does not occur. The on-chip integrated polarization beam splitter has the advantages of being small in size, compact in structure, high in polarization extinction ratio, low in insertion loss, larger in working bandwidth and the like.

In an optical semiconductor device related to the present invention, a first light source outputting light having a first polarization, a second light source outputting light having a second polarization, a first optical modulator being optically connected to an output side of the first light source and modulating the light that is output from the first light source to output a light signal, a second optical modulator being optically connected to an output side of the second light source and modulating the light that is output from the second light source to output a light signal, and an optical multiplexer coupling the light signal that is output from the first optical modulator with the light signal that is output from the second optical modulator to output a coupled light signal, are integrated on a semiconductor substrate together.

The invention provides a superconductive nanowire single-photon detector with a high polarization extinction ratio, and the detector comprises a substrate; a high-reflection film which is located on the surface of the substrate; a superconductive nanowire which is located on the surface of the high-reflection film; a dielectric layer which is located on the surface of the high-reflection film, and wraps the superconductive nanowire; a grating structure which is located on the surface of the dielectric layer. According to the invention, the detector is based on the high-reflection film substrate, can prevent a Fabry-Perot cavity of the substrate from affecting the absorption efficiency in a mode of front optical coupling, and has higher absorption efficiency for a target wavelength. Through the size design of the grating structure, the detector can achieve a function of non-target polarized light filtering, and effectively improves the detection efficiency and polarization extinction ratio of a device.

A polarizing effect is achieved for light having wavelengths less than 250 nm by orienting an antireflector at an incidence angle between 65° and 75°. Despite limited choices for materials, the antireflector is constructed of layers that alternate in refractive index to exploit the mechanism of interference for limiting the reflectivity of one linear polarization component of the light. The same combination of layers supports the reflectivity of an orthogonal linear polarization component. The light reflected from the antireflector is highly polarized.

The invention discloses a resonant type fiber-optic gyroscope frequency locking device.The resonant type fiber-optic gyroscope frequency locking device comprises a light source driving module, a narrow linewidth laser source, a Y waveguide modulator, a first modulation module, a polarization maintaining optical fiber resonant cavity, a signal demodulation detection module, a second modulation module, a digital output module and a lithium niobate straight waveguide modulator.A laser works at constant temperature and constant current and in a steady state, frequency stability is good, and frequency noise introduced by frequency modulation of the laser is effectively lowered.Different from a traditional PZT intra-cavity modulation method, no movable part is arranged in the cavity, the effective refractive index is modulated by modulating the magnitude and direction of an electric field applied to lithium niobate waveguides, equivalent cavity length modulation is achieved, and reliability is high.The modulation voltage is low, no redundish external driver is needed, the structure is simple, and the size and power consumption of a gyroscope are easily reduced.The lithium niobate waveguide modulator has a polarization function and achieves a polarization selection effect in the cavity, the intra-cavity polarization extinction ratio is increased, and noise relevant to polarization is effectively restrained.

The invention discloses a broadband prism multilayer film polarizing beam splitter, which comprises a first prism, a second prism and a polarization beam splitting multilayer film. After incident light vertically enters from a first surface of the first prism, the incident light enters the polarization beam splitting multilayer film through being transmitted by a second face of the first prism and is divided into transmitted p-polarized light and reflected s-polarized light by the polarization beam splitting multilayer film, the p-polarized light exits after the p-polarized light is transmitted sequentially by a first face of the second prism and a second face of the second prism, the s-polarized light exits after the s-polarized light is transmitted sequentially by a second face of the first prism and a third face of the first prism, the light exiting from the second face of the second prism is vertical to the light exiting from the third face of the first prism, an included angle between the first surface of the first prism and the second face of the first prism is 52 degrees, an included angle between the second face of the first prism and the third face of the first prism is 65.6 to 77 degrees, and the index of refraction of the first prism and the second prism is 1.85-1.516. The polarizing beam splitter disclosed by the invention is not only simple to manufacture, but also has very broad polarization bandwidth and an excellent polarization extinction ratio.

The invention provides a fiber pigtail assembly wherein a polarization maintaining fiber is soldered directly to a mounting pad without a sleeve or a ferrule therebetween. A portion of the polarization maintaining fiber near a fiber end is embedded in a vertical slow axis orientation within an asymmetrical solder ball having a flat portion for adhering to the mounting pad. The vertical slow axis orientation of the polarization maintaining fiber within the solder ball enhances power stability and polarization extinction ratio properties of optical modules utilizing the invention.

The invention discloses a polarization maintaining hollow-core anti-resonance optical fiber. The optical fiber comprises an outer cladding layer, two connecting tubes, cladding rings, six semi-elliptical cladding tubes tightly attached to the cladding rings, two round cladding tubes tightly attached to the cladding rings, semi-elliptical nesting tubes which are arranged on the semi-elliptical cladding tubes and have the same inner wall thickness, round nesting tubes which are arranged in the round cladding tubes and have the same wall thickness, and a fiber core area. The gaps between the four semi-elliptical cladding tubes above and below the X axis and the adjacent X-axis semi-elliptical cladding tubes are equal; the gaps between the circular cladding tube and the adjacent semi-elliptical cladding tube are equal; the semi-elliptical nested tubes are arranged at axial symmetry positions in the corresponding semi-elliptical cladding tubes and are connected with the cladding rings; the circular nesting tubes are arranged in the circular cladding tubes in a clinging manner and correspond to the clinging positions of the cladding rings and the round cladding tubes; and each tube is made of pure quartz glass, and the fiber core area and other internal space are filled with air. The optical fiber has the characteristics of low loss, high polarization extinction ratio and good polarization maintaining characteristic at the working wavelength.

The invention provides an on-chip modulation integrated optical resonant cavity, which is applied to a multilayer wave guide structure, and realizes the high-degree integration design of active and passive devices of the integrated optical resonant cavity. The integrated optical resonant cavity provided by the invention is of an integrated two-layer structure including an upper layer and a lower layer; the resonant cavity and transmission wave guide are prepared on the waveguide substrate of the lower layer; a lithium niobate waveguide modulator is manufactured at the upper layer of the resonant cavity and exerts an electric field at the two sides of the lithium niobate waveguide; the effective refractive index of the waveguide is changed; the optical phase delay quantity modulation in the waveguide is realized. A cross-layer coupler is prepared between the lithium niobate waveguide and the resonant cavity or transmission waveguide positioned at the lower layer. The optical fiber coupling structure of the external modulator and the resonant cavity is omitted; the modulator and the resonant cavity are vertically and directly coupled; the attenuation of the cavity-entering light polarization extinction ratio can be reduced, so that higher cavity-entering light polarization extinction ratio can be maintained; the system model is simplified; the system integration degree is improved; the system reliability is enhanced.

The invention discloses a thin film material used for terahertz and infrared light polarization modulation and a preparation method thereof. According to the thin film material, particularly, an ErSb nanowire array is embedded in a GaSb substrate, the direction of the nanowire array is vertical to or parallel with the surface of the substrate, and when the volume by volume concentration of the ErSb is 10%, the direction of the nanowire array is vertical to the surface of the substrate; and when the volume by volume concentration of the GaSb is 15 to 25%, the direction of the nanowire array is parallel with t the surface of the substrate. Through a molecular beam epitaxy method, a composite material of embedding the nanowire structure with a semi metallic property in a semiconductor material is acquired, the material can be used for a broadband terahertz and infrared polarizer and can be integrated with a terahertz and infrared optoelectronic device based on III-V semiconductor materials.

The invention discloses a polarization maintaining fiber side-pumped coupler and a manufacturing method thereof. According to the coupler, a fiber core and a stress structure of a polarization maintaining main fiber connection part are kept complete; the polarization maintaining main fiber connection part is provided with an exposed inner cladding radial outer surface; and an end face structure of a pumped fiber connection end is in complementary fit with and tightly attached to the inner cladding radial outer surface. The manufacturing method comprises the following steps of: removing coatings of the polarization maintaining main fiber connection part and the pumped fiber connection end; preprocessing the pumped fiber connection end to form the end face structure of which the shape is complementary to that of the inner cladding radial outer surface at the polarization maintaining main fiber connection part; and correspondingly matching the end face structure of the pumped fiber connection end with the inner cladding radial outer surface of the polarization maintaining main fiber connection part, and eliminating air between the end face structure and the inner cladding radial outer surface, so that the pumped fiber connection end and the polarization maintaining main fiber connection part are integrated. The fiber core and the stress structure of the connection part are kept complete in the manufacturing process. The stress structure and the fiber core of the polarization maintaining main fiber connection part are not damaged, and the coupler is high in polarization extinction ratio and signal transmittance.

The invention relates to an optical mixer for reflective coherent receives, belongs to optical devices of optical fiber communication and solves the problem that existing optical mixers are non-compact in structure and poor in temperature stability. A polarization separator, a 1 / 2 wave plate, a phase shift plate, a first shift crystal, a 1 / 4 wave plate and a combined reflecting mirror are sequentially arranged along an incident light path, and the 1 / 4 wave plate, the first shift crystal, the 1 / 2 wave plate and a second shift crystal are sequentially arranged on a reflecting light path of the combined reflecting mirror, wherein the 1 / 2 wave plate, the first shift crystal and the 1 / 4 wave plate are shared devices. Polarization separating is realized through a polarization separation prism, 90-degree phase shift is realized through the phase shift plate, safe-phase and orthogonal output light required is obtained by adopting the reflecting structure, birefringent crystals, the 1 / 4 wave plate, the 1 / 2 wave plate and the combined reflecting mirror, and polarization and phase diversity control is realized. The optical mixer is compact in integral structure, mature in processing technique of various devices, good in temperature stability and high in polarization extinction ratio, and can be used for optical signal coherent modulation by advanced modulation formats and polarization multiplexing way in the optical fiber communication.

The invention discloses a two-stage sub-wavelength grating silicon-based light polarization beam splitting rotator based on asymmetric coupling. Silicon dioxide is used as a substrate, and air is usedas an upper cladding to break vertical symmetry; a polarization beam splitting rotator main body is formed by using a silicon waveguide; the silicon waveguide is divided into three parts: a waveguide1 is a primary coupling sub-wavelength grating waveguide, the characteristic size of the waveguide is equivalently expanded, and the manufacturing tolerance is further increased; the waveguide 2 is atwo-stage conical etching waveguide, the first-stage conical etching and the waveguide 1 complete phase matching to achieve polarization rotation, and the second-stage etching recovers the thicknessof the waveguide to participate in second-stage coupling; and the waveguide 3 is a secondary sub-wavelength grating waveguide and is used for carrying out secondary coupling filtering on the residualTM0 polarization mode. According to the polarization beam splitting rotator, multi-stage coupling is adopted, a multi-stage filtering structure achieves the high polarization extinction ratio and thelarge manufacturing tolerance under the compact structure, and the polarization beam splitting rotator has important application in optical communication and photoelectric signal processing.

The invention discloses a single-polarization transmission type photonic crystal fiber resonant cavity comprising a first optical fiber collimator, a second optical fiber collimator, a first photonic crystal fiber collimator, a second photonic crystal fiber collimator, a double-refraction optical beam splitter, and a fixation device. According to the invention, when a resonant cavity is built, a birefringent crystal is used for manufacturing the optical beam splitter and o light and e light in incident light are separated, so that the polarization extinction ratio of the resonant cavity is increased and thus the application potential of the photonic crystal fiber resonant cavity in a gyroscopic system can be improved substantially. On the basis of the polarizing design inside the cavity, the requirement on the alignment precision of the polarization axis of the fiber is low and thus the process difficulty of the resonance cavity is reduced substantially. A transmission resonant cavity structure is realized only by using one beam splitter, so that the total losses inside the cavity can be reduced effectively and the definition of the resonant cavity is enhanced. Meanwhile, the overall size of the resonant cavity can be reduced and miniaturization of the gyroscopic system can be realized.

The present invention provides a polarizing light splitting device comprising: a polarizing beam splitter, a polarizing rotator and a single polarization light splitter that are arranged in sequence.The device is small in additional loss and high in polarization extinction ratio, an input light beam in any polarization state can be split into two beams of linearly polarized lights, a light splitting ratio is hardly affected by the polarization state of an incident light beam, and the device is high in wavelength bandwidth and can be widely applied to the fields of optical fiber communications, optical fiber sensing, scientific research and the like.

The invention, which relates to the technical field of special optical fibers and optical fiber communication, discloses a grapheme-coated side-polishing double-core photonic crystal fiber polarization converter. The polarization converter based on the side-polishing double-core photonic crystal fiber comprises a cladding structure formed by multi-layer air holes (11), two fiber cores (12) and (13), central air holes (14) and (15) arranged near the fiber cores, and two elliptical air holes (16). The background material (17) of the cladding layer is made of a silicon dioxide material. The fiberis polished to form a D-shaped structure and thus the central air hole (14) is opened and the inner surface of the central air hole is coated with a composite layer structure with a graphene layer and a polymethyl methacrylate layer (PMMA). After voltage loading and adjustment of the chemical potential of the coated graphene layer, the output optical power of different polarization directions ischanged and thus a certain extinction ratio is reached to realize polarization conversion. The converter having characteristics of all-fiber structure, small size, high polarization extinction ratio and the like can be applied to the all-optical communication field.

The invention discloses a polarization maintaining fiber pumped coupler and a manufacturing method thereof. The coupler comprises a polarization maintaining main fiber and a pumped fiber bundle containing a plurality of pumped fibers, wherein one end of the pumped fiber bundle is a hollow part formed by a cladding of a tapering end; one end of the polarization maintaining main fiber is a transition zone which exposes an inner cladding and is inserted into the hollow part; the transition zone is provided with a complete stress structure; and the outer surface of the transition zone is in close contact with and integrally fused with the inner surface of the hollow part of the tapering end. The manufacturing method comprises the following steps of: preprocessing a plurality of pumped fibers to form the hollow fiber bundle, and cutting in the middle; reducing or not reducing the diameter of the inner cladding of the polarization maintaining main fiber on the premise of not damaging a fire core and the stress structure; inserting the preprocessed main fiber into the hollow pumped fiber bundle to ensure that the main fiber is in close fit with the fiber bundle; and integrally fusing the main fiber with the fiber bundle, and recoating the main fiber. The fire core and the stress structure of the polarization maintaining main fiber are not damaged during coupling, and signal coupling efficiency and polarization extinction ratio are improved.

The invention is a polarizing method of producing single polarization, belonging to the photoelectron communication and optical information process field. It is based on the theory that surface plasma resonance produces single polarization, excites the resonance on the basal plane of the lengthened prism plated with the metal film, the resonance only attenuating P wave in the laser beam and allowing S wave to completely pass through, and makes the laser beam irradiate at the angle of the resonance for completely getting rid of the P wave and only leaving the S wave, which realizes the polarization of the laser beam.

The invention is a polarizing method based on the wave-guide resonance, belonging to the photoelectron communication and optical information process field. It excites the wave-guide resonance in the lengthened prism with the metal and medium film plated on the bottom surface in order, at the angle of the resonance, the resonance only attenuating S or P wave in the laser beam and allowing the P orS wave to completely pass through, and makes the laser beam irradiate at the angle of the resonance for completely getting rid of the S or P wave and only leaving the P or S wave, which realizes the high polarization.

The invention provides a polarized light irradiating device capable of achieving high polarized light extinction ratio, uniform polarized light orientation, and large irradiating area. The polarized light irradiating device comprises a light source portion emitting ultraviolet light, a parallel light forming portion paralleling the ultraviolet light, and a polarized light forming portion. The polarized light forming portion comprises a plate polarizing beam splitter of a dielectric substance multilayer film disposed on a first face of a transparent board. In order to reflect s polarized light ingredient and transmit p polarized light ingredient in the ultraviolet light incident to the surface of the dielectric substance multilayer film in an inclined manner from the parallel light forming portion, the split s polarized light ingredient is emitted out as an irradiating beam.

The invention discloses a compact on-chip polarization splitter-rotator based on a Bezier curve graded index waveguide. The Bezier curve graded index waveguide structure is based on a standard SOI wafer structure and comprises a substrate with an oxide (SiO2) buried in the bottom layer, silicon waveguides are arranged on the substrate, and the silicon waveguides comprise a common output waveguide and a special structure waveguide containing a Bezier curve boundary. The common waveguide structure is composed of a cuboid waveguide. The special structure waveguide is composed of an input waveguide, an output waveguide, a width gradually-changing waveguide (a Bezier curve gradually-changing structure) and a coupling area, the width of the gradually-changing waveguide is determined by a third-order Bezier curve, and the coupling area is composed of two asymmetric waveguide areas. Polarization beam splitting rotation of two kinds of input polarized light TE0 and TM0 is achieved in a wide working wave band, the insertion loss is low, the polarization conversion efficiency is high, the crosstalk is low, and compared with similar devices, the compact on-chip polarization splitter-rotator is optimal.

The invention provides a superconductive nanowire single-photon detector with a high polarization extinction ratio, and the detector comprises a substrate; a high-reflection film which is located on the surface of the substrate; a superconductive nanowire which is located on the surface of the high-reflection film; a dielectric layer which is located on the surface of the high-reflection film, and wraps the superconductive nanowire; a grating structure which is located on the surface of the dielectric layer. According to the invention, the detector is based on the high-reflection film substrate, can prevent a Fabry-Perot cavity of the substrate from affecting the absorption efficiency in a mode of front optical coupling, and has higher absorption efficiency for a target wavelength. Through the size design of the grating structure, the detector can achieve a function of non-target polarized light filtering, and effectively improves the detection efficiency and polarization extinction ratio of a device.

The invention provides an optical fiber coupling-based high-polarization extinction ratio waveguide polarizer and a manufacturing method thereof. The invention aims to solve the problems of the high insertion loss and low optical power threshold of a lithium niobate annealed proton exchanged waveguide-based waveguide polarizer and further improve the polarization extinction ratio of such kind of devices. According to the optical fiber coupling-based high-polarization extinction ratio waveguide polarizer and the manufacturing method thereof of the invention, a magnesium oxide doped lithium niobate crystal or a near-stoichiometric lithium niobate crystal is adopted, so that the increase of the optical power threshold of the device can be realized; an anti-proton exchanged waveguide is prepared in the magnesium oxide doped lithium niobate crystal or near-stoichiometric lithium niobate crystal, so that the insertion loss of the waveguide is decreased; and the back surface of the magnesiumoxide doped lithium niobate crystal or near-stoichiometric lithium niobate crystal is slotted and is coated with a light absorbing material, so that the polarization extinction ratio of the waveguidepolarizer can be further improved.

The invention discloses an anisotropic plasmon resonant cavity graphene polarization detector and a design method. The anisotropic plasmon resonant cavity graphene polarization detector structurally comprises a substrate material layer, a metal reflecting layer, a dielectric spacer layer, a graphene layer and a metal bar grid layer. The polarization detector is based on a plasmon resonant cavity structure, a plasmon waveguide mode is formed between a top metal surface and a bottom metal surface, the cavity length of a resonant cavity is defined by a top metal boundary, and when the wavelengthand the cavity length meet the interference phase length condition, the mode reaches a resonance state, and a local strong light field of a deep sub-wavelength scale is realized. Due to anisotropy ofthe metal strip structure, the mode can only be excited by incident light with the polarization direction perpendicular to the metal strip grid, and light absorption and light response of graphene canbe improved; most of incident light with the polarization direction parallel to the metal bar grid is reflected, absorption and photoresponse of graphene cannot be effectively excited, and thereforethe high polarization extinction ratio and photoresponse enhancement of the selected polarization state are achieved.

The invention discloses an optical mixer of a coherent reception machine, and belongs to optical devices of optical fiber communication. The optical mixer of the coherent reception machine solves the problems that delayed differences exist among different output components of an existing optical mixer, and temperature stability is poor. The optical mixer of the coherent reception machine is provided with a wave separator, a 50 / 50 beam splitter, a phase shift piece, a wave combiner, a 1 / 2 wave piece and a polarization separator along the direction of an optical path in sequence. The optical mixer of the coherent reception machine serves as a 2*8 optical mixer, and uses characteristics of a single-axis birefringent crystal to achieve polarization separation, beam combination and optical process compensation. Light beams achieve phase shift of an angle of 90 degrees through the phase shift piece, and phase diversity control is achieved. Eight quartz crystals with different thicknesses of the polarization separator are used for compensating the delayed differences among different optical paths. Different devices are mature in machining technology, and good in temperature stability. The optical mixer of the coherent reception machine is compact in overall structure, high in polarization extinction ratio, and capable of being used for coherent demodulation of optical signals by using an advanced modulation format and a polarization multiplexing mode in the optical fiber communication.

The invention provides a linear polarization quasi-continuous fiber laser and relates to the technical field of laser. In order to solve the problems in the prior art, the laser comprises an electric control driving module, a linear polarization laser module and a laser amplification module, and the electric control driving module comprises a direct current power supply DC, a resistor R1, a resistor R2, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, a capacitor C10, a capacitor C11, an MOS tube MOS1, an MOS tube MOS2, a feedback amplifier U1 and a feedback amplifier U2. The linear polarization laser module comprises an indicator light device, N pump lasers, a first polarization-maintaining beam combiner, a polarization-maintaining high-reflection grating, a first polarization-maintaining gain optical fiber, a polarization device, a polarization-maintaining low-reflection grating and a first stripper, and the amplification module comprises M pump lasers, a second polarization-maintaining beam combiner, a second polarization-maintaining gain optical fiber and a second stripper.

The invention is a polarizer based on wave-guide resonance. It consists of lengthened prism, underside metal film, medium film and transmission-increasing film, and uses the metal film and the mediumfilm to form single-side metal-enveloping wave-guide construction and adopts the medium film as wave-guide layer and the metal film as envelope layer. It leads in the laser beam through the fibre-optical joint, makes the beam irradiate at the angle of wave-guide resonance, many times excites the resonance on the basal plane of lengthened prism in order plated with metal and medium films for getting rid of S or P wave and only leaving P or S wave, which realizes the high polarization.

The invention discloses a superconducting nanowire single-photon detector with high polarization extinction ratio and high efficiency. The superconducting nanowire single-photon detector comprises a substrate, a medium partially-reflecting mirror combined on the surface of the substrate, a lower optical cavity combined on the surface of the medium partially-reflecting mirror, NbN nanowires combined at the internal part of the lower optical cavity in a periodic winding structure, an upper optical cavity combined on the surface of the lower optical cavity, metal nanowires combined between the lower optical cavity and the upper optical cavity in a periodic structure, and a totally-reflecting mirror combined on the surface of the upper optical cavity. According to the superconducting nanowire single-photon detector, problems of low light absorptivity and polarization extinction ratio and low efficiency of the superconducting nanowire single-photon detector in the prior art are solved.

The invention discloses a cascaded bent waveguide type lithium niobate polarization rotator, which comprises a first-stage polarization rotator and a second-stage polarization rotator, the first-stage polarization rotator comprises a first bent waveguide, and the second-stage polarization rotator comprises a second bent waveguide. Each of the first bent waveguide and the second bent waveguide is composed of two Euler bent waveguides with gradually changed widths and an arc waveguide, and the first Euler bent waveguide with a gradually changed width, the arc waveguide and the second Euler bent waveguide with a gradually changed width are sequentially connected end to end. The second Euler bent waveguide with the gradually changed width in the first polarization rotator is connected with the first Euler bent waveguide with the gradually changed width in the second polarization rotator. The width of the Euler bent waveguide gradually changes linearly along with the bending angle. According to the cascaded bent waveguide type lithium niobate polarization rotator, lossless conversion of a light field mode of signal light from a straight waveguide mode to a bent waveguide mode can be realized by utilizing the Euler bent waveguides with the gradually changed width, so that the loss of the whole polarization rotator is reduced.