High-extinction-ratio optical switch based on multi-mode interference and electronic equipment

Abstract

The invention provides a multi-mode interference-based high extinction ratio optical switch and electronic equipment, and the optical switch comprises an input assembly which comprises an input waveguide or an input optical fiber; the output component comprises an output waveguide or an output optical fiber; the multi-mode interference area is connected with the input assembly and the output assembly, the multi-mode interference area comprises a refractive index main regulation and control area and a refractive index auxiliary regulation and control area, when the refractive index of the refractive index main regulation and control area is higher than that of areas on the two sides of the refractive index main regulation and control area, or the refractive index of the refractive index main regulation and control area is higher than that of the refractive index auxiliary regulation and control area, the optical switch is in an on state, and the optical switch is in an off state; when the refractive index of the refractive index main regulation and control area is lower than that of the areas on the two sides of the refractive index main regulation and control area, or the refractive index of the refractive index main regulation and control area is lower than that of the refractive index auxiliary regulation and control area, the optical switch is in an off state. The high extinction ratio optical switch based on multi-mode interference has high tolerance characteristic and high extinction ratio.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of optical information processing technology, and in particular to a high extinction ratio optical switch and electronic equipment based on multi-mode interference. Background Art

[0002] Optical switches are one of the key components for optical fiber communication and optical information processing. Currently, commercial optical switches are mostly used in two ways: conventional mechanical electromagnetic switches and MEMS (Micro-Electro-Mechanical System). Conventional mechanical optical switches are large in size, ranging from a few centimeters to tens of centimeters. They use electromagnetic mechanical movement to align the input and output optical fibers to make the signal light conduct or disconnect. The main features of electromagnetic switches are high extinction ratio and low insertion loss. The main disadvantage is that metal debris generated after long-term use of electromagnetic switches will seriously affect the reliability of the switch. MEMS optical switches have been commercialized for more than ten years. Semiconductor processing technology is used to make movable or rotating reflectors on silicon materials. The position or angle of the mirror is controlled to achieve the change of the optical path and achieve the purpose of switching. MEMS optical switches are small in size, usually around the millimeter level, and have a high extinction ratio. The extinction ratio of the above two optical switches can reach more than 50dB. However, the switching speed of these two switches is in the millisecond level, which cannot meet the needs of high-speed optical communication.

[0003] One of the hot research directions in the field of optical switches is optical waveguide optical switches. Searching for optical switch and waveguide on the internationally renowned database Web of Science shows that there have been 700-800 papers researching waveguide optical switches each year in the past five years. The advantage of optical waveguide optical switches is that they use voltage, current, thermal effect or acousto-optic effect to control the refractive index. The switching speed is generally faster than the above two methods, and the device has no moving parts, so the reliability is very high. The manufacturing process of optical waveguides also uses semiconductor technology, which has mass production and cost advantages. However, the biggest problem with waveguide optical switches at present is that the extinction ratio is too low. Due to the inherent optical path characteristics of waveguide optical switches, the extinction ratio of most studies is generally around 25dB, and the few studies above 30dB are only at the laboratory level. The accuracy of the parameters (mainly the change in the refractive index and the control of the size of the key parts of the device) is extremely strict and not universal. Summary of the invention

[0004] The invention provides a high extinction ratio optical switch and electronic equipment based on multi-mode interference which are realized based on the multi-mode interference principle and have high tolerance characteristics and high extinction ratio.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a high extinction ratio optical switch based on multi-mode interference, comprising:

[0006] an input assembly, including an input waveguide or an input optical fiber;

[0007] an output assembly, including an output waveguide or an output optical fiber;

[0008] The multimode interference zone is connected to the input component and the output component respectively, and the multimode interference zone includes a main refractive index control zone and an auxiliary refractive index control zone. When the refractive index of the main refractive index control zone is higher than that of the areas on both sides thereof, or the refractive index of the main refractive index control zone is higher than that of the auxiliary refractive index control zone, the optical switch is in an open state; when the refractive index of the main refractive index control zone is lower than that of the areas on both sides thereof, or the refractive index of the main refractive index control zone is lower than that of the auxiliary refractive index control zone, the optical switch is in a closed state.

[0009] In some embodiments, the multi-mode interference region includes a waveguide component, an optical chip connected to the waveguide component, and a substrate connected to the optical chip.

[0010] In some embodiments, the waveguide assembly includes waveguides having abrupt boundaries, and / or waveguides having gradual boundaries.

[0011] In some embodiments, the waveguide assembly includes at least one of the following:

[0012] Waveguide formed based on dry etching;

[0013] Waveguide formed based on wet etching;

[0014] Waveguides formed by exchanging different ions;

[0015] Waveguides formed by diffusion processes, including waveguides formed by diffusion of lithium titanium niobate.

[0016] In some embodiments, the boundary of the multi-mode interference zone is formed by etching steps, there are three steps, and they respectively form a first upper electrode, a second upper electrode and a third upper electrode, and two adjacent upper electrodes have a target spacing. The multi-mode interference zone includes an upper limiting layer, a waveguide layer, a lower limiting layer and a lower electrode connected in sequence, the first upper electrode, the second upper electrode and the third upper electrode are located on the upper limiting layer, and the lower electrode covers the lower limiting layer.

[0017] In some embodiments, the first upper electrode and the third upper electrode are respectively located on both sides of the second upper electrode, the area between the second upper electrode and the lower electrode forms the refractive index main control area, the area between the first upper electrode and the lower electrode, and the area between the third upper electrode and the lower electrode respectively form the refractive index auxiliary control area, when current is injected into the refractive index auxiliary control area, the refractive index of the refractive index auxiliary control area decreases, and the optical switch is in an on state, and when current is injected into the refractive index main control area, the optical switch is in an off state;

[0018] The refractive index of the main refractive index control area and the auxiliary refractive index control area is affected by the position and size of the injected current.

[0019] In some embodiments, the multi-mode interference region includes an optical chip, a substrate disposed on the optical chip, a planar waveguide formed by a titanium diffusion layer on the substrate, an optical isolation layer on the planar waveguide, and a first electrode and a second electrode on the optical isolation layer, the first electrode and the second electrode are spaced apart, a region corresponding to the space in the multi-mode interference region forms a main refractive index control region, and regions corresponding to the first electrode and the second electrode respectively form two auxiliary refractive index control regions, when a positive voltage and a negative voltage are applied to the first electrode and the second electrode respectively, the optical switch is in an on state, and when a voltage is applied to the region between the first electrode and the second electrode, the optical switch is in an off state;

[0020] The refractive index of the main refractive index control area and the auxiliary refractive index control area is affected by the position and size of the injected voltage.

[0021] In some embodiments, the input waveguide and the output waveguide are both single-mode waveguides.

[0022] In some embodiments, the input waveguide and the output waveguide are at least any one of a common straight waveguide of equal width, a trapezoidal waveguide that is wide on the left and narrow on the right or narrow on the left and wide on the right, or a curved or gradually unequal-width waveguide;

[0023] The input optical fiber and the output optical fiber are at least any one of flat-head, round-head or tapered-head optical fibers.

[0024] Another embodiment of the present invention also provides an electronic device, including a high extinction ratio optical switch based on multi-mode interference as described in any one of the embodiments above.

[0025] Based on the disclosure of the above embodiments, it can be known that the beneficial effects of the embodiments of the present invention include setting the multi-mode interference zone to have a main refractive index control zone and an auxiliary refractive index control zone, and adjusting the refractive index of the two zones by applying different operations to the main refractive index control zone and the auxiliary refractive index control zone, thereby realizing the conduction or non-conduction of the optical switch, and at the same time being able to achieve high extinction ratio and high tolerance.

[0026] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures specifically pointed out in the written description, claims, and drawings.

[0027] The technical solution of the present application is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 Schematic diagram of the structure of a high extinction ratio optical switch based on multi-mode interference in an embodiment of the present invention.

[0030] Figure 2 It is a schematic structural diagram of a high extinction ratio optical switch based on multi-mode interference in another embodiment of the present invention.

[0031] Figure 3 It is a schematic structural diagram of a high extinction ratio optical switch based on multi-mode interference in another embodiment of the present invention.

[0032] Figure 4 It is a schematic structural diagram of a high extinction ratio optical switch based on multi-mode interference in another embodiment of the present invention.

[0033] Figure 5 The measured voltage-output optical power curve of the high extinction ratio optical switch 7684 based on multi-mode interference in this embodiment.

[0034] Reference numerals:

[0035] 1-input component; 2-multimode interference zone; 3, 5-auxiliary refractive index control zone; 4-main refractive index control zone; 6-output component; 7-first upper electrode; 8-second upper electrode; 9-third upper electrode; 10-upper confinement layer; 11-waveguide layer; 12-substrate; 13-lower electrode; 14-first electrode; 15-second electrode; 16-optical isolation layer; 17-titanium diffusion layer. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but are not intended to limit the present invention.

[0037] It should be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the following description should not be considered as limiting, but merely as an example of an embodiment. Other modifications within the scope of the present disclosure will occur to those skilled in the art.

[0038] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the general description of the present disclosure given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure.

[0039] These and other characteristics of the invention will become apparent from the following description of a preferred form of embodiment given as a non-limiting example, with reference to the accompanying drawings.

[0040] It should also be understood that, although the invention has been described with reference to some specific examples, those skilled in the art will be able to realize many other equivalent forms of the invention that have the characteristics recited in the claims and are therefore within the scope of protection defined thereby.

[0041] The above and other aspects, features and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

[0042] Specific embodiments of the present disclosure are described hereinafter with reference to the accompanying drawings; however, it should be understood that the disclosed embodiments are merely examples of the present disclosure, which may be implemented in a variety of ways. Well-known and / or repeated functions and structures are not described in detail to avoid obscuring the present disclosure with unnecessary or redundant details. Therefore, the specific structural and functional details disclosed herein are not intended to be limiting, but merely serve as a basis and representative basis for the claims to teach those skilled in the art to use the present disclosure in a variety of ways with substantially any suitable detailed structure.

[0043] This specification may use the phrases "in one embodiment," "in another embodiment," "in a further embodiment," or "in other embodiments," all of which may refer to one or more of the same or different embodiments according to the present disclosure.

[0044] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0045] As shown in the figure, an embodiment of the present invention provides a high extinction ratio optical switch based on multi-mode interference, comprising:

[0046] Input component 1, including input waveguide or input optical fiber;

[0047] an output assembly, including an output waveguide or an output optical fiber;

[0048] The multimode interference zone 2 is connected to the input component 1 and the output component 6 respectively. The multimode interference zone 2 includes a main refractive index control zone 4 and an auxiliary refractive index control zone (3, 5). When the refractive index of the main refractive index control zone 4 is higher than that of the areas on both sides thereof, or the refractive index of the main refractive index control zone 4 is higher than that of the auxiliary refractive index control zone (3, 5), the optical switch is in an open state. When the refractive index of the main refractive index control zone 4 is lower than that of the areas on both sides thereof, or the refractive index of the main refractive index control zone 4 is lower than that of the auxiliary refractive index control zone (3, 5), the optical switch is in a closed state.

[0049] In this embodiment, when the input component 1 and the output component 6 are both waveguides, they are integrated with the multimode interference area 2 and can be formed by extending the waveguide in the multimode interference area 2. If the input component 1 and the output component 6 are both optical fibers, they can be bonded to the multimode interference area 2 by using a UV curing adhesive through a packaging process. The main refractive index control area 4 is located at the center of the multimode interference area 2, and the auxiliary refractive index control areas (3, 5) are located on both sides of the main refractive index control area 4. The auxiliary refractive index control areas (3, 5) can be adjusted to be lowered or raised when the optical switch is in the on state or in the off state, so as to increase the optical power of the optical switch in the on state or reduce the optical power of the optical switch in the off state, thereby achieving the purpose of optimizing the switch characteristics. Of course, the auxiliary refractive index control areas (3, 5) can be independently set, or the main refractive index control area 4 is independently set, while the auxiliary refractive index control areas (3, 5) are not independently set, and are formed by the areas on both sides of the main refractive index control area 4 of the optical switch. Alternatively, in some other scenarios, the refractive index auxiliary control area (3, 5) may not be set.

[0050] Based on the above content, it can be known that in this embodiment, the multi-mode interference zone 2 is set to have a refractive index main control zone 4 and a refractive index auxiliary control zone (3, 5), and different operations are applied to the refractive index main control zone 4 and the refractive index auxiliary control zone (3, 5) to adjust the refractive index of the two regions, thereby realizing the conduction or not of the optical switch. This method can effectively improve the extinction ratio and tolerance of the optical switch, wherein the extinction ratio can reach more than 45dB.

[0051] Combination Figure 1 As shown, Figure 1 The light propagates from left to right, and the dimensions of each component of the device are along the direction of light field propagation ( Figure 1 The z direction in the figure is called the "length" of the device, which is perpendicular to the direction of light field propagation ( Figure 1The y direction in the y direction is called the "width" of the device. Specifically, the input waveguide and the output waveguide in this embodiment are both single-mode waveguides. The input waveguide and the output waveguide are at least any one of ordinary straight waveguides with equal width, trapezoidal waveguides with wide left and narrow right or narrow left and wide right, and curved or gradually unequal width waveguides; the input optical fiber and the output optical fiber are at least any one of flat-headed, round-headed or tapered optical fibers.

[0052] The multimode interference region 2 is preferably rectangular, and its boundary can be abrupt or gradual. The multimode interference region 2 in this embodiment includes a waveguide component, an optical chip connected to the waveguide component, and a substrate 12 connected to the optical chip. The optical chip can be a rectangular chip formed by grinding and polishing, and its cladding is air, which belongs to abrupt boundary waveguide. The waveguide component includes a waveguide with abrupt boundaries and / or a waveguide with gradual boundaries. For example, the waveguide component includes at least one of the following:

[0053] Waveguide formed based on dry etching;

[0054] Waveguide formed based on wet etching;

[0055] Waveguides formed by exchanging different ions;

[0056] Waveguides formed by diffusion processes, including waveguides formed by diffusion of lithium titanium niobate.

[0057] Among them, the waveguide formed by dry etching can form a sudden boundary waveguide, the waveguide formed by wet etching can form a gradual boundary waveguide, and the waveguide formed by different ion exchanges and the waveguide formed by diffusion process can also form a gradual boundary waveguide. The lithium niobate titanium diffusion layer in this embodiment is formed by the titanium diffusion process of lithium niobate, and the thickness is about 5 microns to 7 microns.

[0058] The shapes of the main refractive index control area 4 and the auxiliary refractive index control area (3, 5) are not fixed, including but not limited to rectangles, or special shapes formed by special curves obtained by optimization. The spacing between two adjacent control areas can be equal spacing, unequal spacing, or gradient spacing.

[0059] The working principle of the optical switch in this embodiment is:

[0060] The input light enters the multimode interference region 2 from a single-mode waveguide or optical fiber, and the incident field At z = 0, the guided modes Φ of each order in the interference region are excited. v The formula for (y, 0) is:

[0061]

[0062] where β v is the propagation constant of each order guided mode, cv is the coupling coefficient of each order guided mode excited by the input field, and its value is given by the following integral:

[0063]

[0064] Among them Ψ v (y) is the intensity distribution function of each order guided mode. Each order guided mode has its own effective refractive index β v forward( Figure 1 The positive z direction in the graph is propagated, that is:

[0065]

[0066] Since the effective refractive index of each guided mode is different, different phase differences will appear during the transmission process. The guided modes of different orders are superimposed in the multimode interference region 2 with different phase differences. The calculation formula for the light field formed on a certain propagation length L is:

[0067]

[0068] |Ψ out (y, L)| 2 That is, it is the light intensity distribution after each order guided mode propagates a distance L in the multimode interference region 2. When the refractive index distribution of the multimode interference region 2 is changed, β v 、c v and Φ v (y, 0) will be affected, and these parameters can be effectively adjusted by changing the refractive index distribution by design, so that the light field presents different states at the output waveguide.

[0069] When a certain control means is used to increase the refractive index of the main refractive index control area 4, the main refractive index control area 4 can be regarded as a narrow multi-mode interference area 2, and most of the optical power will be concentrated in the multi-mode interference area 2. At this time, the optical switch is in the on state. When another control means is used to increase the refractive index of the auxiliary refractive index control area (3, 5), or to reduce the refractive index of the main refractive index control area 4, the auxiliary refractive index control areas (3, 5) will form two approximately independent multi-mode interference areas 2 and form images respectively. Most of the optical power will be concentrated in the auxiliary refractive index control areas (3, 5), resulting in a lower optical power in the main refractive index control area 4. At this time, the optical switch is in the off state.

[0070] For example, the width of the multimode interference zone 2 is set to 3000 microns, the length is set to 19900 microns, the width of the input waveguide and the output waveguide is set to 6 microns, the core refractive index of the multimode interference zone 2 and the input waveguide and the output waveguide is 2.2, and the cladding refractive index is 2.19. The refractive index of the main refractive index control zone 4 is increased by 1x10 -3, the width is set to 10 microns, the length is set to 19900 microns, the refractive index change of the auxiliary refractive index control area (3, 5) is set to zero, and the wavelength is set to 1550nm. Based on the above parameters, simulation calculation can be performed to obtain that when the input light intensity is 1 and the output power is 0.5064, the optical switch is in the open state; when the refractive index of the main refractive index control area 4 is adjusted to decrease by 1x10 -3 When the output power is 1.2x10-7, the optical switch is in the off state. The extinction ratio of the optical switch is -10xlog[0.5064(1.2x10 -7 )] = 66.25 dB. Assume that due to various reasons, the refractive index change of the main refractive index control area 4 does not reach 1x10 -3 , only 5x10 -4 At this time, the on-state power of the optical switch is 0.14357, and the off-state power is 2.1x10 -6 , the extinction ratio can still reach 48.35dB.

[0071] In terms of dimensional tolerance, the current error of contact lithography is 0.3 microns. The width of the refractive index main control area 4, which was originally designed to be 10 microns, is changed to 12 microns. That is, assuming that the semiconductor processes such as lithography and etching cause an error of 2 microns, when the refractive index changes by 1x10 -3 When the optical switch is turned on, the output power is 0.4658, and the output power is turned off. -7 , the extinction ratio is 66.27dB, which is basically unchanged compared with the previous standard design value of 66.25dB. In addition, the width and length of the multimode interference zone 2 are changed by 2 microns, and the simulation results are also basically unchanged. Therefore, the optical switch in this embodiment can obtain an extinction ratio of more than 45dB, and has a considerable tolerance, and has obvious advantages in mass production. When applied, the on-state optical power and off-state optical power of the optical switch can be changed by adjusting the shape of the input waveguide, the output waveguide, the shape and refractive index change of the main refractive index control zone 4, and the shape and refractive index change of the auxiliary refractive index control zone (3, 5) to meet the needs of different scenarios.

[0072] Further, the other data of the above embodiment remain unchanged, and only the refractive index change of the refractive index main control area 4 is changed to 1.6x10 -4 This is the refractive index increase value caused by the common electro-optical effect of lithium niobate. At this time, due to the small change in refractive index, the on-state power of the optical switch is only 0.0798, and the loss is large. It needs to be optimized to reduce the loss. When optimizing, the input waveguide can be changed to a left width of 8 microns, a right width of 16 microns, and a length of 100 microns, and the output waveguide can be changed to a left width of 16 microns, a right width of 8 microns, and a length of 2000 microns. Then the refractive index of the main refractive index control zone 4 is still increased by 1.6x10-4 The refractive index change of the auxiliary refractive index control area (3, 5) is -1.6x10 -4 , the size is the same as the main refractive index control zone 4, the interval between the main control zone and the auxiliary control zone is 10 microns, and the wavelength is 1550nm. At this time, the on-state output power of the optical switch is 0.2803; when the refractive index of the refractive index control zone decreases by 1.6x10 -4 When the refractive index of the auxiliary refractive index control area (3, 5) changes to zero, the output power is 0.00021. At this time, the extinction ratio of the device is 31.25dB, still maintained above 30dB, but the power in the on state is increased to 3.5 times before optimization, which is applicable to some application scenarios with high insertion loss requirements.

[0073] When adjusting the change in the refractive index, that is, the corresponding increase and decrease in the refractive index can be achieved through various effects within the semiconductor such as carrier injection effect (decreased refractive index), thermo-optical effect (generally increased temperature, increased refractive index), electro-optical effect (increase and decrease in refractive index is related to the direction of the electric field), photoelastic effect (the refractive index of the material increases with increasing pressure), etc.

[0074] In order to better introduce the present embodiment, the following is a description in combination with different embodiments:

[0075] Embodiment 1:

[0076] The boundary of the multimode interference zone 2 is formed by etching steps, there are three steps, and form a first upper electrode 7, a second upper electrode 8 and a third upper electrode 9 respectively, and two adjacent upper electrodes have a target spacing. The multimode interference zone 2 includes an upper limiting layer 10, a waveguide layer 11, a lower limiting layer and a lower electrode 13 connected in sequence, the first upper electrode 7, the second upper electrode 8 and the third upper electrode 9 are located on the upper limiting layer 10, and the lower electrode 13 covers the lower limiting layer. The first upper electrode 7 and the third upper electrode 9 are respectively located on both sides of the second upper electrode 8, the area between the second upper electrode 8 and the lower electrode 13 forms the refractive index main control area 4, the area between the first upper electrode 7 and the lower electrode 13, and the area between the third upper electrode 9 and the lower electrode 13 respectively form refractive index auxiliary control areas (3, 5), when current is injected into the refractive index auxiliary control areas (3, 5), the refractive index of the refractive index auxiliary control areas (3, 5) decreases, and the optical switch is in an open state, and when current is injected into the refractive index main control area 4, the optical switch is in a closed state; wherein the refractive indices of the refractive index main control area 4 and the refractive index auxiliary control areas (3, 5) are affected by the position and size of the injected current.

[0077] For example, a 1x1 waveguide optical switch based on multimode interference using GaAs material is taken as an example, and its top view is as follows: Figure 1As shown, both the input component 1 and the output component 6 are single-mode waveguides with a width of 3 microns. The width of the multimode interference region 2 is 2000 microns and the length is 10000 microns. The boundary of the interference region is formed by etching steps (see Figure 2 ), the lengths of the first upper electrode 7, the second upper electrode 8, and the third upper electrode 9 are all 10,000 microns, the width of the second upper electrode 8 is 4 microns, the widths of the first upper electrode 7 and the third upper electrode 9 are 994 microns, the spacing between the first upper electrode 7 and the second upper electrode 8 is 1 micron, and the spacing between the second upper electrode 8 and the third upper electrode 9 is also 1 micron. The thickness / depth of the step is 0.33 microns. The thickness of the upper limiting layer 10 is 0.5 microns, and the thickness of the lower limiting layer is 500 microns. The materials are GaAlAs, and the refractive index is 3.35. The waveguide layer 11 is GaAs, with a thickness of 0.5 microns and a refractive index of 3.42. The size of the lower electrode 13 is to cover the entire lower surface. The upper and lower electrodes 13 are both gold and have a thickness of 50nm. The middle area of ​​the multimode interference zone 2 can be regarded as the core layer, and the areas on both sides are regarded as the cladding. According to the equivalent refractive index method, the equivalent refractive index of the core layer at a wavelength of 1.55 microns is 3.367, and the effective refractive index of the cladding is 3.357.

[0078] All semiconductor materials used in the optical switch of this embodiment are p-type doped. When current is injected into the multimode interference zone 2 from the first upper electrode 7, the refractive index of the material below the first upper electrode 7 will decrease. The decrease value varies depending on the current size. In this embodiment, it decreases by 0.07. When current is injected into the multimode interference zone 2 through the first upper electrode 7 and the third upper electrode 9 at the same time, the refractive index of the two regions corresponding to the two upper electrodes (i.e., the auxiliary refractive index control region) decreases, resulting in the refractive index of the region where the second upper electrode 8 is located being 0.07 higher than that on both sides. If the input power is 1, the output power at this time is calculated to be 0.602 using the BPM method, and the optical switch is in the on state. If current is only injected into the multimode interference zone 2 through the second upper electrode 8, the refractive index of the region where the second upper electrode 8 is located (i.e., the main refractive index control region 4) is 0.07 lower than that of the surrounding area. The output power calculated by the BPM method is 1.1x10-6, and the optical switch is in the off state. After the above calculation, the extinction ratio of the optical switch of this embodiment is -10log[0.602 / (1.1x10 -6 )]=57.4dB.

[0079] Embodiment 2:

[0080] The multimode interference region 2 includes an optical chip, a substrate 12 disposed on the optical chip, a planar waveguide formed by a titanium diffusion layer 17 located on the substrate 12, an optical isolation layer 16 located on the planar waveguide, and a first electrode 14 and a second electrode 15 located on the optical isolation layer 16, wherein the first electrode 14 and the second electrode 15 are spaced apart, and an area corresponding to the space in the multimode interference region 2 forms a main refractive index control area, and areas corresponding to the first electrode 14 and the second electrode 15 respectively form two auxiliary refractive index control areas, when positive voltage and negative voltage are applied to the first electrode 14 and the second electrode 15 respectively, the optical switch is in an on state, and when a voltage is applied to the area between the first electrode 14 and the second electrode 15, the optical switch is in an off state; wherein the refractive indices of the main refractive index control area and the auxiliary refractive index control area are affected by the position and magnitude of the injected voltage.

[0081] For example, a multi-mode interference 1x1 waveguide optical switch using lithium niobate material is used as an example. The basic structure is as follows: Figure 3 and Figure 4 As shown, the substrate 12 of the optical switch is made of lithium niobate, the multimode interference area 2 is formed by grinding and polishing the four edges of the chip itself, and the upper surface of the chip uses a titanium diffusion process to form a wide waveguide that is similar to a planar waveguide, and the waveguide width and length extend to the edge of the chip. In order to increase the refractive index of the chip surface to achieve the purpose of limiting the light field, the thickness of the titanium diffusion layer 17 is about 5-8 microns, for example, 6 microns, the width is 2200 microns, the length is 20000 microns, and the refractive index is about 2.22. The substrate 12 is a lithium niobate substrate 12, the thickness is 500 microns, and the refractive index is about 2.21. The input component 1 and the output component 6 are input optical fiber and output optical fiber respectively, both of which are standard single-mode optical fibers, the width of the input optical fiber is 2200 microns, and the length L is 20000 microns. The first electrode 14 and the second electrode 15 are formed on the titanium diffusion layer 17, the width is 1000 microns, and the electrode spacing d is 10 microns. An optical isolation layer 16 is provided between the electrode and the lithium niobate planar waveguide, ie, the titanium diffusion layer 17, in order to reduce the loss and lower the polarization dependence of the device.

[0082] When a voltage is applied between the first electrode 14 and the second electrode 15, the refractive index of the area between the two electrodes changes due to the electro-optical effect. When a voltage is applied in a certain direction, the refractive index increases, and when the voltage is reversed, the refractive index decreases. In this embodiment, the area between the first electrode 14 and the second electrode 15 is the main refractive index control area. In this embodiment, the main control area has a width of 10 microns, a length of 20,000 microns, and a rectangular shape. The refractive index change is within 10 -4The area where the first electrode 14 and the second electrode 15 are located is the auxiliary refractive index control area. The refractive index change is the same as that in the main control area, but the value is smaller. Assuming that the first electrode 14 is positively charged and the second electrode 15 is negatively charged, the electric field line diagram is as follows: Figure 5 As shown by the middle curve. Since the distance between the first electrode 14 and the second electrode 15 (the main control area) is the shortest, the electric field strength is the highest, and the resulting refractive index change is also the largest. At the leftmost side of the first electrode 14 and the rightmost side of the second electrode 15, the interval is the largest, so the electric field strength in the lower area is the smallest, and the resulting refractive index change is also the smallest. Therefore, the refractive index distribution in the refractive index control area is the largest in the part close to the middle of the first electrode 14 and the second electrode 15, and gradually decreases to the left and right sides, presenting a gradual refractive index change in a large area, that is, this embodiment controls the output light by applying different voltages to control the multi-mode interference area 2.

[0083] like Figure 5 As shown in the figure, it shows the measured voltage-output optical power curve of this embodiment. It can be seen from the curve in the figure that the output power is -17.4dBm when the voltage is 30V, and the output power is -82.0dBm when the voltage is -30.8V. The measured extinction ratio is as high as 64.6dB. As an optical waveguide device, its extinction ratio reaches the level of electromagnetic switches and MEMS optical switches, which is much higher than ordinary waveguide optical switches (about 25-35dB). In addition, the optical switch speed of this embodiment is measured to be 33ns, which is much faster than the typical value of 20 microseconds of MEMS optical switches.

[0084] Another embodiment of the present invention also provides an electronic device, including a high extinction ratio optical switch based on multi-mode interference as described in any one of the embodiments above.

[0085] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A high extinction ratio optical switch based on multimode interference, characterized in that: include: an input assembly, including an input waveguide or an input optical fiber; an output assembly, including an output waveguide or an output optical fiber; The multimode interference zone is connected to the input component and the output component respectively, and the multimode interference zone includes a main refractive index control zone and an auxiliary refractive index control zone. When the refractive index of the main refractive index control zone is higher than that of the areas on both sides thereof, or the refractive index of the main refractive index control zone is higher than that of the auxiliary refractive index control zone, the optical switch is in an open state; when the refractive index of the main refractive index control zone is lower than that of the areas on both sides thereof, or the refractive index of the main refractive index control zone is lower than that of the auxiliary refractive index control zone, the optical switch is in a closed state.

2. The high extinction ratio optical switch based on multimode interference according to claim 1, characterized in that: The multi-mode interference region includes a waveguide component, an optical chip connected to the waveguide component, and a substrate connected to the optical chip.

3. The high extinction ratio optical switch based on multimode interference according to claim 2, characterized in that: The waveguide assembly includes a waveguide with abrupt boundaries and / or a waveguide with gradually changing boundaries.

4. The high extinction ratio optical switch based on multimode interference according to claim 2, characterized in that: The waveguide assembly includes at least one of the following: Waveguide formed based on dry etching; Waveguide formed based on wet etching; Waveguides formed by exchanging different ions; Waveguides formed by diffusion processes, including waveguides formed by diffusion of lithium titanium niobate.

5. The high extinction ratio optical switch based on multimode interference according to claim 1, characterized in that: The boundary of the multi-mode interference zone is formed by etching steps, there are three steps, and they respectively form a first upper electrode, a second upper electrode and a third upper electrode, and two adjacent upper electrodes have a target spacing. The multi-mode interference zone includes an upper limiting layer, a waveguide layer, a lower limiting layer and a lower electrode connected in sequence, the first upper electrode, the second upper electrode and the third upper electrode are located on the upper limiting layer, and the lower electrode covers the lower limiting layer.

6. The high extinction ratio optical switch based on multimode interference according to claim 5, characterized in that: The first upper electrode and the third upper electrode are respectively located on both sides of the second upper electrode, the area between the second upper electrode and the lower electrode forms the main refractive index control area, the area between the first upper electrode and the lower electrode, and the area between the third upper electrode and the lower electrode respectively form auxiliary refractive index control areas, when current is injected into the auxiliary refractive index control area, the refractive index of the auxiliary refractive index control area decreases, and the optical switch is in an on state, and when current is injected into the main refractive index control area, the optical switch is in an off state; The refractive index of the main refractive index control area and the auxiliary refractive index control area is affected by the position and size of the injected current.

7. The high extinction ratio optical switch based on multimode interference according to claim 1, characterized in that: The multi-mode interference region comprises an optical chip, a substrate disposed on the optical chip, a planar waveguide formed by a titanium diffusion layer on the substrate, an optical isolation layer on the planar waveguide, and a first electrode and a second electrode on the optical isolation layer, wherein the first electrode and the second electrode are spaced apart, a region corresponding to the space in the multi-mode interference region forms a main refractive index control region, and regions corresponding to the first electrode and the second electrode respectively form two auxiliary refractive index control regions, when a positive voltage and a negative voltage are respectively applied to the first electrode and the second electrode, the optical switch is in an on state, and when a voltage is applied to a region between the first electrode and the second electrode, the optical switch is in an off state; The refractive index of the main refractive index control area and the auxiliary refractive index control area is affected by the position and size of the injected voltage.

8. The high extinction ratio optical switch based on multimode interference according to claim 1, characterized in that: The input waveguide and the output waveguide are both single-mode waveguides.

9. The high extinction ratio optical switch based on multimode interference according to claim 1, characterized in that: The input waveguide and the output waveguide are at least any one of a common straight waveguide of equal width, a trapezoidal waveguide that is wide on the left and narrow on the right or narrow on the left and wide on the right, or a curved or gradually unequal-width waveguide; The input optical fiber and the output optical fiber are at least any one of flat-head, round-head or tapered-head optical fibers.

10. An electronic device, characterized in that: The invention comprises a high extinction ratio optical switch based on multi-mode interference as claimed in any one of claims 1 to 9.

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