CN116908959A - Lithium niobate thin film chip, optical device and coupling method of optical device - Google Patents
Lithium niobate thin film chip, optical device and coupling method of optical device Download PDFInfo
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- CN116908959A CN116908959A CN202310458881.0A CN202310458881A CN116908959A CN 116908959 A CN116908959 A CN 116908959A CN 202310458881 A CN202310458881 A CN 202310458881A CN 116908959 A CN116908959 A CN 116908959A
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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 169
- 230000003287 optical effect Effects 0.000 title claims abstract description 167
- 239000010409 thin film Substances 0.000 title claims abstract description 147
- 238000010168 coupling process Methods 0.000 title claims abstract description 48
- 239000013307 optical fiber Substances 0.000 claims abstract description 219
- 230000008878 coupling Effects 0.000 claims abstract description 32
- 238000005859 coupling reaction Methods 0.000 claims abstract description 32
- 239000000758 substrate Substances 0.000 claims abstract description 12
- 239000000835 fiber Substances 0.000 claims description 28
- 239000000853 adhesive Substances 0.000 claims description 11
- 230000001070 adhesive effect Effects 0.000 claims description 11
- 230000001678 irradiating effect Effects 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 9
- 230000000007 visual effect Effects 0.000 claims description 3
- 238000005516 engineering process Methods 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 57
- 238000010586 diagram Methods 0.000 description 14
- 238000004519 manufacturing process Methods 0.000 description 6
- 238000005530 etching Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 238000004891 communication Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000005684 electric field Effects 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 210000001503 joint Anatomy 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12035—Materials
- G02B2006/1204—Lithium niobate (LiNbO3)
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Optical Couplings Of Light Guides (AREA)
Abstract
The application provides a lithium niobate thin film chip, an optical device and a coupling method of the optical device. Wherein, lithium niobate thin film chip includes: the lithium niobate substrate comprises a substrate layer, a buffer layer and a lithium niobate layer, wherein the buffer layer is arranged above the substrate layer, and the lithium niobate layer is arranged above the buffer layer; the optical waveguide is arranged on the lithium niobate layer, the optical waveguide and the lithium niobate layer are of an integrally formed structure, the optical waveguide comprises a first waveguide section and a second waveguide section connected with the first waveguide section, the second waveguide section is provided with a first end close to the first waveguide section and a second end far away from the first waveguide section, the cross section area of the second waveguide section is gradually increased in the direction from the first end of the second waveguide section to the second waveguide section, and the cross section area of the first waveguide section is the same as the cross section area of the first end of the second waveguide section. The technical scheme of the application can effectively solve the problem of difficult optical coupling of the optical waveguide of the single-mode optical fiber and the lithium niobate thin film chip in the related technology.
Description
Technical Field
The application relates to the field of optical devices, in particular to a lithium niobate thin film chip, an optical device and a coupling method of the optical device.
Background
The lithium niobate crystal has excellent electrooptical, acousto-optic and nonlinear optical properties, wide light transmission window and stable physicochemical properties.
In the related art, the lithium niobate thin film chip is generally obtained through ion implantation and wafer bonding of lithium niobate, has the advantages of large refractive index difference, small volume, high integration level and the like, and has important application prospects in the fields of optical communication, nonlinear optics, sensing and the like.
At present, an optical waveguide is arranged on a lithium niobate thin film chip, and the structure of the optical waveguide is generally ridge-shaped or strip-shaped. In order to ensure single-mode transmission of the lithium niobate thin film optical waveguide, the width of the optical waveguide is in the order of submicron to micron, and the fiber core diameter of a common single-mode optical fiber is in the order of 10 micron. Fig. 1 shows a schematic diagram of the comparison of the cross-sectional area of a single-mode fiber and the cross-sectional area of an optical waveguide, and as can be seen from fig. 1, the single-mode fiber and the lithium niobate thin film optical waveguide differ in size by an order of magnitude. Optical coupling of the two is very difficult.
Disclosure of Invention
The application provides a lithium niobate thin film chip, an optical device and a coupling method of the optical device, which are used for solving the problem of difficult optical coupling of a single-mode optical fiber and an optical waveguide of the lithium niobate thin film chip.
In one aspect, the present application provides a lithium niobate thin film chip comprising: the lithium niobate substrate comprises a substrate layer, a buffer layer and a lithium niobate layer, wherein the buffer layer is arranged above the substrate layer, and the lithium niobate layer is arranged above the buffer layer; the optical waveguide is arranged above the lithium niobate layer in the first direction, the optical waveguide and the lithium niobate layer are of an integrally formed structure, the optical waveguide comprises a first waveguide section and a second waveguide section connected with the first waveguide section, the second waveguide section is provided with a first end close to the first waveguide section and a second end far away from the first waveguide section, the cross section area of the second waveguide section is gradually increased in the direction from the first end of the second waveguide section to the second end of the second waveguide section, and the second end of the second waveguide section is the input end of the lithium niobate thin film chip.
In some embodiments, the second waveguide segment is the same size as the first waveguide segment in a first direction, the second waveguide segment gradually increasing in size in a third direction from a first end of the second waveguide segment to a second end of the second waveguide segment, the third direction being perpendicular to the first direction, the first end of the second waveguide segment being the same size as the cross-section of the first waveguide segment.
In some embodiments, the second waveguide segment includes a reducing segment connected to the first waveguide segment and an extension segment connected to a side of the reducing segment remote from the first waveguide segment, the reducing segment having a cross-sectional area that gradually increases in a direction from a first end of the second waveguide segment to a second end of the second waveguide segment, the extension segment having a cross-sectional area that is the same size as a maximum cross-sectional area of the reducing segment.
In some embodiments, the lithium niobate thin film chip has a first chip end face proximate to the first end of the second waveguide section and a second chip end face proximate to the second end of the second waveguide section, the second chip end face being disposed obliquely with respect to a plane formed by the first direction and the third direction.
In some embodiments, the second chip end face is disposed obliquely in the third direction; alternatively, the second chip end face is disposed obliquely in the first direction.
In another aspect, the application provides an optical device comprising: an optical fiber; and the optical fiber is coupled with the lithium niobate thin film chip, wherein the lithium niobate thin film chip is the lithium niobate thin film chip.
In some embodiments, the optical fiber includes a single-mode optical fiber and an ultra-high numerical aperture optical fiber connected to the single-mode optical fiber, an end of the ultra-high numerical aperture optical fiber being disposed in coupling relation with the lithium niobate thin film chip.
In another aspect, the present application provides a coupling method of an optical device, where the coupling method of an optical device is used for coupling the optical device, and the coupling method of an optical device includes: clamping an optical fiber array made of a plurality of optical fibers on a first position adjusting device, and clamping a lithium niobate thin film chip on a second position adjusting device; adjusting the position of the optical fiber array to enable the end face of the optical fiber array and the end face of the second chip of the lithium niobate thin film chip to be positioned in the visual field range of the first microscope in the first direction; positioning the end face of the optical fiber array and the end face of the second chip in a third direction within a field of view of the second microscope; performing a preliminary adjustment of the position of the fiber array, the preliminary adjustment comprising: firstly, adjusting an included angle between the optical fiber array and the lithium niobate thin film chip, and then adjusting coaxiality between the optical fiber array and between the optical fiber array and the lithium niobate thin film chip; performing secondary adjustment on the position of the optical fiber array, wherein the amplitude of the secondary adjustment is smaller than that of the primary adjustment; and fixing the optical fiber array and the lithium niobate thin film chip after secondary adjustment.
In some embodiments, the step of adjusting the angle between the fiber array and the lithium niobate thin film chip comprises: opening a coaxial point light source on the first microscope, and adjusting the focal length of the first microscope to enable the first microscope to focus on the second waveguide section; observing the optical fiber array through a first microscope, and adjusting the optical fiber array and the lithium niobate thin film chip so that the optical fiber array and the lithium niobate thin film chip are parallel to planes formed by the second direction and the third direction, the second direction and the first direction are mutually perpendicular; and observing the optical fiber array through a second microscope, and adjusting the optical fiber array and the lithium niobate thin film chip so that the optical fiber array and the lithium niobate thin film chip are parallel to planes formed by the first direction and the second direction.
In some embodiments, the step of adjusting the coaxiality between the fiber array and the lithium niobate thin film chip comprises: closing a coaxial point light source of the first microscope, opening an annular light source of the first microscope, and then irradiating a tail fiber of the optical fiber by using a light pen; observing the optical fiber array through a first microscope, and adjusting the optical fiber array along a third direction to enable an optical path emitted from the optical fiber array to irradiate on the end face of the optical waveguide of the lithium niobate thin film chip; adjusting the optical fiber array along the second direction, and stopping adjusting the optical fiber array along the second direction when a bright light path is formed between the end face of the optical fiber array and the end face of the second chip; turning off the annular light source of the first microscope and turning on the coaxial point light source of the first microscope, and then adjusting the focal length of the first microscope under the maximum magnification of the first microscope so as to focus the first microscope on the second waveguide section; and observing the optical fiber array through a first microscope, adjusting the optical fiber array along the first direction and the third direction, and stopping adjusting when the brightness of the light path injected into the optical waveguide is maximum.
In some embodiments, the step of secondarily adjusting the position of the fiber array comprises: irradiating the tail fiber of the optical fiber through a light source applied by an optical device, and measuring the power of the output end of the optical waveguide by using an optical power meter; adjusting the optical fiber array along a first direction and a third direction, and stopping adjusting when the reading of the optical power meter is maximum; adjusting the optical fiber array along the second direction to enable the end face of the optical fiber array to be in contact fit with the end face of the second chip; the fiber array is adjusted in a first direction and a third direction, and the adjustment is stopped when the reading of the optical power meter is maximum.
In some embodiments, the step of securing the optical fiber array and the lithium niobate thin film chip includes: the point light source of the first microscope is in an open state, the annular light source of the first microscope is in a closed state, the optical fiber array is observed through the first microscope, and the optical fiber adhesive is coated between the optical fiber array and the end face of the second chip; the optical fiber adhesive is cured by irradiating the optical fiber adhesive with an ultraviolet lamp.
The lithium niobate thin film chip provided by the application comprises a substrate layer, a buffer layer, a lithium niobate layer and an optical waveguide which are sequentially arranged from bottom to top in a first direction, wherein the optical waveguide is of a single-layer structure and is of an integrated structure with the lithium niobate layer. The optical waveguide includes a first waveguide segment and a second waveguide segment connected to the first waveguide segment, the second waveguide segment having a first end proximal to the first waveguide segment and a second end distal from the first waveguide segment, the second waveguide segment having a cross-sectional area that gradually increases in a direction from the first end of the second waveguide segment to the second waveguide segment. The second end of the second waveguide section can be coupled with the optical fiber, and the difficulty of optical coupling between the optical fiber and the optical waveguide can be reduced and the optical coupling efficiency of the optical fiber and the optical waveguide can be improved because the cross section area of the second end of the second waveguide section is larger. In addition, compared with the double-layer ridge-shaped optical waveguide structure in the related art, the optical waveguide processing mode of the lithium niobate thin film chip is simpler, a covering layer is not required to be added above the optical waveguide, and the processing technology of the lithium niobate thin film chip is further simplified.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.
FIG. 1 is a schematic diagram of an alignment of a single mode fiber cross-sectional area and an optical waveguide cross-sectional area;
FIG. 2 is a schematic diagram of a related art spot-size converter of a chip;
FIG. 3 is a cross-sectional view in the A-A direction of the spot-size converter of FIG. 2;
fig. 4 is a schematic perspective view of a lithium niobate thin film chip according to an embodiment of the present application;
FIG. 5 is a view in the x-direction of the lithium niobate thin film chip provided in FIG. 4 of the present application;
FIG. 6 is a B-B cross-sectional view of the lithium niobate thin film chip provided in FIG. 4 of the present application;
FIG. 7 is a C-C cross-sectional view of the lithium niobate thin film chip of FIG. 4 of the present application;
FIG. 8 is a D-D cross-sectional view of the lithium niobate thin film chip provided in FIG. 4 of the present application;
FIG. 9 is a z-direction view of the lithium niobate thin film chip provided in FIG. 4 of the present application;
fig. 10 is a schematic structural diagram of a lithium niobate thin film chip according to a second embodiment of the present application;
fig. 11 is a schematic perspective view of a lithium niobate thin film chip according to a third embodiment of the present application;
fig. 12 is a schematic structural diagram of an optical device according to an embodiment of the present application, where fig. 12 shows a schematic structural diagram of a single optical fiber coupled to a lithium niobate thin film chip;
fig. 13 is a schematic structural diagram of an optical device according to an embodiment of the present application, where fig. 13 shows a schematic structural diagram of an optical fiber array coupled to a lithium niobate thin film chip;
fig. 14 is a flowchart of a coupling method of an optical device according to an embodiment of the present application.
Reference numerals illustrate:
1-a first chip end face; 2-a second chip end face;
10-a substrate layer;
20-a buffer layer;
a layer of 30-lithium niobate;
40-optical waveguide; 41-a first waveguide segment; 42-a second waveguide segment; 421-extension; 422-reducing section;
a 50-lithium niobate thin film chip;
60-optical fiber; 61-single mode optical fiber; 62-ultra-high numerical aperture fiber;
70-an optical fiber array;
81-a cover layer; 82-a ridge optical waveguide structure; 821-a first optical waveguide layer; 822-a second optical waveguide layer.
Specific embodiments of the present application have been shown by way of the above drawings and will be described in more detail below. The drawings and the written description are not intended to limit the scope of the inventive concepts in any way, but rather to illustrate the inventive concepts to those skilled in the art by reference to the specific embodiments.
Detailed Description
Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present application and should not be construed as limiting the application.
In the description of the present application, it should be understood that the terms "center," "longitudinal," "length," "width," "upper," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be configured and operated in a particular orientation, and thus should not be construed as limiting the present application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are 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 the present application, unless explicitly specified and limited otherwise, the terms "mounted," "secured," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present application, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
In the description of the present specification, reference to the terms "optionally," "alternative embodiments," and the like, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Currently, the lithium niobate thin film chip 50 is provided with an optical waveguide 40, and the optical waveguide 40 is generally in a ridge shape or a stripe shape. To ensure single mode transmission of the lithium niobate thin film optical waveguide 40, the optical waveguide 40 has a width on the order of submicron to micron, whereas the core diameter of the ordinary single mode optical fiber 61 is on the order of 10 micron, which is an order of magnitude different from the size of the lithium niobate thin film optical waveguide 40. Therefore, optical coupling of the two is very difficult.
In the related art, a chip is designed to solve the above problems.
Fig. 2 is a schematic structural view of a related art spot-size converter of a chip, and fig. 3 is a cross-sectional view of the spot-size converter of fig. 2 in A-A direction.
As shown in fig. 2 and 3, the related art spot-size converter may be divided into a three-layer structure, and in particular, the spot-size converter includes a planar layer located at a bottom layer, a ridge optical waveguide structure 82 located above the planar layer, and a cover layer 81 covering the ridge optical waveguide layer, wherein the ridge optical waveguide structure 82 has a two-layer structure including a first optical waveguide layer 821 located below in an x-direction and a second optical waveguide layer 822 located above the first optical waveguide layer 821 in the x-direction. The first optical waveguide layer 821 has a larger dimension in the z-direction and in the y-direction than the second optical waveguide layer 822. The first end of the first optical waveguide layer 821 has a smaller dimension in the z-direction than the second end of the first optical waveguide layer 821, and likewise, the first end of the second optical waveguide layer 822 has a smaller dimension in the z-direction than the second end of the second optical waveguide layer 822. The ends of the spot-size converter near the first end of the first optical waveguide layer 821 and the first end of the second optical waveguide layer 822 are used to connect the single-mode optical fiber 61. Such a structure in which the cross-sectional area of the ridge optical waveguide structure 82 gradually increases in the conduction direction of the optical path is referred to as an "inverted cone optical waveguide structure".
The mode spot converter with the inverted cone-shaped optical waveguide structure can expand the waveguide light spots, so that the horizontal coupling efficiency is improved, and the coupling loss is reduced. By adopting the structure, the insertion loss of TE/TM mode at 1550nm is 0.54 dB and 0.59dB respectively.
However, the above structure has the disadvantage of complex manufacturing process, and the double-layer inverted cone-shaped spot-size converter is often manufactured by at least two etching steps, wherein the first etching step is used for manufacturing the ridge-shaped optical waveguide structure 82, the second etching step is used for manufacturing the flat plate layer, and the SiON coating layer 81 is also manufactured on the whole chip by Plasma Enhanced Chemical Vapor Deposition (PECVD) after etching. Moreover, due to the limitation of the manufacturing process, the tip width of the lower-layer inverse taper structure is difficult to be small enough and accurate enough, a series of tip widths from 0.26 μm to 0.46 μm are required to be manufactured firstly, the tip width with the best test result is selected after one-to-one test, and the workload of manufacturing and testing is increased.
In order to solve the problems of the lithium niobate thin film chip 50 in the related art, the present application provides a lithium niobate thin film chip 50.
For convenience of description, the first, second and third directions are referred to as x, y and z directions in the drawings. The z direction, the x direction, the y direction and the z direction are perpendicular to each other
Fig. 4 is a schematic perspective view of a lithium niobate thin film chip according to an embodiment of the present application; FIG. 5 is a view in the x-direction of the lithium niobate thin film chip provided in FIG. 4 of the present application; FIG. 6 is a B-B cross-sectional view of the lithium niobate thin film chip provided in FIG. 4 of the present application; FIG. 7 is a C-C cross-sectional view of the lithium niobate thin film chip of FIG. 4 of the present application; FIG. 8 is a D-D cross-sectional view of the lithium niobate thin film chip 50 provided in FIG. 4 of the present application; fig. 9 is a z-direction view of the lithium niobate thin film chip provided in fig. 4 according to the present application.
As shown in fig. 4 and 9, the lithium niobate thin film chip 50 of the first embodiment includes: substrate layer 10, buffer layer 20, lithium niobate layer 30, and optical waveguide 40.
Wherein the substrate layer 10, the buffer layer 20, and the lithium niobate layer 30 are sequentially disposed from bottom to top in the x-direction. The optical waveguide 40 is disposed above the lithium niobate layer 30 in the x-direction, the optical waveguide 40 and the lithium niobate layer 30 are integrally formed, the optical waveguide 40 includes a first waveguide section 41 and a second waveguide section 42 connected to the first waveguide section 41, the second waveguide section 42 has a first end close to the first waveguide section 41 and a second end far from the first waveguide section 41, the cross-sectional area of the second waveguide section 42 gradually increases in a direction from the first end of the second waveguide section 42 to the second end of the second waveguide section 42, and the second end of the second waveguide section 42 is an input end of the lithium niobate thin film chip 50.
The lithium niobate thin film chip 50 of the present embodiment includes a substrate layer 10, a buffer layer 20, a lithium niobate layer 30, and an optical waveguide 40, which are sequentially disposed from bottom to top in the x-direction, the optical waveguide 40 being of a single-layer structure and being of an integrally formed structure with the lithium niobate layer 30. The optical waveguide 40 includes a first waveguide section 41 and a second waveguide section 42 connected to the first waveguide section 41, the second waveguide section 42 having a first end close to the first waveguide section 41 and a second end distant from the first waveguide section 41, the cross-sectional area of the second waveguide section 42 gradually increasing in a direction from the first end of the second waveguide section 42 to the second waveguide section 42. The second end of the second waveguide segment 42 may be coupled to the optical fiber 60, and because the cross-sectional area of the second end of the second waveguide segment 42 is larger, the difficulty in optical coupling between the optical fiber 60 and the optical waveguide 40 can be reduced, and the efficiency in optical coupling between the optical fiber 60 and the optical waveguide 40 can be improved. In addition, compared with the double-layer ridge-shaped optical waveguide structure 82 shown in fig. 2, the optical waveguide 40 of the lithium niobate thin film chip 50 of the embodiment is simpler in processing mode, and the cover layer 81 does not need to be added above the optical waveguide 40, so that the processing technology of the lithium niobate thin film chip 50 is further simplified.
The structure of the optical waveguide 40 in the first embodiment may be referred to as a "forward tapered optical waveguide structure" which refers to a structure in which the cross-sectional area of the optical waveguide 40 gradually decreases in the direction of propagation of the optical path.
In other embodiments, the optical waveguide 40 of the first embodiment may be used to design a spot-size converter, and the spot-size converter may include only the lithium niobate layer 30 and the optical waveguide 40.
Specifically, the width of the first waveguide section 41 is between 600nm and 2 μm, the width of the second end of the second waveguide section 42 is between 2.5 μm and 4 μm, and preferably the width of the second end of the second waveguide section 42 is 3.5 μm.
As shown in fig. 4 to 9, in the first embodiment, the second waveguide section 42 is the same as the first waveguide section 41 in the x-direction, the second waveguide section 42 gradually increases in size in the z-direction in a direction from the first end of the second waveguide section 42 to the second end of the second waveguide section 42, and the first end of the second waveguide section 42 is the same as the cross-section of the first waveguide section 41. In the above structure, the second end of the second waveguide segment 42 is the input end of the optical waveguide 40, and the first end of the first waveguide segment 41 is the output end of the optical waveguide 40, and since the cross-sectional area of the input end of the optical waveguide 40 is larger than that of the output end of the optical waveguide 40, the optical fiber 60 is easier in optical coupling of the optical waveguide 40, and accordingly, the coupling efficiency is higher and the loss is smaller.
As shown in fig. 4 to 9, in the first embodiment, the second waveguide section 42 includes the variable diameter section 422 and the extension section 421, the variable diameter section 422 is connected to the first waveguide section 41, the extension section 421 is connected to a side of the variable diameter section 422 away from the first waveguide section 41, and the cross-sectional area of the variable diameter section 422 is gradually increased in a direction from the first end of the second waveguide section 42 to the second end of the second waveguide section 42, and the cross-sectional area of the extension section 421 is the same as the maximum cross-sectional area size of the variable diameter section 422. In the above-described structure, the size of the lithium niobate thin film chip 50 in the y-direction can be increased by providing the third waveguide section, thereby improving the versatility of the lithium niobate thin film chip 50.
The present application also provides a second embodiment of a lithium niobate thin film chip 50.
Fig. 10 is a schematic structural diagram of a lithium niobate thin film chip 50 according to a second embodiment of the present application;
as shown in fig. 10, the lithium niobate thin film chip 50 of the embodiment differs from the lithium niobate thin film chip 50 of the embodiment one in that: the second chip end face 2 of the lithium niobate thin film chip 50 is different in structure.
In the second embodiment, the lithium niobate thin film chip 50 has the first chip end face 1 near the first end of the second waveguide section 42 and the second chip end face 2 near the second end of the second waveguide section 42, the second chip end face 2 being disposed obliquely.
Specifically, as shown in fig. 10, in the second embodiment, the second chip end face 2 is disposed obliquely in the z direction;
according to the refractive index of the material and the fresnel formula, an inclination angle of 8-12 degrees with the xz plane can be formed on the end face 2 of the second chip through grinding and polishing, and accordingly, the end face of the coupled optical fiber 60 is also processed into a structure parallel to the end face 2 of the second chip, and the arrangement mode can reduce reflection loss of the end face and improve coupling efficiency.
The angle between the second chip end face 2 and the xz plane may be 8 °, 9 °, 10 °, 11 °, or 12 °.
The present application also provides a third embodiment of the lithium niobate thin film chip 50.
Fig. 11 is a schematic structural diagram of a lithium niobate thin film chip 50 according to a third embodiment of the present application;
as shown in fig. 11, the lithium niobate thin film chip 50 of the embodiment differs from the lithium niobate thin film chip 50 of the embodiment three in that: the second chip end face 2 of the lithium niobate thin film chip 50 is different in inclination direction.
Specifically, the second chip end face 2 is disposed obliquely in the x direction. The effect of this oblique direction is the same as the effect of the oblique arrangement of the second chip end face 2 in the z-direction.
The application also provides an optical device.
Fig. 12 is a schematic structural diagram of an optical device according to an embodiment of the present application, in which fig. 12 shows a schematic structural diagram of a single optical fiber 60 coupled to a lithium niobate thin film chip 50, and fig. 13 is a schematic structural diagram of an optical device according to an embodiment of the present application, in which fig. 13 shows a schematic structural diagram of an optical fiber array 70 coupled to a lithium niobate thin film chip 50.
As shown in fig. 12 and 13, the optical device includes an optical fiber 60 and a lithium niobate thin film chip 50, wherein the lithium niobate thin film chip 50 is the above-described lithium niobate thin film chip 50.
Specifically, as shown in fig. 12, in the present embodiment, the optical fiber 60 includes a single-mode optical fiber 61 and an ultra-high numerical aperture optical fiber 62 connected to the single-mode optical fiber 61, and an end of the ultra-high numerical aperture optical fiber 62 is disposed in coupling with the lithium niobate thin film chip 50.
The ultra-high numerical aperture optical fiber 62 has a numerical aperture of between 0.2 and 0.6, and the ultra-high numerical aperture optical fiber 62 has a mode field diameter of between 2.5 μm and 3.5 μm, and the ultra-high numerical aperture optical fiber 62 can be efficiently coupled with the ordinary single-mode optical fiber 61 having a mode field diameter of 10 μm by fusion bonding.
Preferably, in this embodiment, the ultra-high numerical aperture fiber 62 has a numerical aperture of 0.41, a mode field diameter of between 2.9 μm and 3.5 μm, and a mode field diameter of the single mode fiber 61 of 9.6 μm.
In particular, optical coupling requires that the size and shape of the two mode fields being coupled be similar. The mode field matching factor of fiber 60 and optical waveguide 40 is represented by the overlap integral of the mode fields of the two. The method comprises the following steps:
wherein E is 1 E is the complex electric field of the optical fiber 60 2 For the complex electric field of the optical waveguide 40, S is the integrated area of the region where the optical mode field is located, eta is the overlap integral factor of the optical mode field of the optical fiber 60 and the waveguide,
the larger η indicates the more matched the optical mode fields of the optical fiber 60 and the optical waveguide 40, the higher the coupling efficiency; the smaller η, the opposite.
The application provides a coupling method of an optical device.
Fig. 14 is a flowchart of a coupling method of an optical device according to an embodiment of the present application.
As shown in fig. 14, the coupling method of the optical device is used for coupling the optical device, and the coupling method of the optical device includes:
step S100: manufacturing a plurality of optical fibers 60 into an optical fiber array 70, clamping the optical fiber array on a first position adjusting device, and clamping a lithium niobate thin film chip 50 on a second position adjusting device;
step S200: adjusting the position of the optical fiber array 70 so that the end face of the optical fiber array 70 and the second chip end face 2 of the lithium niobate thin film chip 50 are located within the field of view of the first microscope in the x direction; positioning the end face of the fiber array 70 and the second chip end face 2 in the z-direction within the field of view of the second microscope;
step S300: preliminary adjustments are made to the position of the fiber array 70, including: step S310: adjusting the angle between the optical fiber array 70 and the lithium niobate thin film chip 50; step S320: the coaxiality between the optical fiber array 70 and the lithium niobate thin film chip 50 is adjusted.
Step S400: performing a secondary adjustment of the position of the fiber array 70, the secondary adjustment having a smaller amplitude than the primary adjustment;
step S500: the optical fiber array 70 and the lithium niobate thin film chip 50 are fixed.
Specifically, in step S100, the optical fibers 60 in the optical device are generally arranged in the form of an optical fiber array 70, where the optical fiber array 70 has a plurality of optical fibers 60, and the lithium niobate thin film chip 50 is provided with optical waveguides 40 corresponding to the plurality of optical fibers 60 one by one.
The first position adjusting device is a six-axis optical fiber 60 adjusting frame, and can adjust the position and angle of the optical fiber array 70 by adjusting the six-axis optical fiber 60 adjusting frame. The second position adjusting device is a displacement table.
In step S200, the end face of the optical fiber array 70 and the second chip end face 2 of the lithium niobate thin film chip 50 are observed by providing two microscopes, specifically, the first microscope is capable of observing the end face of the optical fiber array 70 and the second chip end face 2 in the x direction, and observing the optical fiber array 70 and the lithium niobate thin film chip 50 in the x direction is advantageous for observing the coaxiality of the optical fiber array 70 and the lithium niobate thin film chip 50. The second microscope is capable of viewing the end face of the optical fiber array 70 and the second chip end face 2 in the z-direction, and viewing the optical fiber array 70 and the lithium niobate thin film chip 50 in the z-direction is advantageous for viewing the angle between the optical fiber array 70 and the lithium niobate thin film chip 50.
It should be noted that, in step S300, step S310 is performed before step S320, that is, the included angle between the optical fiber array 70 and the lithium niobate thin film chip 50 is adjusted, and then the coaxiality between the optical fiber array 70 and the lithium niobate thin film chip 50 is adjusted, so that the design has the advantages that: after the included angle between the optical fiber array 70 and the lithium niobate thin film chip 50 is adjusted, the bonding between the end face of the optical fiber array 70 and the end face 2 of the second chip is facilitated, and the subsequent coaxiality adjustment of the optical fiber array 70 and the lithium niobate thin film chip 50 can be performed more easily. If the coaxiality between the two is adjusted first and then the included angle between the two is adjusted, the coaxiality between the two needs to be calibrated after the included angle adjustment is completed, and the complexity of the coupling step is increased.
It should be noted that, in the above method, the optical coupling efficiency and the adjustment speed of the optical fiber array 70 and the lithium niobate thin film chip 50 can be improved by first performing the primary adjustment on the position of the optical fiber array 70 and then performing the secondary adjustment on the position of the optical fiber array 70.
Further, as shown in fig. 1, in the present embodiment, step S310 includes:
step S311: turning on the coaxial point light source on the first microscope, adjusting the focal length of the first microscope to focus the first microscope onto the second waveguide segment 42;
step S312: observing the optical fiber array 70 through a first microscope, and adjusting the optical fiber array 70 and the lithium niobate thin film chip 50 so that the optical fiber array 70 and the lithium niobate thin film chip 50 are parallel to the yz plane;
step S313: the optical fiber array 70 and the lithium niobate thin film chip 50 were adjusted so that the optical fiber array 70 and the lithium niobate thin film chip 50 were both parallel to the xy plane by observing the optical fiber array 70 with a second microscope.
Specifically, the first microscope and the second microscope are provided with a coaxial point light source and an annular light source, and the coaxial point light source has stronger convergence, higher brightness and smaller visual field compared with the annular light source.
In step S311, the coaxial point light source on the first microscope is turned on, and the focal length of the first microscope is adjusted to focus the first microscope on the second waveguide segment 42, so that the operator can more clearly observe the upper surface of the optical fiber array 70 and the upper surface of the second waveguide segment 42, thereby facilitating the adjustment of the position of the optical fiber array 70 by the operator.
In step S312, the optical fiber array 70 is observed by the first microscope, and the optical fiber array 70 and the lithium niobate thin film chip 50 are adjusted so that the optical fiber array 70 and the lithium niobate thin film chip 50 are parallel to the yz plane, so that the end face of the optical fiber array 70 and the end face 2 of the second chip are parallel to each other, so that the subsequent butt joint of the two is facilitated.
In step S313, the optical fiber array 70 is observed by the first microscope, and the optical fiber array 70 and the lithium niobate thin film chip 50 are adjusted so that the optical fiber array 70 and the lithium niobate thin film chip 50 are both parallel to the xy plane, so that the top and bottom surfaces of the optical fiber array 70 can be parallel to the top and bottom surfaces of the lithium niobate thin film chip 50, respectively.
The order of step S312 and step S313 may be changed.
Further, in the present embodiment, step S320 includes:
step S321: turning off the coaxial point light source of the first microscope, turning on the annular light source of the first microscope, and irradiating the tail fiber of the optical fiber 60 by using a light pen;
step S322: observing the optical fiber array 70 through a first microscope, and adjusting the optical fiber array 70 along the z direction so that the light path emitted from the optical fiber array 70 irradiates the end face of the optical waveguide 40 of the lithium niobate thin film chip 50;
step S323: adjusting the optical fiber array 70 along the y direction, and stopping adjusting the optical fiber array 70 along the y direction when a bright light path is formed between the end face of the optical fiber array 70 and the end face 2 of the second chip;
step S324: turning off the annular light source of the first microscope, turning on the coaxial point light source of the first microscope, adjusting the magnification of the first microscope to the maximum, and adjusting the focal length of the first microscope to focus the first microscope onto the second waveguide segment 42;
step S325: the on-axis point light source of the first microscope is turned off, the ring light source of the first microscope is turned on, the optical fiber array 70 is observed through the first microscope, the optical fiber array 70 is adjusted in the x-direction and the z-direction, and the adjustment is stopped when the brightness of the light path incident into the optical waveguide 40 is maximized.
Specifically, the light pen can emit red light, and since the optical fiber array 70 is made of glass and is transparent in color, the position of the head of the optical fiber 60 transmitting red light can be easily observed.
In step S323, when a bright red light path is formed between the end face of the optical fiber array 70 and the second chip end face 2, it is indicated that the distance between the optical fiber array 70 and the lithium niobate thin film chip 50 in the x direction preliminarily satisfies the requirement, and the distance between the optical fiber array 70 and the lithium niobate thin film chip 50 in the y direction is about hundred micrometers.
After step S323 is completed, focusing operation is performed on the first microscope again through step S324, so that the first microscope is focused on the second waveguide section 42, the optical fiber array 70 is adjusted along the x-direction and the z-direction, and when the brightness of the light path incident into the optical waveguide 40 is maximum, the preliminary adjustment is indicated to be completed.
Further, in the present embodiment, step S400 includes:
step S410: irradiating the tail fiber of the optical fiber 60 by a light source applied by an optical device, and measuring the power of the output end of the optical waveguide 40 by an optical power meter;
step S420: adjusting the fiber array 70 in the x-direction and z-direction, stopping adjustment when the optical power meter reading is maximum;
step S430: adjusting the optical fiber array 70 along the y direction so that the end face of the optical fiber array 70 is in contact fit with the end face 2 of the second chip, wherein the contact fit means that the end face of the optical fiber array 70 is only in contact with the end face 2 of the second chip, but not compressed;
step S440: the fiber array 70 is adjusted in the x-direction and the z-direction, and when the reading of the optical power meter is maximum, the adjustment is stopped, and then the end face of the fiber array 70 is pressed against the end face 2 of the second chip.
In the above manner, the optical device uses the light source to illuminate the pigtail of the optical fiber 60, measures the power at the output end of the optical waveguide 40 with the optical power meter, and adjusts the position of the optical fiber array 70 according to the reading change of the optical power.
Specifically, the fiber array 70 is first adjusted in the x-direction and z-direction, and the adjustment is stopped when the reading of the optical power meter is maximum; then the optical fiber array 70 is adjusted along the y direction, so that the end face of the optical fiber array 70 is contacted and matched with the end face 2 of the second chip; finally, the optical fiber array 70 is finally adjusted along the x direction and the z direction according to the reading of the power meter, and the adjustment is stopped until the reading of the optical power meter is maximum, and the step of secondary adjustment is completed.
Further, in the present embodiment, step S500 includes:
step S510: the point light source of the first microscope is in an on state, the annular light source of the first microscope is in an off state, the optical fiber array 70 is observed through the first microscope, and the optical fiber adhesive is coated between the optical fiber array 70 and the second chip end face 2;
step S520: the optical fiber adhesive is cured by irradiating the optical fiber adhesive with an ultraviolet lamp.
In the above steps, since the refractive index of the optical fiber adhesive is between the refractive index of the optical fiber 60 (made of silicon dioxide) and the refractive index of the lithium niobate, the refractive index matching effect can be achieved, the reflection loss of the end surfaces of the optical fiber 60 and the optical waveguide 40 is reduced, the coupling efficiency is improved, and the optical power is rapidly increased after the adhesive is dispensed in the corresponding coupling process.
If the first chip end face 1 of the lithium niobate thin film chip 50 is further provided with the output optical fiber array 70, the coupling method between the output optical fiber array 70 and the lithium niobate thin film chip 50 is the same as the above method.
Of course, the second end of the lithium niobate thin film chip 50 may also serve as both an input end and an output end, specifically, a part of the optical fibers in the optical fiber array serve as input optical fibers, and another part of the optical fibers in the optical fiber array serve as output optical fibers, and input and output of the optical path are realized by a single optical fiber array.
The coupling method of the optical device is adopted, the position of the lithium niobate thin film chip 50 is unchanged, the position of the optical fiber array 70 is adjusted to enable the optical fiber array 70 to be coupled with the on-chip optical waveguide 40, the angle and the coaxiality of the optical fiber array 70 and the lithium niobate thin film chip 50 are observed in multiple angles through the arrangement of two microscopes, and guarantee is provided for accurate coupling of the optical fiber array 70 and the lithium niobate thin film chip 50.
It should be noted that, after the coupling of the optical fiber array 70 and the lithium niobate thin film chip 50 is completed, the optical fiber array and the lithium niobate thin film chip must be packaged, the packaging adopts a tube shell with round holes at two ends, the optical fiber is penetrated, and the optical fiber flange and the optical fiber sheath matched with the round holes are used for supporting and fixing the optical fiber at two sides of the tube shell, so as to ensure the mechanical stability of the coupling position of the optical fiber and the waveguide. The total insertion loss of the coupled and packaged optical device reaches 10dB.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced with equivalents; such modifications and substitutions do not depart from the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.
Claims (12)
1. A lithium niobate thin film chip, comprising:
the substrate layer, the buffer layer and the lithium niobate layer are sequentially arranged from bottom to top in the first direction;
the lithium niobate thin film chip comprises a lithium niobate thin film chip, and is characterized in that the lithium niobate thin film chip is provided with a lithium niobate thin film chip, and the lithium niobate thin film chip is provided with a first end, a second end, a first end and a second end, and the second end is connected with the lithium niobate thin film chip.
2. The lithium niobate thin film chip of claim 1, wherein the second waveguide segment has the same size as the first waveguide segment in a first direction, the second waveguide segment having a size that gradually increases in a direction from a first end of the second waveguide segment to a second end of the second waveguide segment, the third direction being perpendicular to the first direction, the first end of the second waveguide segment having the same size as a cross-section of the first waveguide segment.
3. The lithium niobate thin film chip of claim 1, wherein the second waveguide section includes a reducing section connected to the first waveguide section and an extension section connected to a side of the reducing section away from the first waveguide section, a cross-sectional area of the reducing section gradually increasing in a direction from a first end of the second waveguide section to a second end of the second waveguide section, and a cross-sectional area of the extension section is the same as a maximum cross-sectional area size of the reducing section.
4. The lithium niobate thin film chip of claim 2, wherein the lithium niobate thin film chip has a first chip end face near a first end of the second waveguide section and a second chip end face near a second end of the second waveguide section, the second chip end face being disposed obliquely with respect to a plane formed by the first direction and the third direction.
5. The lithium niobate thin film chip according to claim 4, wherein,
the second chip end face is obliquely arranged in a third direction;
alternatively, the second chip end face is obliquely arranged in the first direction.
6. An optical device, comprising:
an optical fiber;
a lithium niobate thin film chip, the optical fiber being disposed in coupling with a second waveguide segment of the lithium niobate thin film chip, wherein the lithium niobate thin film chip is the lithium niobate thin film chip of any of claims 1 to 5.
7. The optical device of claim 6, wherein the optical device comprises,
the optical fiber comprises a single-mode optical fiber and an ultra-high numerical aperture optical fiber connected with the single-mode optical fiber, and the end part of the ultra-high numerical aperture optical fiber is coupled with the lithium niobate thin film chip.
8. A method of coupling an optical device for coupling the optical device of claim 6 or 7, the method comprising:
clamping an optical fiber array made of a plurality of optical fibers on a first position adjusting device, and clamping the lithium niobate thin film chip on a second position adjusting device;
adjusting the position of the optical fiber array, so that the end face of the optical fiber array and the end face of the second chip of the lithium niobate thin film chip are positioned in the visual field range of the first microscope in the first direction; positioning the end face of the optical fiber array and the end face of the second chip in a third direction within a field of view of a second microscope;
performing a preliminary adjustment of the position of the fiber array, the preliminary adjustment comprising: firstly adjusting an included angle between the optical fiber array and the lithium niobate thin film chip, and then adjusting coaxiality between the optical fiber array and between the optical fiber array and the lithium niobate thin film chip;
performing secondary adjustment on the position of the optical fiber array, wherein the amplitude of the secondary adjustment is smaller than that of the primary adjustment;
and fixing the optical fiber array and the lithium niobate thin film chip after secondary adjustment.
9. The method of coupling an optical device according to claim 8, wherein the step of adjusting an angle between the optical fiber array and the lithium niobate thin film chip comprises:
opening a coaxial point light source on the first microscope, and adjusting the focal length of the first microscope to focus the first microscope on a second waveguide segment;
observing the optical fiber array through the first microscope, and adjusting the optical fiber array and the lithium niobate thin film chip so that the optical fiber array and the lithium niobate thin film chip are parallel to planes formed by a second direction and a third direction, wherein the third direction, the second direction and the first direction are mutually perpendicular;
and observing the optical fiber array through the second microscope, and adjusting the optical fiber array and the lithium niobate thin film chip so that the optical fiber array and the lithium niobate thin film chip are parallel to planes formed by the first direction and the second direction.
10. The method of coupling an optical device according to claim 8, wherein the step of adjusting coaxiality between the optical fiber array and the lithium niobate thin film chip comprises:
closing a coaxial point light source of the first microscope, opening an annular light source of the first microscope, and then irradiating a tail fiber of the optical fiber by using a light pen;
observing the optical fiber array through the first microscope, and adjusting the optical fiber array along a third direction to enable an optical path emitted in the optical fiber array to irradiate on the end face of the optical waveguide of the lithium niobate thin film chip;
adjusting the optical fiber array along a second direction, and stopping adjusting the optical fiber array along the second direction when a bright light path is formed between the end face of the optical fiber array and the end face of the second chip;
turning off the annular light source of the first microscope and turning on the coaxial point light source of the first microscope, and then adjusting the focal length of the first microscope at the maximum magnification of the first microscope so as to focus the first microscope on the second waveguide segment;
and observing the optical fiber array through the first microscope, adjusting the optical fiber array along a first direction and a third direction, and stopping adjusting when the brightness of the light path injected into the optical waveguide is maximum.
11. The method of coupling an optical device of claim 8, wherein the step of secondarily adjusting the position of the optical fiber array comprises:
irradiating the tail fiber of the optical fiber through a light source applied by the optical device, and measuring the power of the output end of the optical waveguide by using an optical power meter;
adjusting the optical fiber array along a first direction and a third direction, and stopping adjusting when the reading of the optical power meter is maximum;
adjusting the optical fiber array along a second direction to enable the end face of the optical fiber array to be in contact fit with the end face of the second chip;
the fiber array is adjusted in a first direction and a third direction, and the adjustment is stopped when the reading of the optical power meter is maximum.
12. The method of coupling an optical device according to claim 8, wherein the step of fixing the optical fiber array and the lithium niobate thin film chip comprises:
the point light source of the first microscope is in an on state, the annular light source of the first microscope is in an off state, the optical fiber array is observed through the first microscope, and the optical fiber adhesive is coated between the optical fiber array and the end face of the second chip;
the optical fiber adhesive is cured by irradiating the optical fiber adhesive with an ultraviolet lamp.
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| CN202310458881.0A CN116908959A (en) | 2023-04-25 | 2023-04-25 | Lithium niobate thin film chip, optical device and coupling method of optical device |
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