CN119045260A - Adjustable optical waveguide based on ferroelectric domain electro-optic effect - Google Patents
Adjustable optical waveguide based on ferroelectric domain electro-optic effect Download PDFInfo
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- CN119045260A CN119045260A CN202411180424.0A CN202411180424A CN119045260A CN 119045260 A CN119045260 A CN 119045260A CN 202411180424 A CN202411180424 A CN 202411180424A CN 119045260 A CN119045260 A CN 119045260A
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
- G02F1/3544—Particular phase matching techniques
- G02F1/3548—Quasi phase matching [QPM], e.g. using a periodic domain inverted structure
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/355—Non-linear optics characterised by the materials used
- G02F1/3558—Poled materials, e.g. with periodic poling; Fabrication of domain inverted structures, e.g. for quasi-phase-matching [QPM]
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/365—Non-linear optics in an optical waveguide structure
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2201/00—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
- G02F2201/12—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 electrode
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2202/00—Materials and properties
- G02F2202/20—LiNbO3, LiTaO3
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- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
- Optical Integrated Circuits (AREA)
Abstract
本发明公开了一种基于铁电畴电光效应的可调光波导，包括畴结构、第一畴壁、第二畴壁、正电极、负电极以及绝缘层，畴结构分为正畴和负畴，所述负畴夹在中间，两边各设置一个正畴，正畴和负畴交界处分别形成第一畴壁和第二畴壁，所述第一畴壁和第二畴壁上覆盖有金属电极，金属电极与第一畴壁和第二畴壁导通，通过对正电极和负电极施加电压使得负畴被施加电场，在负畴中产生全反射对激光进行约束，当电压很小时波导消失，实现激光在波导中传输的调制。本发明利用铁电晶体的畴壁导电特性，进行电场调制，产生光电效应，升高畴壁间反转的晶体折射率，从而形成平面或者条形波导，制备工艺简单，成本低廉，并实现了激光在波导传输中的调制。
The invention discloses an adjustable optical waveguide based on the electro-optic effect of ferroelectric domains, comprising a domain structure, a first domain wall, a second domain wall, a positive electrode, a negative electrode and an insulating layer, wherein the domain structure is divided into a positive domain and a negative domain, wherein the negative domain is sandwiched in the middle, a positive domain is arranged on each side, and a first domain wall and a second domain wall are formed at the junction of the positive domain and the negative domain, respectively, wherein the first domain wall and the second domain wall are covered with metal electrodes, and the metal electrodes are connected to the first domain wall and the second domain wall, and an electric field is applied to the negative domain by applying voltage to the positive electrode and the negative electrode, and total reflection is generated in the negative domain to constrain the laser, and when the voltage is very small, the waveguide disappears, thereby realizing the modulation of the laser transmission in the waveguide. The invention utilizes the conductive characteristics of the domain wall of the ferroelectric crystal to perform electric field modulation, generate a photoelectric effect, and increase the crystal refractive index of the inversion between the domain walls, thereby forming a plane or strip waveguide, and the preparation process is simple, the cost is low, and the modulation of the laser in the waveguide transmission is realized.
Description
Technical Field
The present invention relates to tunable waveguides, and more particularly to a tunable waveguide based on ferroelectric domain electro-optic effects.
Background
The electro-optic effect can be controlled by an electric field, and the refractive index change is generated by the pockels effect or the pockels cell effect, and although the change of the refractive index caused by the electric field is small, the change can be accurately displayed and measured by an interference method and the like, and the electro-optic effect has many important applications such as optical communication, ranging, display, information processing and sensors. The usual electro-optic crystals are mostly ferroelectric crystals, such as KDP, KDA, KTP, liNbO 3、LiTaO3 and the like. Conventional bulk crystals require relatively high modulation voltages, typically several kilovolts to tens of thousands of volts, in order to produce sufficiently large electro-optic effects. In order to reduce the modulation voltage and increase the modulation speed, waveguides such as buried proton exchange waveguides, titanium diffusion waveguides, or ridge waveguides may be prepared on the crystal, and the modulation voltage may be reduced to several volts or less by shortening the distance between the positive and negative electrodes to increase the electric field strength. However, the light-transmitting area and the power of the strip waveguide are limited by the sectional area, and the planar waveguide is applied with voltage, so that a large-area conductive electrode is embedded in the material, the preparation process is complex, and the cost is high.
In nonlinear optics, one phase matching mode of ferroelectric crystals is quasi-phase matching (QPM). The phase matching is characterized in that the inversion characteristic of ferroelectric domains in the ferroelectric is utilized to perform periodical ferroelectric domain inversion, thereby compensating phase mismatch generated in the nonlinear coupling process. How to form a planar or bar waveguide with a simple preparation process and low cost and adjustable laser transmission is a problem to be solved.
Disclosure of Invention
The invention aims to provide a tunable optical waveguide based on ferroelectric domain electro-optic effect.
The invention comprises a domain structure, a first domain wall, a second domain wall, a positive electrode, a negative electrode and an insulating layer, wherein the domain structure is divided into a positive domain and a negative domain, the negative domain is clamped in the middle, two sides of the negative domain are respectively provided with the positive domain, the first domain wall and the second domain wall are respectively formed at the juncture of the positive domain and the negative domain, the first domain wall and the second domain wall are covered with a metal electrode, the metal electrode is conducted with the first domain wall and the second domain wall, the negative domain is applied with an electric field by applying voltage to the positive electrode and the negative electrode, an electro-optical effect is generated under the action of the electric field, positive and negative voltages and the axial direction of crystals are set, the refractive index of the electro-optical effect is increased to be larger than that of the positive domains at two sides, total reflection is generated in the negative domain to restrain laser, and when the voltage is zero or the voltage is small, the waveguide disappears, and modulation of the laser transmitted in the waveguide is realized.
Further, the positive domain and the negative domain are ferroelectric crystals, and the ferroelectric crystals comprise any one of lithium niobate, lithium tantalate and potassium titanyl phosphate.
Further, the domain structure performs domain inversion by a domain inversion process, and the inverted portion is referred to as a negative domain and the non-inverted portion is referred to as a positive domain.
Further, the covered area under the positive electrode is a positive domain, and the uncovered area is a negative domain.
Further, the domain inversion process adopts any one of a room temperature electric field polarization method, a growth stripe method and a poly-sheet multi-domain method.
Further, the structural size range of the domain inversion is that the domain inversion thickness is 0.1 μm or less and D is 100 μm or less, the waveguide width is 1 μm or less and H is 10mm or less, and the positive and negative electrode thickness is 1nm or less and T is 100 μm or less.
Further, the positive and negative voltages range from 1V to 1000V.
Further, the crystal axis direction is a direction selected so that the refractive index of the domain inversion portion increases according to the electro-optic coefficient of the material.
Further, the waveguides include, but are not limited to, curved, annular, and intersecting structures.
Further, insulation is maintained between the positive electrode and the negative electrode, and the insulation material is used for filling.
Compared with the prior art, the invention has the advantages that the invention utilizes the domain wall conductive property of ferroelectric crystal to modulate electric field, generate photoelectric effect, raise the refractive index of crystal reversed between domain walls, thereby forming planar or bar waveguide, and has simple preparation process and low cost, and realizes the modulation of laser in waveguide transmission.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a schematic cross-sectional view of the present invention;
Fig. 3 is a schematic diagram of a2×2 waveguide beam splitter structure.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, the invention comprises a domain structure, a first domain wall 1, a second domain wall 2, a positive electrode 5, a negative electrode 6 and an insulating layer 7, wherein the domain structure is divided into a positive domain 3 and a negative domain 4, the negative domain 4 is clamped in the middle, two sides of the negative domain are respectively provided with the positive domain 3, the first domain wall 1 and the second domain wall 2 are respectively formed at the juncture of the positive domain 3 and the negative domain 4, the first domain wall 1 and the second domain wall 2 are covered with metal electrodes, the metal electrodes are conducted with the first domain wall 1 and the second domain wall 2, the negative domain 4 is applied with an electric field by applying a voltage to the positive electrode 5 and the negative electrode 6, an electro-optic effect is generated under the action of the electric field, the positive voltage and the crystal axial direction are set, the refractive index of the electro-optic effect is increased, the refractive index is larger than that of the positive domains 3 at two sides, total reflection is generated in the negative domain 4 to restrict laser, and when the voltage is zero or the voltage is small, the waveguide disappears, and the modulation of the laser in the waveguide is realized.
The optical material of the present invention is made of ferroelectric crystal such as lithium niobate (LiNbO 3), lithium tantalate (LiTaO 3), potassium titanyl phosphate (KTiOPO 4) and the like, and domain inversion can be performed by a room temperature electric field polarization method. As shown in the following figures, the inverted portion is referred to as a negative domain, and the non-inverted portion is referred to as a positive domain. Domain walls having a certain conductivity are formed between the positive and negative domains.
The invention covers metal electrodes on two domain walls of the negative domain, and voltage is applied through conduction between the metal electrodes and the domain walls. Under the action of voltage, domain walls are conducted so that the negative domains are applied with an electric field, and an electro-optic effect is generated under the action of the electric field. The proper positive and negative voltages and the proper direction of the crystal axial direction are selected, so that the refractive index of the electro-optic effect is increased and is larger than that of the positive domains on two sides, and total reflection is generated in the negative domains to restrain laser.
In addition, the waveguide is formed when voltage is applied, and the waveguide disappears when the voltage is zero or the voltage is small, so that the characteristic can be utilized to realize the modulation of the transmission of laser in the waveguide, the tail end outputs laser when the waveguide is formed, the light intensity of the tail end is weak when the waveguide disappears, and the intensity modulation effect of the emergent laser is formed.
The cross-sectional view of the present invention is shown in fig. 2, wherein the thickness of the positive and negative electrodes is T, the width of the waveguide is H, and the thickness of the waveguide is D. Lithium niobate is a uniaxial crystal whose optical axis c-axis is symmetrical along the refractive index ellipsoids in the Z direction, X and Y directions. The positive and negative electrodes are insulated and filled with insulating material such as photoresist.
The ferroelectric material includes lithium niobate (LiNbO 3), lithium tantalate (LiTaO 3), potassium titanyl phosphate (KTiOPO 4), and the like, and a preferable material is lithium niobate.
The ferroelectric domain inversion process comprises a room temperature electric field polarization method, a growth stripe method, a poly-sheet multi-domain method and the like, and the room temperature electric field polarization method is preferred.
The structural size range of the domain inversion is that the domain inversion thickness is 0.1 μm or less and D is 100 μm or less, the waveguide width is 1 μm or less and H is 10mm or less, and the positive and negative electrode thickness is 1nm or less and T is 100 μm or less. Of these, the preferred dimensions are D.apprxeq.1 μm, H.apprxeq.1 mm, T.apprxeq.100 nm.
The positive and negative electrodes apply voltages in the range of 1V to 1000V.
According to the electro-optic effect, under the action of an external electric field E, the refractive index principal axis of the lithium niobate crystal changes, and the refractive index principal axis of the lithium niobate crystal changes, so that according to the linear electro-optic effect matrix of the lithium niobate, the electric field E is applied along the X-axis direction, and then E y＝Ex =e, and the refractive index ellipsoidal equation of the lithium niobate crystal changes as follows:
the new refractive index can be obtained by twice coordinate conversion and omitting the second order small quantity:
n′z＝ne (4)
As shown in fig. 1, since the polarization direction of the input light is the Y direction, only expression (3) is focused here. In the expression (3), the electric field in the X direction is generated by charges on the positive and negative domain walls. After voltage is applied to the positive and negative electrodes, positive and negative charges are distributed on adjacent domain walls to form an electric field E in X direction, and the refractive index is changed by the formula (3) to generate electro-optic modulation
The axial direction of the crystal is a direction in which the refractive index of the domain inversion portion is increased by selecting a voltage according to the sign of the electro-optic coefficient of the material. For example, the thickness d=1 μm of domain inversion of lithium niobate crystal, the electro-optic coefficient γ 22 =3.4pm/V, and thus when the voltage difference between the positive and negative electrodes is v=1000V, the formula (5) is followed
This increase in refractive index can be found to be similar in value to the increase in refractive index of the proton exchange waveguide, and a waveguide similar to proton exchange or titanium diffusion can be formed.
The waveguides may have a curved, annular, or crossed structure, for example, a curved crossed waveguide as shown in the following drawings, and a2×2 waveguide beam splitter may be formed by applying a voltage. The negative domain part in the figure is prepared by a method of manufacturing a beam splitter mask, photoetching and room-temperature electric field polarization. The covered area below the prepared positive electrode is a positive domain, and the uncovered area is a negative domain area. The arrangement of the electrodes is shown in fig. 3, and a curved waveguide with an increased refractive index is formed in the waveguide beam splitter.
Embodiment one:
The domain inversion shown in fig. 1 is performed by a room temperature electric field polarization process using a lithium niobate material as a substrate, and positive and negative electrodes shown in fig. 1 are maintained. The dimension of the processing structure is that the waveguide width D=1μm, the waveguide width H=1mm, the electrode material is red copper, and the coating thickness is 100nm. A1000V voltage was applied to the positive electrode shown in FIG. 1, the negative electrode was grounded, a high-intensity electric field was formed at the domain inversion portion, the input laser wavelength was 1.5 μm, the polarization state was along the X-axis, and an increase in refractive index was about 0.018 by the electro-optical effect. When the voltage is removed, the electro-optic effect disappears, the waveguide disappears, the laser can not be transmitted in the waveguide, and the light intensity of the output port is approximately equal to zero, thereby forming the voltage-controlled light intensity modulation.
Embodiment two:
As shown in fig. 3, 2 x 2 waveguide preparation was performed according to the procedure of the above example. First, positive and negative voltages are applied according to positive and negative electrodes of fig. 3, forming a2×2 waveguide coupler as shown in fig. 3. After all voltages are removed, the waveguide structure shown in fig. 3 disappears and the waveguide coupler disappears. Corresponding voltages are only applied to the positive electrode 1, the negative electrode 5 and the negative electrode 2, so that a structure with only left bent waveguides is formed, and only left input ports to left output ports have output signals. And corresponding voltages are only applied to the positive electrode 1, the negative electrode 5, the positive electrode 3 and the negative electrode 4 to form a bent strip waveguide from bottom left to top right, and only the left input port to the right output port have output signals.
Through the combination of the straight waveguide, the 2×2 coupler and other similar waveguide devices, the electric signal can be converted into an optical signal, so as to realize the electric signal operation and the mixed electro-optical chip for optical signal operation.
Claims (10)
1. The tunable optical waveguide based on the ferroelectric domain electro-optic effect is characterized by comprising a domain structure, a first domain wall (1), a second domain wall (2), a positive electrode (5), a negative electrode (6) and an insulating layer (7), wherein the domain structure is divided into a positive domain (3) and a negative domain (4), the negative domain (4) is clamped in the middle, two sides of the negative domain are respectively provided with the positive domain (3), the first domain wall (1) and the second domain wall (2) are respectively formed at the junctions of the positive domain (3) and the negative domain (4), the first domain wall (1) and the second domain wall (2) are covered with a metal electrode, the metal electrode is conducted with the first domain wall (1) and the second domain wall (2), the negative domain (4) is applied with an electric field by applying a voltage to the positive electrode (5) and the negative electrode (6), the electro-optic effect is generated under the action of the electric field, the positive voltage and the negative voltage and the crystal are arranged axially, the refractive index of the electro-optic effect is increased to be greater than that of the two sides of the positive domain (3), the negative domain (4) is generated, the total reflection is generated in the negative domain (4), and the total reflection voltage is zero or the constraint voltage is small when the laser voltage is zero, and the waveguide is vanished, and the laser waveguide is realized.
2. The tunable optical waveguide according to claim 1, wherein the positive domains (3) and the negative domains (4) are ferroelectric crystals, and the ferroelectric crystals include any one of lithium niobate, lithium tantalate, and potassium titanyl phosphate.
3. The tunable optical waveguide according to claim 1, wherein the domain structure is domain inverted by a domain inversion process, the inverted portion is called a negative domain (4), and the non-inverted portion is called a positive domain (3).
4. The tunable optical waveguide based on ferroelectric domain electro-optic effect as claimed in claim 1, wherein the area under the positive electrode (5) is covered with positive domains (3) and the uncovered area is covered with negative domains (4).
5. The tunable optical waveguide based on ferroelectric domain electro-optic effect as defined in claim 3, wherein the domain inversion process is any one of a room temperature electric field polarization method, a growth stripe method, and a poly-sheet multi-domain method.
6. The tunable optical waveguide based on ferroelectric domain electro-optic effect as claimed in claim 3, wherein the domain inversion has a structural size ranging from 0.1 μm to 100 μm in domain inversion thickness, from 1 μm to 10mm in waveguide width, and from 1nm to 100 μm in positive and negative electrode thickness.
7. The tunable optical waveguide based on ferroelectric domain electro-optic effect as claimed in claim 1, wherein the positive and negative voltages range from 1V to 1000V.
8. The tunable optical waveguide based on ferroelectric domain electro-optic effect as claimed in claim 1, wherein the crystal axis is a direction selected to raise the refractive index of the domain inversion portion according to the electro-optic coefficient of the material.
9. The tunable optical waveguide based on ferroelectric domain electro-optic effects as defined in claim 1, wherein the waveguide includes, but is not limited to, curved, annular, and crossed structures.
10. The tunable optical waveguide based on ferroelectric domain electro-optic effect as claimed in claim 1, wherein the positive electrode (5) and the negative electrode (6) are insulated and filled with an insulating material.
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| CN202411180424.0A CN119045260A (en) | 2024-08-26 | 2024-08-26 | Adjustable optical waveguide based on ferroelectric domain electro-optic effect |
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| CN202411180424.0A CN119045260A (en) | 2024-08-26 | 2024-08-26 | Adjustable optical waveguide based on ferroelectric domain electro-optic effect |
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