An integrated tunable optical attenuator based on mode-circulation phase-shift and reflection

Abstract

The application discloses an integrated tunable optical attenuator based on mode-circulating phase shift and reflection, comprising a single-mode optical waveguide, a 2*2 optical coupler, a high-order mode-circulating phase shifter and a waveguide optical reflector; wherein the 2*2 optical coupler is used for splitting the optical energy of the input port into two paths and outputting the optical energy into the high-order mode-circulating phase shifter, the high-order mode-circulating phase shifter uses the high-order mode selectivity of a mode coupler and the staggered arrangement of the mode order of a mode exchanger to make the optical field circulate in the high-order mode-circulating phase shifter for multiple times, thereby achieving the fold increase of the phase modulation efficiency; the waveguide optical reflector reversely couples the optical field modulated by the high-order mode-circulating phase shifter back to the high-order mode-circulating phase shifter, so that the optical field energy and information circulate in the high-order mode-circulating phase shifter for multiple times through the multimode optical phase shift arm, thereby further doubling the optical modulation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of optical communication and integrated optical technology, specifically relating to an integrated tunable optical attenuator based on mode cyclic phase shift and reflection. Background Technology

[0002] In coherent optical communication, tunable optical attenuators are often required to balance the light intensity values ​​of different channels. Commonly used tunable optical attenuators in integrated optics are based on Mach-Zehnder interferometers (MZI) devices. The tunability is achieved by a phase shifter within the interferometer arm. Integrated phase shifters primarily utilize electro-optic or thermo-optic effects to change the waveguide refractive index, thereby shifting the optical signal phase. Current phase shifters only allow the optical field to interact with the modulation waveguide once, thus requiring a large driving voltage or a long phase shifter length, which is not conducive to optoelectronic hybrid integration. Summary of the Invention

[0003] To address the aforementioned problems in the prior art, this invention provides an integrated tunable optical attenuator based on mode cyclic phase shift and reflection. The technical problem to be solved by this invention is achieved through the following technical solution:

[0004] An integrated tunable optical attenuator based on mode cyclic phase shift and reflection includes:

[0005] The system comprises a single-mode optical waveguide 11, a 2×2 optical coupler 12, a high-order mode cyclic phase shifter 13, and a waveguide optical reflector 14; wherein...

[0006] The 2×2 optical coupler 12 has four ports, divided into two groups. Its function is to divide the optical energy of one input port of one group into two outputs of the other group. Two ports on one side are connected to the optical input and optical output of the whole device through a single-mode optical waveguide 11, and two ports on the other side are connected to a high-order mode cyclic phase shifter 13 through a single-mode optical waveguide 11.

[0007] The higher-order mode cyclic phase shifter 13 has two ports. One port is connected to the 2×2 optical coupler 12, and the other port is connected to the waveguide optical reflector 14 through the single-mode optical waveguide 11. The higher-order mode cyclic phase shifter 13 utilizes the higher-order mode selectivity of the mode coupler and the mode exchanger to misalign the order of the higher-order modes, so that the optical field cyclically cycles multiple times in the higher-order mode cyclic phase shifter 13, thereby achieving efficient optical phase modulation.

[0008] Waveguide optical reflector 14 is used to backcouple the optical field modulated by higher-order mode cyclic phase shifter 13 back to the higher-order mode cyclic phase shifter 13.

[0009] In one embodiment of the present invention, the high-order mode cyclic phase shifter 13 includes:

[0010] Single-mode optical waveguide 11, multimode optical waveguide 21, mode coupler 22, mode switcher 23, first multimode optical phase shifter 24, and second multimode optical phase shifter 24; wherein,

[0011] The mode coupler 22 has four ports: two multimode ports and two single-mode ports. The two single-mode ports serve as the optical input and output ports of the higher-order mode cyclic phase shifter 13. One multimode port is connected to the first multimode phase shifter arm 24 via a multimode waveguide 21. The first multimode phase shifter arm 24 is connected to the mode switch 23. The mode switch 23 is connected to the second multimode phase shifter arm 24 and then connected to another multimode port of the mode coupler 22 via the multimode waveguide 21. Thus, the mode coupler 22, the mode switch 23, the first multimode phase shifter arm 24, and the second multimode phase shifter arm 24 are connected via the multimode waveguide 21 to form a loop.

[0012] In one embodiment of the present invention, the multimode optical waveguide 21 is a waveguide whose width is increased to accommodate multiple optical modes passing through simultaneously.

[0013] In one embodiment of the present invention, any multimode optical phase shifter is used to change the refractive index of the multimode optical waveguide 21 through electro-optic effect or thermo-optic effect, thereby changing the actual optical path of light in the multimode optical waveguide 21 and realizing the function of changing the phase of light after passing through the multimode optical phase shifter.

[0014] In one embodiment of the present invention, the mode coupler of the high-order mode cyclic phase shifter 13 has mode selectivity; the mode selectivity is to couple the fundamental mode in the single-mode optical waveguide 11 to a specific mode in the multimode optical waveguide 21, and not to couple with other modes in the multimode optical waveguide 21.

[0015] In one embodiment of the present invention, the mode switch 23 misaligns the order of the optical field modes circulating within the higher-order mode cyclic phase shifter 13. The mode misalignment of the higher-order mode cyclic phase shifter 13 includes: transferring the energy and information carried by a mode to other modes other than itself, while keeping the number of modes in the multimode optical waveguide 21 before passing through the mode switch 23 equal to the number of modes in the multimode optical waveguide 21 after passing through the mode switch 23.

[0016] In one embodiment of the present invention, the operation of the high-order mode cyclic phase shifter 13 is as follows:

[0017] After the input optical field of the higher-order mode cyclic phase shifter 13 achieves the characteristic of traversing all mode channels through the mode exchanger 23 and the mode coupler 22, the mode exchanger 23 returns the optical field to the original mode, and then couples it out through the mode coupler 22 to form a multimode optical waveguide 21, which then leaves the higher-order mode cyclic phase shifter 13, thereby achieving a significant increase in the modulation efficiency of the optical field.

[0018] The beneficial effects of this invention are:

[0019] In the solution provided by the embodiments of the present invention,

[0020] 1. By utilizing the selective passage of higher-order modes by the mode coupler and the variation of the order of higher-order modes by the mode exchanger, the optical field energy and information are cyclically passed through the multimode optical phase shifter multiple times in the higher-order mode cyclic phase shifter, thereby multiplying the optical modulation efficiency.

[0021] 2. The reflective architecture allows the light field to pass through the high-order mode cyclic phase shifter twice in both directions, thus doubling the modulation efficiency on top of the high-order mode cyclic phase shifter. This improved modulation efficiency helps reduce device power consumption and drive voltage, thus facilitating compatibility with traditional CMOS on-chip drivers. It also helps reduce device size, enabling higher integration. Attached Figure Description

[0022] Figure 1 A schematic diagram of an integrated tunable optical attenuator structure based on mode cyclic phase shift and reflection provided in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of a high-order mode cyclic phase shifter structure provided in an embodiment of the present invention;

[0024] Figure 3 This is a diagram of a high-order mode cyclic phase shifter topology provided in an embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures

[0026] 11: Single-mode optical waveguide; 12: 2×2 optical coupler; 13: Higher-order mode cyclic phase shifter; 14: Waveguide optical reflector; 21: Multimode optical waveguide; 22: Mode coupler; 23: Mode switcher; 24: First multimode optical phase shifter arm, second multimode optical phase shifter arm. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] This invention provides an integrated tunable optical attenuator based on mode cyclic phase shift and reflection, such as... Figure 1 As shown, it includes:

[0029] The system comprises a single-mode optical waveguide 11, a 2×2 optical coupler 12, a high-order mode cyclic phase shifter 13, and a waveguide optical reflector 14; wherein...

[0030] The 2×2 optical coupler 12 has four ports, divided into two groups. Its function is to divide the optical energy of one input port of one group into two outputs of the other group. Two ports on one side are connected to the optical input and optical output of the whole device through a single-mode optical waveguide 11, and two ports on the other side are connected to a high-order mode cyclic phase shifter 13 through a single-mode optical waveguide 11.

[0031] The higher-order mode cyclic phase shifter 13 has two ports. One port is connected to the 2×2 optical coupler 12, and the other port is connected to the waveguide optical reflector 14 through the single-mode optical waveguide 11. The higher-order mode cyclic phase shifter 13 utilizes the higher-order mode selectivity of the mode coupler and the mode exchanger to misalign the order of the higher-order modes, so that the optical field cyclically cycles multiple times in the higher-order mode cyclic phase shifter 13 to achieve efficient optical phase modulation.

[0032] Waveguide optical reflector 14 is used to backcouple the optical field modulated by higher-order mode cyclic phase shifter 13 back to the higher-order mode cyclic phase shifter 13.

[0033] The working process of the integrated tunable optical attenuator based on mode cyclic phase shifting and reflection is as follows: The optical field enters the 2×2 optical coupler 12 through the input terminal, and the energy is then evenly split into two beams, which enter two higher-order mode cyclic phase shifters 13 respectively to achieve efficient optical modulation. Subsequently, the beams are reflected by the waveguide optical reflector 14 and re-enter the higher-order mode cyclic phase shifters 13, and then output through the 2×2 optical coupler 12. According to the principle of interference, the light intensity at the output port changes with the phase difference between the two beams, thus achieving the function of optical attenuation. At this time, the optical field passes through each multimode optical phase shifter arm N times in the higher-order mode cyclic phase shifter 13 (N = number of times the optical field circulates in the higher-order mode cyclic phase shifter = number of mode channels supported by the mode switch = number of mode channels supported by the mode coupler = multiple of the higher-order mode cyclic phase shifter to improve modulation efficiency, N≥2). Since the optical field enters the higher-order mode cyclic phase shifter 13 twice from two directions, and the modulation of the optical field in the two directions does not interfere with each other, the optical field passes through each multimode optical phase shifter arm a total of 2N times. Therefore, the overall optical field modulation efficiency of the tunable optical attenuator is improved by 2N times.

[0034] The following is a detailed explanation of each module:

[0035] Single-mode optical waveguide

[0036] Single-mode optical waveguides 11 include: single-mode strip waveguides or ridge waveguides commonly found in integrated photonic devices.

[0037] Optionally, the single-mode optical waveguide 11 is a 220nm×500nm silicon strip square waveguide, beneath which is a 2μm buried oxide silicon dioxide layer, and below the buried oxide silicon dioxide layer is a 750μm thick single-crystal silicon substrate. Its function is to guide the light field to propagate within the integrated chip.

[0038] 2×2 optical coupler

[0039] A 2×2 optical coupler, including: a 50:50 beam splitter based on a directional coupler or a 50:50 beam splitter based on a multimode interference coupler.

[0040] Optionally, the 2×2 optical coupler 12 can be a silicon-based 2×2 multimode interference coupler, or a silicon directional coupler composed of two closely spaced single-mode optical waveguides. Its function is to evenly distribute the input optical energy from any port in one group to the two ports in the other group.

[0041] Higher-order mode cyclic phase shifter

[0042] Higher-order mode cyclic phase shifter 13, such as Figure 2 As shown, it includes:

[0043] Single-mode optical waveguide 11, multimode optical waveguide 21, mode coupler 22, mode switcher 23, first multimode optical phase shifter 24, and second multimode optical phase shifter 24; wherein,

[0044] The mode coupler 22 has four ports: two multimode ports and two single-mode ports. The two single-mode ports serve as the optical input and output ports of the higher-order mode cyclic phase shifter 13. One multimode port is connected to the first multimode phase shifter arm 24 via a multimode waveguide 21. The first multimode phase shifter arm 24 is connected to the mode switch 23. The mode switch 23 is connected to the second multimode phase shifter arm 24 and then connected to another multimode port of the mode coupler 22 via the multimode waveguide 21. Thus, the mode coupler 22, the mode switch 23, the first multimode phase shifter arm 24, and the second multimode phase shifter arm 24 are connected via the multimode waveguide 21 to form a loop.

[0045] The multimode optical waveguide 21 is a waveguide that, with its increased width, can accommodate multiple optical modes passing through simultaneously.

[0046] Optionally, the multimode optical waveguide 21 includes: a multimode strip waveguide or ridge waveguide commonly used in integrated photonic devices.

[0047] Optionally, the multimode optical waveguide 21 is a 220nm×1000nm dual-mode silicon waveguide, beneath which is a 2μm buried oxide silicon dioxide layer, and below the buried oxide silicon dioxide layer is a 750μm thick single-crystal silicon substrate. Its function is to guide the propagation of TE0 mode and TE1 mode optical fields in the integrated chip.

[0048] Among them, the higher-order mode cyclic phase shifter 13 uses the mode selectivity of the mode coupler 22 to selectively pass higher-order modes; the mode selectivity is to couple the fundamental mode in the single-mode optical waveguide 11 to a specific mode in the multimode optical waveguide 21, and not to couple with other modes in the multimode optical waveguide 21.

[0049] Taking the input of a single-mode optical field into the M-order mode of the multimode optical waveguide 21 through the mode coupler 22 as an example, the input single-mode optical field is first coupled to a certain mode (denoted as M, where M is one of the number N of mode channels supported by the mode switch) in the multimode optical waveguide 21 through the mode coupler 22. When the mode order of the optical field changes to something other than M, the optical field will not be coupled out of the multimode optical waveguide 21 by the mode coupler 22. Only when the mode switch 23 restores the mode of the optical field to M will the mode coupler 22 couple the optical field out of the multimode optical waveguide 21 and leave the higher-order mode cyclic phase shifter 13.

[0050] Optionally, the mode coupler 22 includes: an asymmetric directional coupler in an integrated photonic device or a reverse-designed mode multiplexer.

[0051] Optionally, the mode coupler 22 can be a TE0 and TE1 mode multiplexer / demultiplexer based on a silicon-based asymmetric directional coupler, or it can be a silicon-based TE0 and TE1 mode multiplexer / demultiplexer generated through reverse design. Its function is to couple the TE1 mode in the multimode optical waveguide with the fundamental mode in the single-mode optical waveguide.

[0052] Derangements include: specific arrangements that belong to a permutation group where all elements are generators.

[0053] The feature of the higher-order mode cyclic phase shifter 13 in changing the order of higher-order modes is achieved by using the mode switch 23 to stagger the order of the mode channels carrying energy and information, including: transferring the energy and information carried by the mode to other modes other than itself, but keeping the number of modes in the multimode optical waveguide 21 before passing through the mode switch 23 equal to the number of modes in the multimode optical waveguide 21 after passing through the mode switch 23.

[0054] The function of mode switch 23 is to exchange optical energy of different modes in multimode optical waveguide 21. It has two multimode ports and supports at least two modes. Let mode switch 23 support N (N≥2) mode channels, where mode switch 23 should support modes of mode order M (one of the number N of mode channels supported by the mode switch).

[0055] Optionally, the mode switch 23 can be a bidirectional router based on an asymmetric directional coupler or a reverse-engineered mode switch 23.

[0056] Alternatively, the specific arrangement of the derangement belongs to a permutation group where all elements are generators.

[0057] Optionally, the mode switch 23 can be a silicon-based asymmetric directional coupler-based TE0 and TE1 mode switch 23, or a silicon-based TE0 and TE1 mode switch 23 reverse-engineered. Its function is to realize the mutual exchange of energy and information carried by the TE0 and TE1 modes in the waveguide. Here, the mode switch 23 operates on both TE0 and TE1 modes; the mutual exchange of mode orders is equivalent to the misalignment of the mode channels. In this case, N=2.

[0058] Optionally, the number of pattern exchangers 23 in each loop can be one or more, but the pattern order will be missorted once before and after each loop.

[0059] Any multimode optical phase shifter arm is used to change the refractive index of the multimode optical waveguide 21 through electro-optic effect or thermo-optic effect, thereby changing the actual optical path of light in the multimode optical waveguide 21 and realizing the function of changing the phase of light after passing through the multimode optical phase shifter arm.

[0060] Optionally, the multimode optical phase shifter 24 can be an electro-optic or thermo-optic phase modulator.

[0061] Optionally, the multimode optical phase shifter 24 can be a multimode optical waveguide 21 covered with a titanium nitride hot electrode, or it can be a doped multimode optical waveguide 21 doped with nitrogen, phosphorus, or other dopants. Its function is to change the equivalent refractive index of the waveguide through the thermo-optic, plasma dispersion, or acousto-optic effects of silicon material, thereby changing the phase of the light field after passing through the multimode optical phase shifter 24.

[0062] Optionally, the number of multimode phase shifters in each cycle can be one or more, but the optical field will only pass through each multimode phase shifter once in each cycle.

[0063] The topology diagram of the high-order mode cyclic phase shifter is as follows: Figure 3 As shown, the input fundamental mode enters the higher-order mode cyclic phase shifter through the mode coupler. The mode exchanger misaligns its mode channels, and after passing through the mode coupler, it returns to the mode converter in a loop. It traverses all mode channels and finally returns to the original mode. The optical field achieves the characteristic of traversing all mode channels through the combination of the mode exchanger and the mode coupler.

[0064] Optionally, the connection sequence of the mode coupler 22 through the multimode optical waveguide 21 can be multimode optical phase shifter first and then mode switch 23, or mode switch 23 first and then multimode optical phase shifter, or multiple multimode optical phase shifters and multiple mode switches 23 can be arranged arbitrarily.

[0065] Optionally, the number of higher-order mode cyclic phase shifters that each light path passes through can be zero or more, but the overall reflective integrated tunable optical attenuator must contain at least one higher-order mode cyclic phase shifter.

[0066] The operation of the high-order mode cyclic phase shifter 13 is as follows:

[0067] After the input optical field of the high-order mode cyclic phase shifter 13 passes through the mode exchanger 23 and the mode coupler 22 to achieve the characteristic of traversing all mode channels, the mode exchanger 23 returns the optical field to the original mode, and then couples out the multimode optical waveguide 21 through the mode coupler 22, leaving the high-order mode cyclic phase shifter 13. The high-order mode cyclic phase shifter 13 utilizes the parallelism of the multimode waveguide that can carry multiple modes, the selectivity of the mode coupler, and the mode misalignment characteristics of the mode converter to realize that the optical field passes through the phase shift modulation region multiple times in the high-order mode cyclic structure, thereby doubling the modulation efficiency of the optical field.

[0068] The high-efficiency optical modulation process of the high-order mode cyclic phase shifter 13 is as follows: The single-mode optical field enters the M-order mode in the multimode optical waveguide 21 through the mode coupler 22, and then passes through the multimode optical phase shifter 24 in the M-order mode, undergoing a phase shift. Subsequently, it undergoes mode conversion through the mode switcher 23. The converted mode is no longer the M-order mode, and therefore is not coupled to the output of the single-mode optical waveguide 11 by the mode coupler 22. Instead, it re-enters the multimode optical phase shifter 24 in the non-M-order mode through the mode coupler 22, undergoes a phase shift, and then re-enters the mode switcher 23 to complete one cycle. Due to the mode order misalignment function of the mode switcher 23, the optical field will pass through the mode switcher 23 and the multimode optical phase shifter 24 N times in total, until the optical field is restored to the M-order mode by the mode switcher 23 and transformed into the fundamental mode in the single-mode optical waveguide 11 by the mode coupler 22 and output from another port. Therefore, the modulation efficiency of the optical field is improved by N times.

[0069] Taking N=2 as an example, the optical field enters a single-mode port c of the mode coupler 22 through the single-mode optical waveguide 11. The fundamental mode in the single-mode optical waveguide 11 is coupled to the TE1 mode in the multimode optical waveguide 21 and outputs from a multimode port b of the mode coupler 22. After passing through the multimode optical waveguide 21, it is guided to the first multimode optical phase shift arm 24. After passing through the mode switch 23, the TE1 mode of the multimode optical waveguide 21 is converted to the TE0 mode of the multimode optical waveguide 21. After passing through the second multimode optical phase shift arm 24, it arrives at another multimode port a of the mode coupler 22, completing one cycle. At this time, the optical field passes through each multimode optical phase shift arm 24 once. Since the mode arriving at multimode port a of mode coupler 22 is TE0 mode, it will directly pass through mode coupler 22 and arrive at multimode port b, outputting in the original TE0 mode. The TE0 mode will then be guided to the first multimode optical phase shifter arm 24. After passing through mode switcher 23, the TE0 mode is converted to TE1 mode and arrives at another multimode port a of mode coupler 22, completing another cycle. At this point, the optical field passes through each multimode optical phase shifter arm 24 twice. The mode arriving at multimode port a of mode coupler 22 is now TE1 mode, which will be coupled by mode coupler 22 to the fundamental mode in the single-mode optical waveguide, outputting at port d and leaving the higher-order mode cyclic phase shifter 13. Thus, the higher-order mode cyclic phase shifter 13 achieves an N=2 times modulation efficiency improvement.

[0070] waveguide optical reflector

[0071] The function of waveguide optical reflector 14 is to reflect the light field of the input optical waveguide and output it in the opposite direction through the input optical waveguide. Waveguide optical reflectors include any one of the following: reflectors based on Bragg gratings, ultra-compact optical reflectors designed in reverse, and right-angle integrated optical reflectors based on geometric optics.

[0072] Optionally, the waveguide optical reflector 14 includes any one of: a ring reflector based on a 1×2 optical beam splitter, a waveguide reflector based on a Bragg grating, and an ultra-compact waveguide reflector based on reverse design.

[0073] The waveguide optical reflector 14 couples the optical field in the input optical waveguide back to the input waveguide itself in the opposite direction, thereby achieving the reversal of the optical field.

[0074] Taking a silicon-based photonics integrated tunable optical attenuator based on mode cyclic phase shifting and reflection with 4x modulation efficiency as an example, the working principle of this silicon-based photonics integrated tunable optical attenuator based on mode cyclic phase shifting and reflection is as follows: After the optical field enters the 2×2 coupler 12 through the single-mode optical waveguide 11, the energy is evenly split into two beams, which pass through two higher-order mode cyclic phase shifters 13 respectively. Then, the beams are reflected by the waveguide optical reflector 14 and pass through the higher-order mode cyclic phase shifters 13 again, returning to the right set of ports of the 2×2 coupler 12. According to the principle of interference, the light intensity at the output port is controlled by the phase difference of the returned light. Due to reflection, each beam passes through the higher-order mode cyclic phase shifter twice, thus doubling its modulation efficiency again compared to the higher-order mode cyclic phase shifter 13, resulting in a modulation efficiency of 4x.

[0075] This invention enables highly efficient optical modulation of the optical field entering an integrated tunable optical attenuator based on mode cyclic phase shift and reflection. This invention can achieve:

[0076] 1. By utilizing the selective passage of higher-order modes by the mode coupler and the variation of the order of higher-order modes by the mode exchanger, the optical field energy and information are cyclically passed through the multimode optical phase shifter multiple times in the higher-order mode cyclic phase shifter, thereby multiplying the optical modulation efficiency.

[0077] 2. The reflective architecture allows the light field to pass through the high-order mode cyclic phase shifter twice in both directions, thus doubling the modulation efficiency on top of the high-order mode cyclic phase shifter. This improved modulation efficiency helps reduce device power consumption and drive voltage, thus facilitating compatibility with traditional CMOS on-chip drivers. It also helps reduce device size, enabling higher integration.

[0078] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. An integrated tunable optical attenuator based on mode-circulation phase- shifting and reflection, characterized in that, Comprise: Single-mode optical waveguide, 2x2 optical coupler, high-order mode cyclic phase shifter and waveguide optical reflector; wherein, The 2x2 optical coupler has four ports, which are divided into two groups, and its function is to divide the optical energy of one input port of one group into two output paths of the other group; the two ports on one side are connected to the optical input and output of the whole device through single-mode optical waveguide, and the other two ports are connected to one high-order mode cyclic phase shifter through single-mode optical waveguide respectively; The high-order mode cyclic phase shifter has two ports, one of which is connected to the 2x2 optical coupler, and the other is connected to the waveguide optical reflector through single-mode optical waveguide; the high-order mode cyclic phase shifter uses the high-order mode selectivity of the mode coupler and the staggered arrangement of the mode exchanger to high-order mode to make the light field circulate in the high-order mode cyclic phase shifter multiple times, realizing efficient optical phase modulation; the high-order mode cyclic phase shifter comprises: Single-mode optical waveguide, multimode optical waveguide, mode coupler, mode exchanger, first multimode optical phase shift arm and second multimode optical phase shift arm; wherein, The mode coupler has four ports, two of which are multimode ports and two of which are single-mode ports; among them, the two single-mode ports serve as the optical input and output ports of the high-order mode cyclic phase shifter, one multimode port is connected to the first multimode optical phase shift arm through the multimode optical waveguide, the first multimode optical phase shift arm is connected to the mode exchanger, and the mode exchanger is connected to the second multimode optical phase shift arm, which is then connected to the other multimode port of the mode coupler through the multimode optical waveguide, so that the mode coupler, the mode exchanger, the first multimode optical phase shift arm and the second multimode optical phase shift arm are connected through the multimode optical waveguide to form a loop; The waveguide optical reflector is used to couple the modulated light field back to the high-order mode cyclic phase shifter.

2. The integrated tunable optical attenuator based on mode-circulation phase-shift and reflection according to claim 1, characterized in that, The 2x2 optical coupler comprises a 50:50 beam splitter based on a directional coupler or a 50:50 beam splitter based on a multimode interference coupler.

3. The integrated tunable optical attenuator based on mode-circulation phase-shift and reflection according to claim 1, characterized in that, The function of the waveguide optical reflector is to reflect the input waveguide light field and output it through the input waveguide in reverse; The waveguide optical reflector comprises any one of a Bragg grating-based reflector, an inversely designed ultra-compact optical reflector and a right-angle integrated optical reflector based on geometric optics.

4. The integrated tunable optical attenuator based on mode-circulation phase-shift and reflection according to claim 1, characterized in that, The multimode optical waveguide is a waveguide that can accommodate multiple light modes passing through simultaneously after increasing its width.

5. The integrated tunable optical attenuator based on mode-circulation phase-shift and reflection according to claim 1, characterized in that, Any multimode optical phase shift arm is used to change the refractive index of the multimode optical waveguide through electro-optic effect or thermo-optic effect, so as to change the actual optical path of light in the multimode optical waveguide, thereby realizing the function of changing the phase of light passing through the multimode optical phase shift arm.

6. The integrated tunable optical attenuator based on mode-circulation phase-shift and reflection according to claim 1, characterized in that, The mode coupler of the high-order mode cyclic phase shifter has mode selectivity; the mode selectivity is to couple the fundamental mode in the single-mode optical waveguide to a specific mode in the multimode optical waveguide, and not to couple with other modes in the multimode optical waveguide.

7. The integrated tunable optical attenuator based on mode-circulation phase-shift and reflection according to claim 1, characterized in that, The mode exchanger realizes staggered arrangement for the optical field mode order circulating in the high-order mode cyclic phase shifter, and the mode staggered arrangement of the high-order mode cyclic phase shifter includes: converting the energy and information carried by the mode to other modes, but keeping the number of modes in the multimode optical waveguide before the mode exchanger equal to the number of modes in the multimode optical waveguide after the mode exchanger.

8. The integrated tunable optical attenuator based on mode-circulation phase-shift and reflection according to claim 7, characterized in that, The staggered arrangement includes: a specific arrangement belongs to a permutation group in which all elements are generators.

9. The integrated tunable optical attenuator based on mode-circulation phase-shift and reflection of claim 1, wherein, The working process of the high-order mode cyclic phase shifter is as follows: After the input optical field of the high-order mode cyclic phase shifter realizes the characteristic of traversing all mode channels through the mode exchanger and the mode coupler, the mode exchanger returns the optical field to the original mode, and then the mode coupler couples out the multimode optical waveguide, leaving the high-order mode cyclic phase shifter, thereby realizing a fold increase in the modulation efficiency of the optical field.

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