Tunable filter based on phase modulator array grating structure

Abstract

The present invention discloses a tunable filter based on a phase modulator array grating structure. Incident light is coupled to a first polarization rotation separator via a first end-face coupler, separating the incident light into two beams of orthogonal polarized light. The two beams of orthogonal polarized light are then split by a first power separator and a second power separator to produce first and second polarized light, respectively. These light is then transmitted forward and backward through a phase shifter-waveguide array, respectively. During transmission, phase modulation is performed by the phase shifter-waveguide array. The phase-modulated first and second polarized light are combined by a second power separator and a first power separator to produce third and fourth polarized light, respectively. The polarization states of the third and fourth polarized light are restored by a second polarization rotation separator to produce output light, which is then output through a second end-face coupler. Embodiments of the present invention achieve wide-range tunable filtering of light of a specific wavelength and are applicable to the field of filter technology.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a tunable filter based on a phase modulator array grating structure. Background Art

[0002] Optical filters can selectively pass or block light waves in specific wavelength bands. They have functions such as noise filtering, wavelength selection, and gain equalization, and are widely used in scenarios such as optical communication systems, laser systems, and imaging systems for optical measurement. Traditional optical filters are usually based on independent optical components such as filters, dispersion prisms, and interference filters. They are large in size, cannot be integrated with other optical devices, and are difficult to dynamically tune. They can only pass or filter out light in fixed wavelength bands. The on-chip filters used today have the advantages of miniaturization, low cost, and tunability. On-chip filters based on the principle of interference have high transmittance, high precision, and high integration, making them suitable for modern photonic integrated circuit applications.

[0003] Current on-chip tunable filters include microring resonators, Bragg gratings, and photonic crystal microcavities. Microring resonator filters are difficult to achieve wide tunability due to the limited free spectral range and relatively small operating bandwidth. Bragg grating filters and photonic crystal microcavity filters also face challenges in achieving wide tunability due to limited electro-optical modulation efficiency. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a tunable filter based on a phase modulator array grating structure, which realizes wide-range tunable filtering of light of a specific wavelength.

[0005] The first technical solution adopted by the present invention is:

[0006] A tunable filter based on a phase modulator array grating structure includes a first end face coupler, a second end face coupler, a first polarization rotation separator, a second polarization rotation separator, a first power separator, a second power separator, and a phase shifter-waveguide array, wherein:

[0007] The first end face coupler is used to couple the incident light to the first polarization rotation separator, the first polarization rotation separator is used to separate the incident light into two beams of orthogonal polarized light, and transmit the two beams of orthogonal polarized light to the first power separator and the second power separator respectively, the first power separator is used to split the corresponding orthogonal polarized light to obtain multiple beams of first polarized light, and couple the multiple beams of first polarized light to each sub-channel of the phase shifter-waveguide array respectively, the second power separator is used to split the corresponding orthogonal polarized light to obtain multiple beams of second polarized light, and couple the multiple beams of second polarized light to each sub-channel of the phase shifter-waveguide array respectively, and the phase shifter-waveguide array is used to phase the first polarized light and the second polarized light of each sub-channel respectively. Modulation, and forward transmission of the phase-modulated multiple beams of the first polarized light to the second power separator, and backward transmission of the phase-modulated multiple beams of the second polarized light to the first power separator, the second power separator is further used to combine the phase-modulated multiple beams of the first polarized light to obtain a third polarized light, and transmit the third polarized light to the second polarization rotation separator, the first power separator is further used to combine the phase-modulated multiple beams of the second polarized light to obtain a fourth polarized light, and transmit the fourth polarized light to the second polarization rotation separator, the second polarization rotation separator is used to restore the polarization state of the third polarized light and the fourth polarized light to obtain output light, and couple the output light to the second end face coupler, and the second end face coupler is used to output the output light.

[0008] Furthermore, each sub-channel of the phase shifter-waveguide array is used to phase modulate the input first polarized light and the second polarized light, so that the phase difference between the light of the target wavelength in the modulated first polarized light output by each sub-channel is an integer multiple of 2π, and the phase difference between the light of the target wavelength in the modulated second polarized light output by each sub-channel is an integer multiple of 2π.

[0009] Furthermore, each sub-channel of the phase shifter-waveguide array includes a waveguide and an electro-optical phase shifter arranged on the waveguide, and the electro-optical phase shifter is used to change the optical path of the corresponding waveguide so that the optical path difference between each waveguide is an integer multiple of the target wavelength.

[0010] Furthermore, the waveguides of the sub-channels are arranged in sequence to form the phase shifter-waveguide array, and the initial optical path length of each waveguide increases in sequence according to the arrangement order.

[0011] Furthermore, the initial optical path of the waveguide is k*ΔL, where k represents the sequence number of the waveguide in the phase shifter-waveguide array, and ΔL represents a preset unit optical path.

[0012] Furthermore, the phase shifter-waveguide array includes 2 n The sub-channels, the first power splitter includes a first forward coupler, two second forward couplers, four third forward couplers, ..., 2 n-1 n-th forward couplers, where n is a positive integer greater than or equal to 3, the first polarization rotation splitter and the second polarization rotation splitter are both connected to one end of the first forward coupler, the other end of the first forward coupler is connected to one end of two second forward couplers, the other end of each second forward coupler is connected to one end of two third forward couplers, ..., the other end of each (n-1)-th forward coupler is connected to one end of two n-th forward couplers, and the other end of each n-th forward coupler is connected to one end of two subchannels.

[0013] Furthermore, the second power splitter includes a first backward coupler, two second backward couplers, four third backward couplers, ..., 2 n-1 an n-th backward coupler, the first polarization rotation splitter and the second polarization rotation splitter are both connected to one end of the first backward coupler, the other end of the first backward coupler is connected to one end of two second backward couplers, the other end of each second backward coupler is connected to one end of two third backward couplers, ..., the other end of each n-1-th backward coupler is connected to one end of two n-th backward couplers, and the other end of each n-th backward coupler is connected to the other end of the two sub-channels.

[0014] Furthermore, the first power splitter and the second power splitter are both composed of a plurality of multimode interference couplers.

[0015] Furthermore, the first power splitter and the second power splitter are both composed of a plurality of directional couplers.

[0016] Furthermore, the first power splitter and the second power splitter are both composed of a plurality of star couplers.

[0017] The beneficial effect of the present invention is as follows: the present invention provides a tunable filter based on a phase modulator array grating structure, comprising a first end face coupler, a second end face coupler, a first polarization rotation separator, a second polarization rotation separator, a first power separator, a second power separator and a phase shifter-waveguide array, wherein the incident light is coupled to the first polarization rotation separator through the first end face coupler, and the incident light is separated into two beams of orthogonal polarized light through the first polarization rotation separator, and the two beams of orthogonal polarized light are respectively split by the first power separator and the second power separator to obtain multiple beams of first polarized light and multiple beams of second polarized light, so that the first polarized light and the second polarized light are respectively transmitted forward and backward in the phase shifter-waveguide array, and phase modulated by the phase shifter-waveguide array during the transmission process, and the phase modulated multiple beams of first polarized light and multiple beams of second polarized light are respectively combined by the second power separator and the first power separator to obtain third polarized light and fourth polarized light, and the polarization state of the third polarized light and the fourth polarized light is restored by the second polarization rotation separator to obtain output light, and the output light is output through the second end face coupler. The embodiments of the present invention can adjust the phase difference between the target wavelengths of light in each sub-channel of the phase shifter-waveguide array according to the desired target wavelength. During the light combining process, the target wavelength is enhanced and light of other wavelengths is suppressed through the principle of constructive interference, thereby achieving widely adjustable filtering of specific wavelengths of light. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of a tunable filter based on a phase modulator array grating structure provided by an embodiment of the present invention;

[0019] Figure 2 A schematic diagram of forward transmission of a first power splitter, a second power splitter, and a phase shifter-waveguide array provided in an embodiment of the present invention;

[0020] Figure 3 Schematic diagram of backward transmission of the first power splitter, the second power splitter, and the phase shifter-waveguide array provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are provided for ease of description only and do not limit the order of the steps. The order of execution of the steps in the embodiments can be adaptively adjusted based on the understanding of those skilled in the art.

[0022] In the description of the present invention, "a plurality" means more than two. If a first or second is described, it is only used to distinguish technical features and should not be understood as indicating or implying relative importance, implicitly indicating the number of the indicated technical features, or implicitly indicating the order of the indicated technical features. In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terms used in this specification are only for describing specific embodiments and are not intended to limit the present invention.

[0023] Reference Figure 1 The present invention provides a tunable filter based on a phase modulator array grating structure, comprising a first end face coupler, a second end face coupler, a first polarization rotation separator, a second polarization rotation separator, a first power separator, a second power separator, and a phase shifter-waveguide array, wherein:

[0024] The first end face coupler is used to couple the incident light to the first polarization rotation separator, the first polarization rotation separator is used to separate the incident light into two beams of orthogonal polarized light, and transmit the two beams of orthogonal polarized light to the first power separator and the second power separator respectively, the first power separator is used to split the corresponding orthogonal polarized light to obtain multiple beams of first polarized light, and couple the multiple beams of first polarized light to each sub-channel of the phase shifter-waveguide array respectively, the second power separator is used to split the corresponding orthogonal polarized light to obtain multiple beams of second polarized light, and couple the multiple beams of second polarized light to each sub-channel of the phase shifter-waveguide array respectively, and the phase shifter-waveguide array is used to phase the first polarized light and the second polarized light of each sub-channel respectively. Modulation, and forward transmission of the phase-modulated multiple beams of first polarized light to the second power separator, and backward transmission of the phase-modulated multiple beams of second polarized light to the first power separator, the second power separator is further used to combine the phase-modulated multiple beams of first polarized light to obtain a third polarized light, and transmit the third polarized light to the second polarization rotation separator, the first power separator is further used to combine the phase-modulated multiple beams of second polarized light to obtain a fourth polarized light, and transmit the fourth polarized light to the second polarization rotation separator, the second polarization rotation separator is used to restore the polarization state of the third polarized light and the fourth polarized light to obtain output light, and couple the output light to the second end face coupler, and the second end face coupler is used to output the output light.

[0025] Specifically, the tunable filter based on the phase modulator array grating structure of the present invention includes a first end face coupler, a second end face coupler, a first polarization rotation separator, a second polarization rotation separator, a first power separator, a second power separator and a phase shifter-waveguide array. The incident light is coupled to the first polarization rotation separator through the first end face coupler, and the incident light is separated into two beams of orthogonal polarized light through the first polarization rotation separator. The two beams of orthogonal polarized light are respectively split by the first power separator and the second power separator to obtain multiple beams of first polarized light and multiple beams of second polarized light, so that the first polarized light and the second polarized light are respectively transmitted forward and backward in the phase shifter-waveguide array, and phase modulated by the phase shifter-waveguide array during the transmission process. The phase-modulated multiple beams of first polarized light and multiple beams of second polarized light are respectively combined by the second power separator and the first power separator to obtain third polarized light and fourth polarized light. The polarization state of the third polarized light and the fourth polarized light is restored by the second polarization rotation separator to obtain output light, and the output light is output through the second end face coupler.

[0026] The embodiment of the present invention separates the incident light into two beams of orthogonally polarized light, which are respectively transmitted forward and backward in the phase shifter-waveguide array. This achieves separate processing of light of different polarization states, avoids the high birefringence of the silicon waveguide having different effects on light of different polarizations, and prevents cross-coupling between light of different polarization states, thereby improving the performance of the filter.

[0027] As a further optional embodiment, each sub-channel of the phase shifter-waveguide array is used to phase modulate the input first polarized light and the second polarized light, so that the phase difference between the light of the target wavelength in the modulated first polarized light output by each sub-channel is an integer multiple of 2π, and the phase difference between the light of the target wavelength in the modulated second polarized light output by each sub-channel is an integer multiple of 2π.

[0028] As a further optional embodiment, each sub-channel of the phase shifter-waveguide array includes a waveguide and an electro-optical phase shifter arranged on the waveguide, and the electro-optical phase shifter is used to change the optical path of the corresponding waveguide so that the optical path difference between each waveguide is an integer multiple of the target wavelength.

[0029] As a further optional implementation, the waveguides of each sub-channel are arranged in sequence to form a phase shifter-waveguide array, and the initial optical path of each waveguide increases in sequence according to the arrangement order.

[0030] As a further optional implementation, the initial optical path of the waveguide is k*ΔL, where k represents the sequence number of the waveguide in the phase shifter-waveguide array, and ΔL represents a preset unit optical path.

[0031] Specifically, the power splitter can achieve optical power separation and merging. The power splitter evenly distributes the input optical signal power to multiple sub-channels for both forward and backward transmission. After multiple splittings by the power splitter, the light is coupled into a phase shifter-waveguide array. Adjacent array waveguides have a constant length difference ΔL. Each waveguide channel is equipped with a phase shifter. Each phase shifter uses electro-optical phase shifting, that is, applying an external voltage to change the refractive index of the material, thereby changing the optical path of the waveguide, thereby achieving independent control of the optical phase of each sub-channel. Finally, the light of each channel is combined through multiple power dividers, and the polarization state of the light when it was input into the system is restored through a second polarization rotation splitter. The outgoing light is output by the second end face coupler.

[0032] According to the principle of light interference, when the phase difference between two beams of light with the same frequency (same wavelength) is an integer multiple of 2π, the light will undergo coherent growth. Therefore, the embodiment of the present invention adjusts the phase difference between the light of a specific wavelength λ in each sub-channel of the phase shifter-waveguide array. By selecting the light of this wavelength through constructive interference during the final beam combination, the light of this wavelength can be enhanced, and then the enhanced light of this wavelength is output, thereby achieving wide-range adjustable filtering.

[0033] As an optional embodiment, the phase shifter-waveguide array includes 2 n sub-channels, the first power splitter includes a first forward coupler, two second forward couplers, four third forward couplers, ..., 2 n-1 There are n-th forward couplers, where n is a positive integer greater than or equal to 3; the first polarization rotation splitter and the second polarization rotation splitter are both connected to one end of the first forward coupler; the other end of the first forward coupler is connected to one end of the two second forward couplers; the other end of each second forward coupler is connected to one end of the two third forward couplers, ...; the other end of each (n-1)-th forward coupler is connected to one end of the two n-th forward couplers; and the other end of each n-th forward coupler is connected to one end of the two subchannels.

[0034] As an optional embodiment, the second power splitter includes a first backward coupler, two second backward couplers, four third backward couplers, ..., 2 n-1 There are n-th backward couplers, the first polarization rotation splitter and the second polarization rotation splitter are both connected to one end of the first backward coupler, the other end of the first backward coupler is connected to one end of the two second backward couplers, the other end of each second backward coupler is connected to one end of the two third backward couplers, ..., the other end of each n-1-th backward coupler is connected to one end of the two n-th backward couplers, and the other end of each n-th backward coupler is connected to the other ends of the two subchannels.

[0035] The embodiment of the present invention uses a multimode interference coupler as a component of the power splitter. During forward transmission, it evenly distributes the input optical power to two waveguide channels based on the self-imaging principle. Based on the symmetry of the multimode interference effect, it can also couple the two beams of light into a single output beam during reverse propagation.

[0036] like Figure 2 The figure shows a forward transmission schematic diagram of the first power splitter, second power splitter, and phase shifter-waveguide array provided in an embodiment of the present invention. After multiple splittings by the multimode interference coupler, the light is coupled into the phase shifter-waveguide array. The phase shifters in each subchannel use electro-optical methods to change the refractive index of the material, causing the phase of the light in each subchannel to change. Every two subchannels are combined multiple times through the multimode interference coupler until only one beam of light remains. The desired wavelengths continuously interfere constructively during the combination, while other wavelengths of light are suppressed, thereby achieving optical filtering.

[0037] like Figure 3 The figure shows a schematic diagram of the backward transmission of the first power splitter, the second power splitter, and the phase shifter-waveguide array provided in an embodiment of the present invention. Due to the symmetry of the optical path, light of the other polarization state undergoes the same process to achieve optical filtering when it is transmitted backward in the same phase shifter-waveguide array.

[0038] As a further optional implementation, the first power splitter and the second power splitter are both composed of a plurality of multimode interference couplers.

[0039] As a further optional implementation, the first power splitter and the second power splitter are both composed of a plurality of directional couplers.

[0040] As a further optional implementation, the first power splitter and the second power splitter are both composed of a plurality of star couplers.

[0041] Specifically, in addition to the multimode interference coupler, the optical power splitter may also be composed of a directional coupler or a star coupler, which will not be described in detail in the embodiment of the present invention.

[0042] The structure and working principle of the embodiment of the present invention are described above.

[0043] Arrayed waveguide gratings (AWGs) have excellent wavelength selectivity due to their high diffraction order. However, their fixed parameters, such as refractive index, optical path, and spacing, limit their operating wavelength. This paper designs a tunable filter based on a phase modulator array grating structure. Electro-optical phase shifters are used to independently control the phase difference of the waveguide array, thereby achieving wide-range adjustable filtering. Furthermore, a polarization rotation separator is used to separately process light of different polarization states. Cross-coupling of light of different polarization states is prevented by forward and backward transmission of light, thereby improving filter performance.

[0044] It can be appreciated that the embodiments of the present invention can adjust the phase difference between the target wavelengths of light in each sub-channel of the phase shifter-waveguide array according to the desired target wavelength. During the light combining process, the target wavelength is enhanced and light of other wavelengths is suppressed through the principle of constructive interference, thereby achieving widely adjustable filtering of light of a specific wavelength.

[0045] It should be noted that, unless the context clearly requires otherwise, the words "comprise", "include" and similar words throughout the specification and claims should be understood to mean inclusive rather than exclusive or complete. That is, "including but not limited to". The terms "coupled" or "connected" as generally used herein refer to two or more elements that can be directly connected or connected through one or more intermediate elements. In addition, the words "herein", "above", "below" and words of similar meaning, when used in this application, should refer to the entirety of this application rather than to specific parts of this application. If the context permits, detailed descriptions using the singular or plural may include the plural or singular, respectively. The word "or" with respect to a list containing two or more items refers to all of the following interpretations of the word: any item in the list, all items in the list, and all combinations of items in the list.

[0046] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the aforementioned embodiments. As long as the technical effects of the present invention are achieved by the same means, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. Within the scope of protection of the present invention, various modifications and variations of the technical solutions and / or implementation methods are possible.

Claims

1. A tunable filter based on a phase modulator array grating structure, characterized in that: The invention comprises a first end face coupler, a second end face coupler, a first polarization rotation splitter, a second polarization rotation splitter, a first power splitter, a second power splitter and a phase shifter-waveguide array, wherein: The first end face coupler is used to couple the incident light to the first polarization rotation separator, the first polarization rotation separator is used to separate the incident light into two beams of orthogonal polarized light, and transmit the two beams of orthogonal polarized light to the first power separator and the second power separator respectively, the first power separator is used to split the corresponding orthogonal polarized light to obtain multiple beams of first polarized light, and couple the multiple beams of first polarized light to each sub-channel of the phase shifter-waveguide array respectively, the second power separator is used to split the corresponding orthogonal polarized light to obtain multiple beams of second polarized light, and couple the multiple beams of second polarized light to each sub-channel of the phase shifter-waveguide array respectively, and the phase shifter-waveguide array is used to phase the first polarized light and the second polarized light of each sub-channel respectively. Modulation, and forward transmission of the phase-modulated multiple beams of the first polarized light to the second power separator, and backward transmission of the phase-modulated multiple beams of the second polarized light to the first power separator, the second power separator is further used to combine the phase-modulated multiple beams of the first polarized light to obtain a third polarized light, and transmit the third polarized light to the second polarization rotation separator, the first power separator is further used to combine the phase-modulated multiple beams of the second polarized light to obtain a fourth polarized light, and transmit the fourth polarized light to the second polarization rotation separator, the second polarization rotation separator is used to restore the polarization state of the third polarized light and the fourth polarized light to obtain output light, and couple the output light to the second end face coupler, and the second end face coupler is used to output the output light.

2. The tunable filter based on a phase modulator array grating structure according to claim 1, characterized in that: Each sub-channel of the phase shifter-waveguide array is used to phase modulate the input first polarized light and the second polarized light, so that the phase difference between the light of the target wavelength in the modulated first polarized light output by each sub-channel is an integer multiple of 2π, and the phase difference between the light of the target wavelength in the modulated second polarized light output by each sub-channel is an integer multiple of 2π.

3. The tunable filter based on a phase modulator array grating structure according to claim 2, characterized in that: Each sub-channel of the phase shifter-waveguide array includes a waveguide and an electro-optical phase shifter arranged on the waveguide, and the electro-optical phase shifter is used to change the optical path of the corresponding waveguide so that the optical path difference between the waveguides is an integer multiple of the target wavelength.

4. The tunable filter based on a phase modulator array grating structure according to claim 3, characterized in that: The waveguides of the sub-channels are arranged in sequence to form the phase shifter-waveguide array, and the initial optical path of each waveguide increases in sequence according to the arrangement order.

5. The tunable filter based on the phase modulator array grating structure according to claim 4, characterized in that: The initial optical path of the waveguide is k*ΔL, where k represents the sequence number of the waveguide in the phase shifter-waveguide array, and ΔL represents a preset unit optical path.

6. The tunable filter based on a phase modulator array grating structure according to claim 1, characterized in that: The phase shifter-waveguide array includes 2 n The sub-channels, the first power splitter includes a first forward coupler, two second forward couplers, four third forward couplers, ..., 2 n-1 n-th forward couplers, where n is a positive integer greater than or equal to 3, the first polarization rotation splitter and the second polarization rotation splitter are both connected to one end of the first forward coupler, the other end of the first forward coupler is connected to one end of two second forward couplers, the other end of each second forward coupler is connected to one end of two third forward couplers, ..., the other end of each (n-1)-th forward coupler is connected to one end of two n-th forward couplers, and the other end of each n-th forward coupler is connected to one end of two subchannels.

7. The tunable filter based on a phase modulator array grating structure according to claim 6, characterized in that: The second power splitter includes a first backward coupler, two second backward couplers, four third backward couplers, ..., 2 n-1 an n-th backward coupler, the first polarization rotation splitter and the second polarization rotation splitter are both connected to one end of the first backward coupler, the other end of the first backward coupler is connected to one end of two second backward couplers, the other end of each second backward coupler is connected to one end of two third backward couplers, ..., the other end of each n-1-th backward coupler is connected to one end of two n-th backward couplers, and the other end of each n-th backward coupler is connected to the other end of the two sub-channels.

8. The tunable filter based on a phase modulator array grating structure according to claim 1, characterized in that: The first power splitter and the second power splitter are both composed of a plurality of multi-mode interference couplers.

9. The tunable filter based on a phase modulator array grating structure according to claim 1, characterized in that: The first power splitter and the second power splitter are both composed of a plurality of directional couplers.

10. The tunable filter based on a phase modulator array grating structure according to claim 1, characterized in that: The first power splitter and the second power splitter are both composed of a plurality of star couplers.

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