Wavelength selection switch based on metasurface optical element and communication equipment thereof

Abstract

The invention 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 selection switch comprises a light emitting end, a metasurface lens array, a Fourier lens, a metasurface grating lens, a reflection unit and a plurality of light receiving ends. The metasurface lens array is used for carrying out divergence angle compression on the compound 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 carrying out preliminary collimation on the compound light subjected to divergence angle compression to obtain a parallel compound light beam, and is used for realizing return channel coupling of a reflected light beam; the metasurface grating lens is used for carrying out diffraction light splitting, focusing and shaping on the straightened parallel composite light beams to obtain a plurality of separated single-wavelength light; a reflection unit for receiving and reflecting the plurality of single-wavelength light; the plurality of single-wavelength reflected light is received by a light receiving end. The structure of the WSS system is simplified, and the size is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communication networks, and particularly relates to a wavelength selective switch based on a metasurface optical element and a communication device thereof. Background Art

[0002] Wavelength division multiplexing technology (WDM, full name: Wavelength Division Multiplexing) is a basic multiplexing technology that transmits multiple signals in parallel in a single optical fiber by using optical waves of different wavelengths to carry the signals.

[0003] Wavelength selective switch technology (WSS, full name: Wavelength Selective Switch) uses an optical switching device with a 1×N port structure to achieve intelligent scheduling of any wavelength to any output port for the input multi-wavelength signals. The bidirectional transmission characteristic (input / output ports can be interchanged) of the wavelength selective switch technology significantly enhances the flexibility of network reconfiguration and reduces the operating cost, constituting the core switching unit of modern optical networks.

[0004] In a typical optical system architecture with a wavelength selective switch, its core optical components mainly include an optical input / output (I / O) front end based on a microlens array, beam shaping optical devices (such as anamorphic lenses), diffraction gratings, Fourier transform lenses, and a switch engine, which is composed of a spatial light modulator based on liquid crystal on silicon (LCOS, full name: Liquid Crystal on Silicon) technology. At the same time, due to the inherent polarization sensitivity of LCOS devices, a typical optical system usually also needs to integrate polarization-related optical elements to achieve optimal performance. For example, in the prior art, the Chinese patent with the publication number CN100460930C discloses an LCOS optical projection system, in which multiple polarizers are integrated.

[0005] However, there are two significant limitations in this typical optical system architecture: First, due to the need to integrate multiple discrete optical components, the overall volume of the system is larger (a multi-piece traditional lens system contains multiple traditional lenses, and these traditional lenses have the defects of large volume, heavy weight, large number of pieces, and high cost); Second, traditional WSS generally adopts a classical 2f optical system (an imaging system composed of an object plane, a Fourier lens, and an image plane), and this design 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 of these 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 the difficulty of optical alignment, the improvement of mechanical stability requirements, etc., while the cost increase mainly comes from the processing and assembly costs of precision optical components. These factors together have led to severe challenges for the LCOS-based WSS system in multiple dimensions such as volume, cost, and complexity.

[0006] The rise of metasurfaces provides a practical solution for effectively solving the problem of the large size and complexity of WSS systems. A metasurface is a two-dimensional array plane composed of numerous unit structures with subwavelength dimensions. The metasurface controls the properties of diffracted light, including phase, amplitude, and polarization, by adjusting the geometric shape, material composition, and arrangement order of the unit structures, and thus realizes the focusing and imaging functions of the light field. Compared with traditional lenses, as a planar optical component, the core advantages of the metasurface are mainly reflected in the characteristics of being thin, light, and multi-functional integration. Specifically, the thickness of the metasurface is only on the order of a few hundred nanometers, which is 1 / 50 or even lower than the thickness of traditional lenses, and this characteristic significantly improves the integration degree of the optical system; A single-layer metasurface can also simultaneously achieve multiple functions such as achromatism, polarization sensitivity, and dynamic tuning.

[0007] In the construction of metasurfaces, by using their excellent phase modulation ability, it is possible to achieve the functional effects of integrating multiple traditional lenses with only one metasurface. However, currently, metasurface lenses still face some challenges in practical applications. On the one hand, the size of metasurface lenses is generally small, which to a certain extent limits their application scope and the ability to process optical signals. On the other hand, the efficiency and achievable bandwidth of metasurface lenses are relatively limited, making it difficult to meet the requirements of high-speed and large-capacity communication. Therefore, it is necessary to further design and optimize the structure of the metasurface. At the same time, with the development of micro-nano optics and its processing technology, it is possible to explore the processing of metasurface lenses that better meet the theoretical requirements. Summary of the Invention

[0008] In view of the problems in the related art, the present invention proposes a wavelength selection switch based on a metasurface optical element and its communication device to overcome the above-mentioned technical problems existing in the existing related technologies. The metasurface grating lens described in the present invention has multiple functions such as beam splitting, focusing, and shaping. With one optical element, the capabilities of more than three optical elements in a traditional WSS are achieved, significantly improving the integration of the optical system. It also greatly simplifies the optical path design, making the optical path more compact, which helps to reduce the volume and weight of the optical system.

[0009] The technical solution of the present invention is implemented as follows: A wavelength selection switch based on a metasurface optical element includes an optical emission 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 of the optical emission ends is provided; the optical emission end is a one-dimensional fiber array for outputting composite light;

[0011] The metasurface lens array is arranged on the side where the light is emitted from the optical emission end and compresses the divergence angle of the composite light output by the optical emission end; the metasurface lens array includes a first substrate and a first metasurface microstructure, and at least one side surface of the first substrate is provided with the first metasurface microstructure. By adjusting at least one of the phase distribution, shape, size, and density of the first metasurface microstructure, the dispersion adjustment for different light receiving ends is realized;

[0012] The Fourier lens is used to preliminarily collimate the composite light after the divergence angle compression to obtain a parallel composite light beam and is used to realize the return channel coupling of the reflected light beam;

[0013] It should be noted that: the Fourier lens is a transmissive lens.

[0014] The metasurface grating lens is used to perform diffraction beam splitting, focusing, and shaping on the collimated parallel composite light beam to obtain multiple separated single-wavelength lights; the metasurface grating lens includes a second substrate and a second metasurface microstructure, and at least one side surface of the second substrate is provided with the second metasurface microstructure. By adjusting the phase distribution of the second metasurface microstructure, the adjustment of the diffraction angle, beam shaping, and focusing focal length is realized to obtain different beam splitting intervals;

[0015] The reflection unit is used to receive and reflect multiple single-wavelength lights, and the multiple single-wavelength reflected lights after reflection return to the metasurface grating lens;

[0016] It also includes multiple optical receiving ends; multiple single-wavelength reflected lights are sequentially transmitted through the metasurface grating lens, the Fourier lens, and the metasurface lens array, and then received by the optical receiving ends; the optical receiving ends are arranged on the reflection light path of the reflection unit, and the multiple optical receiving ends correspond to the multiple single-wavelength reflected lights one by one; the optical receiving ends and the optical transmitting ends are arranged on the same side, and the optical 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, and one optical receiving end can be corresponding.

[0018] Furthermore, the Fourier lens includes a front focal plane and a rear focal plane arranged in sequence along the light propagation direction. The optical transmitting 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 optical receiving end, so that the light spot of the channel corresponding to the single-wavelength reflected light is coupled to the corresponding optical receiving end.

[0019] Furthermore, there is a spacing d between the metasurface lens array and the optical transmitting end; the parallel composite light beam forms a collimated light spot on the rear 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 light spot are positively correlated; by designing the focal length of different metasurface lens arrays and the spacing d, the collimated light spot can be compressed in the vertical and / or horizontal directions.

[0020] Specifically, increasing the absolute value of the spacing d and the focal length of the metasurface lens array, the diameter of the collimated light spot will increase accordingly; on the contrary, decreasing the absolute value of the spacing d and the focal length of the metasurface lens array, the diameter of the collimated light spot will decrease accordingly.

[0021] Furthermore, the value range of the focal length of the metasurface lens array is 400um - 900um; in the present invention, 400um, 500um, 600um, 700um, 800um, and 900um are preferably selected;

[0022] It should be noted that the larger the focal length of the metasurface lens array, the larger the diameter of the collimated light spot, mainly to match the spacing with the one-dimensional fiber array and the size of the subsequent metasurface grating lens.

[0023] Furthermore, both the first and second substrates are flat substrates; both the first metasurface microstructure and the second metasurface microstructure are metasurface nano-microstructures;

[0024] The first metasurface microstructure includes a plurality of first micro-units uniformly arranged in an array; the second metasurface microstructure includes a plurality of second micro-units uniformly arranged in an array; the shape of each micro-unit includes circular, oval, triangular, square, trapezoidal, pentagonal, hexagonal; the numbers of the first and second micro-units respectively match the number of the optical receiving ends;

[0025] It should be emphasized that: the shape of each micro-unit is not limited in the present invention. Although the present invention provides an implementation scheme with only one of the shapes, in practical applications, it is not limited to the shapes listed above, and can also be designed into other polygons or irregular shapes.

[0026] Further, when the shape of the first micro-unit is circular, the phase of the metasurface lens array is expressed by and the calculation formula of the phase is:

[0027]

[0028] where A i is the coefficient of the 2i-th power of ρ, A i is a constant, A i is also the coefficient of the i-th in the calculation formula of the phase i is a positive integer; ρ is the normalized radial aperture coordinate of the first micro-unit, and in practical applications, ρ is the radius of the first micro-unit; N1 is the serial number of the polynomial coefficient in the calculation formula of the phase and N1 is a positive integer.

[0029] Further, when the shape of the second micro-unit is square, the phase of the metasurface grating lens is expressed by and the calculation formula of the phase is:

[0030]

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

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

[0033] Further, the metasurface grating lens in the present invention is a transmissive type.

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

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

[0036] Under the condition of maintaining the grating phase of the second imaging spot, the spectral splitting interval is reduced by shortening the focal length of the metasurface grating lens to form a third imaging spot;

[0037] The spectral splitting 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 liquid crystal on silicon spatial light modulator (LCOS), or a mirror array based on microelectromechanical systems (MEMS), and the reflection unit can also be other devices capable of realizing optical path switching.

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

[0041] A communication device includes the wavelength selection switch described above.

[0042] Advantages of the present invention:

[0043] (1) Compared with the gratings in traditional WSS, the metasurface grating lens described in the present invention has multiple functions such as spectral splitting, focusing, and shaping. One optical element realizes the capabilities of more than three optical elements in traditional WSS, significantly improving the integration of the optical system; at the same time, in combination with the flexible design of the metasurface device, the present invention integrates the second metasurface microstructure and the cylindrical lens into an integrated structure, reducing the use of optical devices, partially compressing the overall optical path, simplifying the WSS system, reducing the volume of the WSS system, lowering the design difficulty, manufacturing difficulty, and module volume, and saving manufacturing costs.

[0044] (2) The present invention combines the metasurface lens array with the Fourier lens to provide ideal beam conditions for subsequent processing of the metasurface grating lens, ensuring the accuracy and efficiency of operations such as spectral splitting, focusing, and shaping, and ensuring that the reflected beam can be efficiently and accurately coupled back to the original optical path, improving the overall performance and stability of the system. At the same time, the dual functions of beam collimation and coupling of the reflected beam return channel are realized by a single element of the Fourier lens, greatly simplifying the system structure of the wavelength selection switch, significantly reducing the number of optical elements, and further reducing the complexity and cost of the system. Description of the Drawings

[0045] Figure 1 It is a schematic diagram of the optical path structure of the wavelength selection switch of the present invention in the dispersion direction;

[0046] Figure 2 It is a schematic diagram of the optical path structure of the optical emission end, metasurface lens array and Fourier lens combination of the present invention;

[0047] Figure 3 is Figure 2 a schematic diagram of the optical path structure after the metasurface lens array in compresses the light spot;

[0048] Figure 4 It is a schematic diagram of the optical path structure of the wavelength selection switch of the present invention in the port direction;

[0049] Figure 5 It is a schematic diagram of the structure of the metasurface lens array of the present invention;

[0050] Figure 6 It is a schematic diagram of the structure of the metasurface grating lens of the present invention;

[0051] Figure 7 It is the optical path structure and imaging diagram of the parallel composite beam of the present invention after passing through the metasurface grating lens with a large diffraction angle;

[0052] Figure 8 It is the optical path structure and imaging diagram of the parallel composite beam of the present invention after passing through the metasurface grating lens with a small diffraction angle;

[0053] Figure 9 It is the optical path structure and imaging diagram of the parallel composite beam of the present invention after passing through the metasurface grating lens with a short focal length.

[0054] Marking description:

[0055] 10. Optical emission end; 20. Metasurface lens array; 21. First metasurface microstructure; 30. Fourier lens; 40. Metasurface grating lens; 41. Second metasurface microstructure; 50. Reflection unit; 51. First imaging light spot; 52. Second imaging light spot; 53. Third imaging light spot; 60. Optical receiving end. Specific embodiments

[0056] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0057] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0058] As Figure 1-4 shown, this embodiment provides a wavelength selection switch based on a metasurface optical element, which includes an optical emission 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;

[0059] At least one of the optical emission ends 10 is provided; the optical emission end 10 is a one-dimensional fiber array for outputting composite light;

[0060] The metasurface lens array 20 is arranged on the side where the optical emission end 10 emits light and compresses the divergence angle of the composite light output by the optical emission end 10; the metasurface lens array 20 includes a first substrate and a first metasurface microstructure 21, and at least one side surface of the first substrate is provided with the first metasurface microstructure 21. By adjusting at least one of the phase distribution, shape, size, and density of the first metasurface microstructure 21, the dispersion adjustment for different optical receiving ends is realized;

[0061] The Fourier lens 30 is used to preliminarily collimate the composite light after divergence angle compression to obtain a parallel composite light beam, and is used to realize the return channel coupling of the reflected light beam;

[0062] It should be noted that: the Fourier lens 30 is a transmissive lens. If a more compact structure is desired, a mirror with curvature can be used in the actual design process to play the same role and achieve the effect of folding the optical path.

[0063] The metasurface grating lens 40 is used to diffract, split, focus, and shape the collimated parallel composite light beam to obtain multiple separated single-wavelength lights; the metasurface grating lens 40 includes a second substrate and a second metasurface microstructure 41, and at least one side surface of the second substrate is provided with the second metasurface microstructure 41. By adjusting the phase distribution of the second metasurface microstructure 41, the adjustment of the diffraction angle, beam shaping, and focusing focal length is realized to obtain different spectral splitting intervals;

[0064] The reflection unit 50 is configured to receive and reflect multiple single-wavelength lights, and the multiple single-wavelength reflected lights after reflection return to the metasurface grating lens 40;

[0065] It further includes multiple optical receiving ends 60; the multiple single-wavelength reflected lights are sequentially transmitted through the metasurface grating lens 40, the Fourier lens 30, and the metasurface lens array 20 and then received by the optical receiving ends 60; the optical receiving ends 60 are arranged on the reflection optical path of the reflection unit 50, and the multiple optical receiving ends 60 correspond one by one to the multiple single-wavelength reflected lights; the optical receiving ends 60 and the optical transmitting end 10 are arranged on the same side, and the optical receiving ends 60 are a one-dimensional optical fiber array.

[0066] It should be noted that for the separated and focused light spots imaged on the reflection unit 50, giving a reflection angle to the selected separated and focused light spot can correspond to one optical receiving end 60.

[0067] First, compared with the grating in the traditional WSS, the metasurface grating lens 40 described in this embodiment has multiple functions such as beam splitting, focusing, and shaping. One optical element realizes the capabilities of more than three optical elements in the traditional WSS, significantly improving the integration of the optical system; it also greatly simplifies the optical path design, making the optical path more compact, which helps to reduce the volume and weight of the optical system.

[0068] Second, this embodiment greatly reduces the number of independent optical elements required in the traditional wavelength selective switch, improving the integration and compactness of the system.

[0069] Furthermore, by adjusting parameters such as the phase, diffraction angle, and focal length of the second metasurface microstructure 41, the beam splitting interval can be flexibly adjusted to meet the wavelength selection requirements in different application scenarios. At the same time, its efficient beam splitting and shaping capabilities ensure the high quality and stability of multiple separated single-wavelength lights.

[0070] Finally, the setting of the Fourier lens 30 greatly improves the beam quality, provides ideal beam conditions for the subsequent processing of the metasurface grating lens 40, ensures the accuracy and efficiency of operations such as beam splitting, focusing, and shaping, and also ensures that the reflected beam can be efficiently and accurately coupled back to the original optical path, improving the overall performance and stability of the system. At the same time, the dual functions of beam collimation and coupling of the reflected beam return channel are realized through a single element of the Fourier lens 30, greatly simplifying the system structure of the wavelength selective switch. This embodiment significantly reduces the number of elements, further reducing the complexity and cost of the system.

[0071] Such as 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 on the front focal plane, and the reflection unit 50 is located on the rear focal plane. The angle of the single-wavelength reflected light modulated by the reflection unit 50 is converted into a 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, there is a spacing d between the metasurface lens array 20 and the light emitting end 10. The parallel composite 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 the focal length of the metasurface lens array 20 and the spacing d differently, the collimated light spot can be compressed in the vertical and / or horizontal directions.

[0073] Specifically, increasing the absolute value of the spacing d and the focal length of the metasurface lens array 20 will increase the diameter of the collimated light spot. On the contrary, decreasing the absolute value of the spacing d and the focal length of the metasurface lens array 20 will decrease the diameter of the collimated light spot.

[0074] In this embodiment, as Figure 2 shown, when designing a metasurface lens array 20 with a relatively large focal length, the spacing d is increased to d1, and the diameter of the collimated light spot also correspondingly increases to D1.

[0075] As Figure 3 shown, when designing a metasurface lens array 20 with a relatively small focal length, the spacing d is decreased to d2, and the diameter of the collimated light spot also decreases to D2.

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

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

[0078] In this embodiment, the focal length of the metasurface lens array 20 is 500um, and at the same time, it is paired with a Fourier lens 30 with a focal length of 75mm to obtain a collimated light spot with a diameter of about 1.1mm. Different metasurface lens arrays 20 and Fourier lenses 30 with various focal lengths can be paired according to actual needs, and then the function of aberration elimination can be realized by adjusting the phase, shape, size, density, etc. of the first metasurface microstructure 21.

[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 nano-microstructures;

[0080] The first metasurface microstructure 21 includes a plurality of first micro-units uniformly arranged in an array; the second metasurface microstructure 41 includes a plurality of second micro-units uniformly arranged in an array; the shape of each micro-unit includes circular, elliptical, triangular, square, trapezoidal, pentagonal, and hexagonal; the numbers of the first and second micro-units respectively match the number of the optical receiving ends 60;

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

[0082] Such as Figure 5 shown, when the shape of the first micro-unit is circular, the phase of the metasurface lens array 20 is represented by The phase The calculation formula is:

[0083]

[0084] Among them, A i is the coefficient of the 2i-th power of ρ, A i is a constant, A i is still the coefficient of the i-th in the phase Calculation formula, i is a positive integer; ρ is the normalized radial aperture coordinate of the first micro-unit, and in practical applications, ρ adopts the radius of the first micro-unit; N1 is the serial number of the polynomial coefficient in the phase Calculation formula, N1 is a positive integer;

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

[0086] Such as Figure 6 shown, when the shape of the second micro-unit is square, the phase of the metasurface grating lens 40 is represented by The phase The calculation formula is:

[0087]

[0088] Among them, N2 is the serial number of the polynomial coefficient in the phase Calculation formula, N2 is a positive integer; Ai is the coefficient of the i-th polynomial expansion, i is a positive integer; E i(x,y) polynomials are power series of x and y, where x and y are coordinate information of the phase xy plane;

[0089] In this embodiment, N2 preferably takes the value of 9, and the number of polynomials can be increased or decreased according to design requirements;

[0090] By controlling the value of Ai, the diffraction angle and the focused spot of the light exiting through the metasurface grating lens 40 are controlled;

[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 large, it will affect the signal quality. The accuracy of the wavelength selective switch is related to the second metasurface microstructure 41;

[0092] It should be further noted that adding a grating phase in the design of the metasurface grating lens 4 can achieve the same dispersion as a traditional diffraction grating and realize the diffraction splitting function required in the wavelength selective switch; at the same time, adding a cylindrical lens phase, combining and optimizing the two phases can achieve the effects of diffraction splitting and focusing; adding a beam shaping phase can realize the shaping of the mode and intensity of the focused spot after splitting; the focusing distance of the metasurface grating lens 40 can also be flexibly adjusted according to different resolution conditions to achieve free control of the splitting interval, making the design more flexible.

[0093] Specifically, the metasurface grating lens 40 in this embodiment is transmissive. Due to the polarization-insensitive characteristic of the metasurface grating lens 40, it avoids the situation of setting many polarization conversion components in the wavelength selective switch, saves components, reduces costs, and simplifies the optical path.

[0094] Moreover, the metasurface grating lens 40 is fabricated based on semiconductor processing technology with high precision, and the focusing distance of the metasurface grating lens 40 can be flexibly adjusted according to different resolution capabilities, as Figure 7-9 shown, the schematic diagram of the imaging spots of the metasurface grating lenses 40 with different designs and the corresponding reflection units 50 realizes free control of the optical path length and increases the design flexibility.

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

[0096] When the diffraction angle is decreased, 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 splitting ability is weaker and the diffraction efficiency will be lower, but the aberration of the imaged focused spot is smaller;

[0097] While maintaining the grating phase condition of the second imaging spot 52, the spectral splitting interval is reduced by shortening the focal length of the metasurface grating lens 40 to form a third imaging spot 53; it should be noted that, based on the same grating phase condition, since the spectral splitting angle is related to the grating phase, shortening the focal length will reduce the interval of spectral splitting and focusing;

[0098] The spectral splitting interval of the third imaging spot 53 is smaller than that 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 reflection unit 50 is a liquid crystal on silicon spatial light modulator (LCOS) or a mirror array based on microelectromechanical systems (MEMS); the reflection unit 50 can also be other devices capable of realizing optical path switching;

[0101] It should be noted that: both of these two technologies can achieve high-precision beam reflection and regulation. Among them, LCOS can flexibly modulate the phase and amplitude of the reflected light with its high resolution and fast response characteristics to meet the requirements of complex optical field regulation; while the MEMS mirror array realizes fast and accurate deflection and switching of the beam with its advantages of miniaturization, high integration and low power consumption. The two jointly provide an efficient, flexible and reliable beam reflection solution for the system, significantly improving the performance and functional integration of the optical system.

[0102] In this embodiment, the design material of the metasurface grating lens 40 is silicon, which can easily achieve the precise manufacturing of the second metasurface microstructure 41 on the metasurface grating lens 40 to meet the requirements of high-performance optical elements. Other relevant transparent materials in the communication band can also be used to design and prepare the metasurface grating lens 40.

[0103] In addition, compared with traditional ground or mold-processed lenses, the optical elements based on metasurfaces in this embodiment are all fabricated by semiconductor processing technology, with high precision, flexible design, capable of realizing arrayed regulation, and can be processed into a mold at low cost at one time, having broad application space.

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

[0105] Based on the disclosure and teachings of the above specification, those skilled in the art to which the present invention pertains can also 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. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A wavelength selective switch based on a metasurface optical element, characterized in that It includes an optical emission end, a metasurface lens array, a Fourier lens, a metasurface grating lens, and a reflection unit that are sequentially arranged along the light propagation direction; it also includes multiple optical receiving ends; There is at least one of the optical emission ends; the optical emission end is a one-dimensional fiber array for outputting composite light; The metasurface lens array is arranged on the side where the light is emitted from the optical emission end and compresses the divergence angle of the composite light output by the optical emission end; the metasurface lens array includes a first substrate and a first metasurface microstructure, and at least the first metasurface microstructure is provided on 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, the dispersion adjustment for different optical receiving ends is realized; The Fourier lens is used to preliminarily collimate the composite light after the divergence angle compression to obtain a parallel composite light beam and is used to realize the return channel coupling of the reflected light beam; The metasurface grating lens is used to diffract, split, focus, and shape the collimated parallel composite light beam to obtain multiple separated single-wavelength lights; the metasurface grating lens includes a second substrate and a second metasurface microstructure, and at least the second metasurface microstructure is provided on one side surface of the second substrate. By adjusting the phase distribution of the second metasurface microstructure, the adjustment of the diffraction angle, beam shaping, and focusing focal length is realized to obtain different spectral splitting intervals; The reflection unit is used to receive and reflect multiple single-wavelength lights, and the multiple single-wavelength reflected lights after reflection return to the metasurface grating lens; The multiple single-wavelength reflected lights are received by the optical receiving ends after passing through the metasurface grating lens, the Fourier lens, and the transmission of the metasurface lens array in sequence; the optical receiving ends are arranged on the reflection optical path of the reflection unit, and the multiple optical receiving ends correspond to the multiple single-wavelength reflected lights one by one; the optical receiving ends and the optical emission ends are arranged on the same side, and the optical receiving ends are one-dimensional fiber arrays.

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 that are sequentially arranged along the light propagation direction. The optical emission 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 optical receiving end, so that the spot of the channel corresponding to the single-wavelength reflected light is coupled to the corresponding optical receiving end.

3. The wavelength selection switch according to claim 2, characterized in that, There is a spacing d between the metasurface lens array and the optical emission end; the parallel composite light beam forms a collimated spot on the rear 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 of the metasurface lens array and the spacing d, the collimated spot is compressed in the vertical and / or horizontal directions.

4. The wavelength selection 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 selection switch according to claim 1, characterized in that, The first and second substrates are both flat substrates; the first metasurface microstructure and the second metasurface microstructure are both metasurface nano-microstructures; The first metasurface microstructure includes a plurality of first micro-units uniformly arranged in an array; the second metasurface microstructure includes a plurality of second micro-units uniformly arranged in an array; the shape of each micro-unit includes a circle, an ellipse, a triangle, a square, a trapezoid, a pentagon, and a hexagon; the numbers of the first and second micro-units respectively match the number of the optical receiving ends.

6. The wavelength selective switch according to claim 5, characterized in that, When the shape of the first micro-unit is circular, the phase of the metasurface lens array is expressed by and the calculation formula of the phase is as follows: Among them, A i is the coefficient of the 2i-th power of ρ, and A i is a constant. A i is also the coefficient of the i-th in the phase calculation formula, where i is a positive integer; ρ is the normalized radial aperture coordinate of the first micro-unit; N1 is the coefficient sequence number of the polynomial coefficient in the phase calculation formula, and N1 is a positive integer.

7. The wavelength selective switch according to claim 5, characterized in that, When the shape of the second micro-unit is square, the phase of the metasurface grating lens is expressed by and the calculation formula of the phase is as follows: where N2 is the phase the serial number of the polynomial coefficient in the calculation formula, N2 is a positive integer; Ai is the coefficient of the i-th polynomial expansion, i is a positive integer; E i (x, y) polynomial is a power series of x and y, and x and y are the coordinate information of the phase xy plane; The diffraction angle and the focused light spot of the light emitted through the metasurface grating lens are controlled by controlling 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 light spot. When the diffraction angle is decreased, the parallel composite beam passes through the metasurface grating lens to form a second imaging light spot. Under the condition of maintaining the grating phase of the second imaging light spot, the splitting interval is reduced by shortening the focusing distance of the metasurface grating lens to form a third imaging light spot. The splitting interval of the third imaging light spot is smaller than the splitting intervals of the first and second imaging light spots. The aberration of the second imaging light spot is smaller than the aberration of the first imaging light spot.

9. The wavelength selection switch according to claim 1, characterized in that, The reflection unit is a liquid crystal on silicon spatial light modulator or a mirror array based on a microelectromechanical system.

10. A communication device, characterized in that, It includes the wavelength selection switch according to any one of claims 1 to 9.

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