Ferroelectric electro-optic modulator device

Abstract

Ferroelectric electro-optic modulator device comprising at least one supporting substrate or layer, at least one supporting oxide material or layer, at least one ferroelectric material or layer wherein the at least one ferroelectric material or layer includes or delimits at least one elongated waveguide core of at least one elongated waveguide, at least one intermediate layer comprising or consisting of at least one polycrystalline silicon layer or material provided or deposited between the at least one supporting oxide material or layer and the at least one supporting silicon substrate or layer, and a plurality of metal electrodes.

Description

[0001] FERROELECTRIC ELECTRO-OPTIC MODULATOR DEVICE

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] The present application claims priority to European patent application EP24167779.8 filed on March 28th 2024, the disclosure of which is hereby incorporated herein by reference in its entirety for all purposes.

[0004] FIELD OF THE INVENTION

[0005] The present invention concerns the field of electro-optic modulation technology, and in particular relates to a ferroelectric electro-optic modulator device or photonic integrated circuit ferroelectric electro-optic modulator device.

[0006] BACKGROUND

[0007] Photonic integrated electro-optic modulators are key for high-speed signal processing and transmission, converting electronic to optical signals in applications spanning from radio frequency (RF) analog links to digital optical communication networks.

[0008] US2021 / 364696, US2002 / 172487 and WO2023 / 1 18926 each disclose ferroelectric waveguide devices, the disclosure of each of which is hereby incorporated herein by reference in its entirety for all purposes.

[0009] Electro-optic modulators, however, encounter bandwidth and reliability challenges due to electrical losses or radio-frequency RF losses, including ohmic loss of metals and dielectric absorption loss.

[0010] SUMMARY OF THE INVENTION

[0011] A goal of the present invention is to reduce such electrical losses or radio-frequency RF losses in electro-optic modulators.

[0012] The present invention addresses the above-mentioned inconveniences by providing a ferroelectric electro-optic modulator device.

[0013] The ferroelectric electro-optic modulator device may comprise: at least one supporting substrate or layer, wherein the at least one supporting substrate or layer (3) comprises or consists of a mono-crystalline or single-crystalline silicon substrate or layer, at least one supporting oxide material or layer provided or deposited on the silicon substrate or layer, at least one ferroelectric material or layer provided or deposited on the at least one supporting oxide material or layer, wherein the at least one ferroelectric material or layer includes or delimits at least one elongated waveguide core of at least one elongated waveguide, the at least one elongated waveguide core being configured to guide light inside the at least one elongated waveguide and through the at least one ferroelectric material or layer, at least one intermediate layer or material, the at least one intermediate layer or material may comprise or consist of at least one polycrystalline silicon layer or material or at least one amorphous silicon provided or deposited between the at least one supporting oxide material or layer and the at least one supporting silicon substrate or layer, and at least one or plurality of metal electrodes, the at least one or the plurality of metal electrodes being provided on and / or in contact with the at least one ferroelectric material or layer, or the at least one or the plurality of metal electrodes being provided on and / or in contact with the at least one supporting oxide material or layer, or the at least one or the plurality of metal electrodes being provided on and / or in contact with at least one cladding material or layer provided or deposited on the at least one ferroelectric material or layer and / or at least one supporting oxide material or layer; the at least one orthe plurality of metal electrodes being configured to generate an electric field inside the at least one ferroelectric material or layer to modify a refractive index of the at least one elongated waveguide when an electric field generating voltage is applied to the plurality of electrodes.

[0014] The present invention also addresses the above-mentioned inconveniences by providing a ferroelectric electro-optic modulator device fabrication method according to claim 16.

[0015] Other advantageous features can be found in the dependent claims.

[0016] This innovation reduces electrical losses or RF losses of the ferroelectric electro-optic modulator device and enables the provision of ultra-low microwave loss and ultra-high bandwidth photonic integrated modulators and marks a notable advancement in the field of electro-optic modulation technology.

[0017] Figure 2 to 4 shows exemplary enhancements in device performance assured by the ferroelectric electro-optic modulator device of the present disclosure. These and / or other aspects, features, and / or advantages will become apparent and more readily appreciated from the following description of various example embodiments, taken in conjunction with the accompanying drawings showing some preferred embodiments. Thicknesses of layers / elements, and sizes of components / elements, are not necessarily drawn to scale or in actual proportion to one another, but rather are shown as example representations. Like reference numerals may refer to like parts throughout the several views. Each embodiment herein may be used in combination with any other embodiments) described herein.

[0018] A BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A is a cross-sectional schematic illustration of an exemplary and preferred embodiment of a ferroelectric electro-optic modulator device of the present disclosure comprising at least one ridge waveguide or ridge-type waveguide. It is noted that exemplary illustrated directions correspond to crystal orientations of an exemplary x-cut ferroelectric material having a y-propagating waveguide, the crystalline X-axis is vertical, the Z-axis is in the plane of the wafer or substrate, and a waveguide extends along the Y-axis. These directions are also used herein to indicate spatial directions and relative locations of elements of the ferroelectric electro-optic modulator device. It is also noted that a z-cut ferroelectric material may alternatively be used, the exemplary x-cut being provided for the explicatory purposes.

[0020] Figure 1 B is a perspective schematic illustration of an exemplary and preferred embodiment of a ferroelectric electro-optic modulator device of the present disclosure comprising at least one ridge waveguide or ridge-type waveguide. The arrow indicates an exemplary direction of an applied electric field when a potential or voltage is applied to the electrodes, for example, a ground electrode and a modulating electrode to which a voltage or modulating potential signal is applied.

[0021] Figure 1 C is a cross-sectional schematic illustration of an exemplary and preferred embodiment of a ferroelectric electro-optic modulator device of the present disclosure comprising at least one ridge waveguide or ridge-type waveguide, the illustrated embodiment comprising two ridge waveguides or ridge-type waveguides.

[0022] Figure 1 D is a perspective schematic illustration of an exemplary and preferred embodiment of a ferroelectric electro-optic modulator device of the present disclosure comprising at least one ridge waveguide or ridge-type waveguide, the illustrated embodiment comprising two ridge waveguides or ridge-type waveguides.

[0023] Figure 1 E is a SEM cross-sectional SEM image of some constituent exemplary materials of exemplary ferroelectric electro-optic modulator devices according to the present disclosure.

[0024] Figures 1 F and 1 G are cross-sectional schematic illustrations of other exemplary ferroelectric electro-optic modulator devices of the present disclosure.

[0025] Figure 1 H is a top-view schematic illustration of different exemplary waveguide and electrode layout / configurations of exemplary ferroelectric electro-optic modulator devices of the present disclosure.

[0026] Figures 11 to 1 J are schematic illustrations of other exemplary ferroelectric electro-optic modulator devices of the present disclosure in other preferred embodiments comprising at least one ridge waveguide or ridge-type waveguide.

[0027] Figures 2 and 3 show the improved and reduced measured RF loss of the ferroelectric electrooptic modulator devices of the present disclosure.

[0028] Figure 4 shows the calculated substantial enhancement in electro-optical modulation bandwidth of the ferroelectric electro-optic modulator devices of the present disclosure.

[0029] Figure 5 shows that the improved and reduced measured RF loss of the ferroelectric electrooptic modulator devices of the present disclosure is present in devices both exposed and nonexposed to plasma radiation such as a plasma radiation exposure that may occur during plasma etching of the ferroelectric layer or material.

[0030] Figure 6 is a cross-sectional schematic illustration of an exemplary embodiment of a ferroelectric electro-optic modulator device of the present disclosure similar to that illustrated in Figure 1A.

[0031] Figures 7 is a cross-sectional schematic illustration of another exemplary embodiment of a ferroelectric electro-optic modulator device of the present disclosure in which electrode or electrodes are provided or deposited on the supporting oxide material or layer and without the ferroelectric material or layer being located between the supporting oxide material or layer and the electrode or electrodes. An adhesion layer or material may be present between the supporting oxide material or layer and the electrode or electrodes.

[0032] Figures 8 is a cross-sectional schematic illustration of another exemplary embodiment of a ferroelectric electro-optic modulator device of the present disclosure in which electrode or electrodes are provided or deposited on a waveguide covering cladding material or layer superposed on the waveguide or waveguide core.

[0033] Herein, identical reference numerals are used, where possible, to designate identical elements that are common to the Figures.

[0034] DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

[0035] The following detailed structural and / or functional description (s) is / are provided as examples only, and various alterations and modifications may be made. The example embodiments herein do not limit the disclosure and should be understood to include all changes, equivalents, and replacements within ideas and the technical scope herein. Hereinafter, certain examples will be described in detail with reference to the accompanying drawings. When describing various example embodiments with reference to the accompanying drawings, like reference numerals may refer to like components and a repeated description related thereto may be omitted.

[0036] The present disclosure concerns a ferroelectric electro-optic modulator orferroelectric electrooptic modulator device 1.

[0037] Figures 1A to 1 D and 1 F to 1J as well as Figures 6 to 8 schematically show exemplary ferroelectric electro-optic modulator devices 1 of the present disclosure.

[0038] The ferroelectric electro-optic modulator device 1 is, for example, a photonic on-chip integrated ferroelectric electro-optic modulator device.

[0039] The ferroelectric electro-optic modulator device 1 is, for example, a room-temperature operational ferroelectric electro-optic modulator device.

[0040] The ferroelectric electro-optic modulatordevice 1 is, forexample, a planar ferroelectric electrooptic modulator device. The ferroelectric electro-optic modulator device 1 includes a plurality of superposed material or layers, the material or layers are, for example, dielectric and / or semiconductor materials or layers. Coplanar metal electrodes are, for example, included superposed on the, for example, dielectric and / or semiconductor materials or layers.

[0041] The ferroelectric electro-optic modulator device 1 includes, for example, at least one supporting substrate or layer 3, for example, a silicon substrate or layer 3. The supporting substrate or layer 3 defines or extends to define a plane or planar structure or planar layer having a thickness in the x-direction ora direction (substantially) perpendicularto an elongated light propagation direction of the device 1 (see, for example, Figure 1A).

[0042] The supporting substrate or layer 3 is, for example, a mono-crystalline or single-crystalline silicon substrate or layer.

[0043] The substrate 3 may, for example, be a prime grade silicon wafer or substrate that are commercially available. The substrate or layer 3 typically has, for example, a thickness of 525 or 700 microns. The substrate or layer 3 typically is mono-crystalline or single-crystalline Silicon <100>, and may be single or double-side polished. The silicon wafer or substrate 3 are, for example, high-resistivity Si substrates.

[0044] The ferroelectric electro-optic modulator device 1 includes, for example, at least one supporting oxide material or layer 5 provided or deposited on the supporting substrate or layer 3. The supporting oxide material or layer 5 may, for example, comprise or consist of silicon oxide (SiO2). The supporting oxide material or layer 5 may have, for example, a thickness between 1 |j.m and 10|j.m, for example, 3 microns.

[0045] The ferroelectric electro-optic modulator device 1 advantageously includes at least one intermediate layer or material 7 provided or located between the supporting oxide material or layer 5 and the supporting substrate or layer 3, or deposited to be located between the supporting oxide material or layer 5 and the supporting silicon substrate or layer 3.

[0046] The intermediate layer or material 7 is, for example, provided (directly) on or deposited (directly) onto the supporting substrate or layer 3, or a surface 9 of the supporting substrate or layer 3. The supporting substrate or layer 3 includes or defines the surface 9.

[0047] The intermediate layer or material 7 comprises or consists of at least one non-mono-crystalline material or layer 7, or at least one non-single-crystalline material or layer 7. In a preferred exemplary embodiment, the intermediate layer or material 7 comprises or consists of at least one non-mono-crystalline silicon material or layer or at least one non-single-crystalline material or layer 7.

[0048] The intermediate layer or material 7 comprises or consists of, for example, at least one polycrystalline silicon layer or material 7 (or of at least one multicrystalline silicon or polysilicon or poly-Si layer or material 7). The intermediate layer 7 may comprise or consist of at least one amorphous silicon layer or material 7.

[0049] In a preferred embodiment, the intermediate layer or material 7 directly contacts both the at supporting oxide material or layer 5 and the supporting substrate or layer 3.

[0050] The intermediate layer 7 includes or defines a first surface or contact surface CS1 and a second surface or contact surface CS2 (see, for example, Figure 6). The first contact surface CS1 is, for example, located opposite the second contact surface CS2. The first contact surface CS1 , for example, directly contacts a surface 57 (a lower surface illustrated in Figure 1 A) defined by the supporting oxide material or layer 5 or that the supporting oxide material or layer 5 includes.

[0051] The second contact surface CS2 of the intermediate layer 7, for example, directly contacts the surface 9 (upper surface illustrated in Figure 1A) of the supporting silicon substrate or layer 3.

[0052] The polycrystalline silicon layer or material 7 may, for example, include or define the first contact surface CS1 directly contacting the supporting oxide material or layer 5 and / or the second contact surface CS2 directly contacting the supporting silicon substrate or layer 3. The first contact surface CS1 may, for example, consists solely of silicon atoms. The second contact surface CS2 may, for example, consists solely of silicon atoms.

[0053] The first contact surface CS1 may, for example, include at least one area or surface area consisting solely of silicon atoms, or may include for example a plurality of areas or surface areas consisting solely of silicon atoms. The at least one area or each of the plurality of areas is a sub-area or sub-surface of the first contact surface CS1 . The second contact surface CS2 may, for example, include at least one area or surface area consisting solely of silicon atoms, or may include for example a plurality of areas or surface areas consisting solely of silicon atoms. The at least one area or each of the plurality of areas is a sub-area or sub-surface of the second contact surface CS2. The amorphous silicon layer or material 7 may, for example, include or define the first contact surface CS1 directly contacting the supporting oxide material or layer 5 and / or the second contact surface CS2 directly contacting the supporting silicon substrate or layer 3. The first contact surface CS1 may, for example, consists solely of silicon atoms. The second contact surface CS2 may, for example, consists solely of silicon atoms.

[0054] The first contact surface CS1 may, for example, include at least one area or surface area consisting solely of silicon atoms, or may include for example a plurality of areas or surface areas consisting solely of silicon atoms. The at least one area or each of the plurality of areas is a sub-area or sub-surface of the first contact surface CS1 . The second contact surface CS2 may, for example, include at least one area or surface area consisting solely of silicon atoms, or may include for example a plurality of areas or surface areas consisting solely of silicon atoms. The at least one area or each of the plurality of areas is a sub-area or sub-surface of the second contact surface CS2.

[0055] The intermediate layer or material 7 may have for example a thickness of between 100nm and 1000nm, for example, 400nm.

[0056] The ferroelectric electro-optic modulator device 1 includes at least one ferroelectric material or layer 1 1 provided or deposited on the supporting oxide material or layer s. The ferroelectric material or layer 11 is, for example, provided or deposited (and / or fixed / attached) directly on the supporting oxide material or layer 5.

[0057] The ferroelectric material or layer 1 1 can, for example, be a non-etched or non-plasma etched ferroelectric material or layer 1 1 , for example, a non-argon etched, or non-argon plasma etched ferroelectric material or layer 11 . The ferroelectric material or layer 11 can, for example, be a non-plasma radiation exposed ferroelectric material or layer 11 , that is a ferroelectric material or layer 11 that has not been exposed to plasma radiation.

[0058] Alternatively, the ferroelectric material or layer 11 can, for example, be an etched or plasma etched ferroelectric material or layer 11 , forexample, an argon etched, orargon plasma etched ferroelectric material or layer 1 1. The ferroelectric material or layer 11 is, for example, a plasma radiation exposed ferroelectric material or layer 1 1 , that is a ferroelectric material or layer 11 that has been exposed to plasma radiation.

[0059] Figure 5 shows that the improved and reduced measured RF loss of the ferroelectric electrooptic modulator devices of the present disclosure is present in devices 1 both exposed and non-exposed to plasma radiation such as a plasma radiation exposure that may occur during plasma etching of the ferroelectric layer or material.

[0060] The ferroelectric material or layer 11 , for example, is, defines or delimits a slab or planar waveguide layer or material.

[0061] The ferroelectric material or layer 11 forms / in eludes or delimits or defines at least one or a plurality of elongated optical waveguides 15. The ferroelectric material or layer 1 1 forms / includes or delimits or defines a waveguide core 17 of the or of each elongated optical waveguide 15.

[0062] The ferroelectric material or layer 1 1 may, for example, form / include or delimit or define a waveguide cladding or waveguide cladding structure / material 18, of the or each elongated optical waveguide 15, that encloses or surrounds (at least partially or fully) the waveguide core 17 (see, for example, Figures 1 F and 1 G).

[0063] The elongated optical waveguide 15 and / or waveguide core 17 extends in an elongated direction (for example, in the y-direction (into the page)) and / or in an elongated plane (x- direction and z-direction) to guide or propagate light across the device 1 and / or across the ferroelectric material or layer 11 . Light is, for example, propagated or guided in a plane of the ferroelectric material or layer 11 .

[0064] Light is confined inside the waveguide core 17 by at least one wall or side / lateral wall sw1 , sw2 of the waveguide core 17 that extends in an elongated manner across the device 1 to propagate or guide light across the device 1 .

[0065] The ferroelectric material or layer 1 1 and / or the elongated optical waveguide 15 includes, delimits or defines, for example, the at least one or the plurality of waveguide cores 17 configured to guide light inside the elongated waveguide core, and the elongated optical waveguide 15, and through the ferroelectric material or layer 11 .

[0066] The waveguide core 17 may, for example, be formed by structuring or processing the ferroelectric material or layer 11 to define an elongated core 17 located or extending at a distance from a landing, an (for example, outer) interface or surface 21 of the ferroelectric material or layer 11 (see, for example, Figure 1 A or 1 C), and / or located inside the ferroelectric material or layer 11 (see, for example, Figures 1 F and 1G). The or each elongated core 17 includes or defines, for example, at least a first lateral interface or lateral surface LS1 for inputting light (extending, for example, in the x-direction and the z- direction (substantially) perpendicular to the surface 9 of the supporting substrate 3), and at least a second lateral interface or lateral surface LS2 (extending, for example, in the x-direction and the z-direction (substantially) perpendicular to the surface 9 of the supporting substrate 3) for outputting light (see, for example, Figure 1 H).

[0067] In a preferred embodiment (see, for example, Figures 1A to 1 D), the waveguide 15 is or defines a ridge waveguide, or an elongated ridge waveguide, or a ridge waveguide structure, or an elongated ridge waveguide structure.

[0068] The elongated waveguide core 17 defines or is a ridge waveguide core 17, or an elongated ridge waveguide core 17.

[0069] The waveguide core 17 of the waveguide 15 may, for example, define an elongated (ferroelectric) protrusion or (ferroelectric) ridge 50 extending or protruding from a landing, or a first or base surface 21 of the ferroelectric material or layer 11 (see, for example, Figure 1 A) or of the supporting oxide material or layer 5 (see, for example, Figure 7). The elongated ridge 50 includes at least a first side wall sw1 and a second side wall sw2 extending from the base surface 21 to a surface 53 or an upper or outer surface 53 that extends between the first and second side walls sw1 , sw2.

[0070] The first side wall sw1 and the second side wall sw2 may, for example, taper or extend inwards when extending from the base surface 21 to a surface 53, as shown for example in Figures 1 B and 6.

[0071] The waveguide core 17 of the waveguide 15 may, for example, be formed by structuring the ferroelectric material or layer 11 to define the elongated (ferroelectric) protrusion or (ferroelectric) ridge 50 extending or protruding from the first or base surface 21 of the ferroelectric material or layer 11 (see, for example, Figure 1 A).

[0072] Structuring the ferroelectric material or layer 11 to define an elongated protrusion 19 may, for example, be done by photolithography and etching of the ferroelectric material or layer 11 , for example, as described in published international patent application WO2023 / 118926, the entire content of which is hereby incorporated herein by reference in its entirety for all purposes. Figures 1A and 1 B show an embodiment comprising, for example, one waveguide 15, while the embodiment of Figures 1 C and 1 D shows an embodiment comprising, for example, a plurality or two waveguides 15.

[0073] The waveguide core 17 extends across the device 1 , for example, in the manner schematically shown in Figure 1 H, for example, in Figures 1 H (i) and (ii).

[0074] In an alternative embodiment (not shown), the ferroelectric waveguide core 17 and / or waveguide 15 can be provided or deposited as an elongated stripe on the supporting oxide material or layer 5, or alternatively, inside an elongated depression or groove included in the on the supporting oxide material or layer 5.

[0075] The ferroelectric waveguide core 17 of the waveguide 15 can be, for example, surrounded by air, with the surrounding air acting as a cladding enclosure (lower refractive index enclosure) of the waveguide 15.

[0076] Alternatively, a cladding material or layer (for example, silicon oxide SiCh) may be provided or deposited onto the ferroelectric waveguide core 17 to enclose or surround the waveguide core 17. The waveguide 15 thus also includes such a surrounding cladding. At least one electrode 25 may be provided or deposited on the cladding material or layer.

[0077] The cladding material or layer may, for example, be absent (for example, at least partially) from the electrode or electrodes 25, to allow an electrical contact to the surface of the electrode or electrodes 25.

[0078] Figure 8 shows another exemplary embodiment in which a cladding material or layer 55 (for example, silicon oxide SiO2) is provided or deposited onto the ferroelectric waveguide core 17 to enclose or surround the waveguide core 17, and the at least one electrode or electrodes 25A, 25B are provided or deposited on the cladding material or layer 55, for example, either side of the waveguide 17. The at least one electrode or electrodes 25A, 25B are for example provided or deposited on a surface or outer surface 56 of the cladding material or layer 55.

[0079] In another embodiment, the waveguide core 17 may, for example, be formed as classically known by a dopant or dopant implantation, such as titanium, diffused into the ferroelectric material or layer 11 to form a dopant or doped elongated stripe 17 extending across the ferroelectric material or layer 11 (see, for example, Figures 1 F and 1 G). Figure 1 H shows exemplary and non-limiting embodiments of the waveguide 15 layout or configuration. The waveguide 15 and / or waveguide core 17 may, for example, extend to split into a first and a second arm that recombine into a single elongated stripe across or through the ferroelectric material or layer 1 1 (see, for example, Figures 1 H(i) and (iii)), that is, to define or form for example an interferometric or Mach-Zehnder interferometric layout or configuration. The waveguide 15 and / or waveguide core 17 may, for example, extend as a single elongated stripe across or through the ferroelectric material or layer 1 1 (see, for example, Figure 1 H(ii)).

[0080] Light is optically coupled to the waveguide 15 or waveguide core 17 and guiding or propagated across the ferroelectric material or layer 11 or device 1 .

[0081] The at least one ferroelectric material or layer 1 1 may, for example, preferably comprise or consists solely of Lithium Niobate (LiNbOs) or Lithium Tantalate (LiTaOs) or Barium titanate (BaTiO3).

[0082] The at least one ferroelectric material or layer 1 1 may, for example, comprise or consists solely of single crystal Lithium Niobate (LiNbOs), or doped Lithium Niobate (LiNbOs) or doped single crystal Lithium Niobate (LiNbOs), or single crystal Lithium Tantalate (LiTaO3), ordoped Lithium Tantalate (LiTaOs) or doped single crystal Lithium Tantalate (LiTaOs).

[0083] The ferroelectric material or layer 11 may have for example a thickness tf of between 200nm and 1200nm, for example, 600nm. However, other thicknesses are also possible. The waveguide ridge thickness may, for example, be between 200nm and 1000nm, for example, 300nm. The waveguide ridge width may, for example, be between 300nm and 2000nm, for example, 400nm.

[0084] The thickness tf, for example, extends between an interface surface 23 and the surface 53 of the waveguide core 17, in a direction (substantially) perpendicular to the surface 9 of the supporting substrate or layer 3; or, for example, between opposing interface surfaces of the waveguide core 17 in a direction (substantially) perpendicular to the surface 9 of the supporting substrate or layer 3.

[0085] The ferroelectric electro-optic modulator device 1 may include, for example, the first interface or first surface 21 and a second interface or second (inner) surface 23 (see, for example, Figure 1A). The second interface or second (inner) surface 23 is in (for example, direct) contact with an inner layer of material of the device 1 , for example, the supporting oxide material or layer 5. The ferroelectric material or layer 11 may, for example, include or define the first interface or first surface 21 (see, for example, Figure 1A). Alternatively or additionally, the supporting oxide material or layer 5 may, for example, include or define the first interface or first surface 21 (see, for example, Figure 7).

[0086] The first interface or first surface 21 and the second interface or second (inner) surface 23 for example may define planar extremities of the ferroelectric material or layer 1 1 , the ferroelectric material or layer 1 1 extending, for example, to delimit or define a planar layer or material 59 between the first interface or first surface 21 and the second interface or second (inner) surface 23.

[0087] In an embodiment, the ferroelectric material or layer 11 and / or the planar layer or material 59 is absent or is removed (partially or fully), and the at least one electrode or electrodes 25A, 25B are provided or deposited, for example directly, on the supporting oxide material or layer 5 (see, for example, Figure 7). The ferroelectric material or layer 11 is absent between the at least one electrode or electrodes 25A, 25B and the supporting oxide material or layer 5. The supporting oxide material or layer 5 may, for example, include or define both the first interface or first surface 21 and the second interface or second (inner) surface 23. The electrode or electrodes 25 are, for example, in contact with the ferroelectric material or layer 11 , for example, indirectly, via the supporting oxide material or layer 5. The electrode or electrodes 25 are, for example, operatively in contact with the ferroelectric material or layer 11 .

[0088] The first interface or first surface 21 , for example, can receive or is located to receive at least one or a plurality of (operational) electrodes 25 of the device 1. The electrode or electrodes 25 may, for example, be physically and / or operatively in contact with the ferroelectric material or layer 11 and / or the first interface or first surface 21 of the ferroelectric material or layer 1 1 or the supporting oxide material or layer 5 (and / or the cladding material or layer if present).

[0089] The electrode or electrodes 25 are provided or deposited to be in direct contact with the surface (for example, surface 21) upon which the electrode or electrodes 25 are provided or deposited, and / or to be in indirect contact with the surface (for example, surface 21) upon which the electrode or electrodes 25 are provided or deposited with an intermediate layer or material (comprising or consisting of, for example, Ti and / or Al, having a thin thickness of, for example, between 5nm and 20nm, for example 10nm) being provided between the electrode or electrodes 25 and the surface (for example, surface 21). The intermediate layer or material forms, for example, an adhesion layer. The ferroelectric electro-optic modulator device 1 includes, for example, the at least one or a plurality of electrodes 25, for example, in contact with the ferroelectric material or layer 11 (see, for example, Figure 1A), the supporting oxide material or layer 5 (see, for example, Figure 7), or the cladding material or layer 55 (see, for example, Figure 8).

[0090] The device 1 includes, for example, at least a first electrode 25A and at least a second electrode 25B. The electrodes 25 may be, for example, positioned or located coplanar with respect to each other. The electrodes 25 may be, for example, positioned or located coplanar with respect to each other on the ferroelectric material or layer 11 (see, for example Figure 1 A). That is, the electrodes 25 lie or are positioned or extend in the same plane or electrode plane pl (extending for example in the y-direction and z-direction).

[0091] The electrodes or each electrode 25 is, for example, located in contact with the ferroelectric material or layer 11. The electrode or each electrode 25 has a thickness t (in a direction extending for example in the x-direction (substantially) perpendicular to the surface 9 of the supporting substrate 3). The thickness t may for example be between 300nm and 1000nm, for example, 800nm. However, other thicknesses are possible. The electrode or each electrode 25 may, for example, be deposited by electron beam evaporation.

[0092] The or each electrode 25 includes a first interface or first surface 27 and a second interface or second (inner) surface 29 that define extremities or planar extremities of the electrode 25 or each electrode 25.

[0093] The electrode material or layer 25 extends to delimit or define, for example, a planar layer / material or structure between the first interface or first surface 27 and the second interface or second (inner) surface 29. The planar layer / material or structure of the electrodes 25, 25A, 25B or each electrode 25, 25A, 25B overlap so as to be coplanar, that is, they are in the same plane or electrode plane pl or operating in the same plane pl.

[0094] The first surface 27 of the at least one or of the plurality of electrodes 25 may define, for example, an outer exposed voltage contact surface to which an operation voltage for device operation is applied, for example, a modulating potential V or ground potential or voltage is applied. A clearance may be present above, opposite or facing the outer exposed voltage contact surface to permit a voltage terminal or contact to the made to the outer exposed voltage contact surface for an operational voltage to be applied thereto. The electrodes 25 define, for example, a coplanar waveguide CPW arrangement or configuration.

[0095] Each electrode 25 may, for example, be separated from another or adjacent electrode by a gap 31 that defines a clearance (for example, an electrode-free clearance) between the electrodes. For example, the first electrode 25A is, for example separated from the second electrode 25 by a gap 31 of width wg that defines a clearance between the first and second electrodes 25A, 25B.

[0096] For example, a width wg of the clearance may, for instance, be equal or be at least equal to a width wel of the electrodes(s). The width wel of the electrodes(s) may, for example, be 3 times (3x) the width wg of the clearance (wel=3 xwg). The actual implemented widths are of course device dependent and dependent the targeted desired operating characteristics of the device.

[0097] The gap 31 or clearance includes or contains the ridge waveguide 15 and / or the waveguide core 17 in the exemplary embodiments of Figures 1A to 1 D, located for example in the clearance and between, for example, two electrodes 25. In some embodiments, the gap 31 or clearance may contain cladding material, or cladding material superposed on the waveguide core 17 (see, for example, Figure 8).

[0098] The first side wall sw1 of the waveguide core 17 (or each waveguide core 17) can be, for example, located facing or opposite a side wall SD1 of a first electrode 25, and the second side wall sw2 of the waveguide core 17 can be located facing or opposite a side wall SD2 of a second and different electrode 25.

[0099] In an embodiment (not shown), at least one electrode 25 may, for example, be provided or deposited on a surface or outer surface 53 of the waveguide 15. This is, for example, in addition to the least one lateral electrode or electrodes.

[0100] The electrodes 25 are configured for applying a modulating electric field and are, for example, arranged or provided on the same surface 21 (for example, of the ferroelectric material or layer 1 1 or the supporting oxide material or layer 5), and / or extending, for example, from the same surface 21 (for example, of the ferroelectric material or layer 1 1 or the supporting oxide material or layer 5).

[0101] The electrodes or plurality of electrodes 25 are configured, laid out, or operatively located to, for example, generate an electric field inside the at least one ferroelectric material or layer 1 1 and / or inside the waveguide core 17 to modify a refractive index of the ferroelectric material or layer 11 and / or of the waveguide core 17 when a voltage or voltage signal is applied to electrodes 25.

[0102] A first electrode 25A is, for example, grounded (for example a grounded electrode to which a reference potential or voltage is applied) and a voltage or voltage signal is applied to a second electrode 25B (a hot electrode electrically connected to a modulating potential V). A third electrode (or further electrodes) may also be present and may for example also be grounded (for example a second grounded electrode).

[0103] The layout of the electrodes is arranged or configured so as to allow the operation of the device 1 , for example, up to the microwave region of the spectrum of the modulating electric field.

[0104] The electrodes 25 are, for example, elongated electrodes that may extend, for example, in a planar manner across the device 1 or the (surface thereof) ferroelectric material or layer 11 . Figure 1 H shows non-limiting exemplary lay outs or configurations.

[0105] Electrodes 25 may be, for example, located laterally each side of the waveguide core 17, 17B, and for example not directly overlap or directly be superposed on or above the waveguide core 17 or waveguide 15. A first electrode and a second electrode may, for example, be located either side of the waveguide core and extend (substantially) parallel to or with the waveguide core 17, as for example shown in Figure 1 H (i) and (ii).

[0106] Alternatively or additionally, electrodes 25 or at least of the electrodes may directly overlap or directly be superposed on or above the waveguide core 17, as for example shown in Figure 1 H (iii). Other lay outs or configurations are of course possible.

[0107] The electrodes 25 may for example be deposited or provided directly on the ferroelectric material or layer 11 or the surface 21 thereof (or on a cladding material or layer if present, or on the supporting oxide material or layer 5).

[0108] The at least one or the plurality of electrodes 25 or all the electrodes 25 advantageously comprises or consists of at least one metal, or the at least one or the plurality of electrodes 25 or all the electrodes 25 are metal electrodes. The at least one or the plurality of electrodes or all the electrodes 25 comprises or consists of a non-superconducting material.

[0109] The at least one or the plurality of electrodes or all the electrodes 25 may advantageously comprise or consist of silver (Ag). As mentioned, the thickness t may for example be between 300nm and 1000nm, for example, 800nm. However, other thicknesses are possible. The electrodes or each electrode 25 may, for example, be deposited by electron beam evaporation. At least one of the plurality of electrodes, or all or each of the electrodes 25 comprises or consists of silver (Ag).

[0110] Alternatively or additionally, the at least one or the plurality of electrodes 25 may comprises or consists of gold (Au).

[0111] The electrode may optionally for example include a thin adhesion or intermediate layer or material (for example, aluminum or titanium) provided between the electrodes 25 and the surface of the ferroelectric material or layer 1 1 . The adhesion or intermediate layer or material may, for example, be 10nm in thickness and deposited on, for exampole, the ferroelectric material or layer 11 , the supporting oxide material or layer 5, or the cladding material or layer prior to the provision or deposition of an electrode body onto the adhesion or intermediate layer. The electrode 25 may thus comprise of consist of the adhesion or intermediate layer or material deposited or provided (directly) on (the surface 21 of) the ferroelectric material or layer 11 , the supporting oxide material or layer 5, or the cladding material or layer, and upon which the electrode body is deposited or provided, the electrode body comprising or consisting of preferably silver, or alternatively gold; or alternatively gold and silver.

[0112] The electrodes 25 are configured and or arranged to generate an electric field inside the waveguide core 17, 17B to, for example, modify a refractive index of the waveguide core 17 when a voltage or voltage signal voltage difference applied to the electrode(s) 25.

[0113] The plurality of electrodes 25 are configured to, for example, generate an electric field inside the ferroelectric material or layer 1 1 to modify a refractive index of the elongated waveguide 15 when an electric field generating voltage is applied to the plurality of coplanar electrodes 25.

[0114] This allows to electrically manipulate or control the amplitude, phase, or polarization state of an optical beam propagating through the waveguide core 17. The device 1 is used to modulate a beam of light propagating through the waveguide 15, with the modulation being imposed on the phase, frequency, amplitude, or polarization of the beam by an electrical signal applied to the electrodes 25.

[0115] In another embodiment of the present disclosure, the ferroelectric electro-optic modulator device 1 does not necessarily include the intermediate layer or material 7, and may optionally include the intermediate layer or material 7. In this embodiment, the device is identical to that previously described and the at least one or the plurality of electrodes or all the electrodes 25 advantageously comprises or consists of silver (Ag). The electrode may optionally for example include the thin adhesion or intermediate layer or material (for example, aluminum or Ti), with the electrode body being deposited or provided thereon, the electrode body comprising or consisting of preferably silver or alternatively gold and silver.

[0116] The supporting oxide material or layer 5 is provided or deposited on the supporting substrate or layer3 (for example, directly) without the previously described intermediate layer or material 7 being present between the supporting oxide material or layer 5 and the supporting substrate or layer 3.

[0117] The ferroelectric electro-optic modulator device comprises, for example, the at least one supporting substrate or layer 3, the at least one supporting oxide material or layer 5 provided or deposited on the silicon substrate or layer 3 (for example directly), the at least one ferroelectric material or layer 1 1 provided or deposited on the at least one supporting oxide material or layer 5, the at least one ferroelectric material or layer 1 1 includes or delimiting at least one an elongated waveguide 15 and / or waveguide core 17 configured to guide light inside the elongated waveguide core 17 and through the at least one ferroelectric material or layer 11 , and at least one or the plurality of electrodes 25 in contact with the at least one ferroelectric material or layer 11 .

[0118] The plurality of electrodes 25 are, for example, configured to generate an electric field inside the ferroelectric material or layer 11 to modify a refractive index of the ferroelectric material or layer 11 when an electric field generating voltage is applied to the plurality of coplanar electrodes 25. The plurality of electrodes 25 are, for example, configured to generate an electric field inside the ferroelectric material or layer 11 to modify a refractive index of the ferroelectric material or layer 11 when a voltage or voltage difference applied to an electrode(s) 25. Figures 11 and 1 J show exemplary devices in which the ferroelectric electro-optic modulator device 1 does not necessarily include the intermediate layer or material 7. This is similarly the case for the embodiments of Figures 1 F to 1 G which are not illustrated.

[0119] The present disclosure also concerns a ferroelectric electro-optic modulator device fabrication method.

[0120] The method includes, for example, providing at least one supporting silicon substrate or layer 3, providing or depositing the at least one intermediate layer ? comprising or consisting of the at least one polycrystalline silicon layer or material 7, or amorphous silicon layer or material on the at least one silicon substrate or layer 3, providing or depositing the at least one supporting oxide material or layer 5 on the at least one polysilicon layer or material 7 or amorphous silicon layer or material, and forming the at least one elongated waveguide 15 comprising at least one elongated waveguide core 17 in or on the at least one ferroelectric material or layer 1 1 to allow light guiding through the ferroelectric electro-optic modulator device 1 , and providing or depositing the plurality of metal electrodes 25 on and in contact with the at least one ferroelectric material or layer 1 1 .

[0121] The following provides one exemplary fabrication process / method of the exemplary device 1 of the present disclosure for the fabrication / d eposition of device comprising a silicon Si substrate (3), a PolySi (or a-Si) intermediate layer 7, a SiC>2 supporting layer 5 and a ferroelectric LiNbO311 layer, upon which structure silver electrodes 25 are deposited by electron beam evaporation having an exemplary thickness of (about) 800nm. Other fabrication processes or methods of the device 1 are possible.

[0122] The process begins with a clean silicon (Si) wafer 3, serving as the foundation substrate for subsequent layer depositions.

[0123] A layer 7 of polycrystalline silicon (PolySi) can be deposited onto the silicon wafer using Plasma Enhanced Chemical Vapor Deposition (PECVD). This technique allows for precise control of the PolySi layer's thickness and uniformity.

[0124] Alternatively, amorphous silicon a-Si can be deposited by LPCVD and used as the intermediate layer 7. A fast anneal can be carried out of the amorphous silicon a-Si that activates a transition of the amorphous silicon a-Si to poly-crystalline (polySi). Optionally, a polishing planarization (for example, via chemical-mechanical planarization) may be carried out on the surface of the amorphous silicon a-Si or polycrystalline silicon layer 7.

[0125] Silicon dioxide (SiO2) can then, for example, be deposited on top of the PolySi layer 7. This can be achieved through Plasma Enhanced Chemical Vapor Deposition (PECVD) to ensure a conformal coating over the PolySi layer 7.

[0126] Alternatively, Physical Vapor Deposition (PVD) can be used, or a wafer bonding of a SiO2to the PolySi layer 7. The SiO2layer 5 may be supported on a Silicon carrier or substrate which can be subsequently removed using a mechanical grinding technique and a finer removal of the Si material by dry etching (using for example fluorine chemistry). Using wafer-bonding and the grinding technique has shown to provide a high quality SiO2layer 5 on the poly-Si layer surface.

[0127] The lithium niobate (LiNbO3) layer 1 1 is provided using a mature and known smart-cut technique, followed by wafer bonding to the SiO2layer 5 and transfer from another bulk lithium niobate wafer, (see, for example, https: / / www.soitec.com / en / products / smart-cut).

[0128] This approach allows the fabrication of a 600nm thin, high-quality LiNbO3layer 1 1 on top of the SiO2layer 5 ensuring optimal optical properties for applications that require electro-optic modulation.

[0129] Silver electrodes 25 are deposited by electron beam evaporation upon the LiNbOs layer 1 1 and the resulting structure, the Silver electrodes 25 having an exemplary thickness of (about) 800nm.

[0130] The Inventors surprisingly found that the device 1 of the present disclosure that includes the intermediate layer or material 7 enhances modulator performance. The Inventors surprisingly found that the device 1 of the present disclosure that includes the intermediate layer or material 7 of polysilicon provided on a mono-crystalline or single-crystalline silicon substrate or layer 3 enhances modulator performance by exhibiting lower loss performance, as shown by the comparative measurements of Figure 2 that compares a device including the intermediate layer or material 7 with a device in which the intermediate layer or material 7 is absent. Compared to an identical device without the intermediate layer or material 7, the RF loss is reduced by 2 dB / cm at 60 GHz. The device 1 of the present disclosure assures lower RF loss. Without being held to any specific theory, the change in crystallinity from single crystalline to poly-crystalline or amorphous appears to have a role to play in the resulting lower RF loss of the device. This enhancement is obtained regardless of electrode material, that is, regardless of whether a silver or gold electrode is used.

[0131] Additionally, the Inventors surprisingly found that the use of silver electrodes reduces Ohmic loss by up to 30% compared to the traditionally used Au, traditionally used for its stability and conductivity, also assuring a significant efficiency boost. Traditional integrated electro-optic modulators usually employ gold (Au). The Inventor’s results show that replacing gold with silver, while keeping other device design aspects the same, assures a 30% reduction in loss (see, for example, Figure 3). This boost is obtained in addition to the enhancement of the modulator performance previously discussed and presented in Figure 2.

[0132] These innovations provide a clear improvement over existing devices marking a significant advancement in electro-optic modulation technology.

[0133] The inclusion of the intermediate layer or material 7 is surprisingly effective and is obtained by a straightforward structural modification of the electro-optic modulator design.

[0134] Additionally, using silver to reduce ohmic loss by up to 30% challenges traditional material choices, providing a cost-effective and efficient alternative. This material has not been used in integrated photonic based modulators to date. The move to silver involved meticulous experimentation and analysis by the Inventors to ensure that the benefits in conductivity did not introduce other issues, such as increased susceptibility to tarnishing or processing difficulties.

[0135] These findings provide new solutions without contradicting existing literature, instead addressing gaps and proposing novel solutions for enhancing the performance of integrated electro-optic modulators.

[0136] This breakthrough significantly diminishes device loss, collectively slashing losses overall by 60%. This paves the way for photonic integrated modulators with ultra-low microwave losses.

[0137] As illustrated in Figure 4, the incorporation of the intermediate layer or material 7 along with a silver electrode leads to a substantial enhancement in the electro-optical modulation bandwidth - a 200% increase, elevating it from 22.5 GHz to the significant value of 100 GHz. Figure 4 also shows the enhancement obtained by the inclusion of the intermediate layer or material 7. This is manifest when one compares the results for a device including a polycrystalline silicon layer and Au electrodes to those for a device including a non- polycrystalline silicon layer and Au electrodes.

[0138] While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments, and equivalents thereof, are possible without departing from the sphere and scope of the invention. Accordingly, it is intended that the invention not be limited to the described embodiments and be given the broadest reasonable interpretation in accordance with the language of the appended claims. The features of any one of the above-described embodiments may be included in any other embodiment described herein.

Claims

CLAIMS1 . Ferroelectric electro-optic modulator device (1) comprising: at least one supporting substrate or layer (3), wherein the at least one supporting substrate or layer (3) comprises or consists of a mono-crystalline or single-crystalline silicon substrate or layer (3), at least one supporting oxide material or layer (5) provided or deposited on the silicon substrate or layer (3), at least one ferroelectric material or layer (11) provided or deposited on the at least one supporting oxide material or layer (5), wherein the at least one ferroelectric material or layer (11) includes or delimits at least one elongated waveguide core (17) of at least one elongated waveguide (15), the at least one elongated waveguide core (17) being configured to guide light inside the at least one elongated waveguide (15) and through the at least one ferroelectric material or layer (11), at least one intermediate layer (7) comprising or consisting of at least one polycrystalline silicon layer or material (7) provided or deposited between the at least one supporting oxide material or layer (5) and the at least one supporting silicon substrate or layer (3), wherein the at least one intermediate layer (7) directly contacts the at least one supporting oxide material or layer (5) and the at least one supporting silicon substrate or layer (3), and a plurality of metal electrodes (25) comprising gold or silver, the plurality of metal electrodes (25) provided on and in contact with the at least one ferroelectric material or layer (11), the plurality of metal electrodes (25) being configured to generate an electric field inside the at least one ferroelectric material or layer (11) to modify a refractive index of the at least one elongated waveguide (15) when an electric field generating voltage is applied to the plurality of electrodes (25).

2. Ferroelectric electro-optic modulator device (1) according to the previous claim, wherein at least one of the plurality of electrodes (25) comprises or consists of silver or each electrode of the plurality of electrodes (25) comprises or consists of silver.

3. Ferroelectric electro-optic modulator device (1) according to claim 1 or 2, wherein the at least one elongated waveguide core (17) defines or is an elongated ridge waveguide core4. Ferroelectric electro-optic modulator device (1 ) according to any one of the previous claims, wherein the plurality of electrodes are coplanar metal electrodes (25) extending from the at least one ferroelectric material or layer (11), and the device 1 is a coplanar waveguide device.

5. Ferroelectric electro-optic modulator device (1 ) according to any one of the previous claims, wherein at least one of the plurality of electrodes (25) or each electrode of the plurality of electrodes (25) includes an outer exposed voltage contact surface (27), and a clearance located facing the outer exposed voltage contact surface (27) to permit a voltage terminal or contact to the made to the outer exposed voltage contact surface (27) for a device operational voltage to be applied to the outer exposed voltage contact surface (27).

6. Ferroelectric electro-optic modulator device (1 ) according to any one of the previous claims, wherein the at least one polysilicon layer or material (7) directly contacts the at least one supporting oxide material or layer (5) and the at least one silicon substrate or layer (3).

7. Ferroelectric electro-optic modulator device (1 ) according to any one of the previous claims, wherein the at least one ferroelectric material or layer (11) is a non-plasma etched ferroelectric material or layer (11).

8. Ferroelectric electro-optic modulator device (1 ) according to any one of the previous claims, wherein the ferroelectric electro-optic modulator device (1) is a room-temperature operational ferroelectric electro-optic modulator device (1).

9. Ferroelectric electro-optic modulator device (1 ) according to any one of the previous claims, wherein the at least one ferroelectric material or layer (11 ) comprises or consists solely of Lithium Niobate (LiNbO3), orsingle crystal Lithium Niobate (LiNbO3), ordoped Lithium Niobate (LiNbO3) or doped single crystal Lithium Niobate (LiNbO3), or Lithium Tantalate (LiTaO3) or single crystal Lithium Tantalate (LiTaO3), ordoped Lithium Tantalate (LiTaO3) or doped single crystal Lithium Tantalate (LiTaO3) or Barium titanate (BaTiO3).

10. Ferroelectric electro-optic modulator device (1) according to any one of the previous claims, wherein the at least one supporting oxide material or layer (5) comprises or consists of silicon oxide.1 1 . Ferroelectric electro-optic modulator device (1) according to any one of the previous claims, wherein the ferroelectric electro-optic modulator device is a photonic on-chip integrated ferroelectric electro-optic modulator device.

12. Ferroelectric electro-optic modulator device (1) according to any one of the previous claims, wherein the at least one polycrystalline silicon layer or material (7) includes at least one contact surface (CS1 , CS2) directly contacting the at least one supporting oxide material or layer (5) and / or directly contacting the at least one supporting silicon substrate or layer (3), wherein the at least one contact surface (CS1 , CS2) consists solely of silicon atoms.

13. Ferroelectric electro-optic modulator device (1) according to the previous claim, wherein the at least one contact surface (CS1 , CS2) includes at least one area consisting solely of silicon atoms or includes a plurality of areas consisting solely of silicon atoms, the at least one area or each ofthe plurality of areas being a sub-area ofthe at least one contact surface (CS1 , CS2).

14. Ferroelectric electro-optic modulator device (1) according to any one of the previous claims, wherein the plurality of metal electrodes (25) is provided directly on and directly in contact with the at least one ferroelectric material or layer (1 1).

15. Ferroelectric electro-optic modulator device (1) according to any one ofthe previous claims 1 to 13, wherein the plurality of metal electrodes (25) is provided indirectly on and indirectly in contact with the at least one ferroelectric material or layer (11), wherein the ferroelectric electro-optic modulator device (1) includes at least one protective cladding layer or material (55) located between the at least one ferroelectric material or layer (11) and the plurality of metal electrodes (25).

16. Ferroelectric electro-optic modulator device fabrication method, including: providing at least one supporting substrate or layer (3), wherein the at least one supporting silicon substrate or layer (3) is a mono-crystalline or single- crystalline silicon substrate or layer (3), providing or depositing at least one intermediate layer (7) comprising or consisting of at least one polycrystalline silicon layer or material (7) directly on the at least one silicon substrate or layer (3), providing or depositing at least one supporting oxide material or layer (5) directly on the at least one polysilicon layer or material (7), and forming at least one elongated waveguide (15) comprising at least one elongated waveguide core (17) in or on the at least one ferroelectric material or layer (11 ) to allow light guiding through the ferroelectric electro-optic modulator device (1), andproviding or depositing a plurality of metal electrodes (25) comprising silver or gold on and in contact with the at least one ferroelectric material or layer (11).

17. Method according to the previous claim, wherein the at least one supporting oxide material or layer (5) is provided or deposited to directly contact the at least one intermediate layer (7).

18. Method according to any one of the previous claims 16 to 17, wherein the at least one polysilicon layer or material (7) is provided or deposited to directly contact the at least one silicon substrate or layer (3).

19. Method according to any one of the previous claims 16 to 18, wherein at least one of the electrodes (25) or each of the plurality of electrodes (25) comprises or consists of silver.

20. Method according to any one of the previous claims 16 to 19, wherein the at least one ferroelectric material or layer (1 1) comprises or consists solely of Lithium Niobate (LiNbO3), or single crystal Lithium Niobate (LiNbO3), or doped Lithium Niobate (LiNbO3) or doped single crystal Lithium Niobate (LiNbO3), or Lithium Tantalate (LiTaO3) or single crystal Lithium Tantalate (LiTaO3), or doped Lithium Tantalate (LiTaO3) or doped single crystal Lithium Tantalate (LiTaO3) or Barium titanate (BaTiO3). .21 . Method according to any one of the previous claims 16 to 20, wherein the at least one polycrystalline silicon layer or material (7) includes at least one contact surface (CS1 , CS2) directly contacting the at least one supporting oxide material or layer (5) and / or directly contacting the at least one supporting silicon substrate or layer (3), wherein the at least one contact surface (CS1 , CS2) consists solely of silicon atoms.

22. Method according to the previous claim, wherein the at least one contact surface (CS1 , CS2) includes at least one area consisting solely of silicon atoms or includes a plurality of areas consisting solely of silicon atoms, the at least one area or each of the plurality of areas being a sub-area of the at least one contact surface (CS1 , CS2).

23. Method according to any one of the previous claims 16 to 22, wherein the plurality of metal electrodes (25) is provided or deposited directly on and directly in contact with the at least one ferroelectric material or layer (1 1).

24. Method according to any one of the previous claims 16 to 22, wherein the plurality of metal electrodes (25) is provided or deposited indirectly on and indirectly in contact with the at leastone ferroelectric material or layer (1 1), wherein the ferroelectric electro-optic modulator device (1) includes at least one protective cladding layer or material (55) located between the at least one ferroelectric material or layer (1 1) and the plurality of metal electrodes (25).

25. Ferroelectric electro-optic modulator device (1) comprising: at least one supporting substrate or layer (3), wherein the at least one supporting substrate or layer (3) comprises or consists of a mono-crystalline or single-crystalline silicon substrate or layer (3), at least one supporting oxide material or layer (5) provided or deposited on the silicon substrate or layer (3), at least one ferroelectric material or layer (11 ) provided or deposited on the at least one supporting oxide material or layer (5), wherein the at least one ferroelectric material or layer (1 1) includes or delimits at least one elongated waveguide core (17) of at least one elongated waveguide (15), the at least one elongated waveguide core (17) being configured to guide light inside the at least one elongated waveguide (15) and through the at least one ferroelectric material or layer (1 1), at least one intermediate layer (7) comprising or consisting of at least one polycrystalline silicon layer or material (7) provided or deposited between the at least one supporting oxide material or layer (5) and the at least one supporting silicon substrate or layer (3), wherein the at least one intermediate layer (7) directly contacts the at least one supporting oxide material or layer (5) and the at least one supporting silicon substrate or layer (3), and a plurality of metal electrodes (25) comprising silver, the plurality of metal electrodes (25) provided on and in contact with the at least one ferroelectric material or layer (11 ), the plurality of metal electrodes (25) being configured to generate an electric field inside the at least one ferroelectric material or layer (11) to modify a refractive index of the at least one elongated waveguide (15) when an electric field generating voltage is applied to the plurality of electrodes (25).

26. Ferroelectric electro-optic modulator device (1) comprising: at least one supporting substrate or layer (3), wherein the at least one supporting substrate or layer (3) comprises or consists of a mono-crystalline or single-crystalline silicon substrate or layer (3), at least one supporting oxide material or layer (5) provided or deposited on the silicon substrate or layer (3),at least one ferroelectric material or layer (11 ) provided or deposited on the at least one supporting oxide material or layer (5), wherein the at least one ferroelectric material or layer (1 1) includes or delimits at least one elongated waveguide core (17) of at least one elongated waveguide (15), the at least one elongated waveguide core (17) being configured to guide light inside the at least one elongated waveguide (15) and through the at least one ferroelectric material or layer (1 1), at least one intermediate layer (7) comprising or consisting of at least one at least one amorphous silicon layer or material (7) provided or deposited between the at least one supporting oxide material or layer (5) and the at least one supporting silicon substrate or layer (3), wherein the at least one intermediate layer (7) directly contacts the at least one supporting oxide material or layer (5) and the at least one supporting silicon substrate or layer (3), and a plurality of metal electrodes (25) comprising silver, the plurality of metal electrodes (25) provided on and in contact with the at least one ferroelectric material or layer (11 ), the plurality of metal electrodes (25) being configured to generate an electric field inside the at least one ferroelectric material or layer (11) to modify a refractive index of the at least one elongated waveguide (15) when an electric field generating voltage is applied to the plurality of electrodes (25).

27. Ferroelectric electro-optic modulator device (1) according to the previous claim 25 or 26, wherein the at least one amorphous layer or material (7) includes at least one contact surface (CS1 , CS2) directly contacting the at least one supporting oxide material or layer (5) and / or directly contacting the at least one supporting silicon substrate or layer (3), wherein the at least one contact surface (CS1 , CS2) consists solely of silicon atoms.

28. Ferroelectric electro-optic modulator device (1) according to the previous claim, wherein the at least one contact surface (CS1 , CS2) includes at least one area consisting solely of silicon atoms or includes a plurality of areas consisting solely of silicon atoms, the at least one area or each ofthe plurality of areas being a sub-area ofthe at least one contact surface (CS1 , CS2).

29. Ferroelectric electro-optic modulator device (1) according to any one ofthe previous claims 25 to 28, wherein the plurality of metal electrodes (25) is provided or deposited directly on and directly in contact with the at least one ferroelectric material or layer (11).

30. Ferroelectric electro-optic modulator device (1) according to any one ofthe previous claims 25 to 28, wherein the plurality of metal electrodes (25) is provided or deposited indirectly onand indirectly in contact with the at least one ferroelectric material or layer (11), wherein the ferroelectric electro-optic modulator device (1) includes at least one protective cladding layer or material (55) located between the at least one ferroelectric material or layer (11) and the plurality of metal electrodes (25).31 . Ferroelectric electro-optic modulator device fabrication method, including: providing at least one supporting substrate or layer (3), wherein the at least one supporting silicon substrate or layer (3) is a mono-crystalline or single- crystalline silicon substrate or layer (3), providing or depositing at least one intermediate layer (7) comprising or consisting of at least one polycrystalline silicon layer or material (7) directly on the at least one silicon substrate or layer (3), providing or depositing at least one supporting oxide material or layer (5) directly on the at least one polysilicon layer or material (7), and forming at least one elongated waveguide (15) comprising at least one elongated waveguide core (17) in or on the at least one ferroelectric material or layer (11 ) to allow light guiding through the ferroelectric electro-optic modulator device (1), and providing or depositing a plurality of metal electrodes (25) comprising silver on and in contact with the at least one ferroelectric material or layer (1 1).

32. Ferroelectric electro-optic modulator device fabrication method, including: providing at least one supporting substrate or layer (3), wherein the at least one supporting silicon substrate or layer (3) is a mono-crystalline or single- crystalline silicon substrate or layer (3), providing or depositing at least one intermediate layer (7) comprising or consisting of at least one amorphous silicon layer or material (7) directly on the at least one silicon substrate or layer (3), providing or depositing at least one supporting oxide material or layer (5) directly on the at least one amorphous layer or material (7), and forming at least one elongated waveguide (15) comprising at least one elongated waveguide core (17) in or on the at least one ferroelectric material or layer (11 ) to allow light guiding through the ferroelectric electro-optic modulator device (1), and providing or depositing a plurality of metal electrodes (25) comprising silver on and in contact with the at least one ferroelectric material or layer (1 1).

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