WO2024020809A1 - An optical device and method for tuning optical splitting based on electric poling - Google Patents

An optical device and method for tuning optical splitting based on electric poling Download PDF

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Publication number
WO2024020809A1
WO2024020809A1 PCT/CN2022/108046 CN2022108046W WO2024020809A1 WO 2024020809 A1 WO2024020809 A1 WO 2024020809A1 CN 2022108046 W CN2022108046 W CN 2022108046W WO 2024020809 A1 WO2024020809 A1 WO 2024020809A1
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Prior art keywords
waveguide arm
electrodes
waveguide
optical
optical device
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PCT/CN2022/108046
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French (fr)
Inventor
Stephan SCHNEZ
Benbo XU
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Huawei Technologies Co., Ltd.
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Priority to PCT/CN2022/108046 priority Critical patent/WO2024020809A1/en
Publication of WO2024020809A1 publication Critical patent/WO2024020809A1/en

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    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/29Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
    • G02F1/31Digital deflection, i.e. optical switching
    • G02F1/313Digital deflection, i.e. optical switching in an optical waveguide structure
    • G02F1/3136Digital deflection, i.e. optical switching in an optical waveguide structure of interferometric switch type
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/29Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
    • G02F1/31Digital deflection, i.e. optical switching
    • G02F1/313Digital deflection, i.e. optical switching in an optical waveguide structure
    • G02F1/3132Digital deflection, i.e. optical switching in an optical waveguide structure of directional coupler type
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2201/00Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
    • G02F2201/12Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 electrode
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2202/00Materials and properties
    • G02F2202/07Materials and properties poled

Definitions

  • the disclosure relates to a tunable waveguide optical device, for example, for an optical splitter.
  • the disclosure proposes the optical device, and a corresponding method for operating the optical device.
  • the optical device comprises a first waveguide arm, a second waveguide arm, an input coupler, an output coupler, and means for tuning at least the first waveguide arm.
  • a Mach-Zehnder Interferometer is a device used to determine the relative phase shift variations between two collimated beams derived by splitting light from a single source.
  • MZIs have been used to, e.g., measure phase shifts between the two collimated beams caused by a sample or a change in length of one of the two paths.
  • MZIs are used as an electro-optic modulator for phase and amplitude modulation of light.
  • a fiber-optic splitter also known as a beam splitter, is an integrated waveguide optical power distribution device.
  • fiber-optic splitters are one of the most important passive devices for optical to fiber links.
  • a fiber-optic splitter is an optical fiber tandem device with potentially several input and output terminals.
  • a fiber-optic splitter may be applicable to a passive optical network to connect a main distribution frame and a terminal equipment and to branch an optical signal.
  • uneven split ratios may be obtained by optical distribution network (ODN) fast pre-connect architectures.
  • ODN optical distribution network
  • the split ratios of conventional uneven optical splitters are fixed. As a result, the deployment mode is limited and only a few cascading levels are supported.
  • a conventional waveguide Mach-Zehnder interferometer (MZI) structure may comprise a heater on the waveguide of one arm of the MZI, in order to tune the refractive index of the waveguide.
  • the heater may be powered to generate heat and change the temperature in said arm of the MZI, thereby changing the refractive index of the waveguide via the thermo-optic effect.
  • the two arms differ in terms of the refractive index and the optical signal travelling through the two arms acquire a different phase.
  • the interference at the second coupler is changed as a function of the change in refractive index, i.e. of applied heat, and this changes the output optical power as well as the split ratio.
  • embodiments of this disclosure aim to adjustably and efficiently split an optical input signal into a first optical signal in a first waveguide arm and a second optical signal in a second waveguide arm.
  • An object is to improve the flexibility and stability of splitting the optical input signal according to, for example, an optical splitting ratio. After setting the splitting ratio, this value is to be kept without further power consumption.
  • Electric poling is conventionally used during fabrication of certain crystals to phase-match the relative phase between two or more frequencies of light, as the light propagates through a crystal, to stimulate constructive interference and not destructive interference.
  • Periodically-poled lithium niobate is an engineered, quasi-phase-matched material.
  • engineered refers to the fact that the orientation of the ferroelectric domains in lithium-niobate (LN) crystal are periodically inverted and/or poled by applying a voltage to the LN crystal.
  • LN lithium-niobate
  • the process of (electric) poling is a part of the manufacturing process.
  • the newly generated photons may at least partially interfere constructively with previously generated photons.
  • a first aspect of this disclosure provides an optical device comprising: a first waveguide arm and a second waveguide arm, wherein at least the first waveguide arm is made of a material that allows for electric poling; an input coupler configured to receive an optical input signal and to split the optical input signal into a first optical signal in the first waveguide arm and a second optical signal in the second waveguide arm; an output coupler configured to recombine the first optical signal received from the first waveguide arm and the second optical signal received from the second waveguide arm; and at least one pair of electrodes configured to apply an electrical field across at least one part of the first waveguide arm to change an effective refractive index in the at least one part of the first waveguide arm.
  • At least the first waveguide arm may be made of a ferroelectric nonlinear crystal which allows for electric poling via ferroelectric domain engineering.
  • the second waveguide arm may also be made of a material that allows for electric poling.
  • At least one other pair of electrodes may be configured to apply an electrical field across at least one part of the second waveguide arm.
  • each waveguide arm may experience a change in an effective refractive index.
  • the at least one pair of electrodes and the at least one other pair of electrodes may be configured to apply an electrical field in opposite directions and/or may be integrated into each arm with an opposite electric field configuration.
  • the respective parts of the first and second waveguide arms may be electrically poled in opposite directions.
  • the application of a voltage for poling may be applied after installation of the optical device in an optical communication network.
  • the first waveguide arm is made of at least one of lithium niobate, lithium tantalate, potassium titanyl phosphate, potassium titanyl arsenate, rubidium titanyl phosphate, and rubidium titanyl arsenate.
  • the input coupler is configured to split the optical input signal into the first signal and the second signal according to a split ratio, and wherein the change of the effective refractive index in the at least one part of the first waveguide arm changes the split ratio.
  • the optical device further comprises an insulating substrate, wherein the input coupler, the first and the second waveguide arm, and the output coupler form an integral waveguide system on or in the insulation substrate.
  • the at least one pair of electrodes is configured to apply the electrical field across the at least one part of the first waveguide arm to invert an orientation of electric dipoles in each unit cell of a crystal structure of the material in the at least one part of the first waveguide arm.
  • the optical device comprises multiple pairs of electrodes, each pair of electrodes being configured to apply an electrical field across a respective part of the first waveguide arm to change an effective refractive index in the respective part of the first waveguide arm.
  • the optical device further comprises: a controller configured to selectively control one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes to apply the electrical fields across the respective parts of the first waveguide arm to change an effective refractive index in the respective parts of the first waveguide arm.
  • the controller may be comprised in a different device than the other components of the optical device.
  • the controller may be only connected to the other components of the optical device when the effective refractive index in the respective parts of the first waveguide arm are meant to be changed.
  • the controller is further configured to selectively control one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes multiple times to apply the electrical fields across the respective parts of the first waveguide arm to change an effective refractive index in the respective parts of the first waveguide arm multiple times.
  • the effective refractive index in the respective parts of the first waveguide arm may be changed multiple times to new values.
  • the optical split ratio of the optical device may be adjusted during operation or when changes in the optical network infrastructure require a new setpoint.
  • the controller is configured to selectively control the one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes to electrically pole the material in the respective parts of the first waveguide arm after installation of the optical device into an optical network.
  • an optical splitting ratio can be fine-tuned after installation of the optical device into the optical network.
  • the controller may be configured to selectively control the one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes to electrically pole the material in the respective parts of the first waveguide arm before installation of the optical device into the optical network.
  • the controller is configured to control the one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes multiple times to adjust the electric poling of the material in the respective one or more parts of the first waveguide arm based on one or more changes of the optical network.
  • the multiple pairs of electrodes are arranged periodically along the length of the first waveguide arm.
  • the multiple pairs of electrodes may be arranged periodically along the length of the first waveguide arm, wherein the periodicity may be defined by one or more periodic distances along the length of the first waveguide arm.
  • a first periodic distance may define a periodic distance between different pairs of electrodes of a first set of pairs of electrodes
  • a second periodic distance may define a periodic distance between two or more respective first sets of pairs of electrodes.
  • the multiple pairs of electrodes are arranged equispaced along the length of the first waveguide arm.
  • the first waveguide arm and the second waveguide arm are of equal length.
  • the first waveguide arm and the second waveguide arm form a waveguide structure, wherein the waveguide structure is line symmetric regarding a path that is positioned equidistant between the first waveguide arm and the second waveguide arm and extends along a length of the first waveguide arm.
  • the first waveguide arm and the second waveguide arm form a curved waveguide structure.
  • the curved waveguide structure comprises at least a first straight section, a second straight section, and a third straight section, which are arranged along a direction along the first waveguide arm and connected in series by a first curved section and a second curved section of the curved waveguide structure.
  • the curved waveguide structure comprises at least a first section, a second section, and a third curved section, which are arranged along a direction along the first waveguide arm, and wherein the first section and the second section are parallel to each other and connected in series by the third curved section, and/or wherein the first section and the second section are separated by a constant distance in a second direction that is perpendicular to the direction along the first waveguide arm of the first section.
  • a second aspect of this disclosure provides a method for operating an optical device.
  • the optical device comprises: an input coupler, an output coupler, at least one pair of electrodes, a first waveguide arm, and a second waveguide arm, wherein at least the first waveguide arm is made of a material that allows for electric poling.
  • the method comprises: receiving, with the input coupler, an optical input signal and to split the optical input signal into a first optical signal in the first waveguide arm and a second optical signal in the second waveguide arm; recombining, with the output coupler, the first optical signal received from the first waveguide arm and the second optical signal received from the second waveguide arm; and applying, with the at least one pair of electrodes, an electrical field across at least one part of the first waveguide arm to change an effective refractive index in the at least one part of the first waveguide arm.
  • the method of the second aspect may have implementation forms that correspond to the implementation forms of the device of the first aspect.
  • the method of the second aspect and its implementation forms achieve the advantages and effects described above for the optical device of the first aspect and its respective implementation forms.
  • FIG. 1 shows an optical device according to an embodiment of this disclosure.
  • FIG. 2 shows an exemplary optical device comprising an MZI according to an embodiment of this disclosure.
  • FIG. 3a shows an exemplary at least one part of a first waveguide arm comprising a crystal made of a material that allows for electric poling according to an embodiment of this disclosure, wherein all electric dipoles are in parallel.
  • FIG. 3b shows an exemplary at least one part of a first waveguide arm comprising a crystal made of a material that allows for electric poling according to an embodiment of this disclosure, wherein the electric dipoles are periodically flipped.
  • FIG. 4 shows an exemplary optical device comprising a MZI and segmented electrodes according to an embodiment of this disclosure.
  • FIG. 5 shows an exemplary optical device comprising a MZI with curved waveguide arms according to an embodiment of this disclosure.
  • FIG. 6 shows an exemplary optical device comprising a MZI according to an embodiment of this disclosure.
  • FIG. 7 shows a PON system comprising an optical device according to an embodiment of this disclosure.
  • FIG. 8 shows a method according to an embodiment of this disclosure.
  • FIG. 1 shows an optical device 100 according to an embodiment of this disclosure.
  • the device 100 comprises a first waveguide arm 101, a second waveguide arm 102, an input coupler 103, an output coupler 104, and at least one pair of electrodes 105.
  • FIG. 1 shows an optical input signal 200, wherein the input coupler 103 is configured to receive the optical input signal 200 and to split the optical input signal 200 into a first optical signal 200a in the first waveguide arm 101 and a second optical signal 200b in the second waveguide arm 102.
  • the at least one pair of electrodes 105 is configured to apply an electrical field across at least one part 101a of the first waveguide arm 101 to change an effective refractive index in the at least one part 101a of the first waveguide arm 101.
  • the output coupler 104 is configured to recombine the first optical signal 200a received from the first waveguide arm 101 and the second optical signal 200b received from the second waveguide arm 102.
  • At least the first waveguide arm 101 is made of a material that allows for electric poling.
  • the optical device 100 may be a waveguide optical splitter and/or comprise a MZI.
  • the optical device 100 may comprise a waveguide optical splitter and/or a MZI.
  • a waveguide optical splitter may comprise a first waveguide arm 101, a second waveguide arm 102, an input coupler 103, an at least one pair of electrodes 105, and an output coupler 104.
  • a MZI may comprise a first waveguide arm 101, a second waveguide arm 102, an in input coupler 103, and an output coupler 104.
  • FIG. 2 shows an exemplary optical device 100 comprising an MZI.
  • Changing the direction of electric dipoles in, for example, a lithium-niobate-on-insulator (LNOI) material comprised in a first waveguide arm 101 of a waveguide optical splitter may also change the effective refractive index.
  • electric poling may change the effective refractivity in, for example, LNOI in a MZI such that the ratio of optical splitting in the waveguide optical splitter can be adapted to the required value.
  • the ratio of optical splitting may be adapted even after installation of the waveguide optical splitter in an optical system and/or optical network.
  • a MZI may be based on waveguides based on LNOI or another material which can be electrically poled.
  • FIG. 2 shows electrodes 105 that are integrated in one arm 101 of an MZI such that a voltage can be applied over the arm 101 and induce an electric field.
  • the typical separation of the electrodes 105 may be, for example, between 1 and 20 micrometers.
  • the electrodes may be integrated in one arm 101 of the MZI during manufacturing.
  • the effective refractive index in one arm 101 of the MZI may be changed by applying a voltage to the electrodes 105.
  • the optical splitting ratio can be adapted to a desired and/or specific value.
  • the required electric fields for changing the direction of electric dipoles may be, for example, on the order of 22 kV/mm. With the above mentioned spacing of the electrodes 105, typical voltages may be several 100 V to 1000 V. To obtain these voltages, appropriate packaging may be used.
  • a direct current (DC) voltage may be required for only a few milliseconds and the electric poling may be performed by a trained specialist. The required current flow and the required power during poling may be negligible. Only a DC voltage and not an AC voltage may be used for electric poling.
  • a DC voltage source may be required to apply the voltage to the electrodes 105.
  • the required energy may be very small, as the required current flow may be very low. For example, there may be no substantial current flow involved.
  • a DC voltage of 100 V to 1000 V may be applied to the electrodes 105.
  • the voltages applied to the electrodes 105 may be higher compared to voltages applied in conventional devices.
  • the electric fields between the electrodes 105 may be larger than 10 kV/mm.
  • the electric dipoles may be fixed in their new and/or adjusted position.
  • the new effective refractive index may be fixed, for example in a passive state, and it may not be necessary to further apply voltages or temperatures to maintain the new effective refractive index.
  • the optical splitting ratio as set by electric poling may be kept at a specific value even after turning off the voltage.
  • the electric dipoles may stay in a passive state, wherein the passive state may be a new and/or adjusted passive state.
  • Optical losses in the optical device 100 may be lower compared to conventional approaches based on phase-change materials.
  • the word “fixed” may refer to being in a passive state.
  • FIG. 3a shows an exemplary at least one part 101a of a first waveguide arm 101 comprising a crystal made of a material that allows for electric poling, wherein all electric dipoles are in parallel.
  • FIG. 3b shows an exemplary at least one part 101a of a first waveguide arm 101 comprising a crystal made of a material that allows for electric poling, wherein the electric dipoles are periodically flipped.
  • FIGs. 3a and 3b show the at least one pair of electrodes 105 for electric poling of the material.
  • the top electrodes are periodically segmented and the bottom electrode is continuous.
  • a DC voltage is applied between the periodically segmented top electrodes and continuous bottom electrode such that the electric dipoles of the material are periodically flipped.
  • Electric poling of the material that allows for electric poling may be used to phase-match the relative phase between two or more frequencies of light, as the light propagates through a crystal, to stimulate constructive interference and not destructive interference.
  • the material for example periodically-poled lithium niobate (PPLN) , that allows for electric poling may be an engineered quasi-phase-matched material.
  • the term “engineered” may refer to the fact that the orientation of the ferroelectric domains in the material, for example, an LN crystal may be periodically inverted and/or poled.
  • the material that allows for electric poling may form and/or comprise a crystal.
  • the inverted portions of the crystal may generate photons that are 180° out of phase with the generated photon that would have been created at that point in the crystal if it had not been poled.
  • LN forms a ferroelectric crystal, which means that each unit cell in the crystal has a small electric dipole moment.
  • the orientation of the electric dipole in a unit cell is dependent on the positions of the, for example, niobium and lithium, ions in that unit cell.
  • the application of an intense electric field can invert the crystal structure within a unit cell and as a result flip the orientation of the electric dipole.
  • the electric field needed to invert the crystal may be very large, for example on the order of 22kV/mm, and may be applied for only a few milliseconds, after which the inverted sections of the crystal may be permanently imprinted into the crystal structure.
  • a periodic electrode structure may be deposited on the LN wafer, and a voltage may be applied to invert the crystal underneath the electrodes.
  • the material, for example PPLN, that allows for electric poling may be adjusted and/or poled multiple times, and/or may be adjusted and/or poled after installation in an optical network.
  • FIG. 4 shows an exemplary optical device 100 comprising an MZI and segmented electrodes 105 according to an embodiment of this disclosure. Due to the segmented electrodes 105 only a certain fraction 101a of one arm 101 of the MZI can be electrically poled.
  • the electrodes 105 may be segmented and/or voltage may be applied to only some of the segmented electrodes according to the required level of optical splitting.
  • the optical device 100 may be tuned to a specific level of optical splitting.
  • FIG. 5 shows an exemplary optical device 100 comprising a MZI with curved waveguide arms to increase the overall length of the waveguide arms that is accessible to the electrodes for poling.
  • the effect of electric poling on the change of the effective refractivity may be small.
  • the distance over which the waveguides, for example LNOI waveguides, should be poled may be long.
  • a curved waveguide may be used, as shown in FIG. 5.
  • the electrodes may additionally be segmented as also shown in FIG. 2.
  • small and long may be in reference to conventional waveguides and/or conventional waveguide optical splitters.
  • FIG. 6 shows an exemplary optical device 100 comprising a MZI according to an embodiment of this disclosure.
  • FIG. 6 shows two pairs of electrodes 105 that are integrated respectively in the first waveguide arm 101 of the MZI and the second waveguide arm 102 of the MZI such that a voltage can be applied respectively over both arms 101, 102 and induce an electric field over both arms 101, 102.
  • the two pairs of electrodes 105 are integrated into each arm with an opposite electric field configuration.
  • Both waveguide arms 101, 102 may be electrically poled, for example, in opposite directions.
  • ODN optical distribution network
  • Components of the ODN may comprise fiber optic cables, an optical splitter, an optical distribution cabinet (ODC, FDH) , a fiber distribution box (FDB) , an optical connector, an optical joint closure (FOC) , and a terminal box (FTB) .
  • FIG. 7 shows a PON system comprising an optical device 100, which is referred to as “splitter” .
  • the output coupler 104 of the optical device 100 is configured to generate three output signals which are subsequently transmitted to the ONTs.
  • the three output signals may be equal or may be unequal.
  • Splitting the optical input signal 200 is not required to be symmetrical. One signal may be stronger than another one. Hence, the splitter 100 may be required to be tuneable.
  • FIG. 7 shows a device for Wavelength Division Multiplexing (WDM) .
  • WDM Wavelength Division Multiplexing
  • Embodiments of this disclosure may combine some or all of the following benefits:
  • the optical splitting ratio can be changed reversibly.
  • the new value of the optical splitting ratio is in a passive state.
  • the optical device 100 may lead to low optical losses because the phase of the material that allows for electric poling is not changed compared to, for example, phase-change materials which are conventionally used.
  • the controller which may be comprised in the optical device 100 may be a processor.
  • the processor may be configured to perform, conduct or initiate the various operations of the optical device 100 described herein.
  • the processor may comprise hardware and/or may be controlled by software.
  • the hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry.
  • the digital circuitry may comprise components such as application-specific integrated circuits (ASICs) , field-programmable arrays (FPGAs) , digital signal processors (DSPs) , or multi-purpose processors.
  • the optical device 100 may further comprise memory circuitry, which stores one or more instruction (s) that can be executed by the processor in particular under control of the software.
  • the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor causes the various operations of the optical device 100 to be performed.
  • the optical device 100 may comprises one or more processors and a non-transitory memory connected to the one or more processors.
  • the non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the optical device 100 to perform, conduct or initiate the operations or methods described herein.
  • FIG. 8 shows a method 300 according to an embodiment of this disclosure.
  • the method 300 may be performed by the optical device 100.
  • the method 300 comprises a step 301 of receiving, with an input coupler 103, an optical input signal 200 and to split the optical input signal 200 into a first optical signal 200a in a first waveguide arm 101 and a second optical signal 200b in a second waveguide arm 102. Further, the method 300 comprises a step 302 of recombining, with an output coupler 104, the first optical signal 200a received from the first waveguide arm 101 and the second optical signal 200b received from the second waveguide arm 102.
  • the method 300 comprises a step 303 of applying, with an at least one pair of electrodes 105, an electrical field across at least one part 101a of the first waveguide arm 101 to change an effective refractive index in the at least one part 101a of the first waveguide arm.
  • the step of applying 303 may be performed before the step of receiving 301 and the step of recombining 302.

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Abstract

The disclosure relates to a tunable waveguide optical device (100), for example, for an optical splitter. The disclosure proposes the tunable waveguide optical device (100), and a corresponding method for operating the tunable waveguide optical device (100). The tunable waveguide optical device (100) comprises a first waveguide arm (101) and a second waveguide arm (102), wherein at least the first waveguide arm (101) is made of a material that allows for electric poling; an input coupler (103) for splitting the optical input signal (200) into a first optical signal (200a) in the first waveguide arm (101) and a second optical signal (200b) in the second waveguide arm (102); an output coupler (104) for recombining the first optical signal (200a) and the second optical signal (200b); and at least one pair of electrodes (105) configured to apply an electrical field across at least one part (101a) of the first waveguide arm (101) to change an effective refractive index in the at least one part (101a) of the first waveguide arm (101).

Description

AN OPTICAL DEVICE AND METHOD FOR TUNING OPTICAL SPLITTING BASED ON ELECTRIC POLING TECHNICAL FIELD
The disclosure relates to a tunable waveguide optical device, for example, for an optical splitter. The disclosure proposes the optical device, and a corresponding method for operating the optical device. The optical device comprises a first waveguide arm, a second waveguide arm, an input coupler, an output coupler, and means for tuning at least the first waveguide arm.
BACKGROUND
A Mach-Zehnder Interferometer (MZI) is a device used to determine the relative phase shift variations between two collimated beams derived by splitting light from a single source. Conventionally, MZIs have been used to, e.g., measure phase shifts between the two collimated beams caused by a sample or a change in length of one of the two paths. In optical telecommunications, MZIs are used as an electro-optic modulator for phase and amplitude modulation of light.
A fiber-optic splitter, also known as a beam splitter, is an integrated waveguide optical power distribution device. Conventionally, fiber-optic splitters are one of the most important passive devices for optical to fiber links. A fiber-optic splitter is an optical fiber tandem device with potentially several input and output terminals. A fiber-optic splitter may be applicable to a passive optical network to connect a main distribution frame and a terminal equipment and to branch an optical signal.
Conventionally, uneven split ratios may be obtained by optical distribution network (ODN) fast pre-connect architectures. The split ratios of conventional uneven optical splitters are fixed. As a result, the deployment mode is limited and only a few cascading levels are supported.
A conventional waveguide Mach-Zehnder interferometer (MZI) structure may comprise a heater on the waveguide of one arm of the MZI, in order to tune the refractive index of the waveguide. The heater may be powered to generate heat and change the temperature in said arm of the MZI, thereby changing the refractive index of the waveguide via the thermo-optic effect. As a result, the two arms differ in terms of the refractive index and the optical signal travelling through the two arms acquire a different phase. Hence, the interference at the second coupler is changed as a function of the change in refractive index, i.e. of applied heat, and this changes the output optical power as well as the split ratio.
However, maintaining the changed split ratio requires constant heat application and energy consumption.
SUMMARY
In view of the above, embodiments of this disclosure aim to adjustably and efficiently split an optical input signal into a first optical signal in a first waveguide arm and a second optical signal in a second waveguide arm. An object is to improve the flexibility and stability of splitting the optical input signal according to, for example, an optical splitting ratio. After setting the splitting ratio, this value is to be kept without further power consumption.
These and other objectives are achieved by this disclosure as described in the enclosed independent claims. Advantageous implementations are further defined in the dependent claims.
The disclosure is based on the following considerations. Electric poling is conventionally used during fabrication of certain crystals to phase-match the relative phase between two or more frequencies of light, as the light propagates through a crystal, to stimulate constructive interference and not destructive interference.
Periodically-poled lithium niobate (PPLN) is an engineered, quasi-phase-matched material. The term “engineered” refers to the fact that the orientation of the ferroelectric domains in lithium-niobate (LN) crystal are periodically inverted and/or poled by  applying a voltage to the LN crystal. For conventional applications of PPLN, the process of (electric) poling is a part of the manufacturing process.
By choosing a correct periodicity, with which to flip the orientation of the domains in the LN crystal, the newly generated photons may at least partially interfere constructively with previously generated photons.
A first aspect of this disclosure provides an optical device comprising: a first waveguide arm and a second waveguide arm, wherein at least the first waveguide arm is made of a material that allows for electric poling; an input coupler configured to receive an optical input signal and to split the optical input signal into a first optical signal in the first waveguide arm and a second optical signal in the second waveguide arm; an output coupler configured to recombine the first optical signal received from the first waveguide arm and the second optical signal received from the second waveguide arm; and at least one pair of electrodes configured to apply an electrical field across at least one part of the first waveguide arm to change an effective refractive index in the at least one part of the first waveguide arm.
At least the first waveguide arm may be made of a ferroelectric nonlinear crystal which allows for electric poling via ferroelectric domain engineering.
The second waveguide arm may also be made of a material that allows for electric poling. At least one other pair of electrodes may be configured to apply an electrical field across at least one part of the second waveguide arm. Thus, each waveguide arm may experience a change in an effective refractive index. The at least one pair of electrodes and the at least one other pair of electrodes may be configured to apply an electrical field in opposite directions and/or may be integrated into each arm with an opposite electric field configuration. Thus, the respective parts of the first and second waveguide arms may be electrically poled in opposite directions.
In contrast to e.g. conventional PPLN based devices, the application of a voltage for poling may be applied after installation of the optical device in an optical communication network.
In a further implementation form of the first aspect, the first waveguide arm is made of at least one of lithium niobate, lithium tantalate, potassium titanyl phosphate, potassium titanyl arsenate, rubidium titanyl phosphate, and rubidium titanyl arsenate.
In a further implementation form of the first aspect, the input coupler is configured to split the optical input signal into the first signal and the second signal according to a split ratio, and wherein the change of the effective refractive index in the at least one part of the first waveguide arm changes the split ratio.
In a further implementation form of the first aspect, the optical device further comprises an insulating substrate, wherein the input coupler, the first and the second waveguide arm, and the output coupler form an integral waveguide system on or in the insulation substrate.
In a further implementation form of the first aspect, the at least one pair of electrodes is configured to apply the electrical field across the at least one part of the first waveguide arm to invert an orientation of electric dipoles in each unit cell of a crystal structure of the material in the at least one part of the first waveguide arm.
In a further implementation form of the first aspect, the optical device comprises multiple pairs of electrodes, each pair of electrodes being configured to apply an electrical field across a respective part of the first waveguide arm to change an effective refractive index in the respective part of the first waveguide arm.
In a further implementation form of the first aspect, the optical device further comprises: a controller configured to selectively control one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes to apply the electrical fields across the respective parts of the first waveguide arm to change an effective refractive index in the respective parts of the first waveguide arm.
The controller may be comprised in a different device than the other components of the optical device. The controller may be only connected to the other components of the optical device when the effective refractive index in the respective parts of the first waveguide arm are meant to be changed.
In a further implementation form of the first aspect, the controller is further configured to selectively control one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes multiple times to apply the electrical fields across the respective parts of the first waveguide arm to change an effective refractive index in the respective parts of the first waveguide arm multiple times.
Thus, the effective refractive index in the respective parts of the first waveguide arm may be changed multiple times to new values.
By changing an effective refractive index in the respective parts of the first waveguide arm multiple times the optical split ratio of the optical device may be adjusted during operation or when changes in the optical network infrastructure require a new setpoint.
In a further implementation form of the first aspect, the controller is configured to selectively control the one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes to electrically pole the material in the respective parts of the first waveguide arm after installation of the optical device into an optical network.
Thus, an optical splitting ratio can be fine-tuned after installation of the optical device into the optical network.
Additionally or alternatively, the controller may be configured to selectively control the one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes to electrically pole the material in the respective parts of the first waveguide arm before installation of the optical device into the optical network.
In a further implementation form of the first aspect, the controller is configured to control the one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes multiple times to adjust the electric poling of the material in the respective one or more parts of the first waveguide arm based on one or more changes of the optical network.
In a further implementation form of the first aspect, the multiple pairs of electrodes are arranged periodically along the length of the first waveguide arm.
The multiple pairs of electrodes may be arranged periodically along the length of the first waveguide arm, wherein the periodicity may be defined by one or more periodic distances along the length of the first waveguide arm. For example, a first periodic distance may define a periodic distance between different pairs of electrodes of a first set of pairs of electrodes, and a second periodic distance may define a periodic distance between two or more respective first sets of pairs of electrodes.
In a further implementation form of the first aspect, the multiple pairs of electrodes are arranged equispaced along the length of the first waveguide arm.
In a further implementation form of the first aspect, the first waveguide arm and the second waveguide arm are of equal length.
In a further implementation form of the first aspect, the first waveguide arm and the second waveguide arm form a waveguide structure, wherein the waveguide structure is line symmetric regarding a path that is positioned equidistant between the first waveguide arm and the second waveguide arm and extends along a length of the first waveguide arm.
In a further implementation form of the first aspect, the first waveguide arm and the second waveguide arm form a curved waveguide structure.
In a further implementation form of the first aspect, the curved waveguide structure comprises at least a first straight section, a second straight section, and a third straight section, which are arranged along a direction along the first waveguide arm and connected in series by a first curved section and a second curved section of the curved waveguide structure.
In a further implementation form of the first aspect, the curved waveguide structure comprises at least a first section, a second section, and a third curved section, which are arranged along a direction along the first waveguide arm, and wherein the first section and the second section are parallel to each other and connected in series by the third  curved section, and/or wherein the first section and the second section are separated by a constant distance in a second direction that is perpendicular to the direction along the first waveguide arm of the first section.
A second aspect of this disclosure provides a method for operating an optical device.
The optical device comprises: an input coupler, an output coupler, at least one pair of electrodes, a first waveguide arm, and a second waveguide arm, wherein at least the first waveguide arm is made of a material that allows for electric poling. The method comprises: receiving, with the input coupler, an optical input signal and to split the optical input signal into a first optical signal in the first waveguide arm and a second optical signal in the second waveguide arm; recombining, with the output coupler, the first optical signal received from the first waveguide arm and the second optical signal received from the second waveguide arm; and applying, with the at least one pair of electrodes, an electrical field across at least one part of the first waveguide arm to change an effective refractive index in the at least one part of the first waveguide arm.
The method of the second aspect may have implementation forms that correspond to the implementation forms of the device of the first aspect. The method of the second aspect and its implementation forms achieve the advantages and effects described above for the optical device of the first aspect and its respective implementation forms.
It has to be noted that all devices, elements, units and means described in the disclosure could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the disclosure as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof.
BRIEF DESCRIPTION OF DRAWINGS
The above described aspects and implementation forms will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which
FIG. 1 shows an optical device according to an embodiment of this disclosure.
FIG. 2 shows an exemplary optical device comprising an MZI according to an embodiment of this disclosure.
FIG. 3a shows an exemplary at least one part of a first waveguide arm comprising a crystal made of a material that allows for electric poling according to an embodiment of this disclosure, wherein all electric dipoles are in parallel.
FIG. 3b shows an exemplary at least one part of a first waveguide arm comprising a crystal made of a material that allows for electric poling according to an embodiment of this disclosure, wherein the electric dipoles are periodically flipped.
FIG. 4 shows an exemplary optical device comprising a MZI and segmented electrodes according to an embodiment of this disclosure.
FIG. 5 shows an exemplary optical device comprising a MZI with curved waveguide arms according to an embodiment of this disclosure.
FIG. 6 shows an exemplary optical device comprising a MZI according to an embodiment of this disclosure.
FIG. 7 shows a PON system comprising an optical device according to an embodiment of this disclosure.
FIG. 8 shows a method according to an embodiment of this disclosure.
DETAILED DESCRIPTION OF EMBODIMENTS
FIG. 1 shows an optical device 100 according to an embodiment of this disclosure. The device 100 comprises a first waveguide arm 101, a second waveguide arm 102, an input coupler 103, an output coupler 104, and at least one pair of electrodes 105. Further, FIG. 1 shows an optical input signal 200, wherein the input coupler 103 is configured to receive the optical input signal 200 and to split the optical input signal 200 into a first optical signal 200a in the first waveguide arm 101 and a second optical signal 200b in the second waveguide arm 102. The at least one pair of electrodes 105 is configured to apply an electrical field across at least one part 101a of the first waveguide arm 101 to change an effective refractive index in the at least one part 101a of the first waveguide arm 101. Further, the output coupler 104 is configured to recombine the first optical signal 200a received from the first waveguide arm 101 and the second optical signal 200b received from the second waveguide arm 102.
Generally, at least the first waveguide arm 101 is made of a material that allows for electric poling.
The optical device 100 may be a waveguide optical splitter and/or comprise a MZI. Alternatively, the optical device 100 may comprise a waveguide optical splitter and/or a MZI.
For example, a waveguide optical splitter may comprise a first waveguide arm 101, a second waveguide arm 102, an input coupler 103, an at least one pair of electrodes 105, and an output coupler 104.
A MZI may comprise a first waveguide arm 101, a second waveguide arm 102, an in input coupler 103, and an output coupler 104.
FIG. 2 shows an exemplary optical device 100 comprising an MZI.
Changing the direction of electric dipoles in, for example, a lithium-niobate-on-insulator (LNOI) material comprised in a first waveguide arm 101 of a waveguide optical splitter may also change the effective refractive index. Thus, electric poling may change the effective refractivity in, for example, LNOI in a MZI such that the ratio of optical splitting in the waveguide optical splitter can be adapted to the required value. The ratio  of optical splitting may be adapted even after installation of the waveguide optical splitter in an optical system and/or optical network.
Instead of using a phase-change material in the arms of a MZI, where electric heaters are used, a MZI may be based on waveguides based on LNOI or another material which can be electrically poled.
FIG. 2 shows electrodes 105 that are integrated in one arm 101 of an MZI such that a voltage can be applied over the arm 101 and induce an electric field. The typical separation of the electrodes 105 may be, for example, between 1 and 20 micrometers. The electrodes may be integrated in one arm 101 of the MZI during manufacturing.
After installation of the equipment, the effective refractive index in one arm 101 of the MZI may be changed by applying a voltage to the electrodes 105. Thus, the optical splitting ratio can be adapted to a desired and/or specific value. The required electric fields for changing the direction of electric dipoles may be, for example, on the order of 22 kV/mm. With the above mentioned spacing of the electrodes 105, typical voltages may be several 100 V to 1000 V. To obtain these voltages, appropriate packaging may be used. A direct current (DC) voltage may be required for only a few milliseconds and the electric poling may be performed by a trained specialist. The required current flow and the required power during poling may be negligible. Only a DC voltage and not an AC voltage may be used for electric poling.
A DC voltage source may be required to apply the voltage to the electrodes 105. The required energy may be very small, as the required current flow may be very low. For example, there may be no substantial current flow involved.
A DC voltage of 100 V to 1000 V may be applied to the electrodes 105. The voltages applied to the electrodes 105 may be higher compared to voltages applied in conventional devices. The electric fields between the electrodes 105 may be larger than 10 kV/mm.
Once the electric poling is finished, the electric dipoles may be fixed in their new and/or adjusted position. Thus, the new effective refractive index may be fixed, for example in a passive state, and it may not be necessary to further apply voltages or temperatures to  maintain the new effective refractive index. The optical splitting ratio as set by electric poling may be kept at a specific value even after turning off the voltage. The electric dipoles may stay in a passive state, wherein the passive state may be a new and/or adjusted passive state. Optical losses in the optical device 100 may be lower compared to conventional approaches based on phase-change materials. The word “fixed” may refer to being in a passive state.
FIG. 3a shows an exemplary at least one part 101a of a first waveguide arm 101 comprising a crystal made of a material that allows for electric poling, wherein all electric dipoles are in parallel.
FIG. 3b shows an exemplary at least one part 101a of a first waveguide arm 101 comprising a crystal made of a material that allows for electric poling, wherein the electric dipoles are periodically flipped.
Further, the FIGs. 3a and 3b show the at least one pair of electrodes 105 for electric poling of the material. In this example, the top electrodes are periodically segmented and the bottom electrode is continuous.
In this example, a DC voltage is applied between the periodically segmented top electrodes and continuous bottom electrode such that the electric dipoles of the material are periodically flipped.
Electric poling of the material that allows for electric poling may be used to phase-match the relative phase between two or more frequencies of light, as the light propagates through a crystal, to stimulate constructive interference and not destructive interference.
The material, for example periodically-poled lithium niobate (PPLN) , that allows for electric poling may be an engineered quasi-phase-matched material. The term “engineered” may refer to the fact that the orientation of the ferroelectric domains in the material, for example, an LN crystal may be periodically inverted and/or poled. The material that allows for electric poling may form and/or comprise a crystal. The inverted portions of the crystal may generate photons that are 180° out of phase with the generated photon that would have been created at that point in the crystal if it had not been poled.  By choosing a correct periodicity with which to flip the orientation of the crystal, the newly generated photons may at least partially interfere constructively with previously generated photons.
For example, LN forms a ferroelectric crystal, which means that each unit cell in the crystal has a small electric dipole moment. The orientation of the electric dipole in a unit cell is dependent on the positions of the, for example, niobium and lithium, ions in that unit cell. The application of an intense electric field can invert the crystal structure within a unit cell and as a result flip the orientation of the electric dipole. The electric field needed to invert the crystal may be very large, for example on the order of 22kV/mm, and may be applied for only a few milliseconds, after which the inverted sections of the crystal may be permanently imprinted into the crystal structure. To produce and/or pole PPLN, a periodic electrode structure may be deposited on the LN wafer, and a voltage may be applied to invert the crystal underneath the electrodes.
The material, for example PPLN, that allows for electric poling may be adjusted and/or poled multiple times, and/or may be adjusted and/or poled after installation in an optical network.
Conventional devices using phase-change materials may use electric poling according to embodiments of this disclosure instead. Thus, applications in, e.g., routers, optical computers, and modulators can be envisaged.
FIG. 4 shows an exemplary optical device 100 comprising an MZI and segmented electrodes 105 according to an embodiment of this disclosure. Due to the segmented electrodes 105 only a certain fraction 101a of one arm 101 of the MZI can be electrically poled.
In order to offer the possibility to change a level of the effective refractivity and, e.g., the optical splitting ratio, the electrodes 105 may be segmented and/or voltage may be applied to only some of the segmented electrodes according to the required level of optical splitting.
By selecting a specific periodicity the optical device 100 may be tuned to a specific level of optical splitting.
FIG. 5 shows an exemplary optical device 100 comprising a MZI with curved waveguide arms to increase the overall length of the waveguide arms that is accessible to the electrodes for poling.
The effect of electric poling on the change of the effective refractivity may be small. Thus, the distance over which the waveguides, for example LNOI waveguides, should be poled may be long. In order to achieve this with compact footprint, a curved waveguide may be used, as shown in FIG. 5. The electrodes may additionally be segmented as also shown in FIG. 2.
The words “small” and “long” may be in reference to conventional waveguides and/or conventional waveguide optical splitters.
FIG. 6 shows an exemplary optical device 100 comprising a MZI according to an embodiment of this disclosure. FIG. 6 shows two pairs of electrodes 105 that are integrated respectively in the first waveguide arm 101 of the MZI and the second waveguide arm 102 of the MZI such that a voltage can be applied respectively over both  arms  101, 102 and induce an electric field over both  arms  101, 102. In this example, the two pairs of electrodes 105 are integrated into each arm with an opposite electric field configuration. Both waveguide  arms  101, 102 may be electrically poled, for example, in opposite directions.
In a conventional passive optical network (PON) system, data transmission starts at an optical line terminal (OLT) and ends at an optical network terminal (ONT) . An optical distribution network (ODN) connects these two points and provides a physical channel. Components of the ODN may comprise fiber optic cables, an optical splitter, an optical distribution cabinet (ODC, FDH) , a fiber distribution box (FDB) , an optical connector, an optical joint closure (FOC) , and a terminal box (FTB) .
FIG. 7 shows a PON system comprising an optical device 100, which is referred to as “splitter” . In this example, the output coupler 104 of the optical device 100 is configured  to generate three output signals which are subsequently transmitted to the ONTs. The three output signals may be equal or may be unequal. Splitting the optical input signal 200 is not required to be symmetrical. One signal may be stronger than another one. Hence, the splitter 100 may be required to be tuneable. Further, FIG. 7 shows a device for Wavelength Division Multiplexing (WDM) .
The following shows the differences of conventional devices and exemplary embodiments of this disclosure, and the corresponding advantageous effects.
Figure PCTCN2022108046-appb-000001
Embodiments of this disclosure may combine some or all of the following benefits:
● The optical splitting ratio can be changed reversibly.
● The new value of the optical splitting ratio is in a passive state.
● The optical device 100 may lead to low optical losses because the phase of the material that allows for electric poling is not changed compared to, for example, phase-change materials which are conventionally used.
The controller which may be comprised in the optical device 100 may be a processor.
Generally, the processor may be configured to perform, conduct or initiate the various operations of the optical device 100 described herein. The processor may comprise hardware and/or may be controlled by software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs) , field-programmable arrays (FPGAs) , digital signal processors (DSPs) , or multi-purpose processors. The optical device 100 may further comprise memory circuitry, which stores one or more instruction (s) that can be executed by the processor in particular under control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor causes the various operations of the optical device 100 to be performed. In one embodiment, the optical device 100 may comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the optical device 100 to perform, conduct or initiate the operations or methods described herein.
FIG. 8 shows a method 300 according to an embodiment of this disclosure. The method 300 may be performed by the optical device 100. The method 300 comprises a step 301 of receiving, with an input coupler 103, an optical input signal 200 and to split the optical input signal 200 into a first optical signal 200a in a first waveguide arm 101 and a second optical signal 200b in a second waveguide arm 102. Further, the method 300 comprises a step 302 of recombining, with an output coupler 104, the first optical signal 200a received from the first waveguide arm 101 and the second optical signal 200b received from the second waveguide arm 102. Further, the method 300 comprises a step 303 of applying, with an at least one pair of electrodes 105, an electrical field across at least one part 101a of the first waveguide arm 101 to change an effective refractive index in the at least one part 101a of the first waveguide arm.
To preconfigure an optical splitting ratio, the step of applying 303 may be performed before the step of receiving 301 and the step of recombining 302.
The disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by  those persons skilled in the art and practicing the claimed matter, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.

Claims (18)

  1. An optical device (100) comprising:
    a first waveguide arm (101) and a second waveguide arm (102) , wherein at least the first waveguide arm (101) is made of a material that allows for electric poling;
    an input coupler (103) configured to receive an optical input signal (200) and to split the optical input signal (200) into a first optical signal (200a) in the first waveguide arm (101) and a second optical signal (200b) in the second waveguide arm (102) ;
    an output coupler (104) configured to recombine the first optical signal (200a) received from the first waveguide arm (101) and the second optical signal (200b) received from the second waveguide arm (102) ; and
    at least one pair of electrodes (105) configured to apply an electrical field across at least one part (101a) of the first waveguide arm (101) to change an effective refractive index in the at least one part (101a) of the first waveguide arm (101) .
  2. The optical device (100) according to claim 1, wherein the first waveguide arm (101) is made of at least one of lithium niobate, lithium tantalate, potassium titanyl phosphate, potassium titanyl arsenate, rubidium titanyl phosphate, and rubidium titanyl arsenate.
  3. The optical device (100) according to claim 1 or 2, wherein the input coupler (103) is configured to split the optical input signal (200) into the first signal and the second signal according to a split ratio, and wherein the change of the effective refractive index in the at least one part (101a) of the first waveguide arm (101) changes the split ratio.
  4. The optical device (100) according to any one of the preceding claims, further comprising
    an insulating substrate,
    wherein the input coupler (103) , the first and the second waveguide arm (102) , and the output coupler (104) form an integral waveguide system on or in the insulation substrate.
  5. The optical device (100) according to any one of the preceding claims,
    wherein the at least one pair of electrodes (105) is configured to apply the electrical field across the at least one part (101a) of the first waveguide arm (101) to  invert an orientation of electric dipoles in each unit cell of a crystal structure of the material in the at least one part (101a) of the first waveguide arm (101) .
  6. The optical device (100) according to any one of the preceding claims,
    wherein the optical device (100) comprises multiple pairs of electrodes (105) , each pair of electrodes (105) being configured to apply an electrical field across a respective part (101a) of the first waveguide arm (101) to change an effective refractive index in the respective part (101a) of the first waveguide arm (101) .
  7. The optical device (100) according to claim 6, further comprising:
    a controller configured to selectively control one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes (105) to apply the electrical fields across the respective parts (101a) of the first waveguide arm (101) to change an effective refractive index in the respective parts (101a) of the first waveguide arm (101) .
  8. The optical device (100) according to claim 7, wherein the controller is further configured to selectively control one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes (105) multiple times to apply the electrical fields across the respective parts (101a) of the first waveguide arm (101) to change an effective refractive index in the respective parts (101a) of the first waveguide arm (101) multiple times.
  9. The optical device (100) according to claim 7 or 8, wherein the controller is configured to selectively control the one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes (105) to electrically pole the material in the respective parts (101a) of the first waveguide arm (101) after installation of the optical device (100) into an optical network.
  10. The optical device (100) according to claim 9, wherein the controller is configured to control the one pair of electrodes, or some pairs of electrodes, or all pairs of electrodes of the multiple pairs of electrodes (105) multiple times to adjust the electric poling of the material in the respective one or more parts (101a) of the first waveguide arm (101) based on one or more changes of the optical network.
  11. The optical device (100) according to any one of the claims 6 to 10, wherein the multiple pairs of electrodes (105) are arranged periodically along the length of the first waveguide arm (101) .
  12. The optical device (100) according to any one of the claims 6 to 11, wherein the multiple pairs of electrodes (105) are arranged equispaced along the length of the first waveguide arm (101) .
  13. The optical device (100) according to any one of the preceding claims, wherein the first waveguide arm (101) and the second waveguide arm (102) are of equal length.
  14. The optical device (100) according any one of the preceding claims,
    wherein the first waveguide arm (101) and the second waveguide arm (102) form a waveguide structure,
    wherein the waveguide structure is line symmetric regarding a path that is positioned equidistant between the first waveguide arm (101) and the second waveguide arm (102) and extends along a length of the first waveguide arm (101) .
  15. The optical device (100) according to one of the preceding claims, wherein the first waveguide arm (101) and the second waveguide arm (102) form a curved waveguide structure.
  16. The optical device (100) according to claim 15, wherein the curved waveguide structure comprises at least a first straight section, a second straight section, and a third straight section, which are arranged along a direction along the first waveguide arm (101) and connected in series by a first curved section and a second curved section of the curved waveguide structure.
  17. The optical device (100) according to claim 15 or 16,
    wherein the curved waveguide structure comprises at least a first section, a second section, and a third curved section, which are arranged along a direction along the first waveguide arm (101) , and
    wherein the first section and the second section are parallel to each other and connected in series by the third curved section, and/or
    wherein the first section and the second section are separated by a constant distance in a second direction that is perpendicular to the direction along the first waveguide arm (101) of the first section.
  18. A method (300) for operating an optical device (100) ,
    the optical device (100) comprising:
    an input coupler (103) , an output coupler (104) , at least one pair of electrodes (105) , a first waveguide arm (101) , and a second waveguide arm (102) , wherein at least the first waveguide arm (101) is made of a material that allows for electric poling, and
    the method comprising:
    receiving (301) , with the input coupler (103) , an optical input signal (200) and to split the optical input signal (200) into a first optical signal (200a) in the first waveguide arm (101) and a second optical signal (200b) in the second waveguide arm (102) ;
    recombining (302) , with the output coupler (104) , the first optical signal (200a) received from the first waveguide arm (101) and the second optical signal (200b) received from the second waveguide arm (102) ; and
    applying (303) , with the at least one pair of electrodes (105) , an electrical field across at least one part (101a) of the first waveguide arm (101) to change an effective refractive index in the at least one part (101a) of the first waveguide arm (101) .
PCT/CN2022/108046 2022-07-26 2022-07-26 An optical device and method for tuning optical splitting based on electric poling WO2024020809A1 (en)

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CN1434929A (en) * 2000-04-06 2003-08-06 布克哈姆技术公共有限公司 Optical modulator with pre-determined frequency chirp
CN110609399A (en) * 2019-08-05 2019-12-24 华南师范大学 Folding silicon-lithium niobate hybrid integrated electro-optical modulator and preparation method thereof
CN113050309A (en) * 2021-04-09 2021-06-29 嘉兴微智光子科技有限公司 Electro-optical modulator with bent arm

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Publication number Priority date Publication date Assignee Title
US5161206A (en) * 1990-10-03 1992-11-03 Telefonaktiebolaget L M Ericsson Method of linearizing a transmission function of a modulator arrangement, and a linearized modulator
CN1434929A (en) * 2000-04-06 2003-08-06 布克哈姆技术公共有限公司 Optical modulator with pre-determined frequency chirp
US6532315B1 (en) * 2000-10-06 2003-03-11 Donald J. Lenkszus Variable chirp optical modulator having different length electrodes
CN110609399A (en) * 2019-08-05 2019-12-24 华南师范大学 Folding silicon-lithium niobate hybrid integrated electro-optical modulator and preparation method thereof
CN113050309A (en) * 2021-04-09 2021-06-29 嘉兴微智光子科技有限公司 Electro-optical modulator with bent arm

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