CN117991526A - Dual-drive differential film lithium niobate electro-optical modulator chip - Google Patents
Dual-drive differential film lithium niobate electro-optical modulator chip Download PDFInfo
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 230000005684 electric field Effects 0.000 claims abstract description 85
- 239000010409 thin film Substances 0.000 claims abstract description 85
- 230000003287 optical effect Effects 0.000 claims abstract description 38
- 238000004891 communication Methods 0.000 claims abstract description 22
- 238000005253 cladding Methods 0.000 claims description 15
- 239000000758 substrate Substances 0.000 claims description 8
- 230000009977 dual effect Effects 0.000 claims 4
- 230000005540 biological transmission Effects 0.000 abstract description 22
- 238000000034 method Methods 0.000 abstract description 10
- 238000010586 diagram Methods 0.000 description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 239000013307 optical fiber Substances 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 3
- 238000004880 explosion Methods 0.000 description 3
- 230000005693 optoelectronics Effects 0.000 description 3
- 235000012239 silicon dioxide Nutrition 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 235000012431 wafers Nutrition 0.000 description 3
- 230000000295 complement effect Effects 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 239000010421 standard material Substances 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- 230000005670 electromagnetic radiation Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention relates to the technical field of optical communication, in particular to a double-drive differential thin film lithium niobate electro-optical modulator chip, which comprises: the first waveguide arm, the first traveling wave electrode pair arranged at two sides of the first waveguide arm, the second waveguide arm and the second traveling wave electrode pair arranged at two sides of the second waveguide arm; the first row wave electrode pair is used for receiving the positive polarity differential signal generated by the signal generator and generating a first electric field so that the first waveguide arm modulates according to the first electric field; the second traveling wave electrode pair is used for receiving the negative polarity differential signal generated by the signal generator and generating a second electric field so that the second waveguide arm modulates according to the second electric field; the direction of the first electric field is opposite to the direction of the second electric field. Compared with the existing method for modulating by only one path of electric signal, the method adopts the positive polarity differential signal and the negative polarity differential signal to modulate respectively, thereby improving the transmission performance.
Description
Technical Field
The invention relates to the technical field of optical communication, in particular to a double-drive differential thin film lithium niobate electro-optical modulator chip.
Background
With the current explosive development of information society, the information data volume shows an exponential explosion growth, and the exchange and transmission of data are not separated from the basic communication network, and in various communication networks, the optical communication network carries more than 90% of high-speed data interaction and transmission services. The rapid development and commercial large-scale application of optical communication networks are not separated from various optical communication devices with excellent performance. Large bandwidth, low power consumption, ultra-high speed electro-optic modulators are an important engine for optical communication networks. The lithium niobate material is a standard material of an electro-optical modulator in the current optical fiber communication system because of the excellent linear electro-optical effect and very high intrinsic bandwidth. With the large-scale commercial use of thin film lithium niobate (thin-film lithium niobate, TFLN) wafers, a Mach-Zehnder interferometer (MZI) electro-optical modulator (electro-optical modulator, EOM) based on TFLN has the advantages of high modulation bandwidth, small structural size, high modulation efficiency and the like compared with a traditional bulk lithium niobate modulator, and becomes one of common research hotspots in academia and industry.
The thin film lithium niobate electro-optic modulator is a device for modulating electric signals to optical signals by utilizing the first-order electro-optic effect of lithium niobate crystals, and the current thin film lithium niobate MZI electro-optic modulator mostly adopts a GSG electrode structure to realize single-ended push-pull, so that the driving voltage can be effectively reduced, the compatibility of CMOS (Complementary metal-oxide semiconductor) is realized, and the performance and the integrality of the modulator are improved.
However, the existing thin film lithium niobate electro-optical modulator is easy to be influenced by an external electric field because only one electric signal is adopted for modulation, and therefore the performance of the device is unstable and the transmission performance is poor.
The foregoing is provided merely for the purpose of facilitating understanding of the technical solutions of the present invention and is not intended to represent an admission that the foregoing is prior art.
Disclosure of Invention
The invention mainly aims to provide a double-drive differential film lithium niobate electro-optical modulator chip, and aims to solve the technical problems that in the prior art, the electro-optical modulator is unstable in performance and poor in transmission performance due to modulation by adopting one electric signal.
In order to achieve the above object, the present invention provides a dual-drive differential thin film lithium niobate electro-optical modulator chip, which includes: the device comprises a first waveguide arm, a first traveling wave electrode pair arranged on two sides of the first waveguide arm, a second waveguide arm and a second traveling wave electrode pair arranged on two sides of the second waveguide arm;
wherein the first traveling wave electrode pair and the second traveling wave electrode pair are both connected with a signal generator;
The first row wave electrode pair is used for receiving the positive differential signal generated by the signal generator and generating a first electric field so that the first waveguide arm modulates according to the first electric field;
the second traveling wave electrode pair is used for receiving the negative differential signal generated by the signal generator and generating a second electric field so that the second waveguide arm modulates according to the second electric field;
the direction of the first electric field is opposite to the direction of the second electric field.
Optionally, the first row wave electrode pair includes: a positive electrode and a first ground electrode;
The second traveling wave electrode pair includes: a negative polarity electrode and a second ground electrode;
Wherein the positive electrode, the first ground electrode, the negative electrode and the second ground electrode are all connected with the signal generator;
The positive electrode is used for receiving the positive differential signal generated by the signal generator and generating a first electric field based on the positive differential signal, and the direction of the first electric field is directed to the first ground electrode by the positive electrode;
The negative electrode is used for receiving the negative differential signal generated by the signal generator and generating a second electric field based on the negative differential signal, and the direction of the second electric field is directed to the negative electrode by the second ground electrode.
Optionally, the positive electrode is disposed between the first waveguide arm and the second waveguide arm, the first ground electrode is disposed on a side, away from the positive electrode, of the first waveguide arm, the second ground electrode is disposed between the positive electrode and the second waveguide arm, and the negative electrode is disposed on a side, away from the second ground electrode, of the second waveguide arm.
Optionally, the dual-drive differential thin film lithium niobate electro-optic modulator chip further includes: the substrate layer, the buried layer, the thin film lithium niobate and the upper cladding layer;
The buried layer is arranged between the substrate layer and the thin-film lithium niobate, the first waveguide arm, the second waveguide arm, the first traveling wave electrode pair and the second traveling wave electrode pair are all arranged in the upper cladding layer, and the upper cladding layer covers the top of the thin-film lithium niobate.
Optionally, the first waveguide arm and the second waveguide arm are both arranged in contact with the thin film lithium niobate, and the first traveling wave electrode pair and the second traveling wave electrode pair are both arranged in non-contact with the thin film lithium niobate.
Optionally, the first waveguide arm, the second waveguide arm, the first traveling wave electrode pair and the second traveling wave electrode pair are all arranged in contact with the thin film lithium niobate.
Optionally, the dual-drive differential thin film lithium niobate electro-optic modulator chip further includes: a plurality of microelectrode pairs;
the microelectrode pairs are arranged between the first traveling wave electrode pairs and between the second traveling wave electrode pairs.
Optionally, the microelectrodes in the microelectrode pair are at least one of T-shaped, L-shaped or slot-shaped structures.
Optionally, the dual-drive differential thin film lithium niobate electro-optic modulator chip further includes: a third ground electrode;
the third ground electrode is arranged on one side of the first traveling wave electrode pair far away from the second traveling wave electrode pair;
or, the third ground electrode is disposed at a side of the second traveling wave electrode pair away from the first traveling wave electrode pair.
In addition, in order to achieve the above object, the present invention also provides an optical communication system, which includes the dual-drive differential thin film lithium niobate electro-optical modulator chip as described above.
The invention provides a double-drive differential thin film lithium niobate electro-optic modulator chip, which comprises: the device comprises a first waveguide arm, a first traveling wave electrode pair arranged on two sides of the first waveguide arm, a second waveguide arm and a second traveling wave electrode pair arranged on two sides of the second waveguide arm; wherein the first traveling wave electrode pair and the second traveling wave electrode pair are both connected with a signal generator; the first row wave electrode pair is used for receiving the positive differential signal generated by the signal generator and generating a first electric field so that the first waveguide arm modulates according to the first electric field; the second traveling wave electrode pair is used for receiving the negative differential signal generated by the signal generator and generating a second electric field so that the second waveguide arm modulates according to the second electric field; the direction of the first electric field is opposite to the direction of the second electric field. The invention receives the positive differential signal through the first traveling wave electrode pair to generate a first electric field, receives the negative differential signal through the second traveling wave electrode pair to generate a second electric field, and modulates the first electric field and the second electric field. Compared with the existing method for modulating by only one path of electric signal, the method adopts the positive polarity differential signal and the negative polarity differential signal to modulate respectively, thereby improving the transmission performance.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a conventional thin film lithium niobate electro-optic modulator;
FIG. 2 is a schematic diagram of a first embodiment of a dual-drive differential thin-film lithium niobate electro-optic modulator chip according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another embodiment of a dual-drive differential thin-film lithium niobate electro-optic modulator chip according to an embodiment of the present invention;
FIG. 4 is a schematic cross-sectional view of a second embodiment of a dual-drive differential thin-film lithium niobate electro-optic modulator chip according to an embodiment of the present invention;
FIG. 5 is another schematic cross-sectional view of a second embodiment of a dual-drive differential thin-film lithium niobate electro-optic modulator chip according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a third embodiment of a dual-drive differential thin-film lithium niobate electro-optic modulator chip according to an embodiment of the present invention;
FIG. 7 is a schematic diagram showing another configuration of a microelectrode in a third embodiment of a dual-drive differential thin-film lithium niobate electro-optical modulator chip according to an embodiment of the present invention;
fig. 8 is a schematic diagram of another structure of a microelectrode in a third embodiment of the dual-drive differential thin-film lithium niobate electro-optical modulator chip according to the present invention.
Reference numerals illustrate:
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
It should be noted that, with the explosion of information society, the amount of information data has shown an exponential explosion growth, and the exchange and transmission of data are not separated from the underlying communication network, and among various communication networks, the optical communication network carries high-speed data interaction and transmission services of more than 90%. The rapid development and commercial large-scale application of optical communication networks are not separated from various optical communication devices with excellent performance. Large bandwidth, low power consumption, ultra-high speed electro-optic modulators are an important engine for optical communication networks. The lithium niobate material is a standard material of an electro-optical modulator in the current optical fiber communication system because of the excellent linear electro-optical effect and very high intrinsic bandwidth. With the large-scale commercial use of thin film lithium niobate (thin-film lithium niobate, TFLN) wafers, a Mach-Zehnder interferometer (MZI) electro-optical modulator (electro-optical modulator, EOM) based on TFLN has the advantages of high modulation bandwidth, small structural size, high modulation efficiency and the like compared with a traditional bulk lithium niobate modulator, and becomes one of common research hotspots in academia and industry.
The thin film lithium niobate electro-optic modulator is a device for modulating electric signals to optical signals by utilizing the first-order electro-optic effect of lithium niobate crystals, and the current thin film lithium niobate MZI electro-optic modulator mostly adopts a GSG electrode structure to realize single-ended push-pull, so that the driving voltage can be effectively reduced, the compatibility of CMOS (Complementary metal-oxide semiconductor) is realized, and the performance and the integrality of the modulator are improved.
However, in the conventional thin film lithium niobate electro-optical modulator, referring to fig. 1, fig. 1 is a schematic structural diagram of a conventional thin film lithium niobate electro-optical modulator, as shown in fig. 1, a GSG structure is generally adopted in the conventional thin film lithium niobate electro-optical modulator, that is, a G electrode (i.e., G in fig. 1) is disposed at the upper and lower sides of the conventional thin film lithium niobate electro-optical modulator, an S electrode (i.e., S in fig. 1) is disposed between the two G electrodes, and a straight optical waveguide (i.e., a first waveguide arm 1 and a second waveguide arm 2 in fig. 1) is disposed between the S electrode and the two G electrodes, so that one electric signal generated by the signal generator is transmitted to the S electrode, and the directions of electric fields where the upper and lower optical waveguides are located are opposite. Because the structure in fig. 1 only adopts one electric signal, the structure is easily influenced by an external electric field, and thus the device performance is unstable and the transmission performance is poor.
In order to solve the above-mentioned drawbacks, the present embodiment proposes a dual-drive differential thin-film lithium niobate electro-optical modulator chip, which includes: a first waveguide arm 1, a first traveling wave electrode pair arranged at two sides of the first waveguide arm 1, a second waveguide arm 2, and a second traveling wave electrode pair arranged at two sides of the second waveguide arm 2; wherein the first traveling wave electrode pair and the second traveling wave electrode pair are both connected with a signal generator; the first row wave electrode pair is used for receiving the positive polarity differential signal generated by the signal generator and generating a first electric field so that the first waveguide arm 1 modulates according to the first electric field; the second traveling wave electrode pair is configured to receive the negative differential signal generated by the signal generator and generate a second electric field, so that the second waveguide arm 2 modulates according to the second electric field; the direction of the first electric field is opposite to the direction of the second electric field. Since the embodiment receives the positive differential signal through the first traveling wave electrode pair to generate the first electric field, receives the negative differential signal through the second traveling wave electrode pair to generate the second electric field, and modulates the first electric field and the second electric field. Compared with the existing method that only one path of electric signal is used for modulation, the method and the device have the advantages that positive polarity differential signals and negative polarity differential signals are used for modulation respectively, and transmission performance is improved.
For ease of understanding, this embodiment and the embodiments described below are specifically described below with reference to fig. 2 to 8.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a first embodiment of a dual-drive differential thin-film lithium niobate electro-optical modulator chip according to an embodiment of the present invention, as shown in fig. 2, in this embodiment, the dual-drive differential thin-film lithium niobate electro-optical modulator chip includes: a first waveguide arm 1, a first traveling wave electrode pair arranged at two sides of the first waveguide arm 1, a second waveguide arm 2, and a second traveling wave electrode pair arranged at two sides of the second waveguide arm 2; wherein the first traveling wave electrode pair and the second traveling wave electrode pair are connected to a signal generator (not shown).
It should be noted that, the dual-driving differential thin film lithium niobate electro-optical modulator chip in this embodiment may further include: an input waveguide 3, a beam splitter 4, a beam combiner 5, and an output waveguide 6; wherein the input waveguide 3 is connected with the first waveguide arm 1 and the second waveguide arm 2 respectively through the beam splitter 4, and the output waveguide 6 is connected with the first waveguide arm 1 and the second waveguide arm 2 respectively through the beam combiner 5; the end of the input waveguide 3 far away from the beam splitter 4 is also connected with a light source;
It is to be understood that the beam splitter 4 may be a 1*2 multimode interference structure (Multimode Interference, MMI), a2 x 2MMI or a Y-branch optical splitter, etc., and the first waveguide arm 1 and the second waveguide arm 2 are symmetrically disposed.
In practical use, the optical signals emitted by the light source can be coupled into the input waveguide 3 through optical couplers such as a grating coupler and an edge coupler, on-chip optical path transmission is performed, the optical signals are divided into equal first optical signals and second optical signals through the beam splitter 4, the first optical signals enter the upper arm modulation area through the first waveguide arm 1 to be modulated, the second optical signals enter the lower arm modulation area through the second waveguide arm 2 to be modulated, and the modulated first optical signals and the modulated second optical signals are combined through the beam combiner 5 and then output through the output waveguide 6, so that electro-optic modulation is completed.
Further, in order to achieve modulation, as shown in fig. 2, the first row-wave electrode pair is configured to receive the positive differential signal generated by the signal generator and generate a first electric field, so that the first waveguide arm 1 modulates according to the first electric field;
the second traveling wave electrode pair is configured to receive the negative differential signal generated by the signal generator and generate a second electric field, so that the second waveguide arm 2 modulates according to the second electric field;
the direction of the first electric field is opposite to the direction of the second electric field.
In fig. 2, the electrodes on both sides of the first waveguide arm 1 may be referred to as a first traveling wave electrode pair, and the electrodes on both sides of the second waveguide arm 2 may be referred to as a second traveling wave electrode pair; the signal generator is connected with two identical drivers through two paths of strictly differential electric ports, then is connected with probes through two identical high-frequency transmission lines, differential signals are loaded to the first traveling wave electrode pair and the second traveling wave electrode pair through the probes, and before the differential signals are loaded to the first traveling wave electrode pair and the second traveling wave electrode pair, direct-current bias voltage can be loaded to the drivers, so that bias of a working state is realized.
In order to generate the electric field with opposite directions, the positive polarity differential signal in the differential signals generated by the signal generator may be transmitted to the first traveling wave electrode pair, and the negative polarity differential signal in the differential signals may be transmitted to the second traveling wave electrode pair, and the signal generator in this embodiment may be a device for generating the differential signals, which is not limited in this embodiment.
In one embodiment, the negative differential signal of the differential signals generated by the signal generator may be transmitted to the first traveling wave electrode pair, and the positive differential signal of the differential signals may be transmitted to the second traveling wave electrode pair.
The first optical signal in the first waveguide arm 1 is affected by the first electric field, the second optical signal in the second waveguide arm 2 is affected by the second electric field, the refractive indexes of the first waveguide arm 1 and the second waveguide arm 2 which are formed by lithium niobate crystals are changed, the phases of the first optical signal and the second optical signal are affected, modulation is achieved, then the beam combiner 5 is used for combining, destructive and constructive interference is achieved, then the output waveguide 6 is used for outputting, and the whole process is achieved, namely the electric signal is loaded into the optical signal.
Illustratively, based on fig. 2, the direction of the first electric field generated by the first traveling wave electrode pair may be from s+ to G, the direction of the second electric field generated by the second traveling wave electrode pair may be from S-to G, and thus the direction of the first electric field is opposite to the direction of the second electric field, and the first electric field and the second electric field are both from different electrode pairs. Compared with the structure in fig. 1, since only one path of electric signal is needed to be received in fig. 1, the stability is poor, the transmission performance is poor, the differential signal can be adopted to generate the first electric field and the second electric field, the differential signal has stronger anti-interference capability and electromagnetic radiation resistance, the signal distortion and crosstalk can be effectively reduced, the high-speed long-distance transmission is more suitable, and the high-speed long-distance transmission is more reliable and stable.
Meanwhile, the embodiment also realizes the same low driving voltage as that in fig. 1, and loads the differential signal onto the optical signal, so that the differential signal protects the signal in transmission, thereby improving the signal quality and further improving the signal-to-noise ratio.
Further, to generate the first electric field and the second electric field, with continued reference to fig. 2, the first row wave electrode pair includes: a positive electrode 7 (i.e., s+ in fig. 2) and a first ground electrode 8; the second traveling wave electrode pair includes: a negative electrode 9 (i.e., S-in FIG. 2) and a second ground electrode 10; wherein the positive electrode 7, the first ground electrode 8, the negative electrode 9 and the second ground electrode 10 are all connected with the signal generator;
The positive electrode 7 is configured to receive the positive differential signal generated by the signal generator, and generate a first electric field based on the positive differential signal, where a direction of the first electric field is directed by the positive electrode 7 to the first ground electrode 8;
the negative electrode 9 is configured to receive a negative differential signal generated by the signal generator, and generate a second electric field based on the negative differential signal, where a direction of the second electric field is directed by the second ground electrode 10 to the negative electrode 9.
It will be appreciated that the signal generator may transmit a positive polarity differential signal to the positive polarity electrode 7 and a ground signal to the first ground electrode 8, thereby generating a first electric field extending from s+ to G, while the signal generator may transmit a negative polarity differential signal to the negative polarity electrode 9 and a ground signal to the second ground electrode 10, thereby generating a second electric field extending from S-to G.
As an embodiment, the positive electrode 7 is disposed between the first waveguide arm 1 and the second waveguide arm 2, the first ground electrode 8 is disposed on a side of the first waveguide arm 1 away from the positive electrode 7, the second ground electrode 10 is disposed between the positive electrode 7 and the second waveguide arm 2, and the negative electrode 9 is disposed on a side of the second waveguide arm 2 away from the second ground electrode 10, that is, gs+gs-is sequentially disposed from top to bottom in fig. 2.
As another implementation manner, referring to fig. 3, fig. 3 is a schematic diagram of another structure of a first embodiment of a dual-drive differential thin film lithium niobate electro-optical modulator chip according to an embodiment of the present invention, as shown in fig. 3, a first ground electrode 8 may be disposed between a first waveguide arm 1 and a second waveguide arm 2, a negative electrode 9 may be disposed between the first ground electrode 8 and the second waveguide arm 2, a positive electrode 7 may be disposed on a side of the first waveguide arm 1 away from the first ground electrode 8, and a second ground electrode 10 may be disposed on a side of the second waveguide arm 2 away from the negative electrode 9, i.e. s+gs-G is sequentially disposed from top to bottom in fig. 3; the positive polarity differential signal can be transmitted to the positive polarity electrode 7, and the negative polarity differential signal can be transmitted to the negative polarity electrode 9, so that the direction of the generated first electric field is opposite to that of the generated second electric field.
Further, in order to further improve the anti-interference capability, in this embodiment, the dual-drive differential thin film lithium niobate electro-optical modulator chip further includes: a third ground electrode 11;
Wherein the third ground electrode 11 is disposed at a side of the first traveling wave electrode pair away from the second traveling wave electrode pair;
Or, the third ground electrode 11 is disposed at a side of the second traveling wave electrode pair away from the first traveling wave electrode pair.
It should be understood that, as further shown in fig. 2, the third ground electrode 11 may be disposed on a side of the negative electrode 9 of the second traveling wave electrode pair away from the first traveling wave electrode pair, and receives the ground signal generated by the signal generator, so that an electric field may be generated between the negative electrode 9 and the third ground electrode 11, and the resulting structure is gs+gs-G in order from top to bottom.
Similarly, as further shown in fig. 3, the third ground electrode 11 may be disposed on the side of the positive electrode 7 of the first traveling wave electrode pair away from the second traveling wave electrode pair, and receives the ground signal generated by the signal generator, so that an electric field may be generated between the positive electrode 7 and the third ground electrode 11, and the resulting structure is gs+gs-G sequentially from top to bottom.
The first traveling wave electrode pair receives the positive polarity differential signal to generate a first electric field, the second traveling wave electrode pair receives the negative polarity differential signal to generate a second electric field, and the first electric field and the second electric field are modulated. Compared with the existing method that only one path of electric signal is used for modulation, the embodiment adopts the positive polarity differential signal and the negative polarity differential signal for modulation respectively, so that the transmission performance is improved; especially in the face of high-speed long-distance light transmission scenes, the conventional manner is more susceptible to various external uncertainties. Compared with the traditional mode, the electro-optical modulation chip for the differential signal has the advantages of being strong in anti-interference capability, capable of effectively inhibiting electromagnetic interference and the like, and is more suitable for high-speed long-distance data transmission. Modulation using differential signals may also have smaller error vector magnitudes (Error vector magnitude, EVM), with constellation point deviations less than single-ended push-pull modulators after long-range transmission.
In addition, the chirp (chirp) of a signal can be controlled by a differential signal, and in an optical fiber communication system, the transmission distance of the signal is generally limited by the chromatic dispersion of an optical fiber, the chromatic dispersion can be compensated by controlling the chirp of the signal so as to realize the transmission with a longer distance, and the chromatic dispersion compensation can be evaluated by measuring the spurious-free dynamic range.
Referring to fig. 4, fig. 4 is a schematic cross-sectional view of a second embodiment of a dual-drive differential thin-film lithium niobate electro-optic modulator chip according to an embodiment of the present invention, as shown in fig. 4, in this embodiment, in order to implement modulation, the dual-drive differential thin-film lithium niobate electro-optic modulator chip further includes: a substrate layer 12, a buried layer 13, a thin film lithium niobate 14, and an upper cladding layer 15;
The buried layer 13 is disposed between the substrate layer 12 and the thin-film lithium niobate 14, the first waveguide arm 1, the second waveguide arm 2, the first traveling wave electrode pair and the second traveling wave electrode pair are all disposed in the upper cladding layer 15, and the upper cladding layer 15 covers the top of the thin-film lithium niobate 14.
In fig. 4, an interface schematic diagram of the structure shown in fig. 2 is shown, in this embodiment, the dual-drive differential thin film lithium niobate electro-optical modulator chip may use an x-cut thin film lithium niobate 14 wafer, the first ground electrode 8, the positive electrode 7, the second ground electrode 10, the negative electrode 9, and the third ground electrode 11 may use a coplanar waveguide structure, the materials may all be silver, the thickness may be 0.9 micrometer, the electrical signal may be loaded into the first optical signal of the first waveguide arm 1 and the second optical signal of the second waveguide arm 2 by using the electro-optical effect of lithium niobate, the widths of the positive electrode 7 and the negative electrode 9 may be 25 micrometers, and the widths of the first to third ground electrodes 11 may be 100 micrometers.
It is understood that the substrate layer 12 may be a silicon substrate with a thickness of 500 μm, the buried layer 13 may be a low refractive index buried layer 13 may be made of silicon dioxide, the refractive index may be 1.44, the thickness may be 4.7 μm, the thickness of the ridge waveguide formed by the thin film lithium niobate 14 may be 400 nm, the thickness of the first waveguide arm 1 and the second waveguide arm 2 may be 150 nm, the upper cladding layer 15 may be a low refractive index upper cladding layer 15, wherein a layer close to the thin film lithium niobate 14 may be made of silicon dioxide, the thickness of the layer close to the thin film lithium niobate 14 may be 3 μm, and a layer far from the thin film lithium niobate 14 may be made of silicon dioxide, and the thickness may be 3 μm.
It is also understood that the polarization direction of the ferroelectric domains of the thin film lithium niobate 14 is the direction from the positive polarity electrode 7 to the first ground electrode 8 (i.e., arrow to the left in fig. 4), and by the process, the polarization direction of the ferroelectric domains of the lithium niobate crystal may be reversed, and when the polarization direction of the ferroelectric domains is reversed, the electro-optic effect direction of the lithium niobate crystal is reversed along with the polarization direction.
It should be understood that, as shown in fig. 4, the upper cladding layer 15 may be divided into two layers, and the thin film lithium niobate 14 may form a ridge waveguide structure, and then a layer in the upper cladding layer 15 near the thin film lithium niobate 14 forms the first waveguide arm 1 and the second waveguide arm 2, and the first ground electrode 8, the positive polarity electrode 7, the second ground electrode 10, the negative polarity electrode 9, and the third ground electrode 11 are disposed in a layer in the upper cladding layer 15 far from the thin film lithium niobate 14. Therefore, the first waveguide arm 1 and the second waveguide arm 2 are both arranged in contact with the thin film lithium niobate 14, and the first traveling wave electrode pair and the second traveling wave electrode pair are both arranged in non-contact with the thin film lithium niobate 14.
As another implementation manner, referring to fig. 5, fig. 5 is another schematic cross-sectional view of a second embodiment of a dual-drive differential thin-film lithium niobate electro-optical modulator chip according to an embodiment of the present invention, as shown in fig. 5, the embodiment may further be provided with only one upper cladding layer 15, that is, the first waveguide arm 1, the second waveguide arm 2, the first traveling wave electrode pair and the second traveling wave electrode pair are all disposed in contact with the thin-film lithium niobate 14. The remaining specifications are the same as those in fig. 4, and this embodiment will not be described in detail.
Referring to fig. 6, fig. 6 is a schematic structural diagram of a third embodiment of a dual-driving differential thin-film lithium niobate electro-optical modulator chip according to an embodiment of the present invention, as shown in fig. 6, in order to further improve modulation performance, in this embodiment, the dual-driving differential thin-film lithium niobate electro-optical modulator chip further includes: a plurality of microelectrode pairs 16;
Wherein the microelectrode pairs 16 are arranged between the first traveling wave electrode pairs and between the second traveling wave electrode pairs.
As shown in fig. 6, the present embodiment is described with the structure in fig. 2, and the number of the microelectrode pairs 16 is not limited in the present embodiment. Wherein the microelectrode pair 16 may comprise two microelectrodes, one of which may be provided on the first and second ground electrodes 8, 10 and the other of which may be provided on the positive and negative polarity electrodes 7, 9; meanwhile, a plurality of microelectrode pairs 16 may be arranged between the positive electrode 7 and the second electrode 10, and a plurality of microelectrode pairs 16 may be arranged between the negative electrode 9 and the third electrode 11.
It should be noted that the microelectrode pair 16 between the positive electrode 7 and the first ground electrode 8 may be disposed close to the first waveguide arm 1, that is, the first waveguide arm 1 may be disposed between the microelectrode pair 16, and similarly, the microelectrode pair 16 between the negative electrode 9 and the second ground electrode 10 may be disposed close to the second waveguide arm 2, that is, the second waveguide arm 2 may be disposed between the microelectrode pair 16.
For the structure in fig. 3, a plurality of microelectrode pairs 16 may be disposed between the electrodes, which is not described in detail in this embodiment.
It is understood that the material of the microelectrode pair 16 may be made of silver, and the thickness of the microelectrode pair may be the same as that of the positive electrode 7 and the negative electrode 9, the width of the microelectrode pair may be 3 micrometers, the interval between the microelectrodes may be 5 micrometers, and the distance between the microelectrodes and the waveguide arm may be not less than 2 micrometers.
In a specific implementation, the electric field strength of the first electric field and the second electric field can be enhanced by the microelectrode pair 16, so that the photoelectric effect is enhanced, and the modulation efficiency is improved.
It should be further noted that the structure of the microelectrode may be at least one of a T-type structure, an L-type structure, or a groove-type structure, and the microelectrode structure shown in fig. 6 is a T-type structure, referring to fig. 7, fig. 7 is another schematic structural diagram of the microelectrode in the third embodiment of the dual-drive differential thin film lithium niobate electro-optical modulator chip according to the embodiment of the present invention, as shown in fig. 7, the microelectrode structure may be configured as an L-type structure, and referring to fig. 8, fig. 8 is another schematic structural diagram of the microelectrode in the third embodiment of the dual-drive differential thin film lithium niobate electro-optical modulator chip according to the embodiment of the present invention, as shown in fig. 8, the microelectrode structure may be configured as a groove-type structure, and of course, the microelectrode may be configured as another structure according to the embodiment of the present invention, which is not limited thereto.
The present embodiment can enhance the photoelectric effect by the microelectrode pair 16, and improve the modulation efficiency.
In addition, in order to achieve the above objective, the embodiments of the present invention further provide an optical communication system, and since the optical communication system includes the above dual-drive differential thin film lithium niobate electro-optical modulator chip, the optical communication system has at least all the advantages brought by the technical solutions of the above embodiments, which are not described in detail herein.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.
It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
Claims (10)
1. A dual-drive differential thin-film lithium niobate electro-optic modulator chip, the dual-drive differential thin-film lithium niobate electro-optic modulator chip comprising: the device comprises a first waveguide arm, a first traveling wave electrode pair arranged on two sides of the first waveguide arm, a second waveguide arm and a second traveling wave electrode pair arranged on two sides of the second waveguide arm;
wherein the first traveling wave electrode pair and the second traveling wave electrode pair are both connected with a signal generator;
The first row wave electrode pair is used for receiving the positive differential signal generated by the signal generator and generating a first electric field so that the first waveguide arm modulates according to the first electric field;
the second traveling wave electrode pair is used for receiving the negative differential signal generated by the signal generator and generating a second electric field so that the second waveguide arm modulates according to the second electric field;
the direction of the first electric field is opposite to the direction of the second electric field.
2. The dual drive differential thin film lithium niobate electro-optic modulator chip of claim 1, wherein the first pair of row wave electrodes comprises: a positive electrode and a first ground electrode;
The second traveling wave electrode pair includes: a negative polarity electrode and a second ground electrode;
Wherein the positive electrode, the first ground electrode, the negative electrode and the second ground electrode are all connected with the signal generator;
The positive electrode is used for receiving the positive differential signal generated by the signal generator and generating a first electric field based on the positive differential signal, and the direction of the first electric field is directed to the first ground electrode by the positive electrode;
The negative electrode is used for receiving the negative differential signal generated by the signal generator and generating a second electric field based on the negative differential signal, and the direction of the second electric field is directed to the negative electrode by the second ground electrode.
3. The dual-drive differential thin-film lithium niobate electro-optic modulator chip of claim 2, wherein the positive polarity electrode is disposed between the first waveguide arm and the second waveguide arm, the first ground electrode is disposed on a side of the first waveguide arm away from the positive polarity electrode, the second ground electrode is disposed between the positive polarity electrode and the second waveguide arm, and the negative polarity electrode is disposed on a side of the second waveguide arm away from the second ground electrode.
4. The dual-drive differential thin-film lithium niobate electro-optic modulator chip of claim 1, wherein the dual-drive differential thin-film lithium niobate electro-optic modulator chip further comprises: the substrate layer, the buried layer, the thin film lithium niobate and the upper cladding layer;
The buried layer is arranged between the substrate layer and the thin-film lithium niobate, the first waveguide arm, the second waveguide arm, the first traveling wave electrode pair and the second traveling wave electrode pair are all arranged in the upper cladding layer, and the upper cladding layer covers the top of the thin-film lithium niobate.
5. The dual drive differential thin film lithium niobate electro-optic modulator chip of claim 4, wherein the first waveguide arm and the second waveguide arm are both disposed in contact with the thin film lithium niobate, and wherein the first traveling wave electrode pair and the second traveling wave electrode pair are both disposed in non-contact with the thin film lithium niobate.
6. The dual drive differential thin film lithium niobate electro-optic modulator chip of claim 4, wherein the first waveguide arm, the second waveguide arm, the first traveling wave electrode pair, and the second traveling wave electrode pair are all disposed in contact with the thin film lithium niobate.
7. The dual-drive differential thin-film lithium niobate electro-optic modulator chip of claim 1, wherein the dual-drive differential thin-film lithium niobate electro-optic modulator chip further comprises: a plurality of microelectrode pairs;
the microelectrode pairs are arranged between the first traveling wave electrode pairs and between the second traveling wave electrode pairs.
8. The dual drive differential thin film lithium niobate electro-optic modulator chip of claim 7, wherein the microelectrodes in the microelectrode pairs are at least one of T-shaped, L-shaped, or slot-shaped.
9. The dual-drive differential thin-film lithium niobate electro-optic modulator chip of claim 1, wherein the dual-drive differential thin-film lithium niobate electro-optic modulator chip further comprises: a third ground electrode;
the third ground electrode is arranged on one side of the first traveling wave electrode pair far away from the second traveling wave electrode pair;
or, the third ground electrode is disposed at a side of the second traveling wave electrode pair away from the first traveling wave electrode pair.
10. An optical communication system comprising a dual-drive differential thin-film lithium niobate electro-optic modulator chip according to any of claims 1 to 9.
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| US20140153860A1 (en) * | 2012-11-09 | 2014-06-05 | Teraxion Inc. | Mach-zehnder optical modulator having an asymmetrically-loaded traveling wave electrode |
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