CN115586663A - Thin-film lithium niobate electro-optical modulator based on differential drive and push-pull - Google Patents
Thin-film lithium niobate electro-optical modulator based on differential drive and push-pull Download PDFInfo
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- 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
- G02F1/01—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 for the control of the intensity, phase, polarisation or colour
- G02F1/03—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 for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
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- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/13—Integrated optical circuits characterised by the manufacturing method
- G02B6/136—Integrated optical circuits characterised by the manufacturing method by etching
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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
- G02F1/01—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 for the control of the intensity, phase, polarisation or colour
- G02F1/03—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 for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/0305—Constructional arrangements
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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
- G02F1/01—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 for the control of the intensity, phase, polarisation or colour
- G02F1/03—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 for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/035—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 for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12035—Materials
- G02B2006/1204—Lithium niobate (LiNbO3)
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12133—Functions
- G02B2006/12142—Modulator
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12166—Manufacturing methods
- G02B2006/12176—Etching
Abstract
The invention discloses a thin-film lithium niobate electro-optical modulator based on differential drive and push-pull. The device comprises a substrate, an oxygen-buried layer, a lithium niobate layer and a cladding, wherein a thin-film lithium niobate optical waveguide is arranged below the cladding, a differential traveling wave electrode is arranged on the cladding, and the differential traveling wave electrode comprises a periodic structure electrode, a positive signal electrode, a negative signal electrode and a grounding electrode; the periodic structure electrode comprises metal electrode groups connected with the positive signal electrode and the negative signal electrode, each metal electrode group comprises a plurality of T-shaped or soil-shaped metal electrodes which are uniformly distributed at intervals along the waveguide direction, the longitudinal metal strips are connected to the positive signal electrode/the negative signal electrode, and the transverse metal strips are arranged in parallel to the waveguide direction; the metal electrodes of the positive signal electrode and the negative signal electrode are sequentially arranged alternately and are mutually embedded and inserted. The invention combines the differential drive and the push-pull structure on the thin-film lithium niobate platform for the first time, and realizes the double voltage modulation by introducing the periodic electrode with a specific structure.
Description
Technical Field
The invention relates to an electro-optical modulator and a preparation method thereof in the technical field of optical communication, optical sensing and optical integration, in particular to a novel thin-film lithium niobate electro-optical modulator based on a differential drive capacitance load type periodic structure electrode and a preparation method thereof.
Background
With the continuous development of the information age, a large number of new information-oriented industries are continuously approaching people's daily lives, such as 5G, cloud computing, big data processing, artificial intelligence, etc., and these new technologies bring great convenience to our daily lives, and also promote our needs for high-speed, large-bandwidth, low-power data processing and transmission technologies to become strong (i.p. kamine, "Optical integrated circuits: a personal transmission," j.light. Technology. Vol., 26.26, no.9, pp.994-1004, may 2008.). Taking a typical application in short-distance optical communication, namely a data center as an example, in the data comparison given by the leading CISCO company in the optical communication industry, from 17 years to 21 years, the network flow of a simple data center is improved by 174%, the data capacity in the whole data center is increased to 70%, and the power consumption pressure is continuously increased, so that how to effectively solve the problem of high-capacity and low-power-consumption data transmission is a great urgency to be solved in the optical communication industry at present.
At present, silicon-based optoelectronic integration technology using silicon as a substrate has been developed rapidly due to its advantages of low cost, excellent passive performance, CMOS compatibility, and the like. However, since Silicon itself does not have electro-optic effects (G.T. Reed and A.P.Knight, silicon Photonics: an Introduction: john Wiley & Sons, inc., 2004), electro-optic modulation can only be achieved by using the F-K effect of electric absorption or the carrier injection type effect, and the modulation rate cannot reach very high speed (ns level). Except that the modulation rate cannot reach very high speed, the bandwidth of the pure silicon-based electro-optical modulation can only reach about 40GHz at present, and the bandwidth requirement of 100G,400G and even 1.6T in the future required at present cannot be met. Therefore, thin film lithium niobate-based electro-optic modulators with large bandwidth, low power consumption, low insertion loss, and high speed have gained widespread attention in recent years.
The temperature of research on thin film lithium niobate electro-optic modulators has been increasing continuously over the last five years. In 2018, the subject group of harvard university has proposed a CMOS-driven thin-film lithium niobate electro-optical modulator (c.wang, m.zhang, x.chen, m.bertrand, a.shams-Ansari, s.chandrasekhar, p.winzer, and m.local, "Integrated lithium niobate electro-optical modulators operating at CMOS-compatible voltages," Nature 562,101 (2018)), which realizes a large-bandwidth, low-power consumption thin-film lithium niobate electro-optical modulator with a driving voltage of 1.4V and an electro-optical bandwidth up to 45 GHz. After the year, the subject group proposed the first silicon-based hetero-integrated thin-film lithium niobate electro-optic modulator (L.Liu, X.Cai, et al, "High-performance hybrid silicon and lithium niobate Mach-Zehnder modulators for 100 Gbits-1 and beyond," Nature Photonics 13,359-364 (2019)) on Nature Photonics, and realized that the driving voltage was 5.1V and the electro-optic bandwidth was as High as 70GHz, which proved the feasibility of realizing hetero-integration of thin-film lithium niobate electro-optic modulators on silicon-based. However, in the field of high-speed optical communication at present, the modulation rate has been shifted from 100G to 400G in general, and it is likely to move directly to the modulation rate of 1.6T in the future, and for this situation, we need to implement a single-wave higher-rate electro-optical modulator, and at the same time, reduce the driving voltage and meet the requirement of lower power consumption.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides a novel thin-film lithium niobate electro-optical modulator based on a differential drive capacitive load type periodic structure electrode and a preparation method thereof.
The invention combines the differential drive and the push-pull structure on the thin-film lithium niobate modulator for the first time, and meanwhile, the structure of the invention can be applied to the current silicon-based heterogeneous integration platform, thereby also improving the feasibility of the novel electro-optical modulator applied to other fields such as optical communication and the like in the future.
The technical scheme adopted by the invention is as follows:
1. a thin-film lithium niobate electro-optical modulator based on differential driving and push-pull comprises:
the device comprises a substrate, an oxygen burying layer, a lithium niobate layer and a cladding which are sequentially arranged from bottom to top, wherein a thin-film lithium niobate optical waveguide is arranged below the cladding, a differential traveling wave electrode arranged along the waveguide direction is arranged on the cladding, and the differential traveling wave electrode comprises a periodic structure electrode, a positive signal electrode, a negative signal electrode and a grounding electrode; the positive signal electrode and the negative signal electrode are respectively arranged on two sides right above the thin-film lithium niobate optical waveguide, the two grounding electrodes are respectively arranged on the outer sides of the positive signal electrode and the negative signal electrode, and the periodic structure electrode is arranged on a cladding right above the thin-film lithium niobate optical waveguide.
The periodic structure electrode is formed by arranging metal electrodes with periodic structures.
The periodic structure electrode comprises a group of metal electrode groups connected with the positive signal electrode and another group of metal electrode groups connected with the negative signal electrode, each group of metal electrode groups consists of a plurality of metal electrodes which are uniformly distributed at intervals along the waveguide direction and connected with the positive signal electrode/the negative signal electrode, the metal electrodes are in a T shape or a soil shape, a longitudinal metal strip positioned in the middle of the T shape or the soil shape is connected to the positive signal electrode/the negative signal electrode, and transverse metal strips are arranged in parallel to the waveguide direction; the metal electrodes in the metal electrode group of the positive signal electrode and the metal electrodes in the metal electrode group of the negative signal electrode are sequentially and alternately arranged along the waveguide direction, and the transverse branch parts of the metal electrodes in the metal electrode group of the positive signal electrode and the transverse branch parts of the metal electrodes in the metal electrode group of the negative signal electrode are mutually embedded and arranged.
The differential traveling wave electrode is formed by plating on the cladding. And applying voltage to the differential traveling wave electrode for modulating the optical wave signal.
The thin-film lithium niobate optical waveguide is formed by etching on the lithium niobate layer and is coated by a cladding.
The thin-film lithium niobate optical waveguide comprises a 1X 2 beam splitter, a Mach-Zehnder structure and a 2X 1 beam combiner, wherein the 1X 2 beam splitter and the 2X 1 beam combiner are respectively positioned at two sides of the Mach-Zehnder structure, the input end of the 1X 2 beam splitter is used for inputting optical signals, two output ends of the 1X 2 beam splitter are connected with two input ends of the 2X 1 beam combiner through the Mach-Zehnder structure, and the output end of the 2X 1 beam combiner is used for outputting optical signals; the positive signal electrode and the negative signal electrode are respectively arranged on two sides right above the Mach-Zehnder structure, and the periodic structure electrode is arranged right above the Mach-Zehnder structure.
The Mach-Zehnder structure comprises two branch arms, and two output ends of the 1 × 2 beam splitter are respectively connected with two input ends of the 2 × 1 beam combiner through one branch arm. The light is divided into two beams by the 1X 2 beam splitter, passes through the upper branch supporting arm and the lower branch supporting arm of the Mach-Zehnder structure respectively, and is finally synthesized into one beam by the 2X 1 beam combiner.
The two branch arms of the Mach-Zehnder structure are positioned below the metal signal electrode and the middle of the metal signal electrode, and are positioned below the middle of the periodic structure electrode.
The differential driving structure is formed by the differential traveling wave electrode, and the push-pull structure is formed by the differential traveling wave electrode and the Mach-Zehnder structure.
The invention is provided with periodic structure electrodes, and the metal electrodes in the periodic structure electrodes are arranged alternately in pairs and are positioned in the middle of the metal positive signal electrode and the metal negative signal electrode. Thus, the periodic structure electrode is introduced, the differential driving structure and the push-pull structure can be combined to form a differential modulator, the modulation length is halved, and the bandwidth performance is improved.
The substrate is made of silicon, lithium niobate, quartz or air, the oxygen-buried layer is made of silicon dioxide, and the thickness of the oxygen-buried layer is 1-6um.
The waveguide tilt angle of the waveguide modulation area of the thin-film lithium niobate optical waveguide is 60-70 degrees, the total thickness is 200-600nm, and the etching thickness is 100-300nm.
The cladding is silicon dioxide and has a thickness of 0.1-3um.
2. The preparation method of the thin-film lithium niobate electro-optical modulator comprises the following steps:
and simultaneously preparing a 1X 2 beam splitter, a Mach-Zehnder structure and a 2X 1 beam combiner in the process of preparing the thin film lithium niobate optical waveguide.
Step 4, depositing a silicon dioxide cladding on the lithium niobate layer;
and 6, plating a second layer of thick metal in a sputtering or evaporation mode to be used as the residual positive signal electrode, negative signal electrode and grounding electrode to finish the preparation of the thin-film lithium niobate electro-optical modulator.
The photoetching method comprises a stepping photoetching machine, a contact photoetching machine, electron beam direct writing, laser direct writing and the like.
The etching method comprises dry etching and wet etching.
The dry etching comprises focused ion beam etching and reactive ion etching.
The sputtering method comprises magnetron sputtering, electron beam evaporation and electroplating.
The invention innovatively introduces a specific periodic structure electrode. By adopting the electrode with a specific periodic structure, the combination of differential signal driving and a push-pull structure is realized, so that the modulation voltage is doubled, the double-voltage modulation is realized, and the size of the modulator is effectively shortened.
The invention has the following technical effects:
(1) According to the invention, by introducing the electrode with a specific periodic structure, differential signal driving is combined with a push-pull structure, so that double voltage modulation is realized.
(2) By introducing the electrode with the specific periodic structure, the invention can obtain the product of the extremely small half-wave voltage and the length when the electrode distance on the two sides of the waveguide is ensured to be sufficiently small, and simultaneously, the extremely small electrode distance also ensures that the microwave field is limited in a small range, thereby ensuring that the radiation loss caused by the substrate under the high-frequency condition can be greatly weakened.
(3) The invention adopts a mode of modulating the waveguide bending of the area to slow down the slow wave effect caused by the periodic structure electrode, thereby realizing the high-efficiency speed matching of the microwave and the optical wave.
Drawings
The following is a brief description of what is presented in the drawings of the specification:
FIG. 1 is a flow chart of the preparation of the novel thin-film lithium niobate electro-optical modulator in the invention.
Fig. 2 is a top view of the whole device of the novel thin-film lithium niobate electro-optical modulator in the invention.
Fig. 3 is a schematic diagram of a method of bending a waveguide in a modulation region according to the present invention.
FIG. 4 is a cross-sectional view of the structure obtained in step 1 of the manufacturing method of the present invention, shown in FIG. 2 by a black dotted line.
FIG. 5 is a cross-sectional view of the structure obtained in step 2 of the manufacturing method of the present invention, shown in FIG. 2 with black dashed lines.
FIG. 6 is a cross-sectional view of the structure of FIG. 2, taken along the black dashed line, at step 3 of the method of the present invention.
FIG. 7 is a cross-sectional view of the structure of FIG. 2 taken along the black dashed line at step 4 of the method of the present invention.
FIG. 8 is a cross-sectional view of the structure of FIG. 2 taken along the dashed black line at step 5 of the method of the present invention.
FIG. 9 is a cross-sectional view of the structure of step 6 of the method of the present invention, shown in FIG. 2 as a black dashed line.
FIG. 10 is a diagram of another representation of a periodic structure electrode and its relative position to a waveguide.
FIG. 11 is a diagram of another representation of a periodic structure electrode and its position relative to a waveguide.
Fig. 12 is a schematic diagram of a periodic structure electrode enlarged by a black dashed frame in fig. 2.
In the figure, 1-substrate, 2-buried oxide layer, 3-lithium niobate layer, 4-thin film lithium niobate optical waveguide, 5-cladding, 6-periodic structure electrode, 7-positive signal electrode, 8-negative signal electrode, 9-grounding electrode, 10-1 x 2 beam splitter, 11-Mach Zehnder structure, 12-2 x 1 beam combiner.
Detailed Description
The following will explain in detail specific embodiments of the present invention, such as shapes and structures of respective members, interconnection relationships between respective portions, functions and operating principles of the respective portions, manufacturing processes, and methods of operation and use. So as to provide a more complete, accurate and thorough understanding of the conception and technical solution of the present invention.
The invention realizes the combination of a push-pull structure and differential drive on the thin-film lithium niobate modulator for the first time, and the invention is particularly represented by structural innovation.
As shown in fig. 9, which shows a schematic transverse cross-sectional view at a black dashed line in fig. 2, this embodiment includes, sequentially arranged from bottom to top, a substrate 1, a buried oxide layer 2, a lithium niobate layer 3, a thin-film lithium niobate optical waveguide 4, a cladding layer 5, a periodic structure electrode 6, a positive signal electrode 7, a negative signal electrode 8, and a ground electrode 9.
And performing an etching process on the lithium niobate layer 3 to form a thin film lithium niobate optical waveguide 4, wherein the thin film lithium niobate optical waveguide 4 is arranged to form a 1 × 2 beam splitter 10, a Mach-Zehnder structure 11 and a 2 × 1 beam combiner 12.
Two layers of metal electrodes are plated on the cladding 5, the first layer comprises the periodic structure electrode 6 and part of the positive signal electrode 7, the negative signal electrode 8 and the grounding electrode 9, and the second layer comprises the rest of the positive signal electrode 7, the negative signal electrode 8 and the grounding electrode 9. The periodic structure electrodes 6 are respectively arranged in pairs between the positive signal electrode 7 and the negative signal electrode 8, and the positive signal electrode 7 and the negative signal electrode 8 are positioned between the two grounding electrodes 9.
In specific implementation, the substrate 1 is silicon, the buried oxide layer 2 is silicon dioxide and has a thickness of 3um, the total thickness of the lithium niobate layer 3 is 400nm, the thickness of the waveguide 4 is 200nm, and the inclination angle of the waveguide 4 is 60 degrees.
In specific implementation, the periodic structure electrode 6 may be the structure shown in fig. 2, or may be the structure shown in fig. 10, fig. 11, or other similar structures, and the relative positions of the waveguide and the periodic structure electrode are shown in fig. 2, fig. 10, and fig. 11.
The periodic structure electrode 6 comprises a group of metal electrode groups connected with the positive signal electrode 7 and another group of metal electrode groups connected with the negative signal electrode 8, each group of metal electrode groups consists of a plurality of metal electrodes which are uniformly distributed at intervals along the waveguide direction and connected with the positive signal electrode 7/the negative signal electrode 8, the metal electrodes are in a T shape or a soil shape, a longitudinal metal strip positioned in the middle of the T shape or the soil shape is connected to the positive signal electrode 7/the negative signal electrode 8, and transverse metal strips extending between two sides are arranged in parallel to the waveguide direction; the metal electrodes in the same metal electrode group are the same in shape, the metal electrodes in the two metal electrode groups may be different in shape, the metal electrodes in the metal electrode group of the positive signal electrode 7 and the metal electrodes in the metal electrode group of the negative signal electrode 8 are sequentially and alternately arranged along the waveguide direction, the transverse branch portion of the metal electrode in the metal electrode group of the positive signal electrode 7 and the transverse branch portion of the metal electrode in the metal electrode group of the negative signal electrode 8 are mutually inserted, that is, at least one transverse metal strip of the metal electrode in the metal electrode group of the positive signal electrode 7 is inserted between the transverse metal strip of the metal electrode in the metal electrode group of the negative signal electrode 8 adjacent thereto and the negative signal electrode 8, and at least one transverse metal strip of the metal electrode in the metal electrode group of the negative signal electrode 8 is inserted between the transverse metal strip of the metal electrode in the metal electrode group of the positive signal electrode 7 adjacent thereto and the positive signal electrode 7.
As shown in fig. 12, the following dimensioning was carried out for the periodic-structure electrode 6:
in the partial structure electrode connected with the positive signal electrode 7, v is the width of a longitudinal metal strip, t and h are the widths of upper and lower lateral metal strips, a is the distance between the upper lateral metal strip and the partial structure electrode, and l is the distance between the lower lateral metal strip and the partial structure electrode; in the partial structure electrode connected with the negative signal electrode 8, m is the width of a longitudinal metal strip, b and c are the widths of upper and lower lateral metal strips, and w is the length of the lateral metal strip; p is the period of the structural electrode, f is the distance between the lower lateral metal strip connected with the partial structural electrode of the negative signal electrode 8 and the lower lateral metal strip connected with the partial structural electrode of the positive signal electrode 7, g is the distance between the upper lateral metal strip connected with the partial structural electrode of the negative signal electrode 8 and the upper lateral metal strip connected with the partial structural electrode of the positive signal electrode 7, y is the distance between the longitudinal metal strip connected with the partial structural electrode of the negative signal electrode 8 and the lower lateral metal strip connected with the partial structural electrode of the positive signal electrode 7, and u is the distance between the two upper lateral metal strips connected with the partial structural electrode of the positive signal electrode 7.
In the specific implementation, v, t, h, b, c and m are 1-5um, l is 15-150um, a is 1-120um, p is 30-200um, u is 1-24um, w is 25-180um, g, f is 1.5-5um, and y is 0.5-5um.
As shown in fig. 1, the preparation process comprises the following steps:
Step 4, as shown in FIG. 7, a silicon dioxide cladding 5 is deposited on the lithium niobate layer 3 by plasma CVD
And 6, as shown in fig. 9, preparing a micro-nano pattern of the second layer of metal by using a photoetching and electron beam exposure mode, plating a second layer of metal electrode by using an evaporation and electroplating mode, wherein the second layer of metal electrode comprises the residual positive signal electrode 7, the residual negative signal electrode 8 and the residual grounding electrode 9, and finishing the preparation of the device.
In the above steps, the lithography can be performed by a stepper, a contact lithography machine, direct electron beam writing, direct laser writing, etc., the etching can be performed by dry etching (such as ICP, RIE, etc.), wet etching, etc., and the electrode can be performed by magnetron sputtering, electron beam evaporation, electroplating, etc.
As shown in fig. 2, from left to right, there are a 1 × 2 beam splitter 10, a mach-zehnder structure 11, a periodic structure electrode 6, a positive signal electrode 7, a negative signal electrode 8, a ground electrode 9, and a 2 × 1 beam combiner 12.
The light wave is split into two beams by a 1 x 2 beam splitter 10, one beam passing through the upper arm of the mach-zehnder structure 11 and the other beam passing through the lower arm of the mach-zehnder structure 11. The two arms of the mach-zehnder structure are located between the traveling wave positive and negative signal electrodes 7, 8 and between a set of periodic structure electrodes 6. Because the signal loading mode of the traveling wave electrode is a push-pull mode, the refractive indexes of the lithium niobate optical waveguides of the upper arm and the lower arm of the Mach-Zehnder structure are changed to be opposite phases, a certain phase difference is generated between the upper arm and the lower arm after a certain distance, and the lithium niobate optical waveguides are combined into one waveguide to be output through the 2-by-1 beam combiner 12, so that electro-optical modulation is realized.
The invention introduces the capacitance load type periodic structure electrode to cause the introduction of extra capacitance, aggravates the slow wave effect, and realizes the high-efficiency speed matching of the microwave field and the light wave field by adopting a mode of modulating region waveguide bending. Within one bending period, the waveguide in the modulation region satisfies n O *L o ＝n m *L m In the formula n o Denotes the refractive index, L, of the light wave o Representing the optical path of the light wave in one bending period, n m Denotes the refractive index, L, of the microwave m Representing the length of the period, fig. 3 is one manifestation of waveguide bending.
The structure is an innovative structure, differential drive is introduced into the electrode part, and meanwhile, the push-pull structure of the modulator is ensured by the specific periodic structure electrode.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other structures, which are consistent with the changes in materials, thicknesses, etc. of the structures and any other changes, modifications, substitutions, combinations, simplifications which do not depart from the spirit and principle of the present invention, should be regarded as equivalents of the above embodiments, which are included in the protection scope of the present invention.
Claims (10)
1. The utility model provides a film lithium niobate electro-optical modulator based on difference drive and push-pull, includes substrate (1), buried oxide layer (2), lithium niobate layer (3), covering (5) that from the bottom up arranged gradually, covering (5) under be equipped with film lithium niobate optical waveguide (4), its characterized in that: the cladding (5) is provided with differential traveling wave electrodes arranged along the waveguide direction, and the differential traveling wave electrodes comprise periodic structure electrodes (6), positive signal electrodes (7), negative signal electrodes (8) and grounding electrodes (9); the positive signal electrode (7) and the negative signal electrode (8) are respectively arranged on two sides right above the thin-film lithium niobate optical waveguide (4), the two grounding electrodes (9) are respectively arranged on the outer sides of the positive signal electrode (7) and the negative signal electrode (8), and the periodic structure electrode (6) is arranged right above the thin-film lithium niobate optical waveguide (4).
2. The thin-film lithium niobate electro-optic modulator based on differential driving and push-pull of claim 1, wherein: the periodic structure electrode (6) is formed by a metal electrode arrangement with a periodic structure.
3. The differential drive and push-pull based thin film lithium niobate electro-optical modulator according to claim 2, wherein: the periodic structure electrode (6) comprises a group of metal electrode groups connected with the positive signal electrode (7) and another group of metal electrode groups connected with the negative signal electrode (8), each group of metal electrode groups consists of a plurality of metal electrodes which are uniformly distributed at intervals along the waveguide direction and connected with the positive signal electrode (7)/the negative signal electrode (8), the metal electrodes are T-shaped or soil-shaped, a longitudinal metal strip positioned in the middle of the T-shaped or soil-shaped metal electrodes is connected with the positive signal electrode (7)/the negative signal electrode (8), and transverse metal strips are arranged in parallel to the waveguide direction; the metal electrodes in the metal electrode group of the positive signal electrode (7) and the metal electrodes in the metal electrode group of the negative signal electrode (8) are sequentially and alternately arranged along the waveguide direction, and the transverse branch parts of the metal electrodes in the metal electrode group of the positive signal electrode (7) and the transverse branch parts of the metal electrodes in the metal electrode group of the negative signal electrode (8) are mutually embedded and arranged.
4. The differential drive and push-pull based thin film lithium niobate electro-optical modulator according to claim 1, wherein: the differential traveling wave electrode is formed by plating on the cladding (5).
5. The thin-film lithium niobate electro-optic modulator based on differential driving and push-pull of claim 1, wherein: the thin-film lithium niobate optical waveguide (4) is formed by etching on the lithium niobate layer (3) and is coated by the cladding (5).
6. The thin-film lithium niobate electro-optic modulator based on differential driving and push-pull of claim 1, wherein: the thin-film lithium niobate optical waveguide (4) comprises a 1-x 2 beam splitter (10), a Mach-Zehnder structure (11) and a 2-x 1 beam combiner (12), wherein the 1-x 2 beam splitter (10) and the 2-x 1 beam combiner (12) are respectively positioned on two sides of the Mach-Zehnder structure (10), and two output ends of the 1-x 2 beam splitter (10) are connected through two input ends of the Mach-Zehnder structure (10) and the 2-x 1 beam combiner (12); the positive signal electrode (7) and the negative signal electrode (8) are respectively arranged on two sides right above the Mach-Zehnder structure (11), and the periodic structure electrode (6) is arranged right above the Mach-Zehnder structure (11).
7. The thin-film lithium niobate electro-optic modulator based on differential driving and push-pull of claim 1, wherein: the substrate (1) is made of silicon, lithium niobate, quartz or air, the oxygen burying layer (2) is made of silicon dioxide, and the thickness of the oxygen burying layer is 1-6um.
8. The thin-film lithium niobate electro-optic modulator based on differential driving and push-pull of claim 1, wherein: the waveguide inclination angle of the waveguide modulation region of the thin-film lithium niobate optical waveguide (4) is 60-70 degrees, the total thickness is 200-600nm, and the etching thickness is 100-300nm.
9. The thin-film lithium niobate electro-optic modulator based on differential driving and push-pull of claim 1, wherein: the cladding (5) is silicon dioxide and has the thickness of 0.1-3um.
10. The method for preparing the thin-film lithium niobate electro-optical modulator applied to any one of claims 1 to 9, comprising the steps of:
step 1, depositing a buried oxide layer (2) on a substrate (1);
step 2, preparing a lithium niobate layer (3) on the oxygen burying layer (2);
step 3, preparing a micro-nano pattern on the lithium niobate layer (3) by using an electron beam exposure or photoetching method, and preparing and forming a thin film lithium niobate optical waveguide (4) by using an etching method;
step 4, depositing a silicon dioxide cladding (5) on the lithium niobate layer (3);
step 5, plating a first layer of thin metal on the cladding (5) of the silicon dioxide by a sputtering or evaporation mode to be used as a periodic structure electrode (6), a part of positive signal electrode (7), a part of negative signal electrode (8) and a part of grounding electrode (9);
and 6, plating a second layer of thick metal in a sputtering or evaporation mode to serve as the residual positive signal electrode (7), the negative signal electrode (8) and the grounding electrode (9), and finishing the preparation of the thin-film lithium niobate electro-optical modulator.
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|---|---|---|---|
| CN202211280207.XA CN115586663A (en) | 2022-10-19 | 2022-10-19 | Thin-film lithium niobate electro-optical modulator based on differential drive and push-pull |
| PCT/CN2023/123393 WO2024082974A1 (en) | 2022-10-19 | 2023-10-08 | Thin-film lithium niobate electro-optical modulator based on differential drive and push-pull |
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| CN202211280207.XA CN115586663A (en) | 2022-10-19 | 2022-10-19 | Thin-film lithium niobate electro-optical modulator based on differential drive and push-pull |
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|---|---|---|---|---|
| CN116560119A (en) * | 2023-06-25 | 2023-08-08 | 华中科技大学 | Silicon-based thin film lithium niobate broadband electro-optic modulator chip based on traveling wave electrode structure |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116560119A (en) * | 2023-06-25 | 2023-08-08 | 华中科技大学 | Silicon-based thin film lithium niobate broadband electro-optic modulator chip based on traveling wave electrode structure |
| CN116560119B (en) * | 2023-06-25 | 2023-09-19 | 华中科技大学 | Silicon-based thin film lithium niobate broadband electro-optic modulator chip based on traveling wave electrode structure |
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