Micro-ring filter

Abstract

The invention discloses a micro-ring filter. The micro-ring filter comprises a first micro-ring modulator and a second micro-ring modulator, the radius of the first micro-ring modulator is different from that of the second micro-ring modulator; the first micro-ring modulator is used for performing first wavelength selection on the optical signal; and the second micro-ring modulator is used for carrying out second wavelength selection on the optical signal after the first wavelength selection. According to the invention, the comb tooth spacing of the optical frequency comb finally formed by the micro-ring filter is increased through the two stages of micro-ring modulators by using the vernier caliper effect, and the second optical frequency comb with a wide free spectrum range is generated. The interval between the wavelengths of the second optical frequency comb is larger than that of the first optical frequency comb, so that the extraction of the target optical signal is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of photon integrated devices, and in particular to a micro-ring filter. Background Art

[0002] In photon signal processing systems, lithium niobate exhibits a high electro-optic coefficient. Its tunable microring filter has the advantages of small half-wave voltage and fast response speed, and is often used to make microring filters. At present, the manufacturing process of lithium niobate microrings is not mature, and the center wavelength of the microring filters actually manufactured has deviations, and a single microring filter will produce an optical frequency comb with a narrow free frequency range. An optical frequency comb is a series of equally spaced wavelengths. The optical frequency comb filtered by a single microring filter has a narrow free frequency range, and the intervals between wavelengths are often small, making it difficult to distinguish adjacent wavelengths. This optical frequency comb is not conducive to the extraction of optical signals of specific frequencies. Summary of the invention

[0003] The present invention provides a micro-ring filter to solve the technical problem in the prior art that using a single micro-ring filter to generate a periodic optical frequency comb is not conducive to extracting a specific frequency optical signal.

[0004] In order to solve the above technical problems, an embodiment of the present invention provides a micro-ring filter, comprising: a first micro-ring modulator and a second micro-ring modulator;

[0005] The radius of the first micro-ring modulator is different from the radius of the second micro-ring modulator;

[0006] The first micro-ring modulator is used to perform a first wavelength selection on the optical signal;

[0007] The second micro-ring modulator is used to perform a second wavelength selection on the optical signal after the first wavelength selection.

[0008] As a preferred solution, the first micro-ring modulator comprises: a first input waveguide, a first resonant ring waveguide and a first output waveguide;

[0009] The second micro-ring modulator comprises: a second input waveguide, a second resonant ring waveguide and a second output waveguide;

[0010] The first output waveguide is in communication with the second input waveguide.

[0011] As a preferred solution, the first input waveguide, the first resonant ring waveguide, the first output waveguide, the second input waveguide, the second resonant ring waveguide and the second output waveguide are all made of lithium niobate.

[0012] As a preferred solution, the radius of the first micro-ring modulator and the radius of the second micro-ring modulator satisfy the following formula:

[0013]

[0014] Where r1 represents the radius of the first microring modulator; r2 represents the radius of the second microring modulator; λ represents the wavelength of the target optical signal; n eff represents the effective refractive index of the lithium niobate waveguide; k1 and k2 represent two different integers.

[0015] As a preferred solution, the first micro-ring modulator and the second micro-ring modulator are arranged in an alternating manner.

[0016] As a preferred solution, the first micro-ring modulator further includes: a third output waveguide;

[0017] The second micro-ring modulator further includes: a fourth output waveguide;

[0018] The third output waveguide is used to output the wavelength signal not selected in the first wavelength selection;

[0019] The fourth output waveguide is used to output the wavelength signal that is not selected in the second wavelength selection.

[0020] As a preferred solution, the first micro-ring modulator further includes: a first electro-optical modulation electrode; the second micro-ring modulator further includes: a second electro-optical modulation electrode;

[0021] The first electro-optic modulation electrode is used to adjust the refractive index of the first resonant ring waveguide;

[0022] The second electro-optic modulation electrode is used to adjust the refractive index of the second resonant ring waveguide.

[0023] As a preferred embodiment, the method for preparing the manufacturing material comprises:

[0024] Obtain a substrate; wherein the substrate comprises a substrate, a buffer layer and a waveguide layer; the waveguide layer is a lithium niobate layer;

[0025] Cleaning and drying the substrate;

[0026] Performing magnetron sputtering on the waveguide layer to coat a metal film;

[0027] Spin coating a layer of photoresist on the metal film;

[0028] According to a preset layout, the substrate covered with photoresist is exposed;

[0029] The exposed substrate is immersed in a developer to perform development to remove the photoresist in the unexposed area;

[0030] Performing metal etching on the developed substrate;

[0031] Removing the remaining photoresist on the substrate after metal corrosion;

[0032] According to the preset pattern, the substrate with the photoresist removed by ICP-RIE etching;

[0033] removing the metal film on the etched substrate to obtain a resonant ring waveguide pattern;

[0034] Depositing a silicon dioxide cladding layer on the substrate from which the metal film has been removed by PECVD;

[0035] Transferring a preset electrode pattern to the silicon dioxide cladding layer through photoresist by secondary photolithography;

[0036] Connecting the substrate after secondary photolithography to the negative electrode of the power supply for electroplating;

[0037] The photoresist on the electroplated substrate is removed to obtain the manufacturing material.

[0038] As a preferred solution, the substrate is a silicon layer; the buffer layer is a silicon dioxide layer; and the metal film is a chromium film.

[0039] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0040] The present invention provides a microring filter, which includes: a first microring modulator and a second microring modulator; the radius of the first microring modulator is different from the radius of the second microring modulator; the first microring modulator is used to perform a first wavelength selection on an optical signal; and the second microring modulator is used to perform a second wavelength selection on the optical signal after the first wavelength selection. The present invention uses a two-stage microring modulator and a vernier caliper effect to increase the comb tooth spacing of an optical frequency comb finally formed by the microring filter, and generates a second optical frequency comb with a wider free spectrum range. The intervals between the wavelengths of the second optical frequency comb are larger than those of the first optical frequency comb, which is more conducive to the extraction of target optical signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a structural schematic diagram of a micro-ring filter provided by an embodiment of the present invention;

[0042] Figure 2 14 is a schematic diagram of the structure of a micro-ring filter provided by another embodiment of the present invention;

[0043] Figure 3 It is a schematic flow chart of a method for making a material provided by one embodiment of the present invention;

[0044] The reference numerals of the drawings in the specification are as follows:

[0045] A first micro-ring modulator 1, a first input waveguide 11, a first resonant ring waveguide 12, a first output waveguide 13, a third output waveguide 14, a first electro-optical modulation electrode 15, a second micro-ring modulator 2, a second input waveguide 21, a second resonant ring waveguide 22, a second output waveguide 23, a fourth output waveguide 24 and a second electro-optical modulation electrode 25. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Embodiment 1

[0048] Please refer to Figure 1 , is a schematic diagram of the structure of a micro-ring filter provided by an embodiment of the present invention, comprising: a first micro-ring modulator 1 and a second micro-ring modulator 2;

[0049] The radius of the first micro-ring modulator 1 is different from the radius of the second micro-ring modulator 2;

[0050] The first micro-ring modulator 1 is used to perform a first wavelength selection on the optical signal;

[0051] The second micro-ring modulator 2 is used to perform a second wavelength selection on the optical signal after the first wavelength selection.

[0052] It should be noted that the method for using the micro-ring filter provided by the present invention includes:

[0053] The optical signal is input into the first micro-ring modulator 1, so that the first micro-ring modulator 1 performs a first wavelength selection on the optical signal. After the first wavelength selection, a first optical frequency comb with a narrow free spectrum range is generated.

[0054] The optical signal after the first wavelength selection is input into the second micro-ring modulator 2, so that the second micro-ring modulator 2 performs a second wavelength selection on the optical signal. After the second wavelength selection, a second optical frequency comb with a wider free spectrum range is generated.

[0055] Since the radius of the first microring modulator 1 and the second microring modulator 2 are different, their filtering densities are different. For example, assuming that the wavelength range of the original optical signal is [0, 1, 2, 3, 4, 5, 6, 7, 8, 9], if the wavelength of the optical signal obtained by filtering only once through the first microring modulator 1 is [1, 3, 5, 7, 9], if the wavelength of the optical signal obtained by filtering only through the second microring modulator 2 is [1, 2, 4, 5, 7, 8]. Then, if the original optical signal is firstly subjected to the first wavelength selection through the first microring modulator 1, and then subjected to the second wavelength selection through the second microring modulator 2, the wavelength of the optical signal obtained is [1, 5, 7]. It can be seen that the free spectrum range of the optical frequency comb obtained by filtering twice is wider than that obtained by filtering only one side. If the target optical signal to be extracted is an optical signal with a wavelength of 5, then it is obviously easier to extract the target optical signal from [1, 5, 7] than from [1, 3, 5, 7, 9] or from [1, 2, 4, 5, 7, 8].

[0056] The present invention uses a two-stage micro-ring modulator and a vernier caliper effect to increase the comb tooth spacing of the optical frequency comb finally formed by the micro-ring filter, and generates a second optical frequency comb with a wider free spectrum range. The interval between the wavelengths of the second optical frequency comb is larger than that of the first optical frequency comb, which is more conducive to the extraction of the target optical signal.

[0057] In a preferred embodiment, please refer to Figure 2 , is a schematic diagram of the structure of a micro-ring filter provided by an embodiment of the present invention, wherein the first micro-ring modulator 1 comprises: a first input waveguide 11, a first resonant ring waveguide 12 and a first output waveguide 13;

[0058] The second micro-ring modulator 2 comprises: a second input waveguide 21, a second resonant ring waveguide 22 and a second output waveguide 23;

[0059] The first output waveguide 13 is in communication with the second input waveguide 21 .

[0060] In a preferred embodiment, the first input waveguide 11 , the first resonant ring waveguide 12 , the first output waveguide 13 , the second input waveguide 21 , the second resonant ring waveguide 22 , and the second output waveguide 23 are all made of lithium niobate.

[0061] It should be noted that the commonly used lithium niobate material is lithium niobate single crystal film LNOI, which has a wide transparent window, can transmit optical signals in a wide spectral range and has a high refractive index, so that light waves are not easily lost when propagating in it, thereby improving the efficiency of optical devices. In addition, lithium niobate single crystal film LNOI also exhibits high second-order nonlinearity and voltage response. The lithium niobate modulator made from it has the advantages of small half-wave voltage and fast response speed.

[0062] In a preferred embodiment, the radius of the first micro-ring modulator 1 and the radius of the second micro-ring modulator 2 satisfy the following formula:

[0063]

[0064] Where r1 represents the radius of the first microring modulator 1; r2 represents the radius of the second microring modulator 2; λ represents the wavelength of the target optical signal; n eff represents the effective refractive index of the lithium niobate waveguide; k1 and k2 represent two different integers.

[0065] It should be noted that for light waves with wavelengths that meet the basic resonance conditions, a resonance enhancement effect will occur, forming a stronger light field.

[0066] The resonance condition in the optical waveguide resonant cavity is:

[0067] βL=2kπ, k=1, 2, 3,...;

[0068] Where β is the propagation constant of the optical signal in the waveguide, and L is the cavity length of the optical waveguide resonant cavity.

[0069] The phase change of a light wave with a wavelength of λ after circling the micro-ring satisfies the following formula:

[0070]

[0071] Where n eff L is the optical path of the light wave in the microring of length L.

[0072] When the optical path n eff L is an integer multiple of the wavelength λ to satisfy the resonance condition, that is, n eff L = kλ.

[0073] Knowing that L = 2πr, we can derive the conditional formula that the micro-ring modulator should satisfy:

[0074]

[0075] The two different integers are used as the values ​​of k1 and k2 to obtain the radii of the first microring modulator 1 and the second microring modulator 2. A microring filter is manufactured according to the obtained radii, and the manufactured microring filter can realize the extraction of the optical signal with a wavelength of λ.

[0076] In a preferred embodiment, the first micro-ring modulator 1 and the second micro-ring modulator 2 are arranged in a staggered manner.

[0077] It should be noted that the staggered arrangement of the first micro-ring modulator 1 and the second micro-ring modulator 2 is conducive to saving space, reducing the overall front area of ​​the micro-ring filter and lowering the half-wave voltage, so that the power consumption of the micro-ring filter is lower, which is conducive to large-scale device integration.

[0078] In a preferred embodiment, the first micro-ring modulator further includes: a third output waveguide 14;

[0079] The second micro-ring modulator further includes: a fourth output waveguide 24;

[0080] The third output waveguide 14 is used to output the wavelength signal that is not selected in the first wavelength selection;

[0081] The fourth output waveguide 24 is used to output the wavelength signal that is not selected in the second wavelength selection.

[0082] In a preferred embodiment, the first micro-ring modulator 1 further includes: a first electro-optical modulation electrode 15; the second micro-ring modulator 2 further includes: a second electro-optical modulation electrode 25;

[0083] The first electro-optic modulation electrode 15 is used to adjust the refractive index of the first resonant ring waveguide 12;

[0084] The second electro-optic modulation electrode 25 is used to adjust the refractive index of the second resonant ring waveguide 22 .

[0085] It should be noted that by utilizing the excellent electro-optical effect of lithium niobate material, the refractive index of lithium niobate material is controlled by changing the external electric field, thereby changing the resonant wavelength of the lithium niobate microring filter, thereby achieving modulation of the target output band of the two-stage lithium niobate microring filter.

[0086] In a preferred embodiment, please refer to Figure 3 , is a schematic flow chart of a method for preparing a material according to an embodiment of the present invention, wherein the method for preparing the material comprises:

[0087] Obtain a substrate; wherein the substrate comprises a substrate, a buffer layer and a waveguide layer; the waveguide layer is a lithium niobate layer;

[0088] Cleaning and drying the substrate;

[0089] Performing magnetron sputtering on the waveguide layer to coat a metal film;

[0090] Spin coating a layer of photoresist on the metal film;

[0091] According to a preset layout, the substrate covered with photoresist is exposed;

[0092] The exposed substrate is immersed in a developer to perform development to remove the photoresist in the unexposed area;

[0093] Performing metal etching on the developed substrate;

[0094] The remaining photoresist on the substrate after metal corrosion is removed to obtain the manufacturing material.

[0095] It should be noted that the lithium niobate material used in the present invention includes four parts in total, namely: a substrate, a buffer layer located on the substrate, a waveguide layer located on the buffer layer, and a metal layer located on the waveguide layer.

[0096] In this embodiment, the waveguide layer is a 400 nm thick x-cut lithium niobate material.

[0097] In a preferred embodiment, the substrate is a silicon layer; the buffer layer is a silicon dioxide layer; and the metal film is a chromium film.

[0098] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A microring filter, characterized in that: include: a first micro-ring modulator and a second micro-ring modulator; The radius of the first micro-ring modulator is different from the radius of the second micro-ring modulator; The first micro-ring modulator is used to perform a first wavelength selection on the optical signal; The second micro-ring modulator is used to perform a second wavelength selection on the optical signal after the first wavelength selection.

2. The microring filter according to claim 1, wherein: The first micro-ring modulator comprises: a first input waveguide, a first resonant ring waveguide and a first output waveguide; The second micro-ring modulator comprises: a second input waveguide, a second resonant ring waveguide and a second output waveguide; The first output waveguide is in communication with the second input waveguide.

3. The microring filter according to claim 2, characterized in that: The first input waveguide, the first resonant ring waveguide, the first output waveguide, the second input waveguide, the second resonant ring waveguide and the second output waveguide are all made of materials including lithium niobate.

4. The microring filter according to claim 3, characterized in that: The radius of the first micro-ring modulator and the radius of the second micro-ring modulator satisfy the following formula: Where r1 represents the radius of the first microring modulator; r2 represents the radius of the second microring modulator; λ represents the wavelength of the target optical signal; n eff represents the effective refractive index of the lithium niobate waveguide; k1 and k2 represent two different integers.

5. The microring filter according to claim 2, characterized in that: The first micro-ring modulator and the second micro-ring modulator are arranged in an alternating manner.

6. The microring filter according to claim 2, wherein: The first micro-ring modulator further includes: a third output waveguide; The second micro-ring modulator further includes: a fourth output waveguide; The third output waveguide is used to output the wavelength signal not selected in the first wavelength selection; The fourth output waveguide is used to output the wavelength signal that is not selected in the second wavelength selection.

7. The microring filter according to claim 3, characterized in that: The first micro-ring modulator further includes: a first electro-optical modulation electrode; the second micro-ring modulator further includes: a second electro-optical modulation electrode; The first electro-optic modulation electrode is used to adjust the refractive index of the first resonant ring waveguide; The second electro-optic modulation electrode is used to adjust the refractive index of the second resonant ring waveguide.

8. The microring filter according to claim 3, characterized in that: The method for preparing the manufacturing material comprises: Obtain a substrate; wherein the substrate comprises a substrate, a buffer layer and a waveguide layer; the waveguide layer is a lithium niobate layer; Cleaning and drying the substrate; Performing magnetron sputtering on the waveguide layer to coat a metal film; Spin coating a layer of photoresist on the metal film; According to a preset layout, the substrate covered with photoresist is exposed; The exposed substrate is immersed in a developer to perform development to remove the photoresist in the unexposed area; Performing metal etching on the developed substrate; Removing the remaining photoresist on the substrate after metal corrosion; According to the preset pattern, the substrate with the photoresist removed by ICP-RIE etching; removing the metal film on the etched substrate to obtain a resonant ring waveguide pattern; Depositing a silicon dioxide cladding layer on the substrate from which the metal film has been removed by PECVD; Transferring a preset electrode pattern to the silicon dioxide cladding layer through photoresist by secondary photolithography; Connecting the substrate after secondary photolithography to the negative electrode of the power supply for electroplating; The photoresist on the electroplated substrate is removed to obtain the manufacturing material.

9. The microring filter according to claim 8, characterized in that: The substrate is a silicon layer; the buffer layer is a silicon dioxide layer; and the metal film is a chromium film.

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