A wavelength selective switch based on metasurface optical elements and communication device thereof

Abstract

The application discloses a wavelength selective switch based on a metasurface optical element and communication equipment thereof and belongs to the technical field of optical communication networks.The wavelength selective switch comprises a light emitting end, a metasurface lens array, a Fourier lens, a metasurface grating lens, a reflecting unit and a plurality of light receiving ends; the metasurface lens array is used for carrying out divergence angle compression on composite light output by the light emitting end; the metasurface lens array comprises a first base material and a first metasurface microstructure; the Fourier lens is used for preliminarily collimating the composite light after the divergence angle compression to obtain parallel composite light beams and is used for realizing return channel coupling of reflected light beams; the metasurface grating lens is used for carrying out diffraction light splitting, focusing and shaping on the parallel composite light beams after the collimation to obtain a plurality of separated single-wavelength lights; the reflecting unit is used for receiving and reflecting the plurality of single-wavelength lights; and the plurality of single-wavelength reflected lights are received by the light receiving ends.The application simplifies the structure of a WSS system and reduces the volume.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical communication network, and particularly relates to a wavelength selective switch based on a metasurface optical element and a communication device thereof. BACKGROUND

[0002] Wavelength Division Multiplexing (WDM) is a basic multiplexing technology for realizing parallel transmission in a single optical fiber by using different wavelengths of light waves to carry multiple signals.

[0003] Wavelength Selective Switch (WSS) is an optical switching device with a 1xN port structure, which can realize intelligent scheduling of input multi-wavelength signals to any output port. The bidirectional transmission characteristics (input / output ports are interchangeable) of the wavelength selective switch technology significantly enhance the flexibility of network reconstruction and reduce the operating cost, and constitute the core switching unit of modern optical networks.

[0004] In a typical optical system architecture with a wavelength selective switch, the core optical components mainly include an optical input / output (I / O) front end based on a microlens array, a beam shaping optical device (such as a variable lens), a diffraction grating, a Fourier transform lens, and a switch engine composed of a spatial light modulator based on liquid crystal on silicon (LCOS) technology. At the same time, due to the inherent polarization sensitivity of the LCOS device, a typical optical system usually needs to integrate polarization-related optical elements to achieve optimal performance. For example, in the prior art, a Chinese patent with the publication number CN100460930C discloses an LCOS optical projection system, which integrates multiple polarizing plates.

[0005] However, there are two significant limitations in this typical optical system architecture: first, the overall volume of the system is larger due to the need to integrate multiple discrete optical elements (multi-piece traditional lens systems include multiple traditional lenses, which have the defects of large volume, heavy weight, large number of pieces, and high cost); second, traditional WSSs generally use a classic 2f optical system (an imaging system composed of an object plane, a Fourier lens, and an image plane), which requires a long optical channel length. To meet this requirement, the system faces two choices: one is to increase the module size, and the other is to introduce additional folding optical structures, but both solutions will significantly increase the complexity and manufacturing cost of the system. Specifically, the increase in system complexity is mainly reflected in the increase in optical alignment difficulty and the improvement in mechanical stability requirements, while the cost increase is mainly due to the processing and assembly cost of precision optical elements. These factors together pose serious challenges to LCOS-based WSS systems in terms of volume, cost, and complexity.

[0006] The rise of superlenses provides a practical solution to effectively solve the problem of large and complex WSS systems. A superlens is a two-dimensional array plane composed of a large number of subwavelength-sized unit structures. By adjusting the geometric shape, material composition, and arrangement order of the unit structures, the superlens can control the properties of diffracted light, including phase, amplitude, and polarization, and thus realize the focusing and imaging functions of the light field. Compared to traditional lenses, as a planar optical element, the core advantages of superlenses mainly manifest in thinness and multi-functional integration. Specifically, the thickness of a superlens is only on the order of hundreds of nanometers, which is 1 / 50 or even lower than the thickness of a traditional lens, significantly improving the integration level of the optical system; a single layer of superlens can also realize multiple functions such as achromatism, polarization sensitivity, and dynamic tuning.

[0007] In the construction of superlenses, the excellent phase control ability can realize the integration of multiple traditional lens functions with only one super surface. However, super surface lenses still face some challenges in practical applications. On the one hand, the size of super surface lenses is generally small, which to some extent limits their application range and the ability to process optical signals. On the other hand, the efficiency and bandwidth of super surface lenses are limited, making it difficult to meet the demand of high-speed and high-capacity communication. Therefore, further design and optimization of the structure of super surfaces are needed. At the same time, with the development of micro-nano optics and its processing technology, super surface lenses that meet the theoretical requirements can be explored. SUMMARY

[0008] In view of the problems in the prior art, the wavelength selective switch based on the metasurface optical element and the communication equipment thereof are provided to overcome the above technical problems existing in the prior art, and the metasurface grating lens has multiple functions such as light splitting, focusing and shaping. The ability of more than three optical elements in the traditional WSS is realized by using one optical element, and the integration of the optical system is significantly improved. The optical path design is also greatly simplified, so that the optical path is more compact, which helps to reduce the volume and weight of the optical system.

[0009] The technical scheme of the present application is as follows: a wavelength selective switch based on a metasurface optical element, comprising a light emitting end, a metasurface lens array, a Fourier lens, a metasurface grating lens and a reflection unit arranged in sequence along the light propagation direction;

[0010] At least one light emitting end is provided; the light emitting end is a one-dimensional fiber array for outputting composite light;

[0011] The metasurface lens array is arranged on the light emitting side of the light emitting end and performs divergence angle compression on the composite light output by the light emitting end; the metasurface lens array comprises a first substrate and a first metasurface microstructure, and the first metasurface microstructure is arranged on at least one side surface of the first substrate; at least one of the phase distribution, shape, size and density of the first metasurface microstructure is adjusted to realize dispersion adjustment of different light receiving ends;

[0012] The Fourier lens is used for preliminary collimation of the composite light after divergence angle compression to obtain parallel composite light beams, and is used for realizing return channel coupling of reflected light beams;

[0013] It should be noted that the Fourier lens is a transmission type lens.

[0014] The metasurface grating lens is used for diffractive light splitting, focusing and shaping of the collimated parallel composite light beams to obtain a plurality of separated single wavelength lights; the metasurface grating lens comprises a second substrate and a second metasurface microstructure, and the second metasurface microstructure is arranged on at least one side surface of the second substrate; the phase distribution of the second metasurface microstructure is adjusted to realize adjustment of the diffraction angle, beam shaping and focusing focal length to obtain different light splitting intervals;

[0015] The reflection unit is used for receiving and reflecting a plurality of single wavelength lights, and the reflected plurality of single wavelength reflected lights returns to the metasurface grating lens;

[0016] Further comprising a plurality of light receiving ends; a plurality of single-wavelength reflected lights are sequentially transmitted through the super surface grating lens, the Fourier lens and the super surface lens array, and are received by the light receiving ends; the light receiving ends are arranged on the reflected light path of the reflection unit, and the plurality of light receiving ends correspond to the plurality of single-wavelength reflected lights one by one; the light receiving ends and the light emitting ends are arranged on the same side, and the light receiving ends are one-dimensional fiber arrays.

[0017] It should be noted that: for the separated and focused light spots imaged on the reflection unit, a reflection angle is given to the selected separated and focused light spot, which corresponds to a light receiving end.

[0018] Further, the Fourier lens comprises a front focal plane and a back focal plane arranged in sequence along the light propagation direction, the light emitting end is located at the front focal plane, and the reflection unit is located at the back focal plane; the angle of the single-wavelength reflected light modulated by the reflection unit is converted into the displacement in the port direction of the light receiving end, so that the light spot of the channel corresponding to the single-wavelength reflected light is coupled to the corresponding light receiving end.

[0019] Further, a distance d is arranged between the super surface lens array and the light emitting end; the parallel composite light beam forms a collimated light spot on the back focal plane of the Fourier lens; the absolute value of the focal length of the super surface lens array, the distance d and the diameter of the collimated light spot are positively correlated; by designing different focal lengths of the super surface lens array and the distance d, the collimated light spot is compressed in the vertical and / or horizontal directions.

[0020] Specifically, increasing the distance d and the absolute value of the focal length of the super surface lens array will increase the diameter of the collimated light spot; on the contrary, reducing the distance d and the absolute value of the focal length of the super surface lens array will reduce the diameter of the collimated light spot.

[0021] Further, the focal length of the super surface lens array is in the range of 400um-900um; in the present application, it is preferably 400um, 500um, 600um, 700um, 800um and 900um;

[0022] It should be noted that: the greater the focal length of the super surface lens array, the greater the diameter of the collimated light spot, mainly to match the distance of the one-dimensional fiber array and the size of the subsequent super surface grating lens.

[0023] Further, the first and second substrates are both flat substrates; the first and second super surface microstructures are both super surface nano microstructures.

[0024] The first metasurface microstructure includes a plurality of first micro-units arranged in a uniform array; the second metasurface microstructure includes a plurality of second micro-units arranged in a uniform array; the shape of each micro-unit includes circular, elliptical, triangular, square, trapezoidal, pentagonal, and hexagonal; the number of the first and second micro-units is respectively matched with the number of the light receiving end;

[0025] It should be emphasized that the shape of each micro-unit is not limited in this invention. Although this invention provides an embodiment with only one shape, it is not limited to the shape exemplified above in practical applications. It can also be designed as other polygonal or irregular shapes.

[0026] Furthermore, when the first micro-unit is circular, the phase of the metasurface lens array is used... Indicates phase The calculation formula is:

[0027]

[0028] Among them, A i A is the coefficient of ρ raised to the power of 2i. i A is a constant. i or phase The coefficient of the i-th element in the calculation formula, where i is a positive integer; ρ is the normalized radial aperture coordinate of the first micro-unit, which is taken as the radius of the first micro-unit in practical applications; N1 is the phase. The index of the polynomial coefficients in the calculation formula, where N1 is a positive integer.

[0029] Furthermore, when the second micro-unit is square in shape, the phase of the metasurface grating lens is used... Indicates phase The calculation formula is:

[0030]

[0031] Where N2 is the phase The coefficients of the polynomials in the calculation formula are indices, where N² is a positive integer; Ai is the coefficient of the i-th polynomial expansion, where i is a positive integer; E i The (x,y) polynomial is a power series of x and y, where x and y are the coordinate information of the phase xy plane;

[0032] The diffraction angle and focused spot of the light emitted through the metasurface grating lens are controlled by adjusting the value of Ai.

[0033] Furthermore, the metasurface grating lens in this invention is a transmissive type.

[0034] Further, when the diffraction angle is increased, the parallel composite light beam passes through the metasurface grating lens to form a first imaging spot;

[0035] When the diffraction angle is reduced, the parallel composite light beam passes through the metasurface grating lens to form a second imaging spot;

[0036] Under the grating phase condition of maintaining the second imaging spot, the light separation interval is reduced by shortening the focusing distance of the metasurface grating lens to form a third imaging spot;

[0037] The light separation interval of the third imaging spot is smaller than that of the first and second imaging spots;

[0038] The aberration of the second imaging spot is smaller than that of the first imaging spot.

[0039] Further, the reflection unit is based on a silicon-based liquid crystal spatial light modulator (LCOS) or a micro-electro-mechanical system (MEMS) mirror array, and can also be other devices capable of realizing light path switching.

[0040] In the present application, the design material of the metasurface grating lens is silicon.

[0041] A communication device comprising the wavelength selective switch described above.

[0042] The present application has the following advantages:

[0043] (1) Compared with the grating in the traditional WSS, the metasurface grating lens has the functions of light splitting, focusing and shaping. The ability of more than three optical elements in the traditional WSS is realized by using one optical element, which significantly improves the integration of the optical system. At the same time, the second metasurface microstructure and the cylindrical lens are integrated into one structure in combination with the flexible design of the metasurface device, which reduces the use of optical devices, compresses the overall optical path, simplifies the WSS system, reduces the volume of the WSS system, reduces the design difficulty, manufacturing difficulty and module volume, and saves the manufacturing cost.

[0044] (2) The present application combines the metasurface lens array with the Fourier lens to provide ideal light beam conditions for subsequent metasurface grating lens processing, ensuring the accuracy and efficiency of light splitting, focusing and shaping operations, and ensuring that the reflected light beam can be efficiently and accurately coupled back to the original light path, improving the overall performance and stability of the system. At the same time, the single element of the Fourier lens realizes the dual functions of light beam collimation and reflected light beam return channel coupling, greatly simplifies the system structure of the wavelength selective switch, and significantly reduces the number of optical elements, further reducing the complexity and cost of the system. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The optical path structure schematic diagram of the wavelength selective switch in the dispersion direction of the application;

[0046] Figure 2 The optical path structure schematic diagram of the combination of the light emitting end, the super surface lens array and the Fourier lens of the application;

[0047] Figure 3 The optical path structure schematic diagram of the super surface lens array in the application; Figure 2

[0048] Figure 4 The optical path structure schematic diagram of the wavelength selective switch in the port direction of the application;

[0049] Figure 5 The structure schematic diagram of the super surface lens array of the application;

[0050] Figure 6 The structure schematic diagram of the super surface grating lens of the application;

[0051] Figure 7 The optical path structure and imaging diagram of the parallel composite light beam after passing through the super surface grating lens with large diffraction angle of the application;

[0052] Figure 8 The optical path structure and imaging diagram of the parallel composite light beam after passing through the super surface grating lens with small diffraction angle of the application;

[0053] Figure 9 The optical path structure and imaging diagram of the parallel composite light beam after passing through the super surface grating lens with short focal length of the application.

[0054] Marking description:

[0055] 10, light emitting end; 20, super surface lens array; 21, first super surface microstructure; 30, Fourier lens; 40, super surface grating lens; 41, second super surface microstructure; 50, reflection unit; 51, first imaging light spot; 52, second imaging light spot; 53, third imaging light spot; 60, light receiving end. DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0057] ​In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0058] As shown in the embodiment, a wavelength selective switch based on a metasurface optical element is provided, which comprises a light emitting end 10, a metasurface lens array 20, a Fourier lens 30, a metasurface grating lens 40 and a reflection unit 50 arranged in sequence along the light propagation direction. Figures 1-4

[0059] At least one light emitting end 10 is provided; the light emitting end 10 is a one-dimensional fiber array for outputting composite light.

[0060] The metasurface lens array 20 is arranged on the light emitting side of the light emitting end 10 and performs divergence angle compression on the composite light output by the light emitting end 10; the metasurface lens array 20 comprises a first substrate and a first metasurface microstructure 21, and the first metasurface microstructure 21 is arranged on at least one side surface of the first substrate; at least one of the phase distribution, shape, size and density of the first metasurface microstructure 21 is adjusted to realize dispersion adjustment of different light receiving ends.

[0061] The Fourier lens 30 is used for preliminary collimation of the composite light after divergence angle compression to obtain parallel composite light beams and is used for realizing return channel coupling of reflected light beams.

[0062] It should be noted that the Fourier lens 30 is a transmission type lens, and if a more compact structure is required, a curved mirror can be used in the actual design process to achieve the same effect and achieve the effect of folding the optical path.

[0063] The metasurface grating lens 40 is used for diffractive dispersion, focusing and shaping of the parallel composite light beams after collimation to obtain a plurality of separated single-wavelength lights; the metasurface grating lens 40 comprises a second substrate and a second metasurface microstructure 41, and the second metasurface microstructure 41 is arranged on at least one side surface of the second substrate; the phase distribution of the second metasurface microstructure 41 is adjusted to realize adjustment of the diffraction angle, beam shaping and focusing focal length to obtain different dispersion intervals.

[0064] ​The reflection unit 50 is configured to receive and reflect a plurality of single-wavelength lights, and the reflected plurality of single-wavelength reflected lights return to the super surface grating lens 40.

[0065] The wavelength selection switch further comprises a plurality of light receiving ends 60; the plurality of single-wavelength reflected lights sequentially pass through the super surface grating lens 40, the Fourier lens 30 and the super surface lens array 20, and are received by the light receiving ends 60; the light receiving ends 60 are arranged on the reflected light path of the reflection unit 50, and the plurality of light receiving ends 60 correspond to the plurality of single-wavelength reflected lights one by one; the light receiving ends 60 and the light emitting end 10 are arranged on the same side, and the light receiving ends 60 are one-dimensional fiber arrays.

[0066] It should be noted that, for the separated focused light spots imaged on the reflection unit 50, a reflection angle is given to a selected separated focused light spot, and the selected separated focused light spot corresponds to a light receiving end 60.

[0067] Firstly, compared with the gratings in the conventional WSS, the super surface grating lens 40 has multiple functions such as light splitting, focusing and shaping. The super surface grating lens 40 realizes the functions of more than three optical elements in the conventional WSS by using one optical element, significantly improves the integration of the optical system, and greatly simplifies the optical path design, so that the optical path is more compact, which helps to reduce the volume and weight of the optical system.

[0068] Secondly, the embodiment greatly reduces the number of independent optical elements required in the conventional wavelength selection switch, and improves the integration and compactness of the system.

[0069] Thirdly, by adjusting the phase, diffraction angle and focal length of the second super surface microstructure 41, the light splitting interval can be flexibly adjusted to meet the wavelength selection requirements in different application scenarios. At the same time, the efficient light splitting and shaping capability ensures the high quality and stability of the plurality of separated single-wavelength lights.

[0070] Finally, the Fourier lens 30 greatly improves the quality of the light beam, provides ideal light beam conditions for the subsequent super surface grating lens 40 processing, ensures the accuracy and efficiency of the light splitting, focusing and shaping operations, and ensures that the reflected light beam can be efficiently and accurately coupled back to the original light path, thereby improving the overall performance and stability of the system. At the same time, the Fourier lens 30 realizes the dual functions of light beam collimation and reflected light beam return channel coupling by using a single element, which greatly simplifies the system structure of the wavelength selection switch. The embodiment significantly reduces the number of elements, further reduces the complexity and cost of the system.

[0071] For example, Figure 4As shown, the Fourier lens 30 includes a front focal plane and a rear focal plane arranged in sequence along the light propagation direction, the light emitting end 10 is located at the front focal plane, and the reflection unit 50 is located at the rear focal plane; the angle of the single-wavelength reflected light modulated by the reflection unit 50 is converted into the displacement in the port direction of the light receiving end 60, so that the light spot of the channel corresponding to the single-wavelength reflected light is coupled to the corresponding light receiving end 60.

[0072] Specifically, a spacing d is provided between the metasurface lens array 20 and the light emitting end 10; the parallel composite light beam forms a collimated light spot on the rear focal plane of the Fourier lens 30; the absolute value of the focal length of the metasurface lens array 20, the spacing d and the diameter of the collimated light spot are positively correlated; by designing different focal lengths and spacings d of the metasurface lens array 20, the collimated light spot is compressed in the vertical and / or horizontal directions.

[0073] Specifically, increasing the spacing d and the absolute value of the focal length of the metasurface lens array 20 will increase the diameter of the collimated light spot; on the contrary, reducing the spacing d and the absolute value of the focal length of the metasurface lens array 20 will reduce the diameter of the collimated light spot.

[0074] In the embodiment, as shown in Figure 2 When a metasurface lens array 20 with a relatively large focal length is to be designed, the spacing d is increased to d1, and the diameter of the collimated light spot is also increased to D1 accordingly.

[0075] As shown in Figure 3 When a metasurface lens array 20 with a relatively small focal length is to be designed, the spacing d is reduced to d2, and the diameter of the collimated light spot is also reduced to D2.

[0076] More specifically, the focal length of the metasurface lens array 20 ranges from 400um to 900um; in the embodiment, the preferred values are 400um, 500um, 600um, 700um, 800um and 900um.

[0077] It should be noted that the greater the focal length of the metasurface lens array 20, the greater the diameter of the collimated light spot, mainly to match the spacing of the one-dimensional fiber array and the size of the subsequent metasurface grating lens 40.

[0078] In the embodiment, the focal length of the metasurface lens array 20 is 500um, and the Fourier lens 30 with a focal length of 75mm is used to obtain a collimated light spot with a diameter of about 1.1mm; various metasurface lens arrays 20 and Fourier lenses 30 with different focal lengths can be used according to actual needs, and the phase, shape, size and density of the first metasurface microstructure 21 can be adjusted to realize the function of eliminating aberration.

[0079] Specifically, both the first and second substrates are flat substrates; both the first metasurface microstructure 21 and the second metasurface microstructure 41 are metasurface nanostructures.

[0080] The first metasurface microstructure 21 includes a plurality of first micro-units arranged in a uniform array; the second metasurface microstructure 41 includes a plurality of second micro-units arranged in a uniform array; the shape of each micro-unit includes circular, elliptical, triangular, square, trapezoidal, pentagonal, and hexagonal; the number of the first and second micro-units respectively matches the number of the light receiving end 60.

[0081] It should be emphasized that the shape of each micro-unit is not limited in this embodiment. Although this embodiment only provides an implementation scheme with one shape, it is not limited to the shape listed above in practical applications. It can also be designed as other polygonal or irregular shapes.

[0082] like Figure 5 As shown, when the first micro-unit is circular, the phase of the metasurface lens array 20 is... Indicates phase The calculation formula is:

[0083]

[0084] Among them, A i A is the coefficient of ρ raised to the power of 2i. i A is a constant. i or phase The coefficient of the i-th element in the calculation formula, where i is a positive integer; ρ is the normalized radial aperture coordinate of the first micro-unit, which is taken as the radius of the first micro-unit in practical applications; N1 is the phase. The index of the polynomial coefficients in the calculation formula, where N1 is a positive integer;

[0085] In this embodiment, N1 is preferably set to 4, but the number of polynomials can be increased or decreased according to design requirements.

[0086] like Figure 6 As shown, when the second micro-unit is square, the phase of the metasurface grating lens 40 is... Indicates phase The calculation formula is:

[0087]

[0088] Where N2 is the phase The coefficients of the polynomials in the calculation formula are indices, where N² is a positive integer; Ai is the coefficient of the i-th polynomial expansion, where i is a positive integer; E iThe (x,y) polynomial is a power series of x and y, where x and y are the coordinate information of the phase xy plane;

[0089] In this embodiment, N2 is preferably set to 9, but the number of polynomials can be increased or decreased according to design requirements.

[0090] The diffraction angle and focused spot of light emitted through the metasurface grating lens 40 are controlled by controlling the value of Ai.

[0091] In this embodiment, the focusing efficiency of the metasurface lens array 20 affects the loss of the entire WSS system. If the loss is high, it will affect the signal quality. The accuracy of the wavelength selection switch is related to the second metasurface microstructure 41.

[0092] It should be further explained that by adding a grating phase to the design of the metasurface grating lens 40, the dispersion can be made consistent with that of a traditional diffraction grating, thus realizing the diffraction beam splitting function required in the wavelength selective switch. At the same time, by adding a cylindrical lens phase and combining and optimizing the two phases, the diffraction beam splitting and focusing effects can be achieved. In addition, by adding a beam shaping phase, the mode and intensity of the focused spot after beam splitting can be shaped. Furthermore, the focusing distance of the metasurface grating lens 40 can be flexibly adjusted according to different resolution conditions, so as to achieve free control of the beam splitting interval and make the design more flexible.

[0093] Specifically, the metasurface grating lens 40 in this embodiment is a transmissive type. Because the metasurface grating lens 40 is insensitive to polarization, this avoids the need for numerous polarization conversion components in the wavelength selection switch, saving components, reducing costs, and simplifying the optical path.

[0094] Moreover, the metasurface grating lens 40 is fabricated using semiconductor processing technology, resulting in high precision. The focusing distance of the metasurface grating lens 40 can be flexibly adjusted according to different resolution requirements, such as... Figures 7-9 As shown, the diagram illustrates the imaging spot of the metasurface grating lens 40 with the corresponding reflection unit 50, which achieves free control of the optical path length and increases design flexibility.

[0095] Specifically, when the diffraction angle is increased, the parallel composite beam passes through the metasurface grating lens 40 to form the first imaging spot 51; at this time, the designed diffraction angle is larger and the beam splitting capability is stronger, but the focused spot will have a large aberration that needs to be optimized.

[0096] When the diffraction angle is reduced, the parallel composite beam passes through the metasurface grating lens 40 to form a second imaging spot 52. At this time, the designed diffraction angle is smaller, the beam splitting ability is weaker and the diffraction efficiency is lower, but the aberration of the focused spot of the image is smaller.

[0097] While maintaining the grating phase of the second imaging spot 52, the beam splitting interval is reduced by shortening the focusing distance of the metasurface grating lens 40 to form the third imaging spot 53. It should be noted that, under the same grating phase conditions, since the beam splitting angle is related to the grating phase, shortening the focusing distance will reduce the beam splitting and focusing interval.

[0098] The beam splitting interval of the third imaging spot 53 is smaller than the beam splitting interval of the first and second imaging spots 52.

[0099] The aberration of the second imaging spot 52 is smaller than that of the first imaging spot 51.

[0100] Specifically, the reflective unit 50 is based on a liquid crystal spatial light modulator (LCOS) on silicon or a mirror array based on a microelectromechanical system (MEMS); the reflective unit 50 can also be other devices capable of optical path switching.

[0101] It should be noted that both technologies can achieve high-precision beam reflection and control. LCOS, with its high resolution and fast response characteristics, can flexibly modulate the phase and amplitude of the reflected light to meet the needs of complex optical field control. MEMS mirror arrays, with their miniaturization, high integration and low power consumption advantages, can achieve fast and accurate beam deflection and switching. Together, they provide the system with an efficient, flexible and reliable beam reflection solution, which significantly improves the performance and functional integration of the optical system.

[0102] In this embodiment, the metasurface grating lens 40 is designed with silicon as the material. This material allows for the precise fabrication of the second metasurface microstructure 41 on the metasurface grating lens 40, meeting the requirements of high-performance optical components. Other relevant transparent materials used in the communication band can also be employed to design and fabricate the metasurface grating lens 40.

[0103] Furthermore, compared to lenses that are traditionally ground or processed using molds, the metasurface-based optical elements in this embodiment are all manufactured using semiconductor processing technology, which offers high precision, flexible design, array-based control, and low-cost one-time processing, thus having a wide range of applications.

[0104] This embodiment also provides a communication device, including the wavelength selection switch described above.

[0105] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A wavelength selective switch based on metasurface optical elements, characterized in that, It includes a light emitting end, a metasurface lens array, a Fourier lens, a metasurface grating lens, and a reflection unit arranged sequentially along the light propagation direction; it also includes multiple light receiving ends; At least one optical transmitter is provided; the optical transmitter is a one-dimensional fiber array used to output composite light; A metasurface lens array is disposed on one side of the light emitting end and compresses the divergence angle of the composite light output from the light emitting end. The metasurface lens array includes a first substrate and a first metasurface microstructure. The first metasurface microstructure is disposed on at least one side surface of the first substrate. By adjusting at least one of the phase distribution, shape, size, and density of the first metasurface microstructure, dispersion adjustment can be achieved for different light receiving ends. Fourier lenses are used to initially collimate composite light after divergence angle compression to obtain parallel composite beams, and to achieve return channel coupling of reflected beams. A metasurface grating lens is used to diffract, focus, and shape a aligned parallel composite beam to obtain multiple separated single-wavelength beams. The metasurface grating lens includes a second substrate and a second metasurface microstructure. The second metasurface microstructure is provided on at least one side surface of the second substrate. By adjusting the phase distribution of the second metasurface microstructure, the diffraction angle, beam shaping, and focusing focal length can be adjusted to obtain different beam splitting intervals. The reflection unit is used to receive and reflect multiple single-wavelength lights, and the reflected single-wavelength light returns to the metasurface grating lens. Multiple single-wavelength reflected lights are transmitted sequentially through a metasurface grating lens, a Fourier lens, and a metasurface lens array before being received by an optical receiver. The optical receiver is located on the reflected light path of the reflective unit, and multiple optical receivers correspond one-to-one with multiple single-wavelength reflected lights. The optical receiver and the optical transmitter are located on the same side, and the optical receiver is a one-dimensional fiber array.

2. The wavelength selective switch according to claim 1, characterized in that, The Fourier lens includes a front focal plane and a rear focal plane arranged sequentially along the light propagation direction. The light emitting end is located on the front focal plane, and the reflection unit is located on the rear focal plane. The angle of the single-wavelength reflected light modulated by the reflection unit is converted into a displacement in the port direction of the light receiving end, thereby causing the light spot of the channel corresponding to the single-wavelength reflected light to be coupled to the corresponding light receiving end.

3. The wavelength selective switch according to claim 2, characterized in that, A spacing d is provided between the metasurface lens array and the light emitting end; the parallel composite beam forms a collimated spot on the back focal plane of the Fourier lens; the absolute value of the focal length of the metasurface lens array, the spacing d, and the diameter of the collimated spot are positively correlated; by designing different focal lengths and spacing d of the metasurface lens array, compression in the vertical and / or horizontal directions of the collimated spot can be achieved.

4. The wavelength selective switch according to claim 2 or 3, characterized in that, The focal length of the metasurface lens array ranges from 400um to 900um.

5. The wavelength selective switch according to claim 1, characterized in that, Both the first and second substrates are flat plate substrates; both the first and second metasurface microstructures are metasurface nanostructures. The first metasurface microstructure includes a plurality of first micro-units arranged in a uniform array; the second metasurface microstructure includes a plurality of second micro-units arranged in a uniform array; the shape of each micro-unit includes circular, elliptical, triangular, square, trapezoidal, pentagonal, and hexagonal; the number of the first and second micro-units is matched with the number of the optical receivers.

6. The wavelength selective switch according to claim 5, characterized in that, When the first micro-unit is circular, the phase of the metasurface lens array is used. Indicates phase The calculation formula is: Among them, A i A is the coefficient of ρ raised to the power of 2i. i A is a constant. i or phase The coefficient of the i-th element in the calculation formula, where i is a positive integer; ρ is the normalized radial aperture coordinate of the first micro-unit; N1 is the phase. The index of the polynomial coefficients in the calculation formula, where N1 is a positive integer.

7. The wavelength selective switch according to claim 5, characterized in that, When the second micro-unit is square, the phase of the metasurface grating lens is used. Indicates phase The calculation formula is: Where N2 is the phase The coefficients of the polynomials in the calculation formula are indices, where N² is a positive integer; Ai is the coefficient of the i-th polynomial expansion, where i is a positive integer; E i The (x,y) polynomial is a power series of x and y, where x and y are the coordinate information of the phase xy plane; The diffraction angle and focused spot of light emitted through the metasurface grating lens are controlled by adjusting the value of Ai.

8. The wavelength selective switch according to claim 7, characterized in that, When the diffraction angle is increased, the parallel composite beam passes through the metasurface grating lens to form a first imaging spot; When the diffraction angle is reduced, the parallel composite beam passes through the metasurface grating lens to form a second imaging spot; While maintaining the grating phase of the second imaging spot, the beam splitting interval is reduced by shortening the focusing distance of the metasurface grating lens, thereby forming a third imaging spot; The beam splitting interval of the third imaging spot is smaller than the beam splitting interval of the first and second imaging spots. The aberration of the second imaging spot is smaller than that of the first imaging spot.

9. The wavelength selective switch according to claim 1, characterized in that, The reflective unit is either a silicon-based liquid crystal spatial light modulator or a microelectromechanical system-based reflector array.

10. A communication device, characterized in that, Includes the wavelength selection switch as described in any one of claims 1 to 9.

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