CN210243999U - Novel lithium niobate electro-optic modulator based on zinc oxide waveguide - Google Patents
Novel lithium niobate electro-optic modulator based on zinc oxide waveguide Download PDFInfo
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- CN210243999U CN210243999U CN201921249565.8U CN201921249565U CN210243999U CN 210243999 U CN210243999 U CN 210243999U CN 201921249565 U CN201921249565 U CN 201921249565U CN 210243999 U CN210243999 U CN 210243999U
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Abstract
The utility model discloses a novel lithium niobate electro-optic modulator based on zinc oxide waveguide adopts zinc oxide waveguide and not titanium diffusion waveguide or proton exchange waveguide as the guided wave structure of lithium niobate electro-optic modulator, include: the device comprises a lithium niobate wafer, a zinc oxide waveguide formed on the surface of the lithium niobate wafer, and a modulation electrode arranged above the surface of the lithium niobate wafer. The zinc oxide waveguide can also modulate and transmit the TE polarization mode and the TM polarization mode simultaneously, but has a higher optical damage threshold than the titanium diffusion waveguide, and does not have the polarization filtering phenomenon of a proton exchange waveguide.
Description
Technical Field
The utility model relates to a technical field such as fiber communication, optical fiber sensing, microwave optical fiber link, quantum communication especially relates to a novel lithium niobate electro-optic modulator based on zinc oxide waveguide.
Background
Lithium niobate is a crystal material integrating various properties of electro-optic, acousto-optic, piezoelectric, nonlinear optics and the like, and is one of common material choices for preparing integrated optical devices such as electro-optic modulators, acousto-optic modulators, pyroelectric infrared detectors, nonlinear wavelength converters, quantum entanglement light sources and the like. Lithium niobate electro-optical modulators based on optical waveguide structures, such as phase modulators, intensity modulators, QPSK modulators, polarization controllers and the like, have very wide application in the fields of optical fiber communication, optical fiber sensing, microwave optical fiber links, quantum communication and the like, and can realize various functions of phase modulation, intensity modulation, polarization modulation and the like. The existing lithium niobate electro-optical modulator usually adopts a titanium diffusion technology and a proton exchange technology to prepare an optical waveguide to form a titanium diffusion waveguide or a proton exchange waveguide. The lithium niobate electro-optical modulator based on the two optical waveguides has the advantages of low insertion loss, good thermal stability, high modulation bandwidth, high modulation linearity and the like.
The titanium diffusion waveguide can simultaneously transmit two polarization modes of TE and TM, so that the electro-optic modulator based on the lithium niobate titanium diffusion waveguide has wide application in the application fields of simultaneously modulating and transmitting the two polarization modes, such as optical fiber current sensing, electro-optic polarization control, coherent optical communication and the like. However, the titanium diffused waveguide has the obvious defect of low optical damage threshold, and cannot modulate and transmit high-power laser beams.
Although the electro-optical modulator based on the lithium niobate proton exchange waveguide has a high optical damage threshold, the waveguide can only transmit abnormal optical refractive index (n)e) Corresponding polarization mode, no ordinary refractive index (n)o) The corresponding polarization mode, i.e. the waveguide, has natural polarization filtering properties. For some application fields requiring transmission of a single polarization mode, such as a fiber optic gyroscope, an electro-optical modulator based on a lithium niobate proton exchange waveguide is a good choice, but when two polarization modes are required to be modulated and transmitted simultaneously, the application of the electro-optical modulator is greatly limited.
SUMMERY OF THE UTILITY MODEL
For solving the problem that exists in the lithium niobate electro-optic modulator based on current optical waveguide, the utility model provides a novel lithium niobate electro-optic modulator based on zinc oxide waveguide, its innovation part lies in, adopts the zinc oxide waveguide rather than titanium diffusion waveguide or proton exchange waveguide as the guided wave structure of lithium niobate electro-optic modulator. The zinc oxide waveguide can also modulate and transmit the TE polarization mode and the TM polarization mode simultaneously, but has a higher optical damage threshold than the titanium diffusion waveguide, and does not have the polarization filtering phenomenon of a proton exchange waveguide.
Based on the technical principle, the utility model aims to provide a lithium niobate electro-optical modulator based on zinc oxide waveguide. The lithium niobate electro-optical modulator relates to a low-rate phase modulator, a low-rate intensity modulator, a high-rate phase modulator and a high-rate intensity modulator.
To the aforesaid the utility model discloses well low rate phase modulator, low rate intensity modulator, the application provides a low rate lithium niobate electro-optical modulator's based on zinc oxide waveguide preparation method.
To above-mentioned utility model well high-speed phase modulator and high rate intensity modulator, this application provides a preparation method of high rate lithium niobate electro-optical modulator based on zinc oxide waveguide.
In order to realize the purpose of the utility model, the utility model provides
The first technical scheme is as follows:
a zinc oxide waveguide based low rate lithium niobate phase modulator comprising: the device comprises a lithium niobate wafer, a zinc oxide waveguide formed on the surface of the lithium niobate wafer, and a modulation electrode arranged above the surface of the lithium niobate wafer.
Preferably, the lithium niobate wafer is optical grade, the tangential direction of the crystal is X-cut, and the thickness is 0.1mm to 2 mm;
preferably, the zinc oxide waveguide is in a straight strip pattern, and the mode field diameter of a waveguide mode is 1-20 μm;
preferably, the modulation electrode comprises a first electrode and a second electrode to form a lumped electrode structure, the adopted metal thin film material is gold, and the thickness of the metal thin film is 0.1 μm to 1 μm.
The second technical scheme is as follows:
a high-rate lithium niobate phase modulator based on a zinc oxide waveguide, comprising: the device comprises a lithium niobate wafer, a zinc oxide waveguide formed on the surface of the lithium niobate wafer, a modulation electrode arranged above the surface of the lithium niobate wafer, and a buffer layer film arranged between the zinc oxide waveguide and the modulation electrode.
Preferably, the lithium niobate wafer is optical grade, the tangential direction of the crystal is X-cut or Z-cut, and the thickness is 0.1mm to 2 mm;
preferably, the zinc oxide waveguide is in a straight strip pattern, and the mode field diameter of a waveguide mode is 1-20 μm;
preferably, the modulation electrode adopts a coplanar traveling wave electrode structure and comprises a signal electrode and two ground electrodes, the adopted metal film material is gold, and the thickness of the metal film is 1-40 μm;
further, for the X-cut lithium niobate wafer, in order to utilize the maximum electro-optic coefficient of the lithium niobate crystal, the zinc oxide waveguide is positioned between the signal electrode of the modulation electrode and one of the ground electrodes, and the other ground electrode is positioned at the other side of the signal electrode; for the Z-cut lithium niobate wafer, in order to utilize the maximum electro-optic coefficient of the lithium niobate crystal, the zinc oxide waveguide is positioned below the signal electrode of the modulation electrode, and two branches of the ground electrode are respectively positioned on the left side or the right side of the signal electrode;
preferably, the thickness of the buffer layer film is 0.1-2 μm, and the film material is silicon oxide or aluminum oxide.
The third technical scheme is as follows:
a zinc oxide waveguide based low rate lithium niobate intensity modulator comprising: the device comprises a lithium niobate wafer, a zinc oxide waveguide formed on the surface of the lithium niobate wafer, and a modulation electrode arranged above the surface of the lithium niobate wafer.
Preferably, the lithium niobate wafer is optical grade, the tangential direction of the crystal is X-cut, and the thickness is 0.1mm to 2 mm;
preferably, the zinc oxide waveguide is of a Mach-Zehnder interferometer structure, and the mode field diameter of the waveguide mode is 1-20 μm;
preferably, the modulation electrode comprises a first electrode and a second electrode which is respectively arranged on the left side and the right side of the first electrode to form a push-pull type lumped electrode structure, the adopted metal thin film material is gold, and the thickness of the metal thin film is 0.1-1 μm;
the fourth technical scheme is as follows: a zinc oxide waveguide based high rate lithium niobate intensity modulator comprising: the device comprises a lithium niobate wafer, a zinc oxide waveguide formed on the surface of the lithium niobate wafer, a modulation electrode arranged above the surface of the lithium niobate wafer, and a buffer layer film arranged between the zinc oxide waveguide and the modulation electrode.
Preferably, the lithium niobate wafer is optical grade, the tangential direction of the crystal is X-cut or Z-cut, and the thickness is 0.1mm to 2 mm;
preferably, the zinc oxide waveguide is of a Mach-Zehnder interferometer structure, and the mode field diameter of the waveguide mode is 1-20 μm;
preferably, the modulation electrode comprises a signal electrode and two ground electrodes respectively arranged on the left side and the right side of the signal electrode to form a push-pull coplanar traveling wave electrode structure, the adopted metal film material is gold, and the thickness of the metal film is 1-40 μm;
furthermore, for the X-cut lithium niobate wafer, in order to utilize the maximum electro-optical coefficient of the lithium niobate crystal, the signal electrode of the modulation electrode is arranged between the inner sides of the two arms of the waveguide of the Mach-Zehnder interferometer structure, and the two ground electrodes are respectively arranged on the outer sides of the two arms of the waveguide of the Mach-Zehnder interferometer structure; for the Z-cut lithium niobate wafer, the signal electrode in the modulation electrode is arranged above one of the two arms of the waveguide of the Mach-Zehnder interferometer structure, one of the two ground electrodes is arranged above the other arm of the two arms of the waveguide of the Mach-Zehnder interferometer structure, namely the left side or the right side of the signal electrode, and the other one of the two ground electrodes is correspondingly arranged on the right side or the left side of the signal electrode.
To the aforesaid the utility model discloses well low rate phase modulator, low rate intensity modulator, the application provides a low rate lithium niobate electro-optical modulator's preparation method based on zinc oxide waveguide, including following step:
step 1: manufacturing a photoresist mask with an optical waveguide pattern on the surface of a lithium niobate wafer by adopting a photoetching process, wherein the optical waveguide pattern is of a straight bar or Mach-Zehnder interferometer structure;
step 2: preparing a zinc oxide film with the thickness of 10nm to 200nm on a photoresist mask by adopting one of coating process means such as electron beam evaporation, magnetron sputtering, ion sputtering, chemical vapor deposition and the like;
and step 3: a zinc oxide film with an optical waveguide pattern is left on the surface of the lithium niobate wafer by adopting a stripping process, and the width of the zinc oxide film is between 1 and 20 mu m;
and 4, step 4: placing the lithium niobate wafer in the center of a high-temperature diffusion furnace, introducing wet oxygen, keeping the temperature of the diffusion furnace constant for 5-12 hours under the condition that the temperature of the diffusion furnace is increased from the room temperature to 1000-1100 ℃, closing the diffusion furnace, and taking out the lithium niobate wafer after the temperature of the furnace is reduced to the room temperature to obtain the lithium niobate wafer containing the zinc oxide diffusion waveguide;
and 5: preparing a layer of buffer layer film of silicon oxide or aluminum oxide on the surface of a lithium niobate wafer by adopting one of the coating process means of chemical vapor deposition, magnetron sputtering, ion sputtering and the like, wherein the thickness of the film is 0.1-2 mu m;
step 6: manufacturing a photoresist mask with a modulated electrode pattern on the surface of a lithium niobate wafer by adopting a photoetching technology;
and 7: preparing a layer of gold film with the thickness of 0.1-1 mu m on a photoresist mask by adopting one of coating process means such as electron beam evaporation, magnetron sputtering, ion sputtering, electroplating and the like, and preparing a layer of metal chromium film or metal titanium film with the thickness of 10-100 nm before preparing the gold film in order to increase the adhesion between the gold film and the lithium niobate wafer;
and 8: adopting a stripping process to leave a chromium gold or titanium gold film for modulating an electrode pattern on the surface of the lithium niobate wafer;
and step 9: precisely polishing the input end face and the output end face of the lithium niobate wafer;
step 10: and packaging the lithium niobate electro-optical modulator wafer by adopting an optical fiber coupling process and a microelectronic packaging process.
To above-mentioned utility model well high-speed phase modulator and high rate intensity modulator, the application provides a preparation method of high rate lithium niobate electro-optical modulator based on zinc oxide waveguide, including following step:
step 1: manufacturing a photoresist mask with an optical waveguide pattern on the surface of a lithium niobate wafer by adopting a photoetching process, wherein the optical waveguide pattern is of a straight bar or Mach-Zehnder interferometer structure;
step 2: preparing a zinc oxide film with the thickness of 10nm to 200nm on a photoresist mask by adopting one of coating process means such as electron beam evaporation, magnetron sputtering, ion sputtering, chemical vapor deposition and the like;
and step 3: a zinc oxide film with an optical waveguide pattern is left on the surface of the lithium niobate wafer by adopting a stripping process, and the width of the zinc oxide film is between 1 and 20 mu m;
and 4, step 4: placing the lithium niobate wafer in the center of a high-temperature diffusion furnace, introducing wet oxygen, keeping the temperature of the diffusion furnace constant for 5-12 hours under the condition that the temperature of the diffusion furnace is increased from the room temperature to 1000-1100 ℃, closing the diffusion furnace, and taking out the lithium niobate wafer after the temperature of the furnace is reduced to the room temperature to obtain the lithium niobate wafer containing the zinc oxide diffusion waveguide;
and 5: preparing a layer of buffer layer film of silicon oxide or aluminum oxide on the surface of a lithium niobate wafer by adopting one of the coating process means of chemical vapor deposition, magnetron sputtering, ion sputtering and the like, wherein the thickness of the film is 0.1-2 mu m;
step 6: preparing a layer of metal film on the surface of the lithium niobate wafer as an electroplating seed layer, wherein the metal film can be made of titanium or chromium, and the thickness of the film is 10nm to 500 nm;
and 7: manufacturing a photoresist mask with a modulated electrode pattern on the surface of a lithium niobate wafer by adopting a photoetching technology;
and 8: placing the lithium niobate wafer in a gold electroplating solution for electroplating processing to obtain a thick electrode structure with the thickness of 1-40 mu m;
and step 9: removing the photoresist mask of the modulation electrode;
step 10: precisely polishing the input end face and the output end face of the lithium niobate wafer;
step 11: and packaging the lithium niobate electro-optical modulator wafer by adopting an optical fiber coupling process and a microelectronic packaging process.
Compared with the prior art, the beneficial effects of the utility model are that:
(1) compared with the existing lithium niobate electro-optic modulator based on the titanium diffusion waveguide, the lithium niobate electro-optic modulator based on the zinc oxide waveguide provided by the utility model has higher optical damage threshold, and can transmit and modulate waveguide modes with higher optical power and different polarization states;
(2) compare with current lithium niobate electro-optic modulator based on proton exchange waveguide, the utility model provides a lithium niobate electro-optic modulator based on zinc oxide waveguide does not have polarization mode filtering phenomenon.
Drawings
Fig. 1(a) is a schematic cross-sectional view of an X-cut, low-rate lithium niobate phase modulator provided by the present invention;
fig. 1(b) is a schematic plan view of an X-cut, low-rate lithium niobate phase modulator provided by the present invention;
fig. 2(a) is a schematic cross-sectional view of an X-cut, high-rate lithium niobate phase modulator provided by the present invention;
fig. 2(b) is a schematic plan view of an X-cut, high-rate lithium niobate phase modulator provided by the present invention;
fig. 2(c) is a schematic cross-sectional view of a Z-cut, high-rate lithium niobate phase modulator provided by the present invention;
fig. 2(d) is a schematic plan view of a Z-cut, high-rate lithium niobate phase modulator provided by the present invention;
fig. 3(a) is a schematic cross-sectional view of an X-cut, low-rate lithium niobate intensity modulator provided by the present invention;
fig. 3(b) is a schematic plan view of an X-cut, low-rate lithium niobate intensity modulator provided by the present invention;
fig. 4(a) is a schematic cross-sectional view of an X-cut, high-rate lithium niobate intensity modulator provided by the present invention;
fig. 4(b) is a schematic plan view of an X-cut, high-rate lithium niobate intensity modulator provided by the present invention;
fig. 4(c) is a schematic cross-sectional view of a Z-cut, high-rate lithium niobate intensity modulator provided by the present invention;
fig. 4(d) is a schematic plan view of a Z-cut, high-rate lithium niobate intensity modulator provided by the present invention;
in the figure, the names corresponding to the respective marks are: 1. a lithium niobate wafer; 2. a zinc oxide diffusion waveguide; 3. a modulation electrode; 3-1, electrode one of the lumped electrode structure; 3-2, electrode two of the lumped electrode structure; 3-3, signal electrode of coplanar traveling wave electrode structure; 3-4, a ground electrode of the coplanar traveling wave electrode structure; 4. a buffer layer film.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when used in this specification the singular forms "a", "an" and/or "the" include "specify the presence of stated features, steps, operations, elements, or modules, components, and/or combinations thereof, unless the context clearly indicates otherwise.
It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
Example 1
Referring to fig. 1(a) and 1(b), which are diagrams of a first embodiment of a zinc oxide waveguide-based lithium niobate electro-optic modulator according to the present invention, fig. 1(a) is a schematic cross-sectional view of the electro-optic modulator, and fig. 1(b) is a schematic plan view of the electro-optic modulator. The lithium niobate electro-optical modulator based on the zinc oxide waveguide according to the embodiment is a low-rate phase modulator, and comprises:
a lithium niobate wafer 1 formed of an optical-grade material, the crystal having a tangential direction of X-cut and a thickness of 0.1mm to 2 mm;
the zinc oxide waveguide 2 is formed on the surface of the lithium niobate wafer 1, the waveguide is a straight strip pattern, and the mode field diameter of the waveguide mode is 1-20 mu m;
the modulation electrode 3 is formed on the upper surface of the lithium niobate wafer 1, the adopted metal thin film material is gold, the thickness of the metal thin film is 0.1-1 μm, the modulation electrode 3 adopts a lumped structure and consists of a first electrode 3-1 (such as a positive electrode) and a second electrode 3-2 (such as a negative electrode), and the first electrode 3-1 and the second electrode 3-2 are respectively arranged on two sides above the zinc oxide waveguide 2.
Example 2
Referring to fig. 2(a) and 2(b), fig. 2(a) and 2(b) are diagrams showing a second embodiment of the lithium niobate electro-optical modulator based on the zinc oxide waveguide according to the present invention, fig. 2(a) is a schematic cross-sectional view of the electro-optical modulator, and fig. 2(b) is a schematic plan view of the electro-optical modulator. The lithium niobate electro-optic modulator based on the zinc oxide waveguide according to the embodiment is a high-speed phase modulator, and comprises:
a lithium niobate wafer 1 formed of an optical-grade material, the crystal having a tangential direction of X-cut and a thickness of 0.1mm to 2 mm;
the zinc oxide waveguide 2 is formed on the surface of the lithium niobate wafer 1, the waveguide is a straight strip pattern, and the mode field diameter of the waveguide mode is 1-20 mu m;
and the modulation electrode 3 is formed on the upper surface of the lithium niobate wafer 1, the adopted metal film material is gold, the thickness of the metal film is 1-40 μm, and the modulation electrode is composed of a signal electrode 3-3 and a ground electrode 3-4, one of the signal electrode 3-3 and the ground electrode 3-4 is respectively arranged on the left side and the right side above the zinc oxide waveguide 2, and the other one of the ground electrode 3-4 is arranged on the other side of the signal electrode 3-3 to form a coplanar traveling wave electrode structure.
The buffer layer film 4 is made of silicon oxide or aluminum oxide, the thickness of the film is 0.1-2 mu m, and the buffer layer film is placed between the zinc oxide waveguide 2 and the modulation electrode 3 to play a role in increasing the matching degree of the light wave rate and the microwave rate and improving the modulation rate.
Example 3
Referring to fig. 2(c) and 2(d), fig. 2(c) and 2(d) are diagrams showing a third embodiment of the zinc oxide waveguide-based lithium niobate electro-optic modulator according to the present invention, fig. 2(c) is a schematic cross-sectional view of the electro-optic modulator, and fig. 2(d) is a schematic plan view of the electro-optic modulator. The zinc oxide waveguide lithium niobate electro-optic modulator related to the embodiment is a high-speed phase modulator, and comprises:
a lithium niobate wafer 1 formed of an optical-grade material, the crystal having a Z-cut tangential direction and a thickness of 0.1mm to 2 mm;
the zinc oxide waveguide 2 is formed on the surface of the lithium niobate wafer 1, the waveguide is a straight strip pattern, and the mode field diameter of the waveguide mode is 1-20 mu m;
and the modulation electrode 3 is formed on the upper surface of the lithium niobate wafer 1, the adopted metal thin film material is gold, the thickness of the metal thin film is 1-40 mu m, and the modulation electrode 3 consists of a signal electrode 3-3 and a ground electrode 3-4. Taking fig. 2(c) and fig. 2(d) as an example, the signal electrode 3-3 is placed above the zinc oxide waveguide 2, one of the ground electrodes 3-4 is placed on the left side of the signal electrode 3-3, and the other one of the ground electrodes 3-4 is placed on the right side of the signal electrode 3-3, so as to form a coplanar traveling wave electrode structure.
The buffer layer film 4 is made of silicon oxide or aluminum oxide, the thickness of the film is 0.1-2 mu m, and the film is placed between the zinc oxide waveguide 2 and the modulation electrode 3, so that on one hand, the effects of isolating the zinc oxide waveguide 2 from the signal electrode 3-3 and reducing the insertion loss of the zinc oxide waveguide 2 are achieved, and on the other hand, the effects of increasing the matching degree of the optical wave velocity and the microwave velocity and improving the modulation velocity are achieved.
Example 4
Referring to fig. 3(a) and 3(b), which are diagrams illustrating a fourth embodiment of the lithium niobate electro-optical modulator based on the zinc oxide waveguide according to the present invention, fig. 3(a) is a schematic cross-sectional view of the electro-optical modulator, and fig. 3(b) is a schematic plan view of the electro-optical modulator. The lithium niobate electro-optical modulator based on the zinc oxide waveguide related to the embodiment is a low-rate intensity modulator, and comprises:
a lithium niobate wafer 1 formed of an optical-grade material, the crystal having a tangential direction of X-cut and a thickness of 0.1mm to 2 mm;
a zinc oxide waveguide 2 formed on the surface of the lithium niobate wafer 1, wherein the waveguide is in a Mach-Zehnder interferometer pattern structure, and the mode field diameter of the waveguide mode is 1-20 μm;
the modulation electrode 3 is placed on the upper surface of the lithium niobate wafer 1, the adopted metal thin film material is gold, the thickness of the metal thin film is 0.1-1 μm, and the modulation electrode is composed of a first electrode 3-1 (such as a positive electrode) and a second electrode 3-2 (such as a negative electrode) to form a lumped electrode structure;
the first electrode 3-1 is arranged between the inner sides of the two arms of the zinc oxide waveguide 2 of the Mach-Zehnder interferometer structure, and the two branches of the second electrode 3-2 are respectively arranged on the outer sides of the two arms of the zinc oxide waveguide 2 to form a push-pull electrode structure.
Example 5
Referring to fig. 4(a) and 4(b), fig. 4(a) and 4(b) are diagrams illustrating a fifth embodiment of the zinc oxide waveguide-based lithium niobate electro-optic modulator according to the present invention, fig. 4(a) is a schematic cross-sectional view of the electro-optic modulator, and fig. 4(b) is a schematic plan view of the electro-optic modulator. The lithium niobate electro-optical modulator based on the zinc oxide waveguide according to the embodiment is a high-speed intensity modulator, and comprises:
a lithium niobate wafer 1 formed of an optical-grade material, the crystal having a tangential direction of X-cut and a thickness of 0.1mm to 2 mm;
a zinc oxide waveguide 2 formed on the surface of the lithium niobate wafer 1, wherein the waveguide is in a Mach-Zehnder interferometer pattern structure, and the mode field diameter of the waveguide mode is 1-20 μm;
the modulation electrode 3 is placed on the upper surface of the lithium niobate wafer 1, the adopted metal film material is gold, the thickness of the metal film is 1-40 μm, the modulation electrode 3 is composed of a signal electrode 3-3 and a ground electrode 3-4, the signal electrode 3-3 is placed between the inner sides of two arms of a zinc oxide waveguide 2 of a Mach-Zehnder interferometer structure, and two branches of the ground electrode 3-4 are respectively placed on the outer sides of the two arms of the zinc oxide waveguide, so that a push-pull type traveling wave coplanar electrode structure is formed.
The buffer layer film 4 is made of silicon oxide or aluminum oxide, the thickness of the film is 0.1-2 mu m, and the buffer layer film is placed between the zinc oxide waveguide 2 and the modulation electrode 3 to play a role in increasing the matching degree of the light wave rate and the microwave rate and improving the modulation rate.
Example 6
Referring to fig. 4(c) and 4(d), fig. 4(c) and 4(d) are diagrams illustrating a sixth embodiment of the lithium niobate electro-optical modulator based on the zinc oxide waveguide according to the present invention, fig. 4(c) is a schematic cross-sectional view of the electro-optical modulator, and fig. 4(d) is a schematic plan view of the electro-optical modulator. The lithium niobate electro-optical modulator based on the zinc oxide waveguide according to the embodiment is a high-speed intensity modulator, and comprises:
a lithium niobate wafer 1 formed of an optical-grade material, the crystal having a Z-cut tangential direction and a thickness of 0.1mm to 2 mm;
a zinc oxide waveguide 2 formed on the surface of the lithium niobate wafer 1, wherein the waveguide is in a Mach-Zehnder interferometer pattern structure, and the mode field diameter of the waveguide mode is 1-20 μm;
and the modulation electrode 3 is formed on the upper surface of the lithium niobate wafer 1, the adopted metal thin film material is gold, the thickness of the metal thin film is 1-40 mu m, and the modulation electrode 3 consists of a signal electrode 3-3 and a ground electrode 3-4. Taking fig. 4(c) and 4(d) as examples, the signal electrode 3-3 is placed above the right branch of the two arms of the zinc oxide waveguide 2 of the mach-zehnder interferometer structure, the left branch of the ground electrode 3-4 is placed above the left branch of the two arms of the zinc oxide waveguide 2 of the mach-zehnder interferometer structure, and the right branch of the ground electrode 3-4 is symmetrically placed on the right side of the signal electrode 3-3, thereby forming a push-pull traveling wave coplanar electrode structure.
The buffer layer film 4 is made of silicon oxide or aluminum oxide, the thickness of the film is 0.1-2 mu m, and the film is placed between the zinc oxide waveguide 2 and the modulation electrode 3, so that on one hand, the effects of isolating the zinc oxide waveguide 2 from the signal electrode 3-3 and reducing the insertion loss of the zinc oxide waveguide 2 are achieved, and on the other hand, the effects of increasing the matching degree of the optical wave velocity and the microwave velocity and improving the modulation velocity are achieved.
A manufacturing method of a zinc oxide waveguide-based low-rate lithium niobate electro-optic modulator is provided for a low-rate phase modulator and a low-rate intensity modulator, and comprises the following steps:
step 1: a photoresist mask with an optical waveguide pattern is manufactured on the surface of the lithium niobate wafer 1 by adopting a photoetching process, wherein the optical waveguide pattern is a straight bar or Mach-Zehnder interferometer structure;
step 2: preparing a zinc oxide film with the thickness of 10nm to 200nm on a photoresist mask by adopting one of coating process means such as electron beam evaporation, magnetron sputtering, ion sputtering, chemical vapor deposition and the like;
and step 3: a zinc oxide film with an optical waveguide pattern is left on the surface of the lithium niobate wafer 1 by adopting a stripping process, and the width of the zinc oxide film is between 1 and 20 mu m;
and 4, step 4: placing the lithium niobate wafer 1 in the center of a high-temperature diffusion furnace, introducing wet oxygen, keeping the temperature of the diffusion furnace constant for 5-12 hours under the condition that the temperature of the diffusion furnace is increased from the room temperature to 1000-1100 ℃, closing the diffusion furnace, and taking out the lithium niobate wafer 1 after the temperature of the furnace is reduced to the room temperature to obtain the lithium niobate wafer 1 containing the zinc oxide diffusion waveguide 2;
and 5: preparing a buffer layer film 4 of silicon oxide or aluminum oxide on the surface of the lithium niobate wafer 1 by adopting one of the coating process means of chemical vapor deposition, magnetron sputtering, ion sputtering and the like, wherein the thickness of the film is 0.1-2 mu m;
step 6: manufacturing a photoresist mask with a lumped electrode pattern on the surface of the lithium niobate wafer 1 by adopting a photoetching technology;
and 7: preparing a gold film with the thickness of 0.1-1 mu m on a photoresist mask by adopting one of the process means of coating such as electron beam evaporation, magnetron sputtering, ion sputtering and the like, electroplating and the like, and preparing a metal chromium film or a metal titanium film with the thickness of 10-100 nm before preparing the gold film in order to increase the adhesion between the gold film and the lithium niobate wafer 1;
and 8: adopting a stripping process to leave a chromium gold or titanium gold film for modulating an electrode pattern on the surface of the lithium niobate wafer to obtain a modulation electrode 3;
and step 9: precisely polishing the input end face and the output end face of the lithium niobate wafer 1;
step 10: and packaging the lithium niobate electro-optical modulator wafer by adopting an optical fiber coupling process and a microelectronic packaging process.
To high rate phase modulator and high rate intensity modulator, the utility model discloses still provide a manufacturing approach of high rate lithium niobate electro-optical modulator based on zinc oxide waveguide. The manufacturing method comprises the following steps:
step 1: a photoresist mask with an optical waveguide pattern is manufactured on the surface of the lithium niobate wafer 1 by adopting a photoetching process, wherein the optical waveguide pattern is a straight bar or Mach-Zehnder interferometer structure;
step 2: preparing a zinc oxide film with the thickness of 10nm to 200nm on a photoresist mask by adopting one of coating process means such as electron beam evaporation, magnetron sputtering, ion sputtering, chemical vapor deposition and the like;
and step 3: a zinc oxide film with an optical waveguide pattern is left on the surface of the lithium niobate wafer 1 by adopting a stripping process, and the width of the zinc oxide film is between 1 and 20 mu m;
and 4, step 4: placing the lithium niobate wafer 1 in the center of a high-temperature diffusion furnace, introducing wet oxygen, keeping the temperature of the diffusion furnace constant for 5-12 hours under the condition that the temperature of the diffusion furnace is increased from the room temperature to 1000-1100 ℃, closing the diffusion furnace, and taking out the lithium niobate wafer 1 after the temperature of the furnace is reduced to the room temperature to obtain the lithium niobate wafer 1 containing the zinc oxide diffusion waveguide 2;
and 5: preparing a buffer layer film 4 of silicon oxide or aluminum oxide on the surface of the lithium niobate wafer 1 by adopting one of the coating process means of chemical vapor deposition, magnetron sputtering, ion sputtering and the like, wherein the thickness of the film is 0.1-2 mu m;
step 6: preparing a metal film as a plating seed layer on the surface of the lithium niobate wafer 1, wherein the metal film can be made of titanium or chromium, and the thickness of the film is 10nm to 500 nm;
and 7: manufacturing a photoresist mask with a traveling wave type modulation electrode pattern on the surface of a lithium niobate wafer 1 by adopting a photoetching technology;
and 8: placing the lithium niobate wafer 1 in a gold electroplating solution for electroplating processing to obtain a modulation structure 3 with the thickness of 1-40 μm;
and step 9: removing the photoresist mask of the modulation electrode;
step 10: precisely polishing the input end face and the output end face of the lithium niobate wafer 1;
step 11: and packaging the lithium niobate electro-optical modulator wafer by adopting an optical fiber coupling process and a microelectronic packaging process.
Above-mentioned lithium niobate electrooptical modulator only does the utility model discloses an embodiment, this scheme not only can be applied to phase modulator and intensity modulator, to other types of lithium niobate electrooptical modulator, like polarization controller, polarization switch, scrambler, optical switch, QPSK modulator etc. are suitable for equally. In the lithium niobate electro-optical modulator structure described in the embodiments of the present invention, the structure of the present invention can be used regardless of the presence or absence of the buffer layer film.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A novel lithium niobate electro-optic modulator based on zinc oxide waveguide is characterized by comprising: the device comprises a lithium niobate wafer, a zinc oxide waveguide formed on the surface of the lithium niobate wafer, and a modulation electrode arranged above the surface of the lithium niobate wafer.
2. The novel lithium niobate electro-optic modulator based on zinc oxide waveguide of claim 1, wherein the lithium niobate wafer is optical grade, the crystal tangential direction is X-cut, and the thickness is 0.1mm to 2 mm.
3. The novel lithium niobate electro-optic modulator based on zinc oxide waveguide of claim 1, wherein the zinc oxide waveguide has one of the following two structures:
the first structure is as follows: the zinc oxide waveguide is a straight strip pattern, and the mode field diameter of the waveguide mode is 1-20 μm;
the second structure is as follows: the zinc oxide waveguide is of a Mach-Zehnder interferometer structure, and the mode field diameter of the waveguide mode is 1-20 mu m;
when the zinc oxide waveguide is of a first structure, the modulation electrode comprises a first electrode and a second electrode to form a lumped electrode structure, the adopted metal thin film material is gold, and the thickness of the metal thin film is 0.1-1 μm;
when the zinc oxide waveguide is of a second structure, the modulation electrode comprises a first electrode and a second electrode which is respectively arranged on the left side and the right side of the first electrode to form a push-pull type lumped electrode structure, the adopted metal thin film material is gold, and the thickness of the metal thin film is 0.1-1 μm.
4. A novel lithium niobate electro-optic modulator based on zinc oxide waveguide is characterized by comprising: the device comprises a lithium niobate wafer, a zinc oxide waveguide formed on the surface of the lithium niobate wafer, a modulation electrode arranged above the surface of the lithium niobate wafer, and a buffer layer film arranged between the zinc oxide waveguide and the modulation electrode.
5. The novel lithium niobate electro-optic modulator based on zinc oxide waveguide of claim 4, wherein the lithium niobate wafer is optical grade, the crystal tangential direction is X-cut or Z-cut, and the thickness is 0.1mm to 2 mm.
6. The novel lithium niobate electro-optic modulator based on zinc oxide waveguide of claim 4, wherein the zinc oxide waveguide has one of the following two structures:
the first structure is as follows: the zinc oxide waveguide is a straight strip pattern, and the mode field diameter of the waveguide mode is 1-20 μm;
the zinc oxide waveguide is of a Mach-Zehnder interferometer structure, and the mode field diameter of a waveguide mode is 1-20 mu m;
when the zinc oxide waveguide is of a first structure, the modulation electrode adopts a coplanar traveling wave electrode structure and comprises a signal electrode and two ground electrodes, the adopted metal film material is gold, and the thickness of the metal film is 1-40 mu m;
when the zinc oxide waveguide is of a second structure, the modulation electrode comprises a signal electrode and two ground electrodes respectively arranged on the left side and the right side of the signal electrode to form a push-pull coplanar traveling wave electrode structure, the adopted metal film material is gold, and the thickness of the metal film is 1-40 μm.
7. The novel lithium niobate electro-optical modulator based on zinc oxide waveguide of claim 6,
when the zinc oxide waveguide has a first structure, for an X-cut lithium niobate wafer, in order to utilize the maximum electro-optic coefficient of the lithium niobate crystal, the zinc oxide waveguide is positioned between one of the signal electrode and the ground electrode of the modulation electrode, and the other ground electrode is positioned on the other side of the signal electrode; for the Z-cut lithium niobate wafer, in order to utilize the maximum electro-optic coefficient of the lithium niobate crystal, the zinc oxide waveguide is positioned below the signal electrode of the modulation electrode, and two branches of the ground electrode are respectively positioned on the left side or the right side of the signal electrode.
8. The novel lithium niobate electro-optical modulator based on zinc oxide waveguide of claim 6,
when the zinc oxide waveguide is of a second structure, for an X-cut lithium niobate wafer, in order to utilize the maximum electrooptical coefficient of the lithium niobate crystal, the signal electrodes of the modulation electrode are placed between the inner sides of the two arms of the waveguide of the Mach-Zehnder interferometer structure, and the two ground electrodes are respectively placed on the outer sides of the two arms of the waveguide of the Mach-Zehnder interferometer structure; for the Z-cut lithium niobate wafer, the signal electrode in the modulation electrode is arranged above one of the two arms of the waveguide of the Mach-Zehnder interferometer structure, one of the two ground electrodes is arranged above the other arm of the two arms of the waveguide of the Mach-Zehnder interferometer structure, namely the left side or the right side of the signal electrode, and the other one of the two ground electrodes is correspondingly arranged on the right side or the left side of the signal electrode.
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