WO2025052237A1 - Ferroelectric device with electrode for poling - Google Patents

Abstract

An electro-optic method and device that allows efficient poling of a ferroelectric device. The electro-optic device comprises a waveguide, barium titanate (BTO) layer adjacent to the waveguide. One or more poling electrodes are provided for poling the Pockels material.

Description

FERROELECTRIC DEVICE WITH ELECTRODE FOR POLIN

RELATED APPLICATIONS

[ oooi] This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63/580,719, filed on September 6, 2023, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[ 0002] A silicon p-i-n modulator is an optical device that utilizes the properties of a p-i-n (positive-intrinsic-negative) junction to modulate light. In a p-i-n junction, the "p" region is p- doped silicon containing an excess of holes (positive charge carriers), the "n" region is n-doped silicon containing an excess of electrons (negative charge carriers), and the "i" region (intrinsic) is essentially an insulating silicon layer that separates the p and n regions. When a voltage is applied across this junction, it changes the density of free charge carriers present in the junction/intrinsic region. This creates a plasma dispersion effect in the junction/intrinsic region that changes the refractive index and absorption due to the presence of free carriers (electrons and holes).

[ 0003] A Mach-Zehnder (MZ) modulator is a type of interferometer used for modulating the amplitude of an optical signal. The Mach-Zehnder silicon p-i-n phase modulator includes a silicon substrate that is often heavily doped with either n-type or p-type impurities. A waveguide splitter carries the input light and splits it into two separate waveguides forming a ‘Y’ junction. One or both arms of the Y-junction contain a p-i-n phase modulator structure. When a voltage is applied across the p-i-n junction, it changes the refractive index thereby modulating the phase of light travelling through that arm. A waveguide combiner interferes the light from the two arms. The amplitude is controlled by the voltages applied to the p-i-n junction(s) in the arm(s) causing constructive or destructive interference.

[ 0004] Indium Phosphide (InP) is also often used in optical modulators due to its electrooptic properties. In a Mach-Zehnder InP modulator, the modulating mechanism is typically the quantum-confined Stark effect, which refers to the change in the absorption and refractive index of a quantum-well stack resulting from an applied electric field.

[ 0005] MZ modulators can also be fabricated in Pockels materials such as barium titanate (BaTiCh. BTO), lithium niobate (LiNbCh. LN), Lead Zirconate Titanate (PZT), and siliconorganic hybrid (SOH) modulators that exhibit a change of their refractive index under an applied electric field (also known as the Pockels effect). For example, thin films of Lead Zirconate Titanate (PZT) can be grown on a silicon enabling high speed Pockels modulation on SiN waveguide. SOH modulators combine the advantages of large-scale silicon photonic integration with the extraordinarily high electro-optic (EO) coefficients obtained by molecular engineering of organic materials. In these modulators it is not required to apply a DC bias in operation to ensure the reverse-biasing of the junctions as is the case with silicon p-i-n and InP modulators. The circuits are also electrically different as the bias connects through a diode in the case of the silicon p-i-n modulators whereas in the BTO, LN, PZT, and SOH modulators, the bias is capacitively coupled.

SUMMARY OF THE INVENTION

[ 0006] Pockels material such as BTO, LN, PZT and SOH require poling ferroelectric domains in order to have a net nonlinear electro optic (EO) response and/or to create a differential push-pull MZ modulator. In order to achieve push-pull modulation in a MZ modulator, the material polarization and/or modulating radio frequency (RF) signals must be asymmetrically applied in the two arms of the modulator (parallel in one arm, anti-parallel in the other). If not, only one arm can be modulated.

[ 0007 ] The poling voltage required to pole the domains in the MZ modulator is relatively large and therefore needs to be electrically isolated from the often RF modulation signals. This can be achieved by using bias tees, but on-chip bias tees are inefficient to implement, being bulky and expensive and potentially degrading performance. Also, in some cases, poling is needed during operation using a DC bias that is decoupled from the RF signals.

[ 0008 ] The present invention concerns a waveguide device such as a BTO or LN MZ modulator. The modulator could also be constructed from PZT or SOH The waveguide structure includes a Pockels layer with an optical overlap such that a refractive index change in the Pockels layer results in a phase acceleration or retardation of propagating light in the arm or arms of the MZ modulator. The electrode configuration includes two separate sets of electrodes that are electrically decoupled. One set of electrodes are ground electrode(s) G or signal electrodes (S⁺ and S") providing the reference potential and optionally the drive signal (a signal from DC to GHz). (Using ground and signal electrodes on the modulator will result in single- ended driven push-pull MZ modulator; using the same structure with S- and S+ will result in differentially driven push-pull MZ modulator). [ 0009] Another set of electrodes function as poling electrodes for providing a poling voltage. This voltage will be used to create a poling field in the Pockels layer relative to the reference potential resulting in a net ferroelectric polarization.

[ 0010] In one example, the two sets of electrodes are arranged to create alternating regions in the Pockels layer where the drive signal creates an electric field in the Pockels layer that is at the same time parallel to the ferroelectric polarization of one of the regions and anti-parallel to the ferroelectric polarization of the other region resulting in an opposite change of the real part of refractive index in the alternating regions.

[ 0011] In examples, the poling electrodes can be designed with a high inductance to decouple them from the signal electrodes in the case of RF drive signals.

[ 0012] Also, the set of signal electrodes can be configured to carry a single-ended or differential drive signals.

[ 0013] Also, additional GND/common electrodes can be added outside of the signal and poling electrode sets. The signal electrodes can be terminated through a load impedance between signal electrodes or to additional GND electrodes.

[ 0014] In summary, the present approach provides for the introduction of narrow DC poling line between S⁺ and S" electrodes. The addition of the poling electrodes allows for the application of a poling bias to Pockels material during any or all of bum-in/start-up/operation, while also enabling differential driving of the phase shifter.

[ 0015] In general, according to one aspect, the invention features an electro-optic device comprising Pockels material, one or more waveguides on the Pockels material, one or more signal electrodes for phase modulating light propagating in the one or more waveguides, and one or more poling electrodes for poling the Pockels material.

[ 0016] In examples, the inductance is associated the one or more poling electrodes to prevent high frequency current in the one or more poling electrodes.

[ 0017] The Pockels material can be BTO or LN. The poling voltage can be applied to the poling electrodes during bum-in and/or start-up and/or operation in different use cases.

[ 0018] In illustrated examples, the waveguides are arranged as a MZ interferometer, such as with a poling electrode is between arms of the MZ interferometer and signal electrodes can be located on outer sides of the arms. [ 0019 ] The signal electrodes can include two electrodes receiving a differential signal, such as by having signal electrodes include a high frequency ground electrode and a signal electrode.

[ 0020 ] One or more poling electrodes are split in their length to enable equalization.

[ 0021 ] In general, according to one aspect, the invention features a method of operation of an electro-optic device including Pockels material, one or more waveguides associated with the Pockels material, and one or more signal electrodes. The method comprises phase modulating light propagating in the one or more waveguides by applying signal(s) to the signal electrodes and poling the Pockels material with one or more poling electrodes.

[ 0022 ] The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[ 0023 ] In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings:

[ 0024 ] FIGS. 1A and IB are schematic top and cross-sectional views showing a desired MZ modulator with material polarization that is different between the two arms;

[ 0025 ] FIGS . 2A and 2B are schematic top and cross-sectional views showing a MZ modulator when material polarization is the same between the two arms;

[ 0026] FIGS. 3 A and 3B are schematic top and cross-sectional views showing a MZ modulator when there is no material polarization in the arms;

[ 0027 ] FIGS. 4A and 4B are a schematic circuit diagram and a cross-sectional view showing a MZ modulator according to the present invention;

[ 0028 ] FIGS. 4C and 4D are plots of possible poling voltages versus time for poling and operation showing how the poling electrodes are driven; [ 0029 ] FIG. 5 A and 5B are schematic cross-sectional views showing other arrangements of the signal, DC, and ground electrodes for MZ modulators;

[ 0030 ] FIG. 6A, 6B, 6C, 6D, 6E, and 6F are schematic cross-sectional views showing additional arrangements of the signal, DC, and ground electrodes for MZ modulators;

[ 0031 ] FIGS. 7A, 7B, and 7C are a schematic cross-sectional view and schematic circuit diagrams showing another MZ modulator according to the present invention;

[ 0032 ] FIGS . 8 A and 8B are a schematic circuit diagram and a schematic cross-sectional view showing another MZ modulator or phase shifter according to the present invention; and

[ 0033 ] FIG. 9 is a schematic circuit diagram showing a MZ modulator according to the present invention with a split poling electrode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[ 0034 ] The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[ 0035 ] As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Also, all conjunctions used are to be understood in the most inclusive sense possible. Thus, the word "or" should be understood as having the definition of a logical "or" rather than that of a logical "exclusive or" unless the context clearly necessitates otherwise. Further, the singular forms and the articles "a", "an" and "the" are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms: includes, comprises, including and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Further, it will be understood that when an element, including component or subsystem, is referred to and/or shown as being connected or coupled to another element, it can be directly connected or coupled to the other element or intervening elements may be present. [ 0036] It will be understood that although terms such as “first” and “second” are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, an element discussed below could be termed a second element, and similarly, a second element may be termed a first element without departing from the teachings of the present invention.

[ 0037 ] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[ 0038 ] FIGS. 1A and IB are top and cross-sectional views showing a desirable MZ modulator 50 in which material polarization is different between the two waveguides Al A2 forming the two arms. In the illustrated example, the Pockels material P is arranged as a common substrate under the MZ waveguides include the input, Y-splitter Y, arms Al, A2, Y coupler or combiner C, and output. The regions of the substrate Pl, P2 respectively under the waveguides Al, A2 have opposite material polarizations.

[ 0039 ] In general, MZ modulators for transceivers, for example, are desired to be driven by a differential RF signal applied between signal electrodes (S+ and S-) and to operate in a push- pull fashion; the modulating RF voltage advances the phase in one arm waveguide Al while retarding the phase in the other arm waveguide A2. For Pockels modulators, the RF voltage and material polarization must be opposite in the two arms of the Mach-Zehnder interferometer. In most cases, this requires different poling of the Pockels material in regions Pl and Pl.

[ 0040 ] This configuration is generally not possible. Instead, the materials are poled uniformly or are unpoled.

[ 0041 ] FIGS . 2A and 2B are top and cross-sectional views showing a MZ modulator 50 when material polarization Pl, P2 is uniform between the two arms Al, A2. In this case, there will be no difference in the phase changes induced in each arm.

[ 0042 ] FIGS . 3 A and 3B are top and cross-sectional views showing a MZ modulator when there is no material polarization, unpoled, in the arms. Here also, there will be no difference in the phase changes induced in each arm. [ 0043 ] As shown, for Pockels modulators, the RF voltage and material polarization must be opposite in the two arms of the Mach-Zehnder interferometer. In most cases, this requires poling of the Pockels material. Generally poling of the material uses a DC poling voltage that needs to be applied without interfering with the RF signals. The poling voltage can in some implementations be applied prior to operation and is not necessarily required during operation.

[ 0044 ] FIG. 4A is a schematic circuit diagram of MZ modulator according to the present invention.

[ 0045 ] Two waveguides Al, A2 carry an optical signal in two arms of an MZ modulator 50. These waveguides are often made from a material deposited on top of Pockels layer P. The waveguides are often a material such as SiN, Si, amorphous Si, SiOxNy. These waveguides typically 0.1-1 pm thick and 0.2-2 pm wide.

[ 0046] A DC electrode DC is provided between and running parallel with the two signal electrodes S+ and S-. These electrodes are typically 0.01-10pm thick, 0.1-100 pm wide.

[ 0047 ] Different materials can be used for the electrodes S+ and S- and DC including W, Au, Ti, TiN, Cu, Al, AICu, AlCuSi and any combinations of these. It should be noted, however, that the DC electrode can use a material with higher resistivity than the metals listed above. Possibilities of the DC electrode include doped Si, ITO (or other conducting transparent oxides), or other similar materials.

[ 0048 ] A voltage source V provides both a reference voltage Vref and a modulating or signal differential voltage Vppd that is applied across the signal electrodes S+ and S- through termination resistor R. Vref is typically 0V since RF signals have no voltage offset - but it may be for example 3-4V since in some implementations the driver circuit is biased through the RF electrodes of the modulator. A bias poling voltage source Vpol is connected to a center DC electrode DC through an inductor L.

[ 0049 ] A DC poling voltage Vpol can thus be applied between the DC electrode and each of the signal electrodes S⁺ and S" to pole the underlying Pockels material P. A differential signal Vppd is applied across the signal electrodes S⁺ and S". The inductor L makes the DC electrode invisible to this high frequency signal Vppd since it functions as a high frequency/RF choke. Thus, the capacitive coupling between S⁺ and S" or between a G electrode and S electrodes is maintained while the inductance of the DC line ensures that no high-frequency current is flowing to the bias poling source Vpol. [ 0050 ] Thus, in this arrangement there are effectively three sets of electrodes where one set receives a potentially RF signal (S⁺ and S") Vppd and another set (S⁺ and DC) and (S‘ and DC) receives the poling voltage(s) Vpol.

[ 0051 ] FIG. 4B the modulator in cross-section.

[ 0052 ] The substrate P is a Pockels material such as BTO or LN. The differential RF signal Vppd applied between signal electrodes (S+ and S-). The oppositely poled regions Pl and P2 of the Pockels material P are created by establishing the poling voltage between (DC and S⁺) and (DC and S’).

[ 0053 ] The high-inductance DC electrode DC between the signal electrodes S+ and S- allows for the application of DC voltage for poling of the Pockels material substrate P such that region Pl and P2 have different polarizations. Generally, the polarity of the DC voltage is arbitrary and can be positive or negative depending on the needs of the application. In addition, the DC poling voltage can be applied before (e.g. as part of bum-in or startup sequence) and/or during operation.

[ 0054 ] The high inductance of the DC electrode DC due to the inductor L blocks RF current from passing to GND through DC connection. Also, by making the DC electrode dimensionally smaller laterally, the electric field induced by the RF is largely unaffected by the DC electrode's presence.

[ 0055 ] Figs. 4C and 4D show two possible examples of how the bias poling voltage source Vpol is operated.

[ 0056] In Fig. 4C, the Vpol voltage is first raised to a high poling voltage and dropped to an intermediate level for operation when the differential RF signal Vppd is applied between signal electrodes (S+ and S-).

[ 0057 ] In Fig. 4D, the Vpol voltage is raised to the high poling voltage and dropped back to a low voltage, such as zero, for operation when the differential RF signal Vppd is applied between signal electrodes (S+ and S-).

[ 0058 ] In some modes of operation, a current is ran through any, some, or all of the signal S⁺ and S and/or RF ground G, or DC electrodes to resistively heat the Pockels material substrate to facilitate the poling as described in U.S. Prov. Appl. No. 63/431,448, filed 12/09/2022 and PCT Appl. No. PCT/IB2023/061112, both entitled Ferroelectric device with integrated heater for poling, which are both incorporated herein by this reference in their entirety. [ 0059 ] FIGs. 5 A and 5B are cross-sectional views showing other arrangements of the signal, DC, and ground electrodes for MZ modulators 50.

[ 0060 ] In FIG. 5 A, two RF ground electrodes G1 and G2 are added on the outer respective sides of each of the signal electrodes S+ and S-. This configuration is used as a differentially- driven push-pull MZ modulator.

[ 0061 ] G1 and G2 provide isolation minimizing cross talk to other neighboring RF structures / modulators. G1 and G2 also provide a grounding interface for the GSSG signals coming from the driver chip (e.g. S+ and S- minus need to be connected to the modulator, but G1 and G2 as well - this could be done with wirebonds or flip-chip with e.g. Cu pillars.

[ 0062 ] G1 and G2 in some cases are also used to terminate RF signals with a resistor to the RF ground if desired. Another option is to "self-terminate" the differential signal lines to each- other with a resistor between S+ and S-.

[ 0063 ] In FIG. 5B, an RF ground electrode G replaces one of the signal electrodes to provide a single-ended driven push-pull MZ modulator. Here, the signal is not differentially applied but instead applied only to the one signal electrode S. Poling is performed between the DC electrode and the RF ground electrode G for region Pl and between the DC electrode and the signal electrode S for region P2.

[ 0064 ] For some application (usually lower speeds) - there can be benefits in using drivers that work with single-ended signals, including simplification and lower power.

[ 0065 ] FIGs. 6A, 6B, 6C, 6D, 6E, and 6F are cross-sectional views showing still more arrangements of the signal, DC, and ground electrodes for MZ modulators 50.

[ 0066] The arrangement of FIG. 6A is similar to previous FIG. 5C. Here, however, one or more electrodes such as the DC electrode are partially or fully below Pockels material substrate P.

[ 0067 ] In FIG. 6B, the DC electrode DC is embedded in the Pockels material substrate P. DC electrode can be a doped oxide region (e.g. via implantation, ion diffusion, or oxygen content or composition modulation

conductive oxide). In some cases, this arrangement allows the waveguides to be closer together and the doped region will have less absorption than a metal trace.

[ 0068 ] In FIG. 6C, the DC electrode DC, ground electrode G and the signal electrode S are “embedded” by removing the Pockels material and forming the electrodes in the resulting voids. [ 0069 ] In FIG. 6D, the DC electrode DC, ground electrode G and the signal electrode S are spaced away from the Pockels material substrate P such as with an intervening dielectric layer D, such as an oxide layer. Often this dielectric layer is between 5 nm and 500 nm thick.

[ 0070 ] In FIG. 6E, the Pockels material P is only present below the waveguides Al and A2 on mesas Pl and P2. Another material forms the substrate W for the device.

[ 0071 ] In FIG. 6F, the DC electrode DC, ground electrode G and the signal electrode S are spaced away from the Pockels material substrate P such as with an intervening dielectric layer D, such as an oxide layer. The ground electrode G and the signal electrode S are on an opposite side of the Pockels material substrate P from the waveguides Al, A2 and the DC electrode.

[ 0072 ] It should further be appreciated that while these drawings show the waveguides Al, A2 on top of Pockels material P, but the waveguides could also be below the Pockels material. In one example, a SiN or amorphous Si layer is provided from the underlying FEOL process modules.

[ 0073 ] FIG. 7A is a cross-sectional view of an MZ modulator according to another embodiment the present invention.

[ 0074 ] Two DC electrodes -DC, +DC are provided on either side of the waveguides A 1 , A2 and a center signal electrode S.

[ 0075 ] The substrate is polarized in the same direction in regions P 1 and P2. This polarization is induced by establishing a poling voltage Vpol between the two DC electrodes - DC, +DC. The RF signal is applied to the center signal electrode S and the resulting electric field is established between the two DC electrodes -DC, +DC that also function as RF grounds.

[ 0076] FIG. 7B is schematic circuit diagram of the MZ modulator of FIG. 7A.

[ 0077 ] A two poling voltage sources +Vpol, -Vpol provide a bias poling voltage to the two

DC electrodes -DC, +DC.

[ 0078 ] Note that the inductors +L, -L can be explicit inductors or simply line inductances. These electrical connections to the poling voltage sources +/-Vpol would usually be very long (connected to the "power supply delivery" of the chip, while the S line is as short as possible to a driver circuit. Even if the speeds are moderate (e.g. 100MHz, 1GHz), there is substantial line inductance.

[ 0079 ] A reference and signal voltage source Vref+Vs provides the reference and signal voltage to the center signal electrode S. [ 0080 ] FIG. 7C shows a variant that implements a traveling wave design for higher frequency modulation. Here, two outer RF ground electrodes G+, G- are connected to center signal electrode S via two respective termination resistors Rl, R2.

[ 0081 ] FIG. 8A is a schematic circuit diagram of a modulator according to another embodiment. It is designed as single phase shifter for a single waveguide, when no push pull operation is required.

[ 0082 ] A DC electrode DC is provided between and running parallel with the two signal electrodes S⁺ and S" and one waveguide Al.

[ 0083 ] A voltage source provides both a reference voltage Vref and a signal voltage Vppd that is applied across the signal electrodes, which are connected by a resistor R. A poling voltage source Vpol is connected to a center DC electrode DC through an inductor L.

[ 0084 ] FIG. 8B shows cross-sectional view.

[ 0085 ] The high-inductance DC electrode DC between the signal electrodes S+ and S- allows for the application of DC voltage for poling of the Pockels material substrate P in region Pl.

[ 0086] The high inductance of the DC electrode DC due to the inductor L blocks RF current from passing to GND through DC connection.

[ 0087 ] FIG. 9 is a schematic circuit diagram of MZ modulator according another embodiment.

[ 0088 ] Like Fig. 4 A, two waveguides Al, A2 carry an optical signal in two arms of an MZ modulator. The DC electrode DC is provided between and running parallel with the two signal electrodes S+ and S-. A voltage source V provides both a reference voltage Vref and a modulating or signal differential voltage Vppd that is applied across the signal electrodes through termination resistor R.

[ 0089 ] In this example, two bias poling voltage sources Vlpol and V2pol are connected to a center DC electrode through respective inductors LI and L2. The center DC electrode is split along its length, however, into a first section DC1 and a second section DC2. Two poling voltage sources Vlpol and V2pol respectively drive first section DC1 and a second section DC2.

[ 0090 ] The split center DC electrode provides for the creation of an electro-optic (EO) frequency-domain equalizer as described in the article entitled Traveling-Wave Mach-Zehnder Modulator Integrated With Electro-Optic Frequency-Domain Equalizer for Broadband Modulation, by Yuya Yamaguchi, et al. in the Journal of Lightwave Technology, Vol. 41, Issue 12, 15 June 2023, which is incorporated herein by this reference in its entirety.

[ 0091] The previous approach required waveguide/electrode crossings, which are complex and can impact performance, along with U-bend modulators.

[ 0092 ] In contrast, in the example illustrated in FIG. 9, it can be achieved simply by separating the poling electrode into two segments DC1, DC2 with opposite polarity DC voltages. This achieves the inverse phase modulation in the second part of the modulator to achieve the equalizer functionality.

[ 0093] While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

CLAIMS What is claimed is:

1. An electro-optic device comprising:

Pockels material; one or more waveguides on the Pockels material; one or more signal electrodes for phase modulating light propagating in the one or more waveguides; and one or more poling electrodes for poling the Pockels material.

2. The device as claimed in claim 1, further comprising inductance associated the one or more poling electrodes to prevent high frequency current in the one or more poling electrodes.

3. The device as claimed in either of claims 1 or 2, wherein the Pockels material is BTO or LN.

4. The device as claimed in any of claims 1-3, wherein a poling voltage is applied to the poling electrodes during bum-in and/or start-up and/or operation.

5. The device as claimed in any of claims 1-4, wherein the waveguides are arranged as a MZ interferometer.

6. The device as claimed in claim 5, wherein a poling electrode is between arms of the MZ interferometer.

7. The device as claimed in either of claims 5 or 6, wherein the signal electrodes are located on outer sides of the arms.

8. The device as claimed in any of claims 1-7, wherein the signal electrodes include two electrodes receiving a differential signal.

9. The device as claimed in any of claims 1-8, wherein the signal electrodes include a high frequency ground electrode and a signal electrode.

10. The device as claimed in any of claims 1-9, one or more poling electrodes are split in their length to enable equalization.

11. A method of operation of an electro-optic device including Pockels material, one or more waveguides associated with the Pockels material, and one or more signal electrodes, the method comprising: phase modulating light propagating in the one or more waveguides by applying signal(s) to the signal electrodes; and poling the Pockels material with one or more poling electrodes.

12. The method as claimed in claim 11, further associating an inductance associated with the one or more poling electrodes to prevent high frequency current in the one or more poling electrodes.

13. The method as claimed in either of claims 11 or 12, wherein the Pockels material is BTO or LN.

14. The method as claimed in any of claims 11-13, further comprising applying a poling voltage to the poling electrodes during bum-in and/or start-up and/or operation.

15. The method as claimed in any of claims 11-14, wherein the waveguides are arranged as a MZ interferometer.

16. The method as claimed in claim 15, wherein a poling electrode is between arms of the MZ interferometer.

17. The method as claimed in either of claims 15 or 16, wherein the signal electrodes are located on outer sides of the arms.

18. The method as claimed in any of claims 11-17, further comprising applying a differential signal across the signal electrodes include two electrodes receiving a differential signal.

19. The method as claimed in any of claims 11-19, wherein one or more poling electrodes are split in their length to enable equalization.