CN112346175B - 3dB light wave power beam splitter - Google Patents

Abstract

The present invention provides a 3dB optical wave power beam splitter, comprising a substrate, a flat-shaped optical waveguide layer disposed on the substrate, and a cladding layer disposed on the surface of the flat-shaped optical waveguide layer; The waveguide layer includes an optical waveguide layer main body, a strip-shaped input port arranged on one side of the optical waveguide layer main body, and two strip-shaped output ports arranged on the other side of the optical waveguide layer main body; the optical waveguide layer main body A half mirror and a total reflection mirror are provided, the half mirror is used to split the incident beam into a reflected beam and a transmitted beam, and the reflected beam is directed to one of the bar-shaped output ports, and the total reflection mirror It is used to emit all the transmitted light beams to another bar-shaped output port; the optical powers of the reflected light beam and the transmitted light beam are equal; the 3dB light wave power beam splitter has low light loss and a compact structure.

Description

A 3dB Lightwave Power Beam Splitter

technical field

The invention relates to the field of integrated photonic devices, in particular to a 3dB light wave power beam splitter.

Background technique

Silicon photonics can enable low-cost optical devices through the relatively simple integration of semiconductor fabrication techniques with microelectronic chips. This enables the design and fabrication of new devices based on high-contrast refractive index materials using SOI (Silicon-On-Insulator) technology. The 3dB optical beam splitter is an irreplaceable passive device unit to realize the integrated photonic system. It can distribute the optical power to 2 output devices according to the ratio of 1:1 to meet the multi-device cascade requirements of optoelectronic integration.

At present, the optical power beam splitter in the on-chip optoelectronic integrated system is mainly realized by the Y branch, the multi-mode interference coupler, and the directional coupler. However, the light wave propagates in the form of a Gaussian light wave in the waveguide, and the Gaussian light wave has a far-field divergence characteristic; when the light wave propagates in a strip light waveguide, its propagation mode is constrained in both the lateral and longitudinal directions in the waveguide and cannot be At present, due to the limitation of processing technology, there will be rough walls on both sides of the strip optical waveguide during preparation. These rough walls will cause the light wave to cause a large insertion loss when the propagation mode is constrained, about 3dB/cm. Therefore, the existing optical wave power beam splitter has a large loss of light waves, and the device size is large, which is not conducive to the low-loss and high-integration design of optoelectronic integrated circuits.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a 3dB optical power beam splitter with low optical loss and compact structure.

In order to achieve the above object, the present invention has adopted the following technical solutions:

A 3dB optical wave power beam splitter, comprising a substrate, a plate-shaped optical waveguide layer disposed on the substrate, and a cladding layer disposed on the surface of the plate-shaped optical waveguide layer; the plate-shaped optical waveguide layer comprises light a main body of the waveguide layer, a bar-shaped input port arranged on one side of the main body of the optical waveguide layer, and two bar-shaped output ports arranged on the other side of the main body of the optical waveguide layer;

The main body of the optical waveguide layer is provided with a half mirror and a total mirror, the half mirror is used to split the incident light beam into a reflected light beam and a transmitted light beam, and the reflected light beam is directed to one of the strip-shaped output ports , the total reflection mirror is used to emit all the transmitted light beams to another strip-shaped output port; the optical powers of the reflected light beam and the transmitted light beam are equal.

In the 3dB optical power beam splitter, the half mirror and the total reflection mirror are both curved mirrors, and the curved mirror is a concave mirror.

In the 3dB optical power beam splitter, the semi-transparent mirror includes a groove formed on the main body of the optical waveguide layer, the groove is an empty groove, or the groove is filled with a filling material , and the refractive index of the filling material is lower than the refractive index of the material of the main body of the optical waveguide layer.

In the 3dB optical power beam splitter, the total reflection mirror is one side surface of the main body of the optical waveguide layer.

Further, the thickness of the cladding layer clad on the side surface of the total reflection mirror is not less than the total reflection transmission depth of the light wave.

In the 3dB optical wave power beam splitter, the flat optical waveguide layer is silicon, indium phosphide, antimony, gallium arsenide or indium arsenide; the cladding layer is silicon dioxide.

In the 3dB optical power beam splitter, the bar-shaped input port and the bar-shaped output port are both rectangular bar-shaped, and the cross-sectional dimensions of the bar-shaped input port and the bar-shaped output port are the same.

Further, the width and thickness of the strip-shaped input port and the strip-shaped output port satisfy the condition: max(w, 2h)<λ<2w, where w is the width, h is the thickness, and λ is the wavelength of the working light wave.

In the 3dB optical power beam splitter, the positions and sizes of the half mirrors and the total mirrors meet the following conditions:

；

;

；

;

；

;

；

;

是入射光波的光腰半径,

是出射光波的光腰半径，

是条形输入 端口的根部到反射点的入射距离，

是反射点到相应条形输出端口的根部的出射距离，

是曲面镜的焦距，

是入射光波的瑞利距离，

是曲面镜的半径，

是入射光波的入射 角。 in,

is the beam waist radius of the incident light wave,

is the beam waist radius of the outgoing light wave,

is the incident distance from the root of the bar input port to the reflection point,

is the outgoing distance from the reflection point to the root of the corresponding bar output port,

is the focal length of the curved mirror,

is the Rayleigh distance of the incident light wave,

is the radius of the curved mirror,

is the angle of incidence of the incident light wave.

In the 3dB optical power beam splitter, the central axis of the bar-shaped output port is perpendicular to the central axis of the bar-shaped output port.

Beneficial effects:

Compared with the prior art, a 3dB optical power beam splitter provided by the present invention has the following advantages:

1. Through a semi-transparent mirror and a total reflection mirror in the main body of the optical waveguide layer, the optical beam splitting with a power of 1:1 is realized, and the structure is compact, which is conducive to reducing the size;

2. The optical power beam splitter is based on a flat-shaped optical waveguide. When the light wave propagates in the flat-shaped optical waveguide, its propagation mode is limited only in the longitudinal direction, and the light wave can propagate freely in the lateral direction. The transmission efficiency is less affected by the rough sidewall of the waveguide and the insertion loss is low.

Description of drawings

FIG. 1 is a schematic structural diagram of a 3dB optical power beam splitter provided by the present invention.

FIG. 2 is a top view of a flat-shaped optical waveguide layer in the 3dB optical power beam splitter provided by the present invention.

比率的情况下，

比率随

比率的变化趋势图。 Figure 3 shows the different

In the case of the ratio,

The ratio varies with

Graph of the change trend of the ratio.

FIG. 4 is a graph showing the variation trend of the transmission power of the semi-reflective and semi-transparent curved mirror with the thickness of the mirror.

Figure 5 is a simulation result of a simulation performed on a Gaussian light wave with TE polarization.

FIG. 6 is the simulation calculation result of the power of the two output beams.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", " rear, left, right, vertical, horizontal, top, bottom, inside, outside, clockwise, counterclockwise, etc., or The positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, Therefore, it should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, features defined as "first", "second" may expressly or implicitly include one or more of said features. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

The following disclosure provides embodiments or examples for implementing various structures of the invention. In order to simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are only examples and are not intended to limit the invention. Furthermore, the present disclosure may repeat reference numerals and/or reference letters in different instances for the purpose of simplicity and clarity and not in itself indicative of a relationship between the various embodiments and/or arrangements discussed. In addition, the present disclosure provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the application of other processes and/or the use of other materials.

Please refer to FIGS. 1 and 2 , a 3dB optical power beam splitter provided by the present invention includes a substrate 1, a flat-shaped optical waveguide layer 2 disposed on the substrate 1, and a cladding layer disposed on the surface of the flat-shaped optical waveguide layer The plate-shaped optical waveguide layer 2 includes an optical waveguide layer main body 201, a strip-shaped input port 202 arranged on one side of the optical waveguide layer main body 201, and two strip-shaped output ports 203 ( The strip shape here is relative to the flat-shaped waveguide layer main body 201, the width of the strip-shaped input port 202 and the strip-shaped output port 203 is smaller than the width of the corresponding side surface of the waveguide layer main body 201);

The optical waveguide layer main body 201 is provided with a half mirror 204 and a total reflection mirror 205. The half mirror 204 is used for dividing the incident light beam (ie the light beam entering the optical waveguide layer main body 201 from the strip input port 202) into The reflected light beam and the transmitted light beam are directed to one of the bar-shaped output ports 203, and the total reflection mirror 205 is used to emit all the transmitted light beams to the other bar-shaped output port 203; the optical power of the reflected light beam and the transmitted light beam are equal.

When working, the incident beam is injected from the strip input port 202. When the incident beam comes to the half mirror 204, the half mirror 204 divides the incident beam into a reflected beam and a transmitted beam according to a power of 1:1. , wherein the reflected light beam is directed to one of the bar output ports 203 , and the transmitted light beam passes through the half mirror 204 , hits the total reflection mirror 205 and is fully reflected by the total reflection mirror 205 to the other bar output port 203 , so as to realize the optical beam splitting with power 1:1. Compared with the existing technology, it has the following advantages:

1. Through a semi-transparent mirror and a total reflection mirror in the main body of the optical waveguide layer, the optical beam splitting with a power of 1:1 is realized. The structure is simple and compact, which is conducive to reducing the size and realizing the miniaturization design;

2. The optical wave power beam splitter is based on a flat-shaped optical waveguide. The lateral dimension of the optical waveguide layer body is larger than the lateral dimension (width direction) of the strip-shaped input port. When the light wave propagates in the flat-shaped optical waveguide, its propagation mode is only in the longitudinal direction. (thickness direction) is restricted, and the light wave can propagate freely in the lateral direction. Compared with the strip optical waveguide, the light wave transmission efficiency is less affected by the rough sidewall of the waveguide, and the insertion loss is low, so that the light of the entire 3dB optical wave power beam splitter Low losses.

In some preferred embodiments, the half mirror 204 and the total reflection mirror 205 are both curved mirrors, and the curved mirror is a concave mirror. Since the concave mirror-type curved mirror has a light-gathering function, it can converge the Gaussian beam after the far-field divergence, so that the output beam width is less than or equal to the input beam width, so the width of the bar-shaped output port 203 can be set to be the same as that of the bar-shaped input port 202. The widths are equal to meet the versatility requirements of the device structure (in practical applications, the interface used by the external device to transmit the incident beam and receive the output beam is generally the same size); in fact, if the half mirror 204 and the total reflection The mirror 205 does not have the function of concentrating light, so the width of the output beam will be greater than the width of the input beam, so that the width of the bar-shaped output port 203 needs to be larger than that of the bar-shaped input port 202, so the versatility is poor.

In some preferred embodiments, the half mirror 204 includes a groove opened on the optical waveguide layer main body 201 , the groove is an empty groove (as shown in FIG. 1 ), or the groove is filled with filler material, and the refractive index of the filling material is lower than the refractive index of the material of the optical waveguide layer main body 201 . The filler material may be the same as that of the cladding. In fact, when the groove is an empty groove, the filling material in the groove can be considered to be air. The groove is easy to produce and can be directly etched on the main body 201 of the optical waveguide layer.

In some preferred embodiments, the total reflection mirror 205 is one side surface of the optical waveguide layer main body 201 . For example, when the total reflection mirror 205 is a curved mirror, the side surface facing away from the reflection surface of the half mirror 204 can be directly processed into a curved surface, and the processing is simple and convenient.

Further, the side surface of the total reflection mirror may or may not be covered with a cladding layer. In fact, when the side surface is not covered with a cladding layer, it is equivalent to using air as a cladding layer. If the side surface serving as the total reflection mirror is covered with a cladding layer, the thickness of the cladding layer is not less than the total reflection and transmission depth of the light wave. Because, when the light wave is totally reflected, there will be a certain transmission depth in the reflective medium. This phenomenon is called the Goos-Hanshin displacement. The specific calculation formula of the transmission depth is as follows:

为透射深度，

为工作光波的波长（真空波长），n1是光波导层主体材料 的折射率，n2是包层材料的折射率，

是入射光波的入射角。 in,

is the transmission depth,

is the wavelength of the working light wave (vacuum wavelength), n1 is the refractive index of the main material of the optical waveguide layer, n2 is the refractive index of the cladding material,

is the angle of incidence of the incident light wave.

In some embodiments, the plate-shaped optical waveguide layer 2 is made of silicon, indium phosphide, antimony, gallium arsenide or indium arsenide (that is, the waveguide layer body 201 , the bar-shaped input port 202 , and the bar-shaped output port 203 are all silicon, Indium phosphide, antimony, gallium arsenide or indium arsenide), but not limited thereto; the cladding layer is silicon dioxide. Actually, the cladding layer can also be a polymer, air (the cladding layer is air, that is, no cladding layer is provided) or the like.

In this embodiment, the bar-shaped input port 202 and the bar-shaped output port 203 are both rectangular bar-shaped, and the cross-sectional dimensions of the bar-shaped input port 202 and the bar-shaped output port 203 are the same. In fact, the cross-sectional shapes of the bar-shaped input port 202 and the bar-shaped output port 203 are not limited to be rectangular, nor are the cross-sectional dimensions limited to be the same. However, in practical applications, the interfaces used by the external device to transmit the incident beam and receive the output beam are generally of the same size and generally rectangular. Therefore, the cross-sections of the bar-shaped input port 202 and the bar-shaped output port 203 are set as Rectangles with the same size can meet the universal requirements of the device structure, and since the flat-shaped optical waveguide layer 2 is plate-shaped, it can be obtained by directly cutting the plate-shaped material during production. At this time, the strip-shaped input port 202 and the strip The shape output port 203 is set to be rectangular, and no further processing is required for its shape, and the production is more convenient and fast.

Further, the width and thickness of the strip input port 202 and the strip output port 203 should satisfy the conditions: max(w, 2h)<λ<2w, where w is the width, h is the thickness, and λ is the wavelength of the working light wave ( vacuum wavelength). In practical applications, the input light wave and the output light wave are generally transmitted through single-mode fiber. Therefore, to ensure that the 3dB light wave power beam splitter can be used with single-mode fiber, the light wave needs to be transmitted at the strip input port. 202 and the bar-shaped output port 203 are propagated in a single-mode form to reduce coupling loss; only when the above condition "max(w, 2h)<λ<2w" is satisfied, the light wave can propagate between the bar-shaped input port 202 and the bar-shaped output port 202 Propagation in output port 203 occurs in single mode.

In order to meet the requirement that the width of the output beam is less than or equal to the width of the input beam, so that the width of the bar-shaped output port 203 can be set to be equal to the width of the bar-shaped input port 202 to meet the requirement of versatility; in some preferred embodiments, the transflective The positions and dimensions of mirror 204 and total reflection mirror 205 satisfy the following conditions:

；

;

；

;

；

;

；

;

是入射光波的光腰半径（该光腰半径等于条形输入端口202宽度的一 半）,

是出射光波的光腰半径，

是条形输入端口的根部到反射点的入射距离（对于 半透半反射镜204，该入射距离为图2中的oa长度；对于全反射镜205，该入射距离为图2中的 oc长度），

是反射点到相应条形输出端口的根部的出射距离（对于半透半反射镜204，该 出射距离为图2中的ab长度；对于全反射镜205，该出射距离为图2中的cd长度），

是曲面镜 的焦距，

是入射光波的瑞利距离，

是曲面镜的半径，

是入射光波的入射角。 in,

is the optical waist radius of the incident light wave (the optical waist radius is equal to half the width of the strip input port 202),

is the beam waist radius of the outgoing light wave,

is the incident distance from the root of the strip input port to the reflection point (for the half mirror 204, the incident distance is the oa length in Figure 2; for the total reflection mirror 205, the incident distance is the oc length in Figure 2) ,

is the outgoing distance from the reflection point to the root of the corresponding strip output port (for the half mirror 204, the outgoing distance is the length of ab in Figure 2; for the total reflection mirror 205, the outgoing distance is the length of cd in Figure 2 ),

is the focal length of the curved mirror,

is the Rayleigh distance of the incident light wave,

is the radius of the curved mirror,

is the angle of incidence of the incident light wave.

，

是工作光波在平板形光波导层2中的有效波长。可计算在 不同的

比率的情况下，

比率随

比率的关系，以选择合适的

以确定 曲面镜的半径。例如，图3为在不同

比率的情况下，

比率随

比率的变 化趋势图，当

等于1、

大于1时，

约等于1，此时，

，满足设计 条件。 in,

,

is the effective wavelength of the working light wave in the plate-shaped optical waveguide layer 2 . can be calculated at different

In the case of the ratio,

The ratio varies with

ratio relationship to select the appropriate

to determine the radius of the curved mirror. For example, Figure 3 is a different

In the case of the ratio,

The ratio varies with

The trend graph of the ratio, when

is equal to 1,

When greater than 1,

is approximately equal to 1, at this time,

, which satisfies the design conditions.

The thickness of the half mirror 204 is set according to the filling material (including the case where the filling material is air) and the radius of the half mirror. For example, it can be calculated by scanning the Rsoft simulation software based on the time domain finite difference method. The relationship between the thickness of the mirror surface and the transmittance of the curved mirror under the set radius, the thickness of the curved mirror when the normalized energy of light wave transmission is 50% is selected as the thickness of the semi-reflective and semi-transparent curved mirror.

等于45°。 In some embodiments, see FIGS. 1 and 2 , the central axis of the bar-shaped input port 202 is perpendicular to the central axis of the bar-shaped output port 203 . Therefore, the incident beam and the output beam are perpendicular to each other, and the incident angle is

is equal to 45°.

The substrate 1 is made of a material with a lower refractive index than that of the flat-shaped optical waveguide layer 2 , such as silicon dioxide.

To sum up, the 3dB optical power beam splitter can complete the power splitting of the Gaussian beam propagating in the flat optical waveguide by setting a half mirror and a total reflection mirror in the flat optical waveguide. , the curved mirror also has the function of converging the far-field divergent Gaussian beam, so that the output beam width is less than or equal to the input beam width to meet the versatility of the device structure; it also has the following advantages:

1. High-precision 1:1 beam splitting can be achieved at the two output ends;

2. The structure is simple and compact, which is conducive to reducing size and realizing miniaturized design;

3. The optical wave power beam splitter is based on a flat-shaped optical waveguide. The lateral dimension of the main body of the optical waveguide layer is larger than that of the strip-shaped input port. When the light wave propagates in the flat-shaped optical waveguide, its propagation mode is limited only in the longitudinal direction. It can propagate freely in the lateral direction. Compared with the strip optical waveguide, the optical wave transmission efficiency is less affected by the rough sidewall of the waveguide, and the insertion loss is low, so the optical loss of the entire 3dB optical wave power beam splitter is low.

The following is further described by specific examples:

Example 1

The plate-shaped optical waveguide layer 2 of the 3dB optical power beam splitter in this embodiment is silicon (the refractive index is 3.45), and the cladding layer and the substrate 1 are both silicon dioxide (the refractive index is 1.45);

等于45°； The cross section of the bar-shaped input port 202 and the bar-shaped output port 203 are both rectangular, and the width w is 1.4 μm, and the thickness h is 0.5 μm; and the bar-shaped input port 202 and the bar-shaped output port 203 are perpendicular to each other, therefore, the incident horn

equal to 45°;

为 3.42μm；在不同

比率的情况下，

比率随

比率的变化趋势图如图3所 示；选定

等于1（

为3.42μm）、

大于1、

约等于1的条件，从而，半透半 反射镜204和全反射镜205的半径均为9.7μm； The working wavelength is 1.55 μm, which is a common wavelength in optical communication, and its Rayleigh distance in the flat optical waveguide layer 2

3.42μm; at different

In the case of the ratio,

The ratio varies with

The changing trend graph of the ratio is shown in Figure 3;

is equal to 1 (

3.42μm),

Greater than 1,

The condition is approximately equal to 1, so that the radius of the half mirror 204 and the total reflection mirror 205 are both 9.7 μm;

The half mirror 204 includes a groove, the groove is filled with silicon dioxide, and the thickness of the half mirror 204 is 0.105 μm; the change trend of the transmission power of the half mirror with the thickness of the mirror As shown in Figure 4;

为4μm； 半透半反射镜204反射点到相应条形输出端口203的根部的出射距离

为4.3μm； Wherein, the incident distance from the root of the strip input port 202 to the reflection point of the half mirror 204

is 4 μm; the exit distance from the reflection point of the half mirror 204 to the root of the corresponding strip output port 203

is 4.3 μm;

为7.5μm；全 反射镜205反射点到相应条形输出端口203的根部的出射距离

为4.3μm。 Among them, the incident distance from the root of the strip input port 202 to the reflection point of the total reflection mirror 205

is 7.5 μm; the exit distance from the reflection point of the total reflection mirror 205 to the root of the corresponding strip output port 203

is 4.3 μm.

The size of the substrate 1 is 10 μm×10 μm.

Taking the Gaussian light wave with TE polarization as the working light wave (that is, the Gaussian light wave with the polarization direction of the electric field parallel to the plane of the plate), through simulation calculation (the simulation calculation results are shown in Figures 5 and 6), the separation of the two strip output ports 203 is calculated. The wave ratio is 1:0.995, and the insertion losses of the two bar output ports 203 are 0.08dB and 0.10dB, respectively. It can be seen that the 3dB optical power beam splitter has high spectral precision and small optical loss.

In summary, although the present invention has been disclosed above with preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Those of ordinary skill in the art can make various Such alterations and modifications, the solutions of which are substantially the same as those of the present invention.

Claims (9)

1. A3 dB light wave power beam splitter comprises a substrate, a flat light waveguide layer arranged on the substrate, and a cladding layer arranged on the surface of the flat light waveguide layer; the flat-plate-shaped optical waveguide layer comprises an optical waveguide layer main body, a strip-shaped input port arranged on one side of the optical waveguide layer main body and two strip-shaped output ports arranged on the other side of the optical waveguide layer main body;

the optical waveguide layer main body is provided with a semi-transparent and semi-reflective mirror and a total reflector, the total reflector is one side surface of the optical waveguide layer main body, and the semi-transparent and semi-reflective mirror is arranged inside the optical waveguide layer main body; the semi-transparent semi-reflecting mirror is used for dividing an incident beam into a reflected beam and a transmitted beam, the reflected beam is emitted to one of the strip-shaped output ports, and the total reflecting mirror is used for emitting the transmitted beam to the other strip-shaped output port; the optical power of the reflected beam and the transmitted beam is equal.

2. The 3dB optical power splitter according to claim 1, wherein the transflective mirror and the total reflection mirror are curved mirrors, and the curved mirrors are concave mirrors.

3. The 3dB optical wave power splitter according to claim 1, wherein the semi-transparent and semi-reflective mirror comprises a groove formed on the optical waveguide layer body, the groove is a hollow groove, or the groove is filled with a filling material, and the refractive index of the filling material is lower than that of the material of the optical waveguide layer body.

4. The 3dB optical power splitter according to claim 1, wherein the thickness of the cladding layer coated on the side surface as a total reflection mirror is not less than the total reflection transmission depth of the optical wave.

5. The 3dB optical power splitter according to claim 1, wherein the plate-shaped optical waveguide layer is silicon, indium phosphide, antimony, gallium arsenide, or indium arsenide; the cladding is silica.

6. The 3dB optical power splitter according to claim 1, wherein the strip input port and the strip output port are both rectangular strips, and the cross-sectional dimensions of the strip input port and the strip output port are the same.

7. The 3dB optical power splitter of claim 6, wherein the strip input port and the strip output port have widths and thicknesses that satisfy the condition: max (w, 2 h) < λ <2w, where w is the width, h is the thickness, and λ is the wavelength of the operating light wave.

8. The 3dB optical power splitter according to claim 2, wherein the semi-transparent semi-reflecting mirror and the total reflecting mirror are positioned and sized to satisfy the following conditions:

；

；

；

；

wherein,

is the radius of the waist of the incident light wave,

is the radius of the light waist of the outgoing light wave,

is the incident distance from the root of the strip input port to the reflection point,

is the outgoing distance from the reflection point to the root of the corresponding strip-shaped output port,

is the focal length of the curved mirror,

is the rayleigh distance of the incident light wave,

is the radius of the curved mirror and,

is the angle of incidence of the incident light wave.

9. The 3dB optical power splitter according to claim 1, wherein a central axis of the strip-shaped output port is perpendicular to a central axis of the strip-shaped output port.

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