Multi-directional controllable electro-optical switch structure based on grating coupler

Abstract

The invention discloses a multidirectional controllable electro-optical switch structure based on a grating coupler, and belongs to the technical field of optical waveguides and optical switches. The device is realized based on a grating reverse coupler, and comprises an optical loop cascade formed by an asymmetric directional coupler and a grating coupler, the optical loop comprises a grating reverse coupler, an upper waveguide and a lower waveguide, the upper waveguide and the lower waveguide are arranged in parallel to clamp the grating reverse coupler on the inner side, two groups of grating couplers are respectively formed, and the optical loop is formed; the metal electrodes which are independently controlled are arranged on the two sides of the directional coupler, the upper waveguide and the lower waveguide respectively, optical signals are regulated and controlled through the electrodes on the basis of the electro-optical effect, the function that the optical signals can be output from a designated port in different proportions and transmitted reversely is achieved, and the purpose that the optical signals can be controllably transmitted in multiple directions is achieved. According to the invention, the construction of a reconfigurable optical switching network is facilitated, the high-speed stable switching of the switching state can be realized under the action of electro-optical cooperative control by utilizing the excellent electro-optical coefficient of the lithium niobate material, and the flexibility is provided for manufacturing a large-scale optical switch array and an optical interconnection network.

Description

Technical Field

[0001] The present invention relates to the technical field of optical waveguide and optical switch, and in particular to a multi-directional controllable electro-optical switch structure based on a grating coupler, which can be applied to optical communication, optical interconnection and the like. Background Art

[0002] With the explosive growth of interconnected devices and information traffic, information processing technology has gradually reached a bottleneck. In order to achieve faster information processing speed and higher information transmission capacity, silicon-based integrated photonic structures compatible with complementary metal semiconductor (CMOS) processes have begun to be widely studied and applied. In order to build a low-power sustainable data center, researchers have proposed a solution to replace electrical interconnection with optical interconnection and electrical switching with optical switching based on the advantages of optical interconnection such as low crosstalk, low latency, and large capacity. Because optical switches are the core units of silicon-based optoelectronic integrated chips and the core components of optical switching networks, they directly affect chip performance and reliability. In view of the new challenges of multi-directional, low power consumption, and high reliability of optical switches and optical switch networks under the new generation of information technology, research on multi-directional controllable electro-optical switch structures and electrode regulation modes is inevitable.

[0003] Optical switches are an important component of high-speed and large-capacity information interaction and an important device for on-chip interconnection. The materials used to make waveguide optical switches include IIII-V semiconductors, silicon-based silicon dioxide waveguides, lithium niobate, organic polymers and other types. Lithium niobate (LN: Lithium Niobate) material has excellent optical properties, obvious linear electro-optical effect, and stable physical and chemical properties. It is one of the crystal materials with good comprehensive performance and the most widely used. By utilizing its excellent electro-optical coefficient, the high-speed and stable switching of the switch state can be achieved under the electro-optical coordinated control. So far, the micro-machining process of lithium niobate materials is relatively mature. The commonly used manufacturing methods mainly include Ti diffusion method, proton exchange method, and femtosecond laser etching method. Therefore, waveguide optical switches based on lithium niobate materials have become a research hotspot. The many excellent properties of lithium niobate crystals have made waveguide devices based on lithium niobate crystals receive more and more attention, including waveguide gratings. In integrated optical device systems, waveguide gratings play a vital role and are the basic components of many filters and sensors. They have broad application prospects in optical communication systems, optical sensing, lasers and other fields. Summary of the invention

[0004] In view of the new generation of information technology, in order to realize the multi-directional, low power consumption, high reliability and other characteristics of optical switches and optical switch networks, the problem of large-scale integrated optical switches and optical switch networks on a chip is solved. The present invention provides a multi-directional controllable electro-optical switch structure based on a grating coupler, which uses electrodes to regulate optical signals, realizes the function that optical signals can be output from a specified port in different proportions and transmitted in the reverse direction, and achieves the purpose of multi-directional controllable transmission of optical signals. Moreover, the present invention is based on a waveguide grating, has no FSR limitation, and has a large tuning range.

[0005] The present invention is achieved through the following technical solutions:

[0006] A multidirectional controllable electro-optical switch structure based on a grating coupler, wherein the multidirectional controllable electro-optical switch is realized based on a grating reverse coupler, and comprises an optical circuit cascade consisting of an asymmetric directional coupler and a grating coupler; the optical circuit comprises a grating reverse coupler, an upper waveguide and a lower waveguide, wherein the upper waveguide and the lower waveguide are placed in parallel to sandwich the grating reverse coupler inside, respectively constituting two groups of grating couplers to form an optical circuit; independently controlled metal electrodes are respectively arranged on both sides of the directional coupler and the upper and lower waveguides; the waveguide cross section constituting the electro-optical switch structure is suitable for all integrated optical waveguide structures, and at least comprises: a strip waveguide, a ridge waveguide, and a multilayer waveguide; the electro-optical switch should be provided with a silicon substrate, a quartz substrate or a lithium niobate substrate, and a silicon dioxide protective layer is arranged on the optical waveguide layer made of a lithium niobate thin film material, and the refractive index of the protective layer material is less than that of the lithium niobate thin film material.

[0007] In the above technical solution, the electro-optical switch structure uses a curved structure, namely an S-curved waveguide, to cascade the directional coupler and the grating coupler, one end of the curved waveguide is connected to the output port of the asymmetric directional coupler, and the other end is connected to the upper waveguide or the lower waveguide placed in parallel.

[0008] In the above technical solution, the grating reverse coupler structure is a Bragg grating structure, and the Bragg grating includes an upper and a lower waveguide segment. Periodic rectangular etching is performed on the side walls of the upper and lower waveguide segments so that the effective refractive index of the waveguide presents a periodic change.

[0009] In the above technical solution, the reverse coupler structure includes a waveguide segment a and a waveguide segment b. The first half period and the second half period are arranged on opposite sides of the waveguide segment a and the waveguide segment b, and both are extended half outward to form a grating modulated perturbation structure, which does not directly extend outward or shrink inward on the basis of a straight waveguide.

[0010] In the above technical solution, the reverse coupler structure includes a waveguide segment c and a waveguide segment d on opposite sides, wherein the first half cycle is extended outward by half, and the second half cycle is shortened inward by half, thereby forming a grating modulated perturbation structure.

[0011] The present invention has the following beneficial effects:

[0012] The Bragg grating-based reverse coupler of the present invention can change the propagation direction of the original light field in the waveguide. The electrodes are used to regulate the optical signal, so that the optical signal can be output from the designated port in different proportions and transmitted in the reverse direction, so as to achieve the purpose of multi-directional controllable transmission of the optical signal. Moreover, the present invention is based on the waveguide grating, has no FSR limitation, and has a large tuning range.

[0013] The present invention is conducive to building a reconfigurable optical switching network. By utilizing the excellent electro-optical coefficient of lithium niobate material, high-speed and stable switching of switch states can be achieved under electro-optical coordinated control, providing flexibility for making large-scale optical switch arrays and optical interconnection networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of an asymmetric directional coupler in a multi-directional controllable electro-optical switch structure based on a grating coupler of the present invention;

[0015] Figure 2 It is a schematic diagram of the overall structure of the multi-directional controllable electro-optical switch structure based on the grating coupler of the present invention;

[0016] Figure 3 A schematic diagram of the structure of the reverse coupler in the present invention;

[0017] Figure 4 A schematic diagram of the structure of the reverse coupler in the present invention; DETAILED DESCRIPTION

[0018] The present invention is further described in detail below by specific implementation modes in conjunction with the accompanying drawings. The present application can be implemented in a variety of different forms and is not limited to the implementation modes described in this embodiment. The purpose of providing the following specific implementation modes is to facilitate a clearer and more thorough understanding of the content of the invention of the present invention.

[0019] like Figure 1As shown, a multi-directional controllable electro-optical switch structure based on a grating coupler includes an asymmetric directional coupler, curved waveguides 2 and 3, an upper waveguide 4 and a lower waveguide 5. The left end of the curved waveguide 2 is connected to the input port Port1 of the asymmetric directional coupler, and the other end is connected to the upper waveguide 4 placed in parallel; the left end of the curved waveguide 3 is connected to the input port Port2 of the asymmetric directional coupler, and the other end is connected to the lower waveguide 5 placed in parallel. According to the above arrangement, a 2x2 asymmetric directional coupler can be formed. An optical signal is input from the input port Port1, coupled in the asymmetric directional coupler, coupled to the waveguide below, transmitted along the curved waveguide 3, continued to propagate in the lower waveguide 5, and finally output from the output port Port4; when the optical signal is input from the input port Port1, the optical signal is regulated by the electrode group 1, transmitted along the curved waveguide 2, transmitted to the upper waveguide 4 placed in parallel, and finally output from the output port Port3. By applying different voltages to the electrode group 5 to change the size of the refractive index, the conversion of the coupling efficiency can be controlled, so that the output signal can be output in any proportion at different ports, that is, a reconfigurable function is realized.

[0020] like Figure 2 As shown, a multi-directional controllable electro-optical switch structure based on a grating coupler is implemented based on a grating reverse coupler, including an optical circuit cascade consisting of an asymmetric directional coupler and a grating coupler; the circuit includes a grating-assisted upper waveguide 7 and a grating-assisted lower waveguide 8, an upper waveguide 4 and a lower waveguide 5 in the reverse coupler. Specifically, the waveguide widths of the grating-assisted upper waveguide 7 and the grating-assisted lower waveguide 8 are different. Due to the different widths, the propagation constants of the two are also different. When the propagation constants of the two are greatly different, the efficiency of the same-direction coupling will be particularly low, and the same-direction coupling cutoff will occur. The straight waveguide sections of the upper waveguide 4, the grating-assisted upper waveguide 7, the grating-assisted lower waveguide 8 and the lower waveguide 5 are placed parallel to each other, and the spacing between them is in the micrometer range, generally about 5 to 10 micrometers.

[0021] During operation, light enters from Port1. When it propagates to the straight waveguide area close to the upper waveguide 4 of the optical circuit, the electrode group 6 is used to regulate the optical signal. By applying different voltages to the electrode group 5 to change the refractive index, the optical signal is transmitted to the parallel grating-assisted upper waveguide 7, and finally output from the output port Port5. Similarly, the optical signal can also be output from the output port Port6. When the optical signal is input from Port3, it enters the straight waveguide area of ​​the upper waveguide 4. Based on the grating assistance, the light is reversely coupled from the upper waveguide 4 to the grating-assisted upper waveguide 7, and then propagates in the direction indicated by the arrow; in the straight waveguide 7, the optical signal is reversely coupled to the grating-assisted lower waveguide 8, and is transmitted in the straight waveguide area along the direction indicated by the arrow. Finally, the light is reversely coupled to the lower waveguide 5 again, and is transmitted to the output port Port4 along the direction indicated by the arrow for output. Similarly, the optical signal can be input from Port4 and output from Port3, which realizes the function of multi-directional controllable transmission of the optical signal.

[0022] like Figure 3 As shown, the reverse coupler includes a waveguide section a and a waveguide section b, which are arranged parallel to each other up and down, and a periodic tooth structure is arranged on the opposite sides of the waveguide section a and the waveguide section b, and the first half period and the second half period are arranged on the opposite sides of the waveguide section a and the waveguide section b, and both extend half of the period outward to form a grating. The length of the grating period is related to the propagation wavelength and the waveguide material, and is generally several hundred nanometers, wherein the depth and width of a single tooth structure are designed according to the specific situation.

[0023] like Figure 4 As shown, the reverse coupler includes a waveguide segment c and a waveguide segment d, the waveguide segment c and the waveguide segment d are arranged parallel to each other, and a periodic tooth structure is arranged on the opposite sides of the waveguide segment c and the waveguide segment d, and the first half period is extended half outward and the second half period is shortened half inward on the opposite sides of the waveguide segment c and the waveguide segment d to form a grating. The structure of this embodiment can maintain the average effective refractive index of the grating perturbation zone within one period to be not much different from that of the original straight waveguide, thereby ensuring that the Bragg wavelength drift is small and a result closer to the theoretical value can be obtained.

[0024] The above is only a preferred specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims

1. The present invention proposes a multi-directional controllable electro-optical switch structure based on a grating coupler, characterized in that: The multi-directional controllable electro-optical switch is realized based on a grating reverse coupler, and includes an optical circuit cascade consisting of an asymmetric directional coupler and a grating coupler; the optical circuit includes a grating reverse coupler, an upper waveguide and a lower waveguide, the upper waveguide and the lower waveguide are placed in parallel to clamp the grating reverse coupler inside, respectively forming two groups of grating couplers to form an optical circuit; independently controlled metal electrodes are respectively provided on both sides of the directional coupler and the upper and lower waveguides; The waveguide cross section constituting the electro-optical switch structure is applicable to all integrated optical waveguide structures, including at least: a strip waveguide, a ridge waveguide, and a multilayer waveguide; The electro-optical switch should be provided with a silicon substrate, a quartz substrate or a lithium niobate substrate, and a silicon dioxide protective layer is arranged on the optical waveguide layer made of lithium niobate thin film material, and the refractive index of the protective layer material is smaller than the refractive index of the lithium niobate thin film material.

2. The multi-directional controllable electro-optical switch structure based on a grating coupler according to claim 1, characterized in that: The electro-optical switch structure uses a curved structure, namely an S-curved waveguide, to cascade a directional coupler and a grating coupler. One end of the curved waveguide is connected to the output port of the asymmetric directional coupler, and the other end is connected to an upper waveguide or a lower waveguide placed in parallel.

3. The multi-directional controllable electro-optical switch structure based on grating coupler according to claims 1 and 2, characterized in that: The grating reverse coupler structure is a Bragg grating structure, and the Bragg grating includes an upper and a lower waveguide segment. Periodic rectangular etching is performed on the side walls of the upper and lower waveguide segments to make the effective refractive index of the waveguide present a periodic change.

4. The multi-directional controllable electro-optical switch structure based on a grating coupler according to claims 1-3, characterized in that: The reverse coupler structure includes a waveguide section a and a waveguide section b. On opposite sides of the waveguide section a and the waveguide section b, the first half period and the second half period are both extended halfway outward to form a grating modulated perturbation structure, which is not directly extended outward or directly reduced inward on the basis of a straight waveguide. Alternatively, the reverse coupler structure includes arranging the first half cycle to extend half outward and the second half cycle to shrink half inward on opposite sides of the waveguide segment c and the waveguide segment d, thereby forming a grating modulated perturbation structure.

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