Optical isolator core

Abstract

In some embodiments, the optical isolator core includes a Faraday rotator and a plurality of birefringent crystal plates. The plurality of birefringent crystal plates may include a first birefringent crystal plate for separating input light into light having a first polarization and light having a second polarization, and a second birefringent crystal plate for combining light having the first polarization and light having the second polarization in output light laterally shifted by the single-stage optical isolator. The Faraday rotator may be disposed between the first birefringent crystal plate and the second birefringent crystal plate. In some embodiments, the plurality of birefringent crystal plates further includes a third birefringent crystal plate disposed between the Faraday rotator and the second birefringent crystal plate. Additionally or alternatively, the optical isolator core may also include a half-wave plate disposed between the Faraday rotator and the first birefringent crystal plate.

Description

[0001] Division Application Description

[0002] This application is a divisional application of the invention patent application with the application date of September 30, 2020, entering the Chinese national stage on November 4, 2022, with the Chinese national application number 202080100540.0 and the invention title "Optical Isolator Core".

[0003] Cross - reference to Related Applications

[0004] This application claims the priority of the Patent Cooperation Treaty (PCT) application PCT / CN2020 / 088952 titled "Optical Isolator Core in Between Fiber and Collimator Lens" filed on May 7, 2020 and the PCT application PCT / CN2020 / 119360 titled "Optical Isolator Core" filed on September 30, 2020, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0005] The present disclosure generally relates to optical systems and optical isolator core designs to provide a walk - off of light received at the optical isolator core. Background Art

[0006] An optical isolator (sometimes referred to as an optical diode or a Faraday isolator, etc.) is an optical device that transmits light in a specific direction and blocks light in the opposite direction. Optical isolators are typically used to prevent unwanted feedback from outside an optical oscillator (such as a laser cavity). For example, in some cases (e.g., at high power), optical feedback may damage or disrupt the operation of a laser system. To reduce optical feedback, an optical isolator can be inserted into a laser system. An optical isolator can be a passive unidirectional, non - reciprocal device that utilizes the magneto - optical rotation phenomenon to isolate the source and protect the laser oscillator from reflections. Summary of the Invention

[0007] In some embodiments, an optical component includes: a first optical fiber and a second optical fiber; a pump laser for providing pump light having a first wavelength, the pump light being coupled into the first optical fiber through a first collimating lens, a wavelength division multiplexing filter, a second collimating lens, and a compensator disposed between the first optical fiber and the second collimating lens; and an isolator disposed between the second optical fiber and the second collimating lens to transmit signal light having a second wavelength, wherein the isolator includes a Faraday rotator and a plurality of birefringent crystal plates to laterally shift the signal light.

[0008] In some embodiments, a single-stage optical isolator includes a Faraday rotator and a plurality of birefringent crystal plates, wherein the plurality of birefringent crystal plates includes a first birefringent crystal plate and a second birefringent crystal plate. The first birefringent crystal plate is configured to separate input light into light having a first polarization and light having a second polarization, and the second birefringent crystal plate is configured to combine the light having the first polarization and the light having the second polarization in output light, which is laterally displaced by the single-stage optical isolator. The Faraday rotator is disposed between the first birefringent crystal plate and the second birefringent crystal plate.

[0009] In some embodiments, a two-stage optical isolator includes a first isolator core and a second isolator core. The first isolator core includes a first set of layers that includes a first Faraday rotator and a first half-wave plate disposed between a first pair of birefringent crystal plates; and a second isolator core that includes a second set of layers that includes a second Faraday rotator and a second half-wave plate disposed between a second pair of birefringent crystal plates, wherein the first set of layers and the second set of layers have the same thickness and corresponding magnetic orientations to cancel material tolerances and assembly tolerances relative to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figures 1A - 1E One or more exemplary embodiments of a single-stage isolator are shown.

[0011] Figures 2A - 2C One or more exemplary embodiments of a two-stage isolator including two isolator cores arranged in parallel are shown.

[0012] Figures 3A - 3C One or more exemplary embodiments of a two-stage isolator including two isolator cores arranged in series are shown. DETAILED DESCRIPTION

[0013] The following detailed description of example embodiments refers to the accompanying drawings. The same reference numerals in different drawings may identify the same or similar elements.

[0014] An optical isolator is a device that is typically designed to allow light to travel in the forward direction while blocking reflections that would travel in the backward direction. Optical isolators are important in many optical systems and applications. For example, single-frequency semiconductor lasers are very sensitive to external optical feedback. Among other examples, even very low levels of optical reflection from an external optical circuit (e.g., on the order of about -50 dB) are sufficient to cause a significant increase in laser phase noise, intensity noise, and / or wavelength instability. Thus, in applications that require low optical noise and a stable single optical frequency, an optical isolator is typically provided at the output of each laser diode. Another example is in optical amplifiers that require unidirectional optical amplification. In this case, if the external optical reflections from, for example, connectors and other optical components are strong enough, the bidirectional nature of the optical amplification in the optical gain medium will cause self-oscillation.

[0015] Conventional optical isolators are based on a Faraday rotator disposed between two polarizers (e.g., an input polarizer and an output polarizer). In this configuration, the input light received at the optical isolator passes through the input polarizer, which has an optical axis that matches the polarization orientation of the input light. The Faraday rotator then rotates the polarization of the input optical signal by 45 degrees in the clockwise direction. The optical axis of the output polarizer is oriented 45 degrees with respect to the input polarizer, which allows the optical signal to pass through with very little attenuation. If there are reflections from one or more components downstream of the output polarizer, the reflected light must pass through the output polarizer and the Faraday rotator. Because the Faraday rotator is a non-reciprocal device, the polarization state of the reflected light will be rotated an additional 45 degrees in the same direction as the input light, thus becoming orthogonal to the optical axis of the input polarizer. Thus, the input polarizer effectively blocks the reflected light and ensures unidirectional light transmission through the optical isolator.

[0016] Therefore, in traditional optical isolator designs, the optical core deflects the collimated beam at a small angle, which can be used in collimated beam applications. For example, a collimated beam application can involve integrating the isolator core with a wavelength division multiplexer filter and a pump chip in an optical component (e.g., a pump combiner) that combines beams of different wavelengths. For example, the optical component can include an input leg that receives an input signal at a first wavelength (e.g., 1550 nanometers (nm)) and an output leg where the input signal at the first wavelength is combined with pump light having a second wavelength (e.g., 980 nm). A typical method in such collimated beam applications is to place the optical isolator in the region between the WDM filter and the collimating lens, which has the most physical space to integrate the optical isolator within the device. However, if the optical isolator is placed in the region between the WDM filter and the collimating lens, the optical isolator can block the pump light that travels in the opposite direction with respect to the input light (e.g., because the optical isolator typically includes a material that has high absorption for 980 nm pump light, such as garnet).

[0017] Some embodiments described herein provide an isolator core and / or an optical system (e.g., an optical component and / or an optical device) that includes an isolator core designed to provide a lateral shift away. For example, rather than deflecting light in an input beam received at the isolator core, the isolator core can include a Faraday rotator, a plurality of birefringent crystal plates, and / or a half-wave plate (HWP) that are arranged to spatially separate and / or combine orthogonal polarization components of the input beam having low polarization mode dispersion (PMD), polarization-dependent loss (PDL), and / or insertion loss (IL). Additionally, the isolator core can be designed to prevent backward-propagating light entering the output side of the optical isolator from coupling to the input side of the optical isolator, which can achieve optical isolation. In some embodiments, the isolator core can be located between an optical fiber and a collimating lens in an optical component to achieve same-side input / output optical fibers (i.e., on the same side of the component), integrated 980 nm / 1550 nm wavelength division multiplexing (WDM) functionality, self-compensating PMD, and / or self-compensating PDL. In some embodiments, the isolator core can be designed to save space by utilizing the space between the optical fiber and the collimating lens. Additionally, the isolator core design can provide flexibility in placing the isolator core in the input leg of the optical component, the output leg of the optical component, or both the input leg and the output leg of the optical component. For example, in a forward-pumped erbium-doped fiber amplifier (EDFA) where 980 nm pump light is coupled into the output leg through a WDM filter, the isolator core can be arranged in the input leg (e.g., because the isolator core might otherwise block the 980 nm pump light). In another example, in a backward-pumped EDFA where 980 nm pump light is coupled into the input leg through a WDM filter, the isolator core can be provided in the output leg. In some embodiments, the optical isolator design can enable the input and output optical fibers to be located on the same side of the component, which can enable integration with a 980 nm pump laser chip and / or a monitor photodiode.

[0018] Figures 1A - 1E One or more exemplary embodiments 100 of a single-stage isolator 110 are shown. As Figures 1A - 1C shown, for a forward-pumped EDFA, the single-stage isolator 110 (which can be referred to herein as the isolator core 110) can be arranged in an optical component to laterally shift an input beam received at the isolator core 110. For example, as shown, the isolator 110 can be used in an optical component such as a pump combiner that includes or docks with a dual-fiber pigtail 120 that includes an input optical fiber in the input leg of the optical component and an output optical fiber in the output leg of the optical component. As Figures 1A - 1CAs shown, the single-stage isolator core 110 can be located between the dual-fiber pigtail 120 and the first collimating lens 130-1 (e.g., the first aspherical lens (A lens)). The optical component can also include a pump chip (or pump laser) 160 to provide pump light having a first wavelength (e.g., 980 nm), which can be coupled into the output branch through the second collimating lens 130-2 (e.g., the second A lens), the WDM filter 140, the first collimating lens 130-1, and the compensator 150 disposed between the dual-fiber pigtail 120 and the first collimating lens 130-1.

[0019] As Figures 1A - 1C shown, the optical component can be a pump combiner, a forward-pumped EDFA, or other suitable device, where the single-stage isolator core 110 is disposed in the input branch to receive signal light having a second wavelength (e.g., 1550 nm), and the signal light is combined with the pump light from the pump chip 160 in the output branch. In this case, the pump light can be coupled into the output branch through the second collimating lens 130-2, the WDM filter 140 (which is transmissive at the wavelength of the pump light), the first collimating lens 130-1, and the compensator 150. Alternatively, in a backward-pumped EDFA (not shown) or another suitable device where the pump light is to be coupled into the input branch, the single-stage isolator core 110 can be disposed in the output branch, and the pump light can be coupled into the input branch through the second collimating lens 130-2, the WDM filter 140, the first collimating lens 130-1, and the compensator 150. Thus, the isolator core 110 and the compensator 150 can be disposed adjacent to each other between the dual-fiber pigtail 120 and the first collimating lens 130-1, in the input branch and the output branch (and vice versa).

[0020] In some embodiments, the optical component can be disposed in an integrated module having a highly integrated pump platform design. For example, as Figure 1AAs shown, the integrated module may include various mechanical components, such as a metal bracket 170, to fix or otherwise support optical components, such as a dual fiber pigtail 120, an isolator core, a compensator 150, a collimating lens 130, and a WDM filter 140. Additionally, in the case where the isolator core 110 is integrated with the pump chip 160, the integrated module may include a package 180 for mounting the pump chip 160 and package pins 190 for interfacing with one or more external components. In another example, the isolator core 110 may be used in an input leg and / or an output leg of a free space optical device configuration or another suitable configuration, which may be part of a larger assembly, without having fibers directly coupled to and / or from the isolator core 110 and the compensator 150. Thus, it should be understood that the components described herein are merely exemplary, and the isolator core 110 and / or its variants may be used in any suitable optical device or application.

[0021] In some embodiments, optical isolation greater than 18 decibels (dB) may be achieved between the input leg and the output leg by positioning the isolator core 110 and the compensator 150 between the dual fiber pigtail 120 and the first collimating lens 130-1. In some embodiments, the compensator 150 may compensate for the optical path between the input leg and the output leg. In some embodiments, in Figure 1A the optical component shown, the fiber cores of the input leg and the output leg may have a fiber core-to-fiber core distance of 460 micrometers (μm), the collimating lens 130 may have a focal length of 2.7 millimeters (mm), and the WDM filter 140 may be a 980 nm (transmissive) / 1550 nm (reflective) filter. The input leg and the output leg may be thermally expanded core (TEC) fibers that expand the fiber mode diameter from 6 μm to 9 μm. In this way, the optical device including the isolator core 110 may have a diameter of 3.0 mm or less.

[0022] In some embodiments, as described herein, isolator core 110 may be configured to receive and provide a walk-off to direct signal light towards first collimating lens 130-1, which produces a collimated beam that is reflected by WDM filter 140 (e.g., WDM filter 140 is transmissive at wavelengths associated with pump light and reflective at wavelengths associated with signal light). In this way, the pump light and the signal light are combined and coupled into compensator 150 through first collimating lens 130-1. Additionally, by positioning isolator core 110 between dual fiber pigtail 120 and first collimating lens 130-1 (instead of between first collimating lens 130-1 and WDM filter 140), isolator core 110 does not block the pump light that propagates in the opposite direction with respect to (the input) signal light. In some embodiments, to walk-off the signal light, isolator core 110 may include a set of layers or components that are designed to spatially separate and combine the orthogonal polarization components of the signal light with low PMD, low PDL, and / or low IL. As described herein, isolator core 110 may include a Faraday rotator, an input polarizer (e.g., a first birefringent crystal plate), an output polarizer (e.g., a second birefringent crystal plate), and additional components (e.g., a third birefringent crystal plate or a half-wave plate), which are combined together (e.g., by an adhesive material such as epoxy resin, etc.). Additionally, as described herein, the thicknesses and angles of the respective layers or components of isolator core 110 may be controlled to produce a walk-off.

[0023] For example, as Figure 1D shown, isolator core 110 may include a Faraday rotator 112 made of garnet, and a first birefringent crystal plate 114-1 to receive input light including orthogonal polarization components (e.g., O light and E light, which may respectively refer to light having horizontal polarization and light having vertical polarization). In some embodiments, the input light may be spatially separated into orthogonal polarization components by first birefringent crystal plate 114-1. By way of example, first birefringent crystal plate 114-1 may comprise a birefringent material such as yttrium orthovanadate (YVO 4 )), or another suitable material having refractive indices that depend on the polarization and propagation direction of light. Thus, because the orthogonal polarization components have different polarizations, first birefringent crystal plate 114-1 has different refractive indices with respect to O light and E light, which causes the O light and E light to be spatially separated. However, at the output of isolator core 110, the O light and E light must be precisely combined together to avoid polarization-related losses or other performance issues. Therefore, after the O light and E light pass through first birefringent crystal plate 114-1, the O light and E light are rotated by Faraday rotator 112, and another pair of birefringent crystal plates 114-2, 114-3 are provided to combine the O light and E light.

[0024] Typically, controlling the thickness and angles of the Faraday rotator 112 and the three birefringent crystal plates 114 during the assembly process can be challenging because the Faraday rotator 112 and the three birefringent crystal plates 114 can have different material tolerances (e.g., plus or minus ten microns relative to the desired thickness) and different assembly tolerances (e.g., plus or minus a certain number of degrees relative to the desired angle). Thus, in some embodiments, the Faraday rotator 112 can have a fixed orientation relative to one of the adjacent birefringent crystal plates 114 (e.g., birefringent crystal plate 114-1 or birefringent crystal plate 114-2), and the other two birefringent crystal plates 114 can be rotated in two degrees of freedom to adjust the necessary angles to ensure that the O-ray and the E-ray are precisely combined at the output from the third birefringent plate 114-3. For example, in some embodiments, the Faraday rotator 112 and the first birefringent crystal plate 114-1 can be fixed, and the other birefringent crystal plates 114-2, 114-3 can be rotated to compensate for different materials and / or assembly tolerances. Alternatively, the Faraday rotator 112 and the second birefringent crystal plate 114-2 can be fixed, and the other birefringent crystal plates 114-1, 114-3 can be rotated to compensate for materials and / or assembly tolerances. In this way, as Figure 1D shown, the O-ray and the E-ray can be combined in the light output from or otherwise transmitted by the isolator core 110. In one example, Table 1 below shows the design characteristics of an isolator core 110 that can achieve a lateral shift away, where α, β, and γ are the azimuth angles of the optical axes of each birefringent crystal plate 114, one of the birefringent crystal plates is fixed relative to the Faraday rotator 112, and two of them are rotatable.

[0025]

[0026] Table 1

[0027] Alternatively, in some embodiments, the single-stage isolator core 110 can have a design as Figure 1E shown, where the isolator includes a first birefringent crystal plate 114-1, a half-wave plate (HWP), a Faraday rotator 112, and a second birefringent crystal plate 114-2. In this case, different layers (e.g., the first birefringent crystal plate 114-1 and the second birefringent crystal plate 114-2) can be cut from a larger block (e.g., YVO 4 ). Thus, Figure 1D the design shown achieves precise control of the thickness and angles of the components of the isolator core 110 by rotating two of the three birefringent crystal plates 114, Figure 1EThe design shown can ensure that the O - light and E - light are combined together to minimize PDL and / or insertion loss because the different layers have the same material tolerances. In this way, even if the layers in the isolator core 110 are not perfectly adjusted, the O - light and E - light will be combined at the output from the isolator core 110 because the birefringent crystal plate 114 - 1, 114 - 2 layers have the same thickness and corresponding magnetic orientations (e.g., opposite or the same magnetic orientations) to cancel the material tolerances and assembly tolerances relative to each other.

[0028] In some embodiments, as described above, the Faraday rotator 112 can be made of garnet. For example, the Faraday rotator 112 can be made of a rare - earth iron garnet (RIG) single crystal, which generally requires a magnetic field to be used as the Faraday rotator 112 and / or a non - magnetic garnet (referred to herein as a locking garnet). For example, when the Faraday rotator 112 is made of an RIG single crystal and the RIG is exposed to an external magnetic field greater than the saturation field, the magnetic domains in the direction opposite to the external magnetic field are neutralized, and a single magnetic domain is formed in the direction of the aligned magnetization direction. In this way, since light passing through the RIG with a single magnetic domain undergoes Faraday rotation in one direction, the RIG single crystal can be used as the Faraday rotator 112. Alternatively, in the case where the Faraday rotator 112 is made of a locking (or non - magnetic) garnet, once magnetized in a strong external magnetic field, the Faraday rotator 112 can maintain its single - domain structure even if the external magnetic field is removed later (although the single - domain structure can be reversed by applying a strong external magnetic field). Thus, when used as the Faraday rotator 112, the locking garnet does not require an external magnetic field. In other words, the locking garnet is used as the Faraday rotator 112 without being exposed to an external magnetic field.

[0029] As described above, Figures 1A - 1E is provided as one or more examples. Other examples may be different from the examples described with respect to Figures 1A - 1E the examples.

[0030] Figures 2A - 2C shows one or more exemplary embodiments 200 of a two - stage isolator including two isolator cores arranged in parallel. For example, as Figures 2A - 2C shown, the two - stage isolator can include a first isolator core 210 - 1 and a second isolator core 210 - 2 arranged in parallel. For example, as Figure 2A shown, the first isolator core 210 - 1 can be disposed in the input leg of the optical component, and the second isolator core 210 - 2 can be disposed in the output leg of the optical component. In this case, the two - stage isolator can be used together with a collimating lens 230 and a WDM filter 240 in a single - isolator application to transmit only light with a specific wavelength (e.g., 1550 nm) without being integrated with a pump.

[0031] As Figure 2B shown, the first isolator core 210-1 and the second isolator core 210-2 (collectively referred to as the dual-stage isolator 210) include a first set of layers and a second set of layers cut from the same block. For example, the first isolator core 210-1 includes a first HWP 216-1 and a first Faraday rotator 212-1 disposed between a first pair of birefringent crystal plates 214-11, 214-12, and the second isolator core 210-2 includes a second HWP 216-2 and a second Faraday rotator 212-2 disposed between a second pair of birefringent crystal plates 214-22, 214-21. In this case, each of the first isolator core 210-1 and the second isolator core 210-2 has four crystal layers, the first isolator core 210-1 and the second isolator core 210-2 are both cut from one large block, and the first isolator core 210-1 and the second isolator core 210-2 are disposed adjacent to each other with different crystal layer orientations. For example, in some embodiments, the first Faraday rotator 212-1 and the second Faraday rotator 212-2 may be oriented such that the magnetic domain direction of the first Faraday rotator 212-1 is opposite to the magnetic domain direction of the second Faraday rotator 212-2. Thus, because the respective layers are cut from the same raw material, the dual-stage isolator 210 may include two isolator cores 210-1, 210-2, where each layer has certain properties (e.g., opposite orientations, the same thickness, the same angle, etc.) such that the isolator cores 210-1, 210-2 cancel out each other's material and / or assembly tolerances. In this way, the input light received at the input polarizer (e.g., birefringent plate 214-11) of the first isolator core 210-1 can be spatially separated into components with orthogonal polarizations (e.g., O light and E light), and these components can be recombined at the output polarizer (e.g., birefringent plate 214-12) of the first isolator core 210-1 even if the first set of layers is not perfectly adjusted. In a similar aspect, after the light laterally shifted by the first isolator core 210-1 passes through the collimating lens 230 and is reflected back by the WDM filter 240 toward the output branch, the reflected light received at the input polarizer (e.g., birefringent plate 214-21) of the second isolator core 210-2 can be spatially separated into orthogonal components, which are recombined again at the output polarizer (e.g., birefringent plate 214-22) of the second isolator core 210-2 such that the second isolator core 210-2 laterally shifts the light received at the input polarizer. Additionally, as Figure 2CAs shown and indicated by reference numeral 250, any backward-propagating light reflected from the output leg to the input leg is split into components having orthogonal polarizations. In this way, the design of the dual-stage isolator 210 is such that the backward-propagating light is directed or otherwise steered away from the location or point where light is input through the input leg. In this way, the backward-propagating light is not coupled into the input leg, which achieves high isolation between the input leg and the output leg.

[0032] As described above, Figures 2A - 2C are provided as one or more examples. Other examples may be different from the examples described with respect to Figures 2A - 2C the examples described.

[0033] Figures 3A - 3C One or more exemplary embodiments 300 of a dual-stage isolator including two isolator cores arranged in series are shown. For example, as Figures 3A - 3C shown, the dual-stage isolator may include a first isolator core 310-1 and a second isolator core 310-2 arranged in series. For example, as Figure 3A shown, both the first isolator core 310-1 and the second isolator core 310-2 may be disposed in the input leg of the optical assembly, where the compensator 350 is disposed in the output leg. Alternatively, in some embodiments, both the first isolator core 310-1 and the second isolator core 310-2 (collectively referred to as the dual self-compensating isolator core 310) may be disposed in the output leg of the optical assembly, where the compensator 350 is disposed in the input leg. In this case, the dual-stage isolator may be used with a collimating lens 330 and a WDM filter 340 in an isolated isolator application to transmit only light having a specific wavelength (e.g., 1550 nm) without integration with a pump, or the dual-stage isolator may be used in a pump combiner or another suitable device or application to achieve higher isolation relative to the single-stage design described above.

[0034] As Figure 3BAs shown, the first isolator core 310-1 and the second isolator core 310-2 respectively include a first set of layers and a second set of layers cut from the same block. For example, the first isolator core 310-1 includes a first HWP 316-1 and a first Faraday rotator 312-1 disposed between a first pair of birefringent crystal plates 314-11, 314-12, and the second isolator core 310-2 includes a second HWP 316-2 and a second Faraday rotator 312-2 disposed between a second pair of birefringent crystal plates 314-22, 314-21. In this case, when the first isolator core 310-1 and the second isolator core 310-2 are arranged in series, the first Faraday rotator 312-1 and the second Faraday rotator 312-2 can be oriented such that the magnetic domain directions of the first Faraday rotator 312-1 and the second Faraday rotator 312-2 are the same. Thus, since the respective layers are cut from the same raw material (e.g., the same garnet and / or YVO 4 block), the dual-stage isolator 310 can include two isolator cores 310-1, 310-2 having specific properties (e.g., the same magnetic orientation, thickness, angle, etc.). In this way, the input light received at the input polarizer (e.g., the birefringent plate 314-11) of the first isolator core 310-1 can be spatially separated into components having orthogonal polarizations (e.g., O light and E light), and the components can be recombined at the output polarizer (e.g., the birefringent plate 314-12) of the first isolator core 310-1 even if the first set of layers is not perfectly adjusted. In a similar aspect, the light laterally shifted by the first isolator core 310-1 is received at the input polarizer (e.g., the birefringent plate 314-21) of the second isolator core 310-2, where the light is again spatially separated into orthogonal components, and the orthogonal components are recombined at the output polarizer (e.g., the birefringent plate 314-22) of the second isolator core 310-2. Thus, after the light laterally shifted by the second isolator core 310-2 passes through the collimating lens 330, the light including components having orthogonal polarizations is reflected back to the output branch by the WDM filter 340. In addition, as Figure 3C shown and indicated by reference numeral 350, any backward-traveling light reflected from the output branch to the input branch is separated into components having orthogonal polarizations. In this way, the design of the dual-stage isolator 310 is such that the backward-traveling light is guided or otherwise steered away from the location or point where the light is input through the input branch, whereby the backward-traveling light is not coupled into the input branch, and high isolation is achieved between the input branch and the output branch.

[0035] As described above, Figures 3A - 3C is provided as one or more examples. Other examples may be different from the examples described with respect to Figures 3A - 3C the description.

[0036] The foregoing disclosure provides illustrations and descriptions, but is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Modifications and variations can be made in light of the above disclosure, or can be obtained from practice of the embodiments. Additionally, unless the foregoing disclosure explicitly provides a reason why one or more embodiments cannot be combined, any of the embodiments described herein can be combined.

[0037] As used herein, the terms circuit, integrated circuit, chip, chipset, die, semiconductor device, electronic device, and / or the like are intended to be broadly interpreted to apply to the various embodiments described herein, as these terms are used interchangeably in the electronics art. With respect to circuits, integrated circuits, and / or the like, power, ground, and various signals can be coupled between circuit elements (e.g., resistors, inductors, capacitors, transistors, and / or the like) via physical conductive connections. Such connections can be referred to as inputs, outputs, input / output (I / O), terminals, wires, pins, pads, ports, interfaces, or similar variations and combinations. Although connections between and within circuits can be made via electrical conductors, circuits and other circuit elements can additionally or alternatively be coupled by optical, mechanical, magnetic, electrostatic, electromagnetic, and / or other suitable interfaces.

[0038] It is apparent that the systems and / or methods described herein can be implemented in different forms of hardware, software, circuits, or combinations thereof. The actual specific control hardware, software code, or circuits used to implement these systems and / or methods do not limit the implementation. Accordingly, the operation and behavior of the systems and / or methods are described herein without reference to specific software code—it being understood that software and hardware (e.g., integrated circuits) can be designed to implement the systems and / or methods based on the description herein.

[0039] Although specific combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of the various embodiments. In fact, many of these features can be combined in ways not specifically recited in the claims and / or disclosed in the specification. Although each of the dependent claims listed below can directly depend on only one claim, the disclosure of the various embodiments includes the combination of each dependent claim with every other claim in the claim set.

[0040] Unless explicitly described as such, elements, acts, or instructions used herein should not be construed as critical or essential. Additionally, as used herein, the article "a" is intended to include one or more items and may be interchangeable with "one or more." Further, as used herein, the article "the" is intended to include one or more items referenced in conjunction with the article "the" and may be interchangeable with "one or more." Additionally, as used herein, the term "set" is intended to include one or more items (e.g., related items, unrelated items, combinations of related and unrelated items, etc.). In cases where only one item is intended, the phrase "only one" or similar language is used. Additionally, as used herein, the terms "have," "having," "possess," etc. are intended to be open-ended terms. Additionally, unless otherwise explicitly stated, the phrase "based on" is intended to mean "at least partially based on." Further, as used herein, the term "or" when used in series is intended to be inclusive and may be interchangeable with "and / or" unless otherwise explicitly stated (e.g., if used in combination with "either" or "only one").

[0041] In addition, for ease of description, spatial relative terms such as "below," "lower," "above," "upper," etc. may be used herein to describe the relationship of one element or feature to another element or feature as shown in the figures. Spatial relative terms are intended to encompass different orientations of a device, apparatus, and / or element in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatial relative descriptors used herein may be interpreted accordingly.

Claims

1. A device, comprising: a plurality of birefringent crystal plates, comprising: a first birefringent crystal plate for separating input light, a second birefringent crystal plate for combining light, wherein the first birefringent crystal plate and the second birefringent crystal plate can be rotated to corresponding angles such that the light is combined into an output, and a third birefringent crystal plate configured to have a fixed orientation relative to a Faraday rotator.

2. The device according to claim 1, wherein the third birefringent crystal plate is a half-wave plate.

3. The device according to claim 1, wherein the third birefringent crystal plate is configured to be located between the first birefringent crystal plate and the second birefringent crystal plate.

4. The device according to claim 1, wherein the third birefringent crystal plate is configured to be located between the Faraday rotator and the first birefringent crystal plate.

5. The device according to claim 1, wherein the device is configured to be arranged at an input branch of an optical component or to be arranged at an output branch of the optical component.

6. The device according to claim 1, wherein an additional device is configured to be serially coupled to the device, and wherein the additional device comprises: an additional Faraday rotator; and an additional plurality of birefringent crystal plates, comprising: a fourth birefringent crystal plate for separating input light, a fifth birefringent crystal plate for combining the separated light, wherein the fourth birefringent crystal plate and the fifth birefringent crystal plate are rotated to corresponding angles such that the light is combined into an additional output, and a sixth birefringent crystal plate configured to have a fixed orientation relative to the additional Faraday rotator.

7. The device according to claim 6, wherein the third birefringent crystal plate and the sixth birefringent crystal plate are half-wave plates.

8. The device according to claim 6, wherein the Faraday rotator and the additional Faraday rotator are configured to have the same magnetic domain direction.

9. The device according to claim 6, wherein the output includes output light laterally shifted by the device, and wherein the output light is received by the additional device as an input.

10. The device according to claim 6, wherein the additional device is configured to be coupled to a collimating lens.

11. An optical component, comprising: a collimating lens; and an isolator, comprising: a plurality of birefringent crystal plates, comprising: a first birefringent crystal plate for separating input light, a second birefringent crystal plate for combining light, wherein the first birefringent crystal plate and the second birefringent crystal plate can be rotated to corresponding angles such that the light is combined into an output, and a third birefringent crystal plate configured to have a fixed orientation relative to a Faraday rotator.

12. The optical component according to claim 11, wherein the third birefringent crystal plate is a half-wave plate.

13. The optical component according to claim 11, wherein the third birefringent crystal plate is configured to be located between the first birefringent crystal plate and the second birefringent crystal plate.

14. The optical component according to claim 11, wherein the third birefringent crystal plate is configured to be located between the Faraday rotator and the first birefringent crystal plate.

15. The optical component according to claim 11, wherein the isolator is configured to be arranged at the input branch of the optical component or to be arranged at the output branch of the optical component.

16. The optical component according to claim 11, further comprising: an additional isolator, comprising: an additional Faraday rotator; and an additional plurality of birefringent crystal plates, comprising: a fourth birefringent crystal plate for separating input light, a fifth birefringent crystal plate for combining the separated light, wherein the fourth birefringent crystal plate and the fifth birefringent crystal plate can be rotated to corresponding angles such that the light is combined into an additional output, and a sixth birefringent crystal plate configured to have a fixed orientation relative to the additional Faraday rotator.

17. The optical component according to claim 16, wherein the third birefringent crystal plate and the sixth birefringent crystal plate are half-wave plates.

18. The optical component according to claim 16, wherein the Faraday rotator and the additional Faraday rotator are configured to have the same magnetic domain direction.

19. The optical component according to claim 16, wherein the output includes output light that is laterally displaced by the isolator, and wherein the output light is received by the additional isolator as an input.

20. The optical component according to claim 16, wherein the additional isolator is configured to be coupled to the collimating lens.

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