CN114488574A - Low-crosstalk efficient thermo-optic phase shifter and application thereof - Google Patents

Abstract

One or more embodiments of the present specification provide a low-crosstalk and high-efficiency thermo-optic phase shifter and an application thereof. The thermo-optic phase shifter includes a substrate, a propagation waveguide disposed on the substrate, and a heater for heating the propagation waveguide, By setting the heater as a ring-shaped curved structure and the propagation waveguide as a helical curved structure, a compact structure factor and negligible crosstalk can be formed, which not only solves the problem of low integration of the phase shifter while achieving low crosstalk of the phase shifter The problem of π phase shift is also achieved with high phase modulation.

Description

A low-crosstalk high-efficiency thermo-optic phase shifter and its application

technical field

One or more embodiments of this specification relate to the technical field of optical communication, and in particular, to a low-crosstalk and high-efficiency thermo-optical phase shifter and its application.

Background technique

The boom in silicon-based photonics in recent years has greatly increased the demand for tunable components. Phase shifter is one of them. From optical phased array, lidar to photonic neural network, it is necessary to integrate phase shifter.

The optical phase shifter is an important part of the optical information system, and its function is to change the optical path or logical operation of the optical signal in the integrated optical transmission system. The work of the optical phase shifter is based on the dependence of the refractive index of silicon on temperature. Adding a metal heater to the SOI can change the temperature in the waveguide near the heater, thereby changing the effective refractive index of the waveguide, that is, The phase change of the light in the waveguide is realized, which is the basis of the thermo-optic phase shifter. High-performance thermo-optic phase shifters have the characteristics of low optical insertion loss, low power consumption, and low crosstalk between phase shifters.

However, there is a problem of high crosstalk in the currently designed thermo-optic phase shifter structure.

SUMMARY OF THE INVENTION

In view of this, the purpose of one or more embodiments of this specification is to provide a low crosstalk and high efficiency thermo-optic phase shifter and its application, so as to solve the problem of high crosstalk of the existing thermo-optic phase shifter.

Based on the above purpose, one or more embodiments of this specification provide a low-crosstalk and high-efficiency thermo-optical phase shifter, including:

a substrate, a propagating waveguide disposed on the substrate, and a heater for heating the propagating waveguide;

The heater is arranged as a ring-shaped curved structure;

The propagating waveguide is arranged in a helical curved structure, and its shape conforms to the shape of the heater.

Preferably, the propagation waveguide includes a first input waveguide, a modulation waveguide and a first output waveguide connected in sequence, the first input waveguide, the modulation waveguide and the first output waveguide are connected to form a helical bending structure, and the first input waveguide is arranged in the thermo-optic phase shift The input end of the waveguide of the heater is placed beside the beginning of the heater, the modulation waveguide is arranged close to the heater, and the first output waveguide is arranged at the end away from the heater.

Preferably, the material of the heater is copper; the materials of the first input waveguide, the modulation waveguide and the first output waveguide are all silicon.

Preferably, the length of the propagation waveguide is 320 μm, the width is 0.4 μm, and the height is 0.2 μm, wherein the length of the modulation waveguide is 160 μm;

The heater has a length of 160 μm, a width of 0.8 μm, and a height of 0.26 μm.

Preferably, the distance between the modulation waveguide and the heater is 0.1 μm, and the distance between the first output waveguide and the heater is 3 μm.

Preferably, the heater includes a thermal electrode, and the positive electrode and the negative electrode of the thermal electrode are distributed at the beginning and the end of the heater, respectively.

Preferably, both the positive electrode and the negative electrode are made of aluminum.

Preferably, the modulation waveguide, the first output waveguide and the heater are all wrapped in a silicon dioxide layer.

This specification also provides an optical phased array using any one of the above thermo-optic phase shifters, the optical phased array comprising an optical beam splitter, a grating antenna array and the above thermo-optic phase shifter;

The optical beam splitter includes a second input waveguide and a second output waveguide, the second input waveguide is used to introduce the optical signal into the optical beam splitter, and the optical beam splitter is used to perform equal-power beam splitting processing on the optical signal entering the optical beam splitter , so that one optical signal becomes multiple optical signals;

The waveguide input end of the thermo-optic phase shifter is connected with the second output waveguide;

The grating antenna array is connected to the waveguide output end of the thermo-optic phase shifter for scattering the optical signal to free space.

Preferably, the thermo-optic phase shifter includes a positive electrode arranged at the beginning of the heater and a negative electrode arranged at the end of the heater, and the optical phased array further includes a positive and negative thermal electrode control bus and a digital-to-analog converter, the digital-to-analog conversion The device is used to convert the decoded data into a voltage signal and input it to the positive and negative electrode control buses. The positive and negative thermode control buses are respectively connected to the positive electrode and the negative electrode, and are used to input the voltage signal to the positive electrode and the negative electrode of the thermo-optic phase shifter. electrode to make the heater work.

It can be seen from the above that one or more embodiments of this specification provide a low-crosstalk and high-efficiency thermo-optic phase shifter and its application. The thermo-optic phase shifter includes a substrate, a propagation waveguide disposed on the substrate, and a pair of The heater for the heating of the propagation waveguide, by setting the heater as a ring-shaped curved structure and the propagation waveguide as a helical curved structure, a compact structure factor and negligible crosstalk can be formed, which not only solves the problem of low crosstalk in the phase shifter The problem of low integration degree of the phase shifter also achieves high phase modulation of π phase shift amount, which solves the problems of low phase shifting efficiency, high crosstalk and low integration degree of the existing thermo-optic phase shifter.

Description of drawings

In order to more clearly illustrate one or more embodiments of the present specification or the technical solutions in the prior art, the following briefly introduces the accompanying drawings used in the description of the embodiments or the prior art. Obviously, in the following description The accompanying drawings are only one or more embodiments of the present specification, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

1 is a schematic structural diagram of a thermo-optic phase shifter according to one or more embodiments of the specification;

2 is a schematic cross-sectional view of a thermo-optic phase shifter according to one or more embodiments of the present specification;

3 is a schematic structural diagram of an optical phased array according to one or more embodiments of the specification;

FIG. 4 is a temperature distribution diagram of the modulated waveguide and the first output waveguide according to one or more embodiments of the present specification as a function of input power;

FIG. 5 is a coupling relationship diagram between the modulation waveguide and the first output waveguide according to one or more embodiments of the present specification;

FIG. 6 is a graph of input power and phase shift amount of a thermo-optic phase shifter according to one or more embodiments of the present specification.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to specific embodiments.

It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of the present specification shall have the usual meanings understood by those with ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and similar terms used in one or more embodiments of this specification do not denote any order, quantity, or importance, but are merely used to distinguish the various components. "Comprises" or "comprising" and similar words mean that the elements or things appearing before the word encompass the elements or things recited after the word and their equivalents, but do not exclude other elements or things. Words like "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right", etc. are only used to represent the relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

The embodiment of the present specification provides a low crosstalk high-efficiency thermo-optic phase shifter 3, as shown in FIG. 1, comprising a substrate, a propagation waveguide disposed on the substrate, and heaters 3-6 for heating the propagation waveguide, wherein the heating The heater 3-6 is arranged in an annular curved structure, and the propagation waveguide is arranged in a spiral curved structure, and its shape fits the shape of the heater 3-6.

The high-efficiency thermo-optical phase shifter 3 with low crosstalk provided by the embodiment of the present specification can form a compact structure factor and negligible crosstalk by setting the heaters 3-6 as annular curved structures and the propagation waveguides as helical curved structures , while realizing the low crosstalk of the phase shifter, it not only solves the problem of low integration of the phase shifter, but also achieves the high phase modulation of the π phase shift amount.

As an embodiment, the propagation waveguide includes a first input waveguide 3-1, a modulation waveguide 3-2 and a first output waveguide 3-3 connected in sequence, and the first input waveguide 3-1, the modulation waveguide 3-2 and the first output waveguide 3-1 An output waveguide 3-3 is connected to form a helical curved structure, wherein the first input waveguide 3-1 is arranged from the input end of the waveguide of the thermo-optic phase shifter 3 to the beginning of the heater 3-6, and the modulation waveguide 3-2 is close to the heating The first output waveguide 3-3 is arranged at one end away from the heater 3-6. This structure ensures that the optical signal can be input and output in the same root waveguide, and does not need to be coupled through other waveguides, which reduces the phase shift. thermal crosstalk within the device.

As an embodiment, the material of the heaters 3-6 is copper (Cu), and the thermal conductivity of the metal copper material is 401 (W/m.K), which not only has the advantages of good heat transfer performance, good ductility and strong corrosion resistance, And it is very abundant in nature, with excellent performance, low price and convenient processing.

As an embodiment, the materials of the first input waveguide 3-1, the modulation waveguide 3-2 and the first output waveguide 3-3 are all silicon (Si), and the refractive index of the Si material is temperature-dependent, so the The refractive index change of Si material can be changed by adjusting the temperature change of Si material. At the same time, Si material has a high refractive index for light (n=3.42), which is far superior to other materials, and is very abundant in nature, with low cost, which is conducive to mass production.

Further, the good heat transfer performance of the metal copper material of the heaters 3-6 makes the generated heat have a greater influence on the refractive index variation range of the Si material waveguide, which is beneficial to the phase modulation of the optical signal.

The modulation waveguide 3-2, the first output waveguide 3-3 and the heater 3-6 are all wrapped in a silicon dioxide layer 3-7, and the silicon dioxide layer 3-7 is filled with air to form an air layer , the air layer is located above the heater 3-6 and the first output waveguide 3-3, and the air layer is made to reduce the longitudinal heat conduction.

Referring to FIG. 2, which is a cross-sectional view of the thermo-optic phase shifter of the present invention, it can be seen that to achieve a high-efficiency phase shifter structure with low crosstalk, it is necessary to design the spacing of the heaters 3-6 that affect the modulation waveguide 3-2, and the pair of heaters 3-6. The spacing of the output waveguides 3-3 without thermal crosstalk and the minimum spacing of the modulation waveguides 3-2 without coupling with the output waveguides 3-3.

As an embodiment, the distance between the modulation waveguide 3-2 and the heater 3-6 is 0.1 μm, and the distance between the first output waveguide 3-3 and the heater 3-6 is 3 μm. This structure makes the heat generated by the heater 3-6 change the refractive index of the Si material of the modulation waveguide 3-2, so that the optical signal entering the modulation waveguide 3-2 can achieve phase modulation of the π phase shift amount, and at the same time, it also avoids the Waveguides create thermal crosstalk.

Further, the semiconductor substrates 3-8 of the thermo-optic phase shifter 3 can be selected according to actual conditions, including but not limited to semiconductor materials such as silicon materials, silicon nitride, and III-V compounds.

As an embodiment, the heater 3-6 includes a hot electrode, and the positive electrode 3-4 and the negative electrode 3-5 of the hot electrode are distributed at the beginning and the end of the heater 3-6, for example, the positive electrode 3- 4 and the materials of the negative electrodes 3-5 are all aluminum.

The present specification also provides an optical phased array using the above thermo-optic phase shifter 3 , as shown in FIG. The optical beam splitter 2 includes a second input waveguide 1 and a second output waveguide. The second input waveguide 1 introduces the optical signal into the optical beam splitter 2, and the optical beam splitter 2 is used to perform the optical signal processing on the optical signal entering the optical beam splitter 2. The equal-power beam splitting process turns one optical signal into multiple optical signals; the waveguide input end of the thermo-optic phase shifter 3 is connected to the second output waveguide, and the optical signal is split by the optical beam splitter 2 and then input to the phase shifter The input waveguide of the phase shifter, the grating antenna array 6 is connected to the waveguide output end of the thermo-optic phase shifter 3, and the phase-modulated optical signal is output from the output waveguide of the phase shifter to the grating antenna array 6 to scatter to free space.

As an embodiment, the thermo-optic phase shifter 3 includes a positive electrode 3-4 arranged at the beginning of the heater 3-6 and a negative electrode 3-5 arranged at the end of the heater 3-6, and the optical phased array further includes The positive and negative thermal electrode control bus 4 and the digital-to-analog converter 5, wherein the digital-to-analog converter 5 is an inverted triangle structure arranged at the top of the positive and negative thermal electrode control bus 4, and is used to convert the decoded data into a voltage signal and input it to the positive and negative thermal electrodes. The electrode control bus 4, the positive and negative hot electrode control bus 4 are respectively connected with the positive electrode 3-4 and the negative electrode 3-5, for inputting the voltage signal to the hot electrode and the negative electrode 3-5 of the thermo-optic phase shifter 3, The heater 3-6 is operated, and the heat generated by the heater 3-6 changes the refractive index of the modulation waveguide 3-2, thereby modulating the phase of the optical signal in the modulation waveguide 3-2. The digital-to-analog converter 5 quickly applies the converted voltage signal to the positive and negative hot electrodes. This shortens the startup time of the heaters 3-6 and improves the efficiency with which the thermo-optical phase shifter 3 operates.

Set the above-mentioned thermo-optic phase shifter 3, let the heater 3-6 be in an environment with a temperature of 300K, and apply an input power of 30-40mW to the heater 3-6 and place a temperature detector on the modulation waveguide 3-2 for Let's observe the temperature change around the modulation waveguide 3-2. Referring to FIG. 4 , it is a temperature change distribution diagram around the modulation waveguide 3-2 and the output waveguide under an input power of 30 mW. From the observation of the heat distribution in Fig. 4, it is found that there is a temperature change of about 26K in the area around the modulation waveguide 3-2, indicating that the heat generated by the heater 3-6 has a good effect on the refractive index change of the material of the modulation waveguide 3-2, which can make the light The signal is phase-modulated with a π phase shift amount. The heaters 3-6 of the present invention cannot generate thermal crosstalk to the output waveguide, otherwise the phase modulation of the optical signal will be affected. Therefore, according to Fig. 4, it can be seen that there is almost no temperature change in the area around the output waveguide, indicating that the heaters 3-6 have no thermal crosstalk to the output waveguide, which meets the design requirements.

Referring to FIG. 5, FIG. 5 is a diagram showing the coupling relationship between the modulation waveguide 3-2 and the first output waveguide 3-3 in the present invention. When two waveguides are coupled, an electric field E exists between the two waveguides. The parameter electric field E also changes with the distance between the two waveguides, so according to the change of the parameter electric field E, the coupling between the modulation waveguide 3-2 and the first output waveguide 3-3 can be obtained. Because the present invention needs to ensure that the optical signal is input into the first output waveguide 3-3 after the phase shift occurs in the modulation waveguide 3-2, it can no longer occur with the modulation waveguide 3-2 during the output process of the first output waveguide 3-3. Otherwise, the phase modulation of the thermo-optic phase shifter 3 will fail and the integration degree of the thermo-optic phase shifter 3 will be improved. Therefore, the modulation waveguide 3-2 and the first output waveguide 3-3 should be found according to the parameter electric field E. The minimum spacing at which coupling does not occur. Therefore, according to the analysis of FIG. 5, it can be seen that when the distance D between the modulation waveguide 3-2 and the first output waveguide 3-3 is D<46nm, there is an electric field between them, which indicates that coupling occurs between the two waveguides; When the distance D≥46nm, the electric field strength between the two waveguides tends to 0, which means that the two waveguides are hardly coupled; therefore, the minimum distance between the modulation waveguide 3-2 and the first output waveguide 3-3 is designed to be 46nm.

和调制波导3-2温度变化ΔT，则调制波导3-2的长度L可表示为Further, in the present invention, the phase change of the optical signal through the phase shifter

and the temperature change ΔT of the modulation waveguide 3-2, the length L of the modulation waveguide 3-2 can be expressed as

为波导Si材料的热光系数的倒数，对于Si材料而言，该热光系数为1.86×10^-4K^-1。where λ is the wavelength of the optical signal 1550nm and

is the reciprocal of the thermo-optic coefficient of the waveguide Si material, and for the Si material, the thermo-optic coefficient is 1.86×10 ^-4 K ^-1 .

Further, in the present invention, the temperature change ΔT of the modulated waveguide 3-2 is 26K as shown in FIG. 4 . Therefore, when the phase modulation of the light reaches the phase shift amount of π, the length L of the modulated waveguide 3-2 is calculated by the above formula. = 160 μm. Therefore, the designed total length of the waveguide in the present invention is set to be 320 μm, the width is 0.4 μm, and the height is 0.2 μm, and the length L of the modulation waveguide 3-2 is 160 μm.

Further, in the present invention, the heater 3-6 heats the modulation waveguide 3-2 in a ring-shaped curved structure, which does not involve the influence on the first output waveguide 3-3, so the heater 3-6 is set to be 160 μm in length, The width is 0.8 μm and the height is 0.25 μm.

的关系图。设置所加的输入功率为30-40mW，再将上述调制波导3-2随输入功率变化的温度数据处理后，用于计算环境温度为300K下的有效折射率。然后记录结果数据，作为公式函数的有效指数n_eff。最后根据得到的有效指数n_eff，通过公式

来计算出输入功率函数的相位变化。Referring to FIG. 6, the input power P and the phase shift amount added to the thermo-optic phase shifter 3 of the present invention

relationship diagram. Set the added input power to 30-40mW, and then process the temperature data of the modulated waveguide 3-2 as a function of the input power to calculate the effective refractive index at an ambient temperature of 300K. The resulting data is then recorded as the effective exponent _neff of the formula function. Finally, according to the obtained effective exponent n _eff , through the formula

to calculate the phase change of the input power function.

为移相器的相移量，arr_P为输入功率长度的数组值,n_eff0为有效指数n_eff的整数部分，λ为入射光信号的波长且取1550nm，l为波导的长度且取320μm。从图6的关系图中看出当相移量

变化了π的相移量，此时输入功率为36mW。同时依据图6为输入功率与相移量的线性关系图可推算出该结构的移相器发生2π的相移量所需的输入功率为72mW。In the above formula

is the phase shift amount of the phase shifter, arr _P is the array value of the input power length, n _eff0 is the integer part of the effective exponent n _eff , λ is the wavelength of the incident optical signal and takes 1550nm, l is the length of the waveguide and takes 320μm. It can be seen from the relationship diagram in Figure 6 that when the phase shift amount

The phase shift amount of π is changed, and the input power is 36mW at this time. Meanwhile, according to the linear relationship between the input power and the phase shift amount shown in FIG. 6 , it can be deduced that the input power required for the phase shifter of this structure to generate a phase shift amount of 2π is 72 mW.

To sum up, compared with the traditional phase shifter, the present invention adopts the thermo-optical regulation, so that it has the advantages of low light loss, low power consumption and fast response time. The invention is designed as a helical bending structure, which has a compact structure factor and negligible crosstalk, not only solves the problem of low integration of the phase shifter, but also achieves a π phase shift while achieving low crosstalk of the phase shifter. amount of high phase modulation. Moreover, the present invention has the feasibility of application, and the manufacturing process is compatible with CMOS.

Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary, and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples; under the spirit of the present disclosure, the above embodiments or Combinations between technical features in different embodiments are also possible, and there are many other variations of the different aspects of one or more embodiments of the specification as described above, which are not provided in detail for the sake of brevity.

The embodiment or embodiments of this specification are intended to cover all such alternatives, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of one or more embodiments of the present specification should be included within the protection scope of the present disclosure.

Claims (10)

1. a high-efficiency thermo-optical phase shifter with low crosstalk is characterized in that, comprising: a substrate, a propagating waveguide disposed on the substrate, and a heater for heating the propagating waveguide; The heater is arranged in an annular curved structure; The propagating waveguide is arranged in a helical curved structure, and its shape fits the shape of the heater. 2 . The high-efficiency thermo-optic phase shifter with low crosstalk according to claim 1 , wherein the propagation waveguide comprises a first input waveguide, a modulation waveguide and a first output waveguide connected in sequence, and the first input waveguide , the modulation waveguide and the first output waveguide are connected to form a helical curved structure, the first input waveguide is arranged from the input end of the waveguide of the thermo-optic phase shifter to the beginning of the heater, and the modulation waveguide is close to the A heater is disposed, and the first output waveguide is disposed at one end away from the heater. 3 . The high-efficiency thermo-optic phase shifter with low crosstalk according to claim 1 , wherein the heater is made of copper; the first input waveguide, the modulation waveguide and the first output waveguide are 3 . The material is silicon. 4 . The high-efficiency thermo-optic phase shifter with low crosstalk according to claim 3 , wherein the length of the propagation waveguide is 320 μm, the width is 0.4 μm, and the height is 0.2 μm, and the length of the modulation waveguide is 160 μm; 5 . The heater has a length of 160 μm, a width of 0.8 μm and a height of 0.26 μm. 5 . The high-efficiency thermo-optic phase shifter with low crosstalk according to claim 1 , wherein the distance between the modulation waveguide and the heater is 0.1 μm, and the first output waveguide and the heater are 0.1 μm. 6 . The spacing between the devices is 3 μm. 6 . The high-efficiency thermo-optic phase shifter with low crosstalk according to claim 1 , wherein the heater comprises a thermal electrode, and the positive electrode and the negative electrode of the thermal electrode are respectively distributed at the beginning of the heater. 7 . and end. 7 . The high-efficiency thermo-optic phase shifter with low crosstalk according to claim 6 , wherein the positive electrode and the negative electrode are both made of aluminum. 8 . 8 . The high-efficiency thermo-optic phase shifter with low crosstalk according to claim 1 , wherein the modulation waveguide, the first output waveguide and the heater are all wrapped in a silicon dioxide layer. 9 . 9. An optical phased array applying the thermo-optic phase shifter according to any one of claims 1-8, wherein the optical phased array comprises an optical beam splitter, a grating antenna array and all the thermo-optic phase shifter; The optical beam splitter includes a second input waveguide and a second output waveguide, the second input waveguide is used for introducing an optical signal into the optical beam splitter, and the optical beam splitter is used for splitting the incoming light The optical signal of the device is processed by equal power beam splitting, so that one optical signal becomes multiple optical signals; The waveguide input end of the thermo-optic phase shifter is connected to the second output waveguide; The grating antenna array is connected to the waveguide output end of the thermo-optic phase shifter, and is used for scattering optical signals to free space. 10. The optical phased array according to claim 9, wherein the thermo-optic phase shifter comprises a positive electrode arranged at the beginning of the heater and a negative electrode arranged at the end of the heater, The optical phased array also includes a positive and negative electrode control bus and a digital-to-analog converter, the digital-to-analog converter is used to convert the decoded data into a voltage signal and input it to the positive and negative electrode control bus. The electrode control bus is respectively connected with the positive electrode and the negative electrode, and is used for inputting a voltage signal to the positive electrode and the negative electrode of the thermo-optical phase shifter to make the heater work.

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