Adjustable filter based on phase modulator array grating structure

Abstract

The invention discloses an adjustable filter based on a phase modulator array grating structure, which is characterized in that incident light is coupled to a first polarization rotation separator through a first end face coupler, and the incident light is separated into two beams of orthogonal polarized light; two beams of orthogonal polarized light are split through a first power separator and a second power separator respectively to obtain first polarized light and second polarized light, the first polarized light and the second polarized light are transmitted forwards and backwards in a phase shifter-waveguide array respectively, and phase modulation is performed through the phase shifter-waveguide array in the transmission process; the first polarized light and the second polarized light after phase modulation are combined through a second power separator and a first power separator to obtain third polarized light and fourth polarized light, and the third polarized light and the fourth polarized light are subjected to polarization state recovery through a second polarization rotation separator to obtain emergent light. And outputting through the second end face coupler. The embodiment of the invention realizes large-range adjustable filtering of light with specific wavelength, and can be applied to the technical field of filters.

Description

Technical Field

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

[0002] Optical filters can selectively pass or block light waves in a specific band. They have functions such as noise filtering, wavelength selection, and gain equalization. They are widely used in optical communication systems, laser systems, and imaging system optical measurements. Traditional optical filters are usually based on independent optical components such as filters, dispersion prisms, and interference filters. They are large in size and cannot be integrated with other optical devices. They are also difficult to dynamically tune and can only pass or filter out light in fixed bands. The on-chip filters used today have the advantages of miniaturization, low cost, and tunability. The on-chip filters based on the interference principle 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 resonant cavities, Bragg gratings, and photonic crystal microcavities. Microring resonant cavity filters are difficult to adjust over a wide range due to the limitation of the free spectral range, and the working bandwidth is relatively small. Bragg grating filters and photonic crystal microcavity filters are difficult to adjust over a wide range due to the limitation of electro-optic 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 comprises a first end coupler, a second end 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 forwardly transmit the phase-modulated multiple beams of the first polarized light to the second power separator, and backwardly transmit the phase-modulated multiple beams of the second polarized light to the first power separator, the second power separator is also 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 also 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 states of the third polarized light and the fourth polarized light to obtain an outgoing light, and couple the outgoing light to the second end face coupler, and the second end face coupler is used to output the outgoing light.

[0008] Furthermore, each of the sub-channels 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 of the sub-channels 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 of the sub-channels 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 each of the sub-channels are arranged in sequence to form the phase shifter-waveguide array, and the initial optical path of each of the waveguides 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] Further, the phase shifter-waveguide array comprises 2 n The sub-channels, the first power separator includes a first forward coupler, two second forward couplers, four third forward couplers, ..., 2 n-1 n-th forward couplers, n is a positive integer greater than or equal to 3, the first polarization rotation separator and the second polarization rotation separator 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 sub-channels.

[0013] Further, the second power separator 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 separator and the second polarization rotation separator 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 two sub-channels.

[0014] Furthermore, the first power separator and the second power separator are both composed of a plurality of multi-mode interference couplers.

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

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

[0017] The beneficial effects of the present invention are as follows: the present invention provides an adjustable 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, 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, the first polarized light and the second polarized light are respectively transmitted forward and backward in the phase shifter-waveguide array, and phase modulation is performed by the phase shifter-waveguide array during the transmission process, the multiple beams of first polarized light and multiple beams of second polarized light after phase modulation 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 by the second end face coupler. The embodiment of the present invention can adjust the phase difference between the light of the target wavelength in each sub-channel of the phase shifter-waveguide array according to the required target wavelength, enhance the light of the target wavelength and suppress the light of other wavelengths through the principle of constructive interference in the light combining process, thereby realizing widely adjustable filtering of light of specific wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of an adjustable 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 separator, a second power separator and a phase shifter-waveguide array provided in an embodiment of the present invention;

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

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0022] In the description of the present invention, the meaning of "a plurality" is more than two. If there is a description of "a first" or "a second", it is only used to distinguish the technical features, and it cannot be understood as indicating or implying the relative importance or 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 in this article have the same meaning as those commonly understood by those skilled in the art. The terms used in this specification are only for describing specific embodiments, not for limiting 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 coupler, a second end 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 also 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 also 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, 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 by the second end face coupler.

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

[0027] Further as an optional implementation, 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 implementation, each sub-channel of the phase shifter-waveguide array includes a waveguide and an electro-optical phase shifter disposed 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.

[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 separator can realize the separation and combination of optical power. The power separator evenly distributes the input optical signal power to multiple sub-channels for both forward and backward transmission. After multiple splittings by the power separator, the light is coupled to the 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 changes the optical path of the waveguide by electro-optical phase shifting, that is, applying an external voltage to change the refractive index of the material, thereby realizing independent regulation of the optical phase of each sub-channel. Finally, the optical beams of each channel are combined through multiple power dividers, and the polarization state of the light when it is input into the system is restored through the second polarization rotation separator, and 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 separator includes a first forward coupler, two second forward couplers, four third forward couplers, ..., 2 n-1 n-th forward couplers, n is a positive integer greater than or equal to 3, the first polarization rotation separator and the second polarization rotation separator 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 sub-channels.

[0034] As an optional implementation, the second power separator includes a first backward coupler, two second backward couplers, four third backward couplers, ..., 2 n-1 An n-th backward coupler is provided, the first polarization rotation separator and the second polarization rotation separator 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 ends of the two sub-channels.

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

[0036] like Figure 2 The figure shows a forward transmission schematic diagram of a first power separator, a second power separator and a phase shifter-waveguide array provided in an embodiment of the present invention. After the multimode interference coupler splits the light multiple times, the light is coupled to the phase shifter-waveguide array. The phase shifter of each sub-channel uses an electro-optical method to change the refractive index of the material, so that the phase of the light of each sub-channel changes. Every two sub-channels are combined multiple times through the multimode interference coupler until only one beam of light remains, wherein the required 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 backward transmission of the first power separator, the second power separator and the phase shifter-waveguide array provided in an embodiment of the present invention. Due to the symmetry of the optical path, light of another 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 separator and the second power separator are both composed of a plurality of multi-mode interference couplers.

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

[0040] As a further optional implementation, the first power separator and the second power separator 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 embodiments of the present invention.

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

[0043] Arrayed waveguide gratings have good wavelength selectivity due to their high diffraction order, but their fixed parameters such as refractive index, optical path, spacing, etc. limit their working wavelength. The present invention designs an adjustable filter based on a phase modulator array grating structure, and independently adjusts the phase difference of the waveguide array through an electro-optical phase shifter, thereby achieving wide-range adjustable filtering. In addition, the present invention uses a polarization rotation separator to process light of different polarization states separately, and avoids cross-coupling of light of different polarization states through forward and backward transmission of light, thereby improving the performance of the filter.

[0044] It can be appreciated that the embodiments of the present invention can adjust the phase difference between the light of the target wavelength in each sub-channel of the phase shifter-waveguide array according to the required target wavelength, enhance the light of the target wavelength and suppress the light of other wavelengths through the principle of constructive interference during the light combining process, thereby realizing 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" generally used here 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 a specific part of this application. If the context permits, detailed descriptions using the singular or plural may include the plural or singular, respectively. The word "or" is about a list containing two or more items, and refers to all of the following interpretations of this word: any item in the list, all items in the list, and all combinations of items in the list.

[0046] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above implementation. As long as the technical effect of the present invention is achieved by the same means, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the present invention. Within the scope of protection of the present invention, its technical scheme and / or implementation method may have various modifications and changes.

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 separator, a second polarization rotation separator, a first power separator, a second power separator 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 forwardly transmit the phase-modulated multiple beams of the first polarized light to the second power separator, and backwardly transmit the phase-modulated multiple beams of the second polarized light to the first power separator, the second power separator is also 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 also 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 states of the third polarized light and the fourth polarized light to obtain an outgoing light, and couple the outgoing light to the second end face coupler, and the second end face coupler is used to output the outgoing light.

2. The tunable filter based on the phase modulator array grating structure according to claim 1, characterized in that: Each of the sub-channels 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 of the sub-channels 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 of the sub-channels is an integer multiple of 2π.

3. The tunable filter based on the phase modulator array grating structure according to claim 2, characterized in that: Each of the sub-channels 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 the phase modulator array grating structure according to claim 3, characterized in that: The waveguides of each of the sub-channels are arranged in sequence to form the phase shifter-waveguide array, and the initial optical path of each of the waveguides 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 the phase modulator array grating structure according to claim 1, characterized in that: The phase shifter-waveguide array comprises 2 n The sub-channels, the first power separator includes a first forward coupler, two second forward couplers, four third forward couplers, ..., 2 n-1 n-th forward couplers, n is a positive integer greater than or equal to 3, the first polarization rotation separator and the second polarization rotation separator 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 sub-channels.

7. The tunable filter based on the 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 separator and the second polarization rotation separator 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 two sub-channels.

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

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

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