CN114035268B - Optical cross waveguide unit - Google Patents
Optical cross waveguide unit Download PDFInfo
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- CN114035268B CN114035268B CN202111550624.7A CN202111550624A CN114035268B CN 114035268 B CN114035268 B CN 114035268B CN 202111550624 A CN202111550624 A CN 202111550624A CN 114035268 B CN114035268 B CN 114035268B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/125—Bends, branchings or intersections
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12083—Constructional arrangements
- G02B2006/12104—Mirror; Reflectors or the like
Abstract
The invention belongs to the field of integrated photonic devices, and particularly relates to an optical cross waveguide unit which comprises a flat optical waveguide and at least two strip optical waveguide groups, wherein each strip optical waveguide group comprises two strip optical waveguides which are respectively an input strip optical waveguide and an output strip optical waveguide; the planar optical waveguide comprises at least two total internal reflection mirror groups, the total internal reflection mirror groups are arranged in one-to-one correspondence with the strip optical waveguide groups, each total internal reflection mirror group comprises a plurality of total internal reflection mirrors, and each total internal reflection mirror group is used for guiding all optical waves input by the input strip optical waveguide in the corresponding strip optical waveguide group to the corresponding output strip optical waveguide; the output end of the input strip-shaped optical waveguide and the input end of the output strip-shaped optical waveguide extend into the lower part of the flat plate-shaped optical waveguide, and a gap is formed between the output end of the input strip-shaped optical waveguide and the flat plate-shaped optical waveguide, and the thickness of the gap is 0.01-0.2 μm. The structure greatly reduces the loss of light wave energy and ensures the low energy loss of the crossed waveguide.
Description
Technical Field
The invention belongs to the field of integrated photonic devices, and particularly relates to an optical cross waveguide unit.
Background
Optical waveguides are the most basic unit in optical integrated circuits, and are connected to different optical devices to guide the propagation of optical signals. According to the difference of the geometrical shapes of the optical waveguides, the optical waveguides can be divided into flat optical waveguides and strip optical waveguides, when the optical waves propagate in the strip optical waveguides, the propagation modes of the optical waveguides have refractive index differences in the transverse direction and the longitudinal direction in the waveguides, the optical waves propagate in the core layer along the length direction of the strip optical waveguides, and when the flat optical waveguides propagate the optical waves, the optical waves are limited only in the longitudinal direction when propagating in the core layer. In optical integrated circuits, various optical devices are typically integrated on a single layer of space. Most of the existing crossed waveguides are strip-shaped optical waveguides with rough side walls, the energy loss of light waves in the X direction is large, and when two optical waveguides are directly crossed and placed, nearly half of the energy of the light waves is lost due to diffraction caused by sudden change of the width of the side walls.
Accordingly, there is a need for improvement and development in the art.
Disclosure of Invention
The application aims to provide an optical cross waveguide unit, and aims to solve the problem of a large amount of optical wave energy loss in the existing cross wave transmission process, so that the low energy loss of cross waveguides is ensured.
In order to achieve the purpose, the invention adopts the following technical scheme: an optical cross waveguide unit comprises a flat optical waveguide and at least two strip optical waveguide groups, wherein each strip optical waveguide group comprises two strip optical waveguides which are an input strip optical waveguide and an output strip optical waveguide respectively;
the planar optical waveguide comprises at least two total internal reflection mirror groups, the total internal reflection mirror groups are arranged in one-to-one correspondence with the strip optical waveguide groups, each total internal reflection mirror group comprises a plurality of total internal reflection mirrors, and each total internal reflection mirror group is used for guiding all optical waves input by the input strip optical waveguides in the corresponding strip optical waveguide group to the corresponding output strip optical waveguides;
the output end of the input strip-shaped optical waveguide and the input end of the output strip-shaped optical waveguide extend into the lower part of the flat-plate-shaped optical waveguide, a gap is formed between the output end of the input strip-shaped optical waveguide and the flat-plate-shaped optical waveguide, and the thickness of the gap is 0.01-0.2 μm.
According to the optical cross waveguide unit, through a double-layer structure formed by at least two strip-shaped optical waveguide groups and a flat-plate-shaped optical waveguide, a gap is formed between each strip-shaped optical waveguide group and the corresponding flat-plate-shaped optical waveguide group, the thickness of the gap is 0.01-0.2 μm, and the coupling efficiency of optical waves from the strip-shaped optical waveguide groups to the flat-plate-shaped optical waveguides is high; when light waves are input from the input strip-shaped optical waveguide and coupled to the flat-plate-shaped optical waveguide at the output end of the input strip-shaped optical waveguide, the total internal reflection mirror group guides all the input light waves to the corresponding output strip-shaped optical waveguide, and due to the action of the total internal reflection mirror group, the light waves are not in contact with the rough side surface wall when being transmitted in the flat-plate-shaped optical waveguide, so that the loss of light wave energy is greatly reduced, the low energy loss of the crossed waveguide is ensured, and the transmission efficiency and the overall performance of optical signals in the optical integrated chip are improved.
Further, the flat optical waveguide includes four straight edges, where the four straight edges are a first straight edge, a second straight edge, a third straight edge, and a fourth straight edge, the first straight edge is parallel to the third straight edge, and the second straight edge is parallel to the fourth straight edge; two strip optical waveguides of one strip optical waveguide group are respectively arranged over against the first straight line edge and the third straight line edge, and two strip optical waveguides of the other strip optical waveguide group are respectively arranged over against the second straight line edge and the fourth straight line edge.
The flat plate-shaped optical waveguide is provided with four straight line edges, the two strip-shaped optical waveguides of one strip-shaped optical waveguide group are respectively over against the first straight line edge and the third straight line edge, the two strip-shaped optical waveguides of the other strip-shaped optical waveguide group are respectively over against the second straight line edge and the fourth straight line edge, and because the two strip-shaped optical waveguide groups are separately arranged, signal crosstalk does not exist like direct crossing of other strip-shaped optical waveguides, and signal low crosstalk of cross waves is realized.
Further, the strip-shaped optical waveguide includes an equal-width portion which is away from one end of the flat-shaped optical waveguide and has a constant width in the axial direction of the strip-shaped optical waveguide, and a widened portion which is toward the one end of the flat-shaped optical waveguide and has a gradually increasing width from the end facing away from the flat-shaped optical waveguide to the end facing toward the flat-shaped optical waveguide.
The width that the equal width portion of dull and stereotyped optical waveguide one end was kept away from to strip optical waveguide in this application is unchangeable, when using the gaussian beam that single mode fiber communication was used commonly as the incident light ripples, equal wide portion and light wave mode field phase-match that can be fine, set up the widening portion that strip optical waveguide is close to dull and stereotyped optical waveguide one end, the one end of directional dull and stereotyped optical waveguide is followed from the one end of dull and stereotyped optical waveguide dorsad to the widening portion, the width crescent, be for reducing diffraction effect, thereby further reduce the loss.
Further, the total internal reflection mirror is a curved mirror, and the curved mirror is a concave mirror.
In this application, the total internal reflection mirror is the curved mirror, and this curved mirror is the concave mirror, because the concave mirror has the spotlight effect, can make parallel light converge in the focus, can also make the light reflection that the focus sent become the parallel light, further reduces the loss of light wave energy.
Furthermore, the flat optical waveguide is rectangular, the two total internal reflection mirror groups are arranged in the rectangle, each total internal reflection mirror group comprises two total internal reflection mirrors, namely a first total internal reflection mirror and a second total internal reflection mirror, the first total internal reflection mirror is used for reflecting all incident light waves of the corresponding input strip-shaped optical waveguide to the corresponding second total internal reflection mirror, and the second total internal reflection mirror is used for reflecting all reflected light waves of the corresponding first total internal reflection mirror to the corresponding output strip-shaped optical waveguide.
Further, the distance from the starting point of the input light wave of the flat optical waveguide to the corresponding reflection point of the first total internal reflection mirror is equal to the rayleigh distance of the gaussian light wave; and the distance from the reflection point of the first total internal reflector to the corresponding reflection point of the second total internal reflector is equal to twice the Rayleigh distance of the Gaussian light wave.
Further, the strip optical waveguide and the slab optical waveguide each have an outer cladding, and the outer cladding is silicon dioxide.
Further, the thickness of the strip-shaped optical waveguide is 0.22 μm, the width of the equal-width portion is 0.45 μm, and the width of the end face of the widened portion near one end of the slab-shaped optical waveguide is 1.5 μm.
Further, the width-widening portion has a length of 5 μm to 7 μm.
Further, the reflecting surface of the total internal reflector is a circular arc surface, and the radius of the circular arc surface is
And F is the Rayleigh distance of the Gaussian light wave.
The optical cross waveguide unit has the advantages that the optical cross waveguide unit is provided with a double-layer structure formed by at least two strip-shaped optical waveguide groups and a flat-plate-shaped optical waveguide, the flat-plate-shaped optical waveguide comprises at least two total internal reflection mirror groups, each strip-shaped optical waveguide group comprises an input strip-shaped optical waveguide and an output strip-shaped optical waveguide, each total internal reflection mirror group comprises a plurality of total internal reflection mirrors, the output end of the input strip-shaped optical waveguide and the input end of the output strip-shaped optical waveguide extend into the lower part of the flat-plate-shaped optical waveguide and form a gap with the thickness of 0.01-0.2 mu m with the flat-plate-shaped optical waveguide, and the coupling efficiency of optical waves is high. When light waves are input from the input end of the input strip-shaped light waveguide and are coupled to the flat-plate-shaped light waveguide from the output end of the input strip-shaped light waveguide, all the light waves entering the flat-plate-shaped light waveguide are guided to the output strip-shaped light waveguide by the total internal reflector group through multiple reflections. Due to the action of the total internal reflection mirror, the light wave does not contact the rough side wall when propagating in the flat light waveguide, so that the loss of light wave energy is greatly reduced, and the low energy loss of the crossed waveguide is ensured; and the strip-shaped optical waveguide groups are not directly crossed, so that the crosstalk of the optical wave signals can be greatly reduced, and the transmission efficiency and the overall performance of the optical signals in the optical integrated chip are improved.
Drawings
Fig. 1 is a schematic top view of an optical cross waveguide unit provided in the present application.
Fig. 2 is a schematic front view structure diagram of an optical cross waveguide unit provided in the present application.
Fig. 3 is a top view of another structure of an optical cross-waveguide unit provided in the present application.
Description of the reference symbols: 1. a strip-shaped optical waveguide; 100. equal width parts; 101. a width-widening part; 102. an overlapping portion; 110. inputting a strip-shaped optical waveguide; 111. an output strip optical waveguide; 2. a plate-shaped optical waveguide; 201. a first straight edge; 202. a second straight edge; 203. a third straight edge; 204. a fourth straight edge; 211. a first arcuate side, 212, a second arcuate side; 213. a third arcuate side; 214. a fourth arcuate side; 3. a total internal reflection mirror; 311. a first total internal reflection mirror; 312. a second total internal reflection mirror.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "facing away," and the like are used in the orientations and positional relationships indicated in the figures, which are based on the orientation or positional relationship shown in the figures, and are used for convenience in describing the present invention and to simplify the description, but are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed in a particular orientation, and be operated in a particular orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The following disclosure provides many different embodiments or examples for implementing different features of the invention. To simplify the disclosure of the present invention, specific example components and arrangements are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
As shown in fig. 1 and fig. 2, an optical cross waveguide unit of the present invention includes a slab optical waveguide 2 and at least two strip optical waveguide groups, each strip optical waveguide group includes two strip optical waveguides 1, and the two strip optical waveguides 1 are an input strip optical waveguide 110 and an output strip optical waveguide 111 respectively; the flat light waveguide 2 comprises at least two total internal reflection mirror groups, the total internal reflection mirror groups are arranged in one-to-one correspondence with the strip light waveguide groups, each total internal reflection mirror group comprises a plurality of total internal reflection mirrors 3, and each total internal reflection mirror group is used for guiding all light waves input by the input strip light waveguides 110 in the corresponding strip light waveguide group to the corresponding output strip light waveguides 111;
the output end of the input strip optical waveguide 110 and the input end of the output strip optical waveguide 111 extend below the slab optical waveguide 2 with a gap having a thickness a of 0.01 μm to 0.2 μm from the slab optical waveguide 2.
For convenience of description, referring to fig. 2, the fact that the output end of the input strip optical waveguide 110 and the input end of the output strip optical waveguide 111 extend below the slab optical waveguide 2 means that the projection of the strip optical waveguide 1 on the plane of the lower surface of the slab optical waveguide 2 partially overlaps the lower surface of the slab optical waveguide 2 (the overlapping portions 102 are the output end of the input strip optical waveguide 110 and the input end of the output strip optical waveguide 111, respectively). Generally, the incident light wave mostly adopts a gaussian beam with a wavelength of 1.55 μm, which is commonly used for single-mode fiber communication.
Specifically, an optical cross waveguide unit includes a flat optical waveguide 2 and at least two strip optical waveguide sets, the flat optical waveguide 2 includes at least two total internal reflection mirror sets, where the strip optical waveguide set and the total internal reflection mirror set each have at least two, and may be three or four strip optical waveguide sets and total internal reflection mirror sets, but is not limited thereto, in this embodiment, it is preferable that an optical cross waveguide unit includes the flat optical waveguide 2 and two strip optical waveguide sets, and the flat optical waveguide includes two total internal reflection mirror sets for example.
In practical applications, two strip optical waveguide groups and two slab optical waveguides form a double-layer structure, since the output end of the input strip optical waveguide 110 and the input end of the output strip optical waveguide 111 extend below the slab optical waveguide 2, the overlapping portion 102 is affected by the thickness of the gap between the strip optical waveguide group and the slab optical waveguide 2 (i.e. the coupling distance), and the difference in the coupling distance affects the length of this overlapping portion 102, generally speaking, the smaller the coupling distance, the smaller the length of the overlapping portion 102 (i.e. the distance from the extending point of the strip optical waveguide to the other end pointing to the slab optical waveguide), and the thickness a of the gap between the strip optical waveguide group and the slab optical waveguide 2 is 0.01 μm-0.2 μm, then the length L4 of the corresponding overlapping portion 102 is specifically in the range of: 0.2-12 μm; the coupling efficiency when the incident light wave is coupled from the input strip optical waveguide 110 to the slab optical waveguide 2 is high; after the incident light waves are coupled to the slab-shaped optical waveguides 2 at the output ends of the input strip optical waveguides 110, one of the total internal reflection mirrors 3 totally reflects the light waves input by the flat light waveguide 2, and after the light waves are reflected by the other total internal reflection mirror 3, the light waves are collected and coupled to the output strip-shaped light waveguide 111 again, by arranging the two strip-shaped optical waveguide groups and the two total internal reflection lens groups, two incident light waves form cross waves in the flat-plate-shaped optical waveguide 2, when the incident light waves are transmitted in the flat-plate-shaped optical waveguide 2, the propagation mode of which is limited only in the longitudinal direction (thickness direction), the incident light wave is free to propagate in the transverse direction, due to the action of the total internal reflection mirror group, light waves do not contact the rough side wall when propagating in the flat light waveguide 2, so that the loss of light wave energy is greatly reduced, the low energy loss of the crossed waveguide is ensured, and the propagation efficiency and the overall performance of optical signals in the optical integrated chip are improved.
In some embodiments, as shown in fig. 1 and 3, the slab optical waveguide 2 of the present application is provided with four straight edges, which are a first straight edge 201, a second straight edge 202, a third straight edge 203, and a fourth straight edge 204, respectively, where the first straight edge 201 is parallel to the third straight edge 203, and the second straight edge 202 is parallel to the fourth straight edge 204; two strip optical waveguides 1 of a strip optical waveguide group are respectively opposite to a first straight edge 201 and a third straight edge 203 (here, the arrangement of the strip optical waveguides 1 opposite to the straight edges means that the strip optical waveguides 1 extend into the lower part of the flat optical waveguide 2 along the direction perpendicular to the straight edges at the straight edges), that is, the input strip optical waveguide 110 is opposite to the first straight edge 201, the output strip optical waveguide 111 is opposite to the third straight edge 203 (also can be that the input strip optical waveguide 110 is opposite to the third straight edge 203, and the output strip optical waveguide 111 is opposite to the first straight edge 201), and the working principle is as follows: the incident light wave is input from the input strip optical waveguide 110 at the first straight edge 201 and coupled to the slab optical waveguide 2 via the output end of the input strip optical waveguide 110, and the total internal reflection mirror 3 guides the incident light wave of the slab optical waveguide 2 to the output strip optical waveguide 111 at the third straight edge 203, thereby realizing the propagation of the incident light wave. Two strip optical waveguides 1 of another strip optical waveguide group are respectively opposite to the second straight line edge 202 and the fourth straight line edge 204, that is, the input strip optical waveguide 110 is opposite to the second straight line edge 202, and the output strip optical waveguide 111 is opposite to the fourth straight line edge 204 (or the input strip optical waveguide 110 is opposite to the fourth straight line edge 204, and the output strip optical waveguide 111 is opposite to the second straight line edge 202), and its working principle is: the incident light waves are input from the input strip optical waveguide 110 at the second straight edge 202 and coupled to the plate shaped optical waveguide 2 via the output end of the input strip optical waveguide 110, and the total internal reflection mirror 3 guides the incident light waves of the plate shaped optical waveguide 2 all to the output strip optical waveguide 111 at the fourth straight edge 204. If two strip optical waveguide groups are directly crossed, because the structure is a single-layer structure, the width of the crossed part of the strip optical waveguide groups is increased, when an incident light wave is input from the input strip optical waveguide 110, a large amount of light wave diffraction is caused because the side wall of the center of the crossed part of the two strip optical waveguide groups is suddenly changed, the same incident light wave cannot be correspondingly output, and the diffraction of the two incident light waves at the crossed center can cause signal crosstalk. The two strip-shaped optical waveguide groups are separately arranged, and the strip-shaped optical waveguide groups and the flat optical waveguide 2 are of a double-layer structure, so that two incident light waves can not generate crosstalk between the strip-shaped optical waveguide groups, the incident light waves form cross waves in the flat optical waveguide 2, the structure can not generate signal crosstalk existing in direct crossing of other strip-shaped optical waveguides, and the signal low crosstalk of the cross waves is realized.
Generally, the first straight edge 201 and the third straight edge 203 are perpendicular to the second straight edge 202 and the fourth straight edge 204, so that the two strip optical waveguides 1 of the same strip optical waveguide group are parallel to each other, and the strip optical waveguides 1 of the two strip optical waveguide groups are perpendicular to each other; but is not limited thereto.
In some embodiments, as shown in fig. 2, the width of the constant-width part 100 of the strip-shaped optical waveguide 1 far from the end of the slab-shaped optical waveguide 2 is not changed, when a gaussian beam commonly used for single-mode fiber communication is used as an incident light wave, the constant-width part 100 can be well matched with an optical mode field, a widening part 101 of the strip-shaped optical waveguide 1 close to the end of the slab-shaped optical waveguide 2 is arranged, and the width of the widening part 101 gradually increases from the end back to the end of the slab-shaped optical waveguide 2 to the end pointing to the slab-shaped optical waveguide 2, so as to reduce diffraction effect and further reduce loss; wherein the two side edges of the variable width part 101 can be a straight line, a parabola, other quadratic function type curves or irregular shaped curves.
In particular, the total internal reflection mirror 3 is a curved mirror, which is a concave mirror. Because the concave mirror has the function of light condensation, parallel light rays can be converged to a focus, and light rays emitted by the focus can be reflected into parallel light rays, when incident light waves are input from the flat plate-shaped light waveguide 2, the incident light waves are focused by one total internal reflection mirror 3 and then are totally reflected to the other total internal reflection mirror 3 in the form of the parallel light rays, the other total internal reflection mirror 3 is focused and then is reflected to the output strip-shaped light waveguide 111 in the form of the parallel light rays, and the loss of light wave energy in the transmission process is further reduced.
In some embodiments, as shown in fig. 1, if the slab optical waveguide 2 is rectangular, two tir mirror groups are arranged in the rectangle, each tir mirror group is arranged corresponding to each slab optical waveguide group, each tir mirror group comprises two total internal reflection mirrors, namely a first total internal reflection mirror 311 and a second total internal reflection mirror 312, when an incident light wave is input from the input slab optical waveguide 110, the first total internal reflection mirror 311 is used for totally reflecting the corresponding incident light wave of the input slab optical waveguide 110 to the corresponding second total internal reflection mirror 312, the second total internal reflection mirror 312 is used for totally reflecting the corresponding reflected light wave of the first total internal reflection mirror 311 to the corresponding output slab optical waveguide 111, so as to form two incident light waves crossing in the slab optical waveguide 2, since the light wave does not directly contact with the rough side wall in the slab optical waveguide 2, the diffraction can be greatly reduced by the incident light waves and the degree of interference between the cross waves is relatively low.
In practical applications, the flat light waveguide 2 is not limited to be rectangular, for example, in fig. 3, in other embodiments, the flat light waveguide 2 further includes four arc-shaped side surfaces, which are a first arc-shaped side surface 211, a second arc-shaped side surface 212, a third arc-shaped side surface 213, and a fourth arc-shaped side surface 214, and each arc-shaped side surface is coated with a reflective layer, and the thickness of the coated reflective layer is not less than the total reflection transmission depth of the light wave, so that each arc-shaped side surface serves as a total internal reflection mirror 3, where the first arc-shaped side surface 211 and the third arc-shaped side surface 213 correspond to a first total internal reflection mirror 311 and a second total internal reflection mirror 312 of the same total internal reflection mirror group, respectively; the second arc-shaped side surface 212 and the fourth arc-shaped side surface 214 correspond to the first total internal reflector 311 and the second total internal reflector 312 of the same tir mirror group, respectively. Compared with the rectangular plate-shaped optical waveguide 2, the plate-shaped optical waveguide 2 saves more materials and is beneficial to reducing the cost.
In some embodiments, as shown in fig. 1, when a gaussian beam commonly used for single-mode fiber communication is used as an input light wave, a distance from a starting point of an input light wave of the flat optical waveguide 2 to the corresponding first total internal reflection mirror 311 is equal to a rayleigh distance of the gaussian light wave (i.e., the rayleigh distance of the input light wave), and an incident angle and a reflection angle of the input light wave of the flat optical waveguide 2 with respect to the total internal reflection mirror 3 are both 45 °, where the gaussian beam can obtain the highest laser gain; the distance from the reflection point of the first total internal reflection mirror 311 to the corresponding reflection point of the second total internal reflection mirror 312 is equal to twice the rayleigh distance of the gaussian light wave, and at this time, the total internal reflection mirror group and the strip-shaped optical waveguide group are in a rotationally symmetrical shape on the flat-plate-shaped optical waveguide 2.
Specifically, the strip optical waveguide 1 and the slab optical waveguide 2 each have an outer cladding, the outer cladding is silicon dioxide, and the outer cladding refers to the upper surface and the lower surface of the strip optical waveguide 1 and the slab optical waveguide 2, respectively.
In some embodiments, for a gaussian beam with a wavelength of 1.55 μm, the standard interface size of the crossed waveguide element is 0.45 μm × 0.22 μm, when a gaussian beam with a wavelength of 1.55 μm is used as an input light wave, the thickness of the strip-shaped optical waveguide 1 is 0.22 μm, the width L1 of the equal-width part is 0.45 μm, and the cross-sectional size of the equal-width part 100 is made to be the standard size, so as to improve the applicability of the optical crossed waveguide element, and the width L2 of the end face of the widened part 102 close to one end of the flat-plate-shaped optical waveguide 2 is set to be 1.5 μm, so that when the incident light wave enters the flat-plate-shaped optical waveguide 2, the incident light wave can be well collected by the total internal reflection mirror 3.
In some embodiments, the coupling efficiency of the incident light wave may be improved when the widening portion length L3 is 5 μm to 7 μm, considering the manufacturing tolerance when the optical waveguide is actually manufactured, and may reach 93% when the widening portion length L3 is 5 μm, 97% when the widening portion length L3 is 6 μm, and 99% when the widening portion length L3 is 7 μm.
In a specific application, the reflecting surface of the total internal reflection mirror 3 is a circular arc surface with a radius of
And F is the Rayleigh distance of the Gaussian light wave (the radius of the arc surface is 9 mu m for the Gaussian light beam with the wavelength of 1.55 mu m), so that the focusing capacity of the incident light wave energy can be further improved.
The following is further illustrated by the specific examples:
in the first embodiment, a gaussian beam with the wavelength of 1.55 μm commonly used in single-mode optical fiber communication is used as an input light wave, and simulation calculation shows that when one group of incident light waves propagates in the structure, the loss energy of the light waves is less.
As shown in FIG. 2, in which the thickness of the strip optical waveguide 1 is 0.22. mu.m, the width L1 of the constant width portion is 0.45. mu.m, the width L2 of the end surface of the widened portion 101 near one end of the slab optical waveguide 2 is 1.5. mu.m, the length L3 of the widened portion is 7 μm, the lengths L4 of the overlapping portions 102 where the output ends of the input strip optical waveguide 110 and the output ends of the output strip optical waveguide 111 are respectively projected on the bottom surface of the slab optical waveguide 2 are each 0.4. mu.m, and the thickness a of the gap between the strip optical waveguide group and the slab optical waveguide 2 is 0.02. mu.m. The incident light wave is input from the equal-width portion 100 of the input strip optical waveguide 110 and output from the output end (i.e., the end face of the widening portion 101) of the input light waveguide 110, so that the coupling efficiency of the incident light wave is high.
Wherein the plate-shaped optical waveguide2 is a rectangle, as shown in fig. 1, two total internal reflection mirror groups are arranged in the rectangle, the reflecting surfaces of the total internal reflection mirrors 3 are all arc surfaces with the radius of the arc surfaces
F is the Rayleigh distance of Gaussian light waves, namely the radius of the arc surface is 9 mu m; and the distance F from the starting point of the input light wave of the flat optical waveguide 2 to the reflection point of the corresponding first total internal reflection mirror 311 is equal to the rayleigh distance of the input gaussian light wave, i.e., 3.27 μm, and the distance from the reflection point of the first total internal reflection mirror 311 to the reflection point of the corresponding second total internal reflection mirror 312 is equal to twice the rayleigh distance of the gaussian light wave, i.e., 6.54 μm. At the moment, the top views of the two strip-shaped optical waveguide groups and the two total internal reflection mirror groups in the rectangle are in a rotationally symmetrical shape. Incident light waves of the flat light waveguide 2 are collected by the first total internal reflection mirror 311 and then are all reflected to the corresponding second total internal reflection mirror 312 by parallel light, reflected light of the corresponding first total internal reflection mirror 311 is collected by the second total internal reflection mirror 312 and then is reflected to the corresponding output strip light waveguide 111 by parallel light again, the other strip light waveguide group and the other total internal reflection mirror group are completed in the same working mode, so that cross waves are formed in the flat light waveguide 2, the cross waves are not directly contacted with the rough side wall in the flat light waveguide 2, and the cross waves are only guided and transmitted by the total internal reflection mirror 3 in the flat light waveguide 2, so that the loss of light wave energy is greatly reduced, and the low energy loss of the cross light waveguide is ensured; and the strip-shaped optical waveguide groups are not directly crossed, so that the crosstalk of the optical wave signals can be greatly reduced.
In a second embodiment, as shown in fig. 2 and 3, the strip-shaped optical waveguide has a thickness of 0.22 μm, the equal width portion L1 is 0.45 μm, the end face of the widening portion 102 near one end of the slab-shaped optical waveguide 2 has a width L2 of 1.5 μm, the widening portion has a length L3 of 7 μm, the lengths L4 of the overlapping portions 102 where the output end of the input strip-shaped optical waveguide 110 and the output end of the output strip-shaped optical waveguide 111 are respectively projected on the bottom face of the slab-shaped optical waveguide 2 are both 0.4 μm, and the gap thickness a between the strip-shaped optical waveguide group and the slab-shaped optical waveguide is 0.02 μm. The incident light wave is input from the equal-width portion 100 of the input strip-shaped optical waveguide 110 and output from the output end (i.e., the end face of the widening portion 101) of the input strip-shaped optical waveguide 110, so that the coupling efficiency of the incident light wave is high.
The flat optical waveguide 2 comprises four straight line edges and four arc-shaped side faces, each arc-shaped side face is an arc-shaped side face, the four straight line edges are a first straight line edge 201, a second straight line edge 202, a third straight line edge 203 and a fourth straight line edge 204 respectively, the first straight line edge 201 is parallel to the third straight line edge 203, and the second straight line edge 202 is parallel to the fourth straight line edge 204; the four arc-shaped side surfaces are respectively a first arc-shaped side surface 211, a second arc-shaped side surface 212, a third arc-shaped side surface 213 and a fourth arc-shaped side surface 214, each arc-shaped side surface is used as a total internal reflection mirror 3, the radius of the arc surface of each arc-shaped side surface is 9 micrometers, each arc-shaped side surface is coated with a reflection layer, and the thickness of the coated reflection layer is not less than the total reflection transmission depth of the light wave. Because, when the light wave is totally reflected, a certain transmission depth exists in the reflecting medium. The first arc-shaped side surface 211 is connected with the first straight line edge 201, the second arc-shaped side surface 212 is connected with the second straight line edge 202, the third arc-shaped side surface 213 is connected with the third straight line edge 203, and the fourth arc-shaped side surface 214 is connected with the fourth straight line edge 204; the first arc-shaped side surface 211 and the third arc-shaped side surface 213 are respectively equivalent to the first total internal reflector 311 and the second total internal reflector 312 of the same tir mirror group; the second arc-shaped side surface 212 and the fourth arc-shaped side surface 214 are respectively equivalent to the first total internal reflector 311 and the second total internal reflector 312 of the same tir mirror group; two strip-shaped optical waveguides 1 of one strip-shaped optical waveguide group are respectively arranged right opposite to the first straight edge 201 and the third straight edge 203, and two strip-shaped optical waveguides 1 of the other strip-shaped optical waveguide group are respectively arranged right opposite to the second straight edge 202 and the fourth straight edge 204.
Wherein the distance from the starting point of the input optical wave of the slab optical waveguide 2 to the reflection point of the corresponding first curved side surface 211 is equal to the rayleigh distance of the input gaussian optical wave, i.e., 3.27 μm, and the distance from the reflection point of the first curved side surface 211 to the reflection point of the third curved side surface 213 and the distance from the reflection point of the second curved side surface 212 to the reflection point of the fourth curved side surface 214 are equal to twice the rayleigh distance of the gaussian optical wave, i.e., 6.54 μm.
When an incident light wave is input from the input strip optical waveguide 110 and coupled to the flat plate shaped optical waveguide 2, the incident light wave of the flat plate shaped optical waveguide 2 is totally reflected by the first curved side surface 211 to the third curved side surface 213, the third curved side surface 213 totally reflects the reflected light wave of the first curved side surface 211 to the corresponding output strip optical waveguide 111, another incident light wave of the flat plate shaped optical waveguide 2 is totally reflected by the second curved side surface 212 to the fourth curved side surface 214, and the fourth curved side surface 214 totally reflects the reflected light wave of the second curved side surface 212 to the corresponding output strip optical waveguide 111. The structure can also greatly reduce the loss of light wave energy and ensure the low energy loss of the crossed waveguide; and the strip-shaped optical waveguide groups are not directly crossed, so that the crosstalk of the optical wave signals can be greatly reduced. In addition, compared with the rectangular flat optical waveguide 2, the flat optical waveguide 2 saves more materials and is beneficial to reducing the cost.
In the description herein, reference to the terms "in a first embodiment," "in a second embodiment," "in some embodiments," "an example," "specifically," or "in practice," etc., 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 invention. In this specification, schematic representations of the above terms do not necessarily refer 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.
What has been described above are merely some embodiments of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the inventive concept thereof, and these changes and modifications can be made without departing from the spirit and scope of the invention.
Claims (7)
1. An optical cross waveguide unit comprises a flat optical waveguide and at least two strip optical waveguide groups, wherein each strip optical waveguide group comprises two strip optical waveguides which are an input strip optical waveguide and an output strip optical waveguide respectively; the planar optical waveguide comprises at least two total internal reflection mirror groups, the total internal reflection mirror groups are arranged in one-to-one correspondence with the strip optical waveguide groups, each total internal reflection mirror group comprises a plurality of total internal reflection mirrors, and each total internal reflection mirror group is used for guiding all optical waves input by the input strip optical waveguides in the corresponding strip optical waveguide group to the corresponding output strip optical waveguides;
The output end of the input strip-shaped optical waveguide and the input end of the output strip-shaped optical waveguide extend into the lower part of the flat-plate-shaped optical waveguide, and a gap is formed between the output end of the input strip-shaped optical waveguide and the flat-plate-shaped optical waveguide, and the thickness of the gap is 0.01-0.2 μm;
the flat optical waveguide comprises four straight edges which are respectively a first straight edge, a second straight edge, a third straight edge and a fourth straight edge, wherein the first straight edge is parallel to the third straight edge, and the second straight edge is parallel to the fourth straight edge; two strip optical waveguides of one strip optical waveguide group are respectively arranged right opposite to the first straight line edge and the third straight line edge, and two strip optical waveguides of the other strip optical waveguide group are respectively arranged right opposite to the second straight line edge and the fourth straight line edge;
the planar optical waveguide is rectangular, the two total internal reflection mirror groups are arranged in the rectangle, each total internal reflection mirror group comprises two total internal reflection mirrors, namely a first total internal reflection mirror and a second total internal reflection mirror, the first total internal reflection mirror is used for reflecting all incident light waves of the corresponding input strip-shaped optical waveguide to the corresponding second total internal reflection mirror, and the second total internal reflection mirror is used for reflecting all reflected light waves of the corresponding first total internal reflection mirror to the corresponding output strip-shaped optical waveguide;
The distance from the starting point of the input light wave of the flat light waveguide to the corresponding reflection point of the first total internal reflection mirror is equal to the Rayleigh distance of the Gaussian light wave; the distance from the reflection point of the first total internal reflector to the corresponding reflection point of the second total internal reflector is equal to the Rayleigh distance of two times of Gaussian light waves.
2. The optical cross waveguide unit according to claim 1, wherein the strip optical waveguide includes an equal-width portion which is distant from one end of the slab optical waveguide and has a constant width in an axial direction of the strip optical waveguide, and a widened portion which is close to one end of the slab optical waveguide and has a width which gradually increases from one end facing away from the slab optical waveguide to one end facing toward the slab optical waveguide.
3. The optical cross-waveguide unit of claim 1, wherein the total internal reflection mirror is a curved mirror, and the curved mirror is a concave mirror.
4. The optical cross-waveguide unit of claim 1 wherein the strip optical waveguide and the slab optical waveguide each have an outer cladding, the outer cladding being silicon dioxide.
5. The optical cross waveguide unit according to claim 2, wherein the thickness of the strip-shaped optical waveguide is 0.22 μm, the width of the equal-width portion is 0.45 μm, and the width of the end surface of the widened portion near one end of the slab-shaped optical waveguide is 1.5 μm.
6. The optical cross-waveguide unit of claim 2, wherein the widened portion has a length of 5 μm to 7 μm.
7. The optical cross waveguide unit of claim 1, wherein the reflective surface of the total internal reflection mirror is a circular arc surface having a radius of
And F is the Rayleigh distance of the Gaussian light wave.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101248379A (en) * | 2004-03-24 | 2008-08-20 | 斯欧普迪克尔股份有限公司 | Optical crossover in thin silicon |
| CN201707515U (en) * | 2010-03-03 | 2011-01-12 | 李淑萍 | Non-collinear Bragg diffraction waveguide acousto-optic device structure |
| CN112180507A (en) * | 2020-09-25 | 2021-01-05 | 联合微电子中心有限责任公司 | Multi-waveguide cross device, waveguide chip and forming method thereof |
| CN112346175A (en) * | 2021-01-06 | 2021-02-09 | 季华实验室 | 3dB light wave power beam splitter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2004295138A (en) * | 2002-05-27 | 2004-10-21 | Keio Gijuku | Waveguide type optical function element |
| JP5692865B2 (en) * | 2012-04-11 | 2015-04-01 | 独立行政法人産業技術総合研究所 | Wavelength cross-connect equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101248379A (en) * | 2004-03-24 | 2008-08-20 | 斯欧普迪克尔股份有限公司 | Optical crossover in thin silicon |
| CN201707515U (en) * | 2010-03-03 | 2011-01-12 | 李淑萍 | Non-collinear Bragg diffraction waveguide acousto-optic device structure |
| CN112180507A (en) * | 2020-09-25 | 2021-01-05 | 联合微电子中心有限责任公司 | Multi-waveguide cross device, waveguide chip and forming method thereof |
| CN112346175A (en) * | 2021-01-06 | 2021-02-09 | 季华实验室 | 3dB light wave power beam splitter |
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