CN-121986297-A - Ferroelectric device with electrodes for polarization

Abstract

An electro-optic method and device that allows efficient polarization of ferroelectric devices. The electro-optic device includes a waveguide, a Barium Titanate (BTO) layer adjacent to the waveguide. One or more polarizing electrodes are provided for polarizing the pockels material.

Inventors

• F. Eltis
• L. Zornomats
• EBERLE STEFAN

Assignees

• 鲁米菲斯股份公司

Dates

Publication Date

20260505

Application Date

20240902

Priority Date

20230906

Claims (19)

1. 1. An electro-optic device comprising: A 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 polarizing electrodes for polarizing the pockels material.
2. 2. The device of claim 1, further comprising an inductance associated with the one or more polarized electrodes to prevent high frequency current in the one or more polarized electrodes.
3. 3. The device of claim 1 or 2, wherein the pockels material is BTO or LN.
4. 4. A device according to any of claims 1-3, wherein a polarizing voltage is applied to the polarizing electrode during burn-in and/or start-up and/or operation.
5. 5. The device of any of claims 1-4, wherein the waveguide is arranged as an MZ interferometer.
6. 6. The device of claim 5, wherein polarizing electrodes are between arms of the MZ interferometer.
7. 7. A device according to claim 5 or 6, wherein the signal electrode is located outside the arm.
8. 8. The device of any of claims 1-7, wherein the signal electrode comprises two electrodes that receive a differential signal.
9. 9. The device of any of claims 1-8, wherein the signal electrode comprises a high frequency ground electrode and a signal electrode.
10. 10. The device of any of claims 1-9, one or more polarizing electrodes being segmented over their length to achieve equalization.
11. 11. A method of operating an electro-optic device comprising a 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 one or more signals to the signal electrode, and The pockels cell is polarized with one or more polarizing electrodes.
12. 12. The method of claim 11, further associating an inductance associated with the one or more polarized electrodes to prevent high frequency current in the one or more polarized electrodes.
13. 13. The method of claim 11 or 12, wherein the pockels material is BTO or LN.
14. 14. The method according to any of claims 11-13, further comprising applying a polarizing voltage to the polarizing electrode during aging and/or start-up and/or operation.
15. 15. The method of any of claims 11-14, wherein the waveguide is arranged as an MZ interferometer.
16. 16. The method of claim 15, wherein polarizing electrodes are between arms of the MZ interferometer.
17. 17. A method according to claim 15 or 16, wherein the signal electrode is located outside the arm.
18. 18. The method of any of claims 11-17, further comprising applying a differential signal across the signal electrodes, the signal electrodes comprising two electrodes that receive a differential signal.
19. 19. The method of any one of claims 11-19, wherein one or more polarizing electrodes are segmented over their length to achieve equalization.

Description

Ferroelectric device with electrodes for polarization RELATED APPLICATIONS The present application is in accordance with 35 U.S. c. ≡119 (e) claims to the benefit of U.S. provisional application No.63/580,719 filed on 6/9 at 2023, which is incorporated herein by reference in its entirety. Background Silicon p-i-n modulators are optical devices that utilize the characteristics of the p-i-n (positive-intrinsic-negative) junction to modulate light. In the p-i-n junction, the "p" region is p-doped silicon containing excess holes (positive charge carriers), the "n" region is n-doped silicon containing excess electrons (negative charge carriers), and the "i" region (intrinsic) is essentially a layer of silicon insulator separating the p and n regions. When a voltage is applied across the junction, it changes the density of free charge carriers present in the junction/intrinsic region. This causes a plasma dispersion effect in the junction/intrinsic region, which changes the refractive index and absorption due to the presence of free carriers (electrons and holes). A Mach-Zehnder (MZ) modulator is an interferometer for modulating the amplitude of an optical signal. The Mach-Zehnder silicon p-i-n phase modulator comprises a silicon substrate typically heavily doped with n-type or p-type impurities. The 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 to modulate the phase of the light traveling through the arm. The waveguide combiner causes light from the two arms to interfere. The amplitude is controlled by the voltage applied to the p-i-n junction(s) in the arm(s), resulting in constructive or destructive interference. Indium phosphide (InP) is also commonly used in optical modulators due to its electro-optical properties. In mach-zehnder InP modulators, the modulation mechanism is typically the quantum confinement stark effect, which refers to the absorption and refractive index changes of the quantum well stack caused by an applied electric field. MZ modulators may also be made of pockels materials such as barium titanate (BaTiO 3, BTO), lithium niobate (LiNbO 3, LN), lead zirconate titanate (PZT), and silicon-organic hybrid (SOH) modulators that exhibit a change in their refractive index under an applied electric field (also known as the pockels effect). For example, a thin film of lead zirconate titanate (PZT) may be grown on silicon so that high speed pockels modulation on SiN waveguides is achieved. SOH modulators combine the advantages of large-scale silicon photonic integration with extremely high electro-optic (EO) coefficients obtained by molecular engineering of organic materials. In these modulators, a DC bias need not be applied in operation to ensure reverse bias of the junction, as is the case with silicon p-i-n and InP modulators. The circuit is also electrically different because in the case of a silicon p-i-n modulator the bias is connected by a diode, whereas in BTO, LN, PZT and SOH modulators the bias is capacitively coupled. Disclosure of Invention Pockels materials such as BTO, LN, PZT and SOH require polarizing ferroelectric domains to obtain a net nonlinear electro-optic (EO) response and/or create a differential push-pull MZ modulator. In order to achieve push-pull modulation in an MZ modulator, the material polarization and/or the modulated Radio Frequency (RF) signal must be applied asymmetrically in the two arms of the modulator (parallel in one arm and antiparallel in the other). If this is not the case, only one arm can be modulated. The polarization voltage required to polarize the domains in an MZ modulator is relatively large and thus needs to be electrically isolated from the usual RF modulated signal. This can be achieved by using an offset tee, but on-chip offset tee implementations are inefficient, bulky and expensive, and may reduce performance. Furthermore, in some cases, polarization is required during operation using a DC bias that is decoupled from the RF signal. The present invention relates to waveguide devices such as BTO or LN MZ modulators. The modulator may also be constructed of PZT or SOH. The waveguide structure includes a pockels layer having an optical overlap such that a refractive index change in the pockels layer causes a phase acceleration or retardation of propagating light in one or more arms of the MZ modulator. The electrode configuration includes two separate sets of electrodes that are electrically decoupled. One set of electrodes is the ground electrode (S) G or signal electrode (S) providing a reference potential and optionally a drive signal (signal from DC to GHz) (S + and S -). (use of ground and signal electrodes on the modulator will produce a single-ended driven push-pull MZ modulator; use of the same structure with S + and