Spectrometer based on thermally tuned micro-ring cascaded flat-top MZI (Mach Zehnder Interferometer) unit structure filter

Abstract

The invention discloses a spectrometer based on a thermally tuned micro-ring cascaded flat-top MZI unit structure filter, which is characterized by comprising a thermally tuned micro-ring resonator, a directional coupler, a first flat-top cascaded MZI unit structure filter and a second flat-top cascaded MZI unit structure filter, the output end of the thermal tuning micro-ring resonator is connected with any input end of the directional coupler, the first output end and the second output end of the directional coupler are connected to the input ends of the first flat-top cascaded MZI unit structure filter and the second flat-top cascaded MZI unit structure filter respectively, and the first flat-top cascaded MZI unit structure filter comprises a plurality of cascaded flat-top MZI filter units. Each flat-top MZI filter unit comprises a plurality of connected phase shifters, the structures of the second flat-top cascaded MZI unit structure filter and the first flat-top cascaded MZI unit structure filter and other parameters except the arm length difference of the phase shifters are the same, and the difference value of the arm length difference of the first flat-top cascaded MZI unit structure filter and the second flat-top cascaded MZI unit structure filter is a preset fixed value. The invention has the advantages of high resolution and large working bandwidth.

Description

Technical Field

[0001] This invention relates to spectrometers, and more particularly to a spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter structure. Background Technology

[0002] Spectrometers play a crucial role in spectral analysis and are widely used in fields such as biomedicine, food and drug safety testing, environmental monitoring, industrial manufacturing, optical communication, and optical sensing. Compared to traditional spectrometers, on-chip spectrometers based on photonic integrated chips offer better resolution while requiring less space and cost, and thus have enormous development potential.

[0003] Current on-chip spectrometers are mainly divided into two categories: dispersive on-chip spectrometers and Fourier transform on-chip spectrometers. On-chip dispersive elements are represented by arrayed waveguide gratings (AWGs), which offer excellent dispersive performance and high stability; however, AWG-based spectrometers struggle to achieve narrow channel spacing, and the large size of AWGs hinders integration. Fourier transform spectrometers, on the other hand, offer multi-channel benefits, resulting in higher light throughput and signal-to-noise ratio. Fourier transform spectrometers are typically based on Mach-Zehnder interferometers (MZIs), requiring thermal or electrical tuning of the optical path difference between the MZI arms. Therefore, their resolution is limited by the maximum achievable heating temperature and the high propagation loss accumulated over long optical paths. The pursuit of high resolution in on-chip spectrometers often leads to a reduction in operating bandwidth. Therefore, with the continuous development of spectral analysis technology, there is an urgent need for a spectrometer with both high resolution and a large operating bandwidth. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a high-resolution spectrometer with a large operating bandwidth based on a thermally tuned microring cascaded flat-top MZI unit filter structure.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A spectrometer based on a thermally tunable microring cascaded flat-top MZI unit structure filter includes a thermally tunable microring resonator, a directional coupler, a first flat-top cascaded MZI unit structure filter, and a second flat-top cascaded MZI unit structure filter. Both the first and second flat-top cascaded MZI unit structure filters have input terminals and multiple output terminals. The output terminal of the thermally tunable microring resonator is connected to any input terminal of the directional coupler. The first output terminal of the directional coupler is connected to the input terminal of the first flat-top cascaded MZI unit structure filter, and the second output terminal of the directional coupler is connected to the second flat-top cascaded MZI unit structure filter. The input terminal of the cascaded MZI unit structure filter is as follows: the first flat-topped cascaded MZI unit structure filter includes several cascaded flat-topped MZI filter units, each of which includes several connected phase shifters; the second flat-topped cascaded MZI unit structure filter has the same structure and parameters as the first flat-topped cascaded MZI unit structure filter except for the arm length difference of the phase shifters; the arm length difference of each phase shifter in the second flat-topped cascaded MZI unit structure filter is equal to the sum of the arm length difference of the corresponding phase shifter in the first flat-topped cascaded MZI unit structure filter and a preset arm length interpolation value.

[0007] Furthermore, the thermally tuned microring resonator includes a first straight waveguide, a second straight waveguide, a microring waveguide, and a metal heater. The first straight waveguide and the second straight waveguide are placed in parallel, and the microring waveguide is placed between the first straight waveguide and the second straight waveguide. The two ports on the same side of the first straight waveguide and the second straight waveguide are respectively the input terminal and the output terminal of the thermally tuned microring resonator. The metal heater covers the microring waveguide.

[0008] Furthermore, the first flat-top cascaded MZI unit structure filter includes a first flat-top MZI filter unit, a second flat-top MZI filter unit, a third flat-top MZI filter unit, a fourth flat-top MZI filter unit, a fifth flat-top MZI filter unit, a sixth flat-top MZI filter unit, a seventh flat-top MZI filter unit, an eighth flat-top MZI filter unit, and a ninth flat-top MZI filter unit;

[0009] Any input terminal of the first flat-top MZI filter unit serves as the input terminal of the first flat-top cascaded MZI unit structure filter. Any input terminal of the second and third flat-top MZI filter units is connected to the first and second output terminals of the first flat-top MZI filter unit, respectively. Any input terminal of the fourth flat-top MZI filter unit is connected to the first output terminal of the second flat-top MZI filter unit. Any input terminal of the fifth flat-top MZI filter unit is connected to the second output terminal of the third flat-top MZI filter unit. Any input terminal of the sixth and seventh flat-top MZI filter units is connected to the first and second output terminals of the fourth flat-top MZI filter unit, respectively. Any input terminal of the eighth and ninth flat-top MZI filter units is connected to the first and second output terminals of the fourth flat-top MZI filter unit, respectively.

[0010] The first output terminal of the sixth flat-top MZI filter unit, the second output terminal of the seventh flat-top MZI filter unit, the first output terminal of the eighth flat-top MZI filter unit, and the second output terminal of the ninth flat-top MZI filter unit serve as the four output terminals of the first flat-top cascaded MZI unit structure filter.

[0011] Furthermore, the remaining input terminals of each flat-top MZI filter unit are left unused.

[0012] Furthermore, the first flat-top MZI filter unit, the second flat-top MZI filter unit, and the third flat-top MZI filter unit have the same structure and parameters, and each includes a first directional coupler, a first phase shifter, a second directional coupler, a second phase shifter, a third directional coupler, a third phase shifter, and a fourth directional coupler connected in sequence. The first input terminal and the second input terminal of the first directional coupler serve as the first input terminal and the second input terminal of the corresponding flat-top MZI filter unit, respectively, and the first output terminal and the second output terminal of the fourth directional coupler serve as the first output terminal and the second output terminal of the corresponding flat-top MZI filter unit, respectively.

[0013] Furthermore, the fourth, fifth, sixth, seventh, eighth, and ninth flat-top MZI filter units have the same structure, each including a fifth directional coupler, a fourth phase shifter, a sixth directional coupler, a fifth phase shifter, and a seventh directional coupler connected in sequence. The first and second input terminals of the fifth directional coupler serve as the first and second input terminals of the corresponding flat-top MZI filter unit, respectively, and the first and second output terminals of the seventh directional coupler serve as the first and second output terminals of the corresponding flat-top MZI filter unit, respectively.

[0014] Furthermore, the coupling coefficients of the first directional coupler, the second directional coupler, the third directional coupler, and the fourth directional coupler are 0.5, 0.2, 0.2, and 0.04, respectively.

[0015] Furthermore, the coupling coefficients of the fifth, sixth, and seventh directional couplers are 0.5, 0.29, and 0.08, respectively.

[0016] Furthermore, the preset arm length interpolation value is specifically as follows:

[0017] ΔL E =ΔL shift / 2

[0018]

[0019] In the formula, ΔL E For the preset arm length interpolation value, ΔL shift The difference in arm length is λ, where λ is the wavelength of light, and n is the wavelength of light. eff The effective refractive index of the waveguides in both arms of the phase shifter.

[0020] Compared with the prior art, the beneficial effects of this invention are as follows: The spectrometer based on the thermally tunable microring cascaded flat-top MZI unit structure filter provided by this invention has the advantages of high resolution, large operating bandwidth, low crosstalk, and ease of use. It adopts a thermally tunable microring resonator, which has a simple structure, is easy to integrate, and achieves high resolution. It uses several cascaded flat-top filter units to achieve extremely low crosstalk between adjacent channels and a large operating bandwidth. The flat-top filter spectrum facilitates spectral recovery. It uses two flat-top cascaded MZI unit structure filters to avoid the influence of channel overlap. Attached Figure Description

[0021] Figure 1 A schematic diagram of the overall structure of the spectrometer based on the thermally tuned microring cascaded flat-top MZI unit filter provided by the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of the thermally tuned microring resonator provided by the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of the first flat-top MZI filter unit provided by the present invention;

[0024] Figure 4 This is a schematic diagram of the structure of the fourth flat-top MZI filter unit provided by the present invention;

[0025] Figure 5 The transmission spectrum of the thermally tuned microring resonator of the present invention under different voltages is shown below.

[0026] Figure 6 The transmission spectrum diagram of the two flat-topped cascaded MZI unit structure filters of the present invention;

[0027] Figure 7 This is the output spectrum of the spectrometer of the present invention. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0029] This invention provides a spectrometer based on a thermally tunable microring cascaded flat-top MZI unit filter structure, such as... Figure 1 As shown, the spectrometer includes a thermally tuned microring resonator 1, a directional coupler 2, a first flat-topped cascaded MZI unit structure filter 3, and a second flat-topped cascaded MZI unit structure filter 4. The entire spectrometer is fabricated on an SOI platform, with a cladding material of silicon dioxide, a core material of silicon, and a rectangular waveguide type.

[0030] like Figure 2 As shown, the thermally tunable microring resonator 1 includes a first straight waveguide 11, a second straight waveguide 12, a microring waveguide 13, and a metal heater. The first straight waveguide 11 and the second straight waveguide 12 are placed in parallel, and the microring waveguide 13 is placed between the first straight waveguide 11 and the second straight waveguide 12. The two ports on the same side of the first straight waveguide 11 and the second straight waveguide 12 are the input and output terminals of the thermally tunable microring resonator, respectively. The metal heater covers the microring waveguide 13. The radius of the microring waveguide 13 is 12 μm, and the metal heater is made of nickel-chromium alloy and is placed 1 μm above the microring waveguide 13.

[0031] In one specific embodiment, the output terminal of the thermally tuned microring resonator 1 is connected to any input terminal of the directional coupler 2, the first output terminal of the directional coupler 2 is connected to the input terminal of the first flat-top cascaded MZI unit structure filter 3, the second output terminal of the directional coupler is connected to the input terminal of the second flat-top cascaded MZI unit structure filter 4, and the coupling coefficient of the directional coupler 2 is 0.5.

[0032] In one specific embodiment, the structure of the first flat-topped cascaded MZI unit filter 3 and the second flat-topped cascaded MZI unit filter 4 are identical in all parameters except for the difference in arm length of the phase shifters. Therefore, the first flat-topped cascaded MZI unit filter 3 will be used as an example for the following description. The first flat-topped cascaded MZI unit filter 3 has an input terminal and multiple output terminals. The first flat-topped cascaded MZI unit filter 3 includes several cascaded flat-topped MZI filter units, and each flat-topped MZI filter unit includes several connected phase shifters.

[0033] In one specific embodiment, the first flat-top cascaded MZI unit structure filter 3 includes a first flat-top MZI filter unit 31, a second flat-top MZI filter unit 32, a third flat-top MZI filter unit 33, a fourth flat-top MZI filter unit 34, a fifth flat-top MZI filter unit 35, a sixth flat-top MZI filter unit 36, a seventh flat-top MZI filter unit 37, an eighth flat-top MZI filter unit 38, and a ninth flat-top MZI filter unit 39. The first flat-top MZI filter unit 31 has two input terminals, either of which serves as the input terminal of the first flat-top cascaded MZI unit structure filter 3. Either input terminal of the second flat-top MZI filter unit 32 and the third flat-top MZI filter unit 33 is connected to the first output terminal and the second output terminal of the first flat-top MZI filter unit 31, respectively. Either input terminal of the fourth flat-top MZI filter unit 34 is connected to the first output terminal of the second flat-top MZI filter unit 32. Either input terminal of the fifth flat-top MZI filter unit 35 is connected to the second output terminal of the third flat-top MZI filter unit 33. Either input terminal of the sixth flat-top MZI filter unit 36 ​​and the seventh flat-top MZI filter unit 37 is connected to the first output terminal and the second output terminal of the fourth flat-top MZI filter unit 34, respectively. Either input terminal of the eighth flat-top MZI filter unit 38 and the ninth flat-top MZI filter unit 39 is connected to the first output terminal and the second output terminal of the fourth flat-top MZI filter unit 34, respectively. The remaining input terminals of each flat-top MZI filter unit are left unused. The first output terminal of the sixth flat-top MZI filter unit 36, the second output terminal of the seventh flat-top MZI filter unit 37, the first output terminal of the eighth flat-top MZI filter unit 38, and the second output terminal of the ninth flat-top MZI filter unit 39 serve as the four output terminals of the first flat-top cascaded MZI unit structure filter 3.

[0034] In one specific embodiment, the first flat-top MZI filter unit 31, the second flat-top MZI filter unit 32, and the third flat-top MZI filter unit 33 have the same structure and parameters. Taking the first flat-top MZI filter unit 31 as an example, as follows... Figure 3As shown, the system includes a first directional coupler 311, a first phase shifter 312, a second directional coupler 313, a second phase shifter 314, a third directional coupler 315, a third phase shifter 316, and a fourth directional coupler 317 connected in sequence. The first and second input terminals of the first directional coupler 311 serve as the first and second input terminals of the first flat-top MZI filter unit 31, respectively. The first and second output terminals of the fourth directional coupler 317 serve as the first and second output terminals of the first flat-top MZI filter unit 31, respectively. The coupling coefficients of the first directional coupler 311, the second directional coupler 313, the third directional coupler 315, and the fourth directional coupler 317 are 0.5, 0.2, 0.2, and 0.04, respectively.

[0035] In one specific embodiment, the fourth flat-top MZI filter unit 34, the fifth flat-top MZI filter unit 35, the sixth flat-top MZI filter unit 36, the seventh flat-top MZI filter unit 37, the eighth flat-top MZI filter unit 38, and the ninth flat-top MZI filter unit 39 have the same structure. Taking the fourth flat-top MZI filter unit 34 as an example, as... Figure 4 As shown, the filter unit includes a fifth directional coupler 341, a fourth phase shifter 342, a sixth directional coupler 343, a fifth phase shifter 344, and a seventh directional coupler 345 connected in sequence. The first and second input terminals of the fifth directional coupler 341 serve as the first and second input terminals of the fourth flat-top MZI filter unit 34, respectively. The first and second output terminals of the seventh directional coupler 345 serve as the first and second output terminals of the fourth flat-top MZI filter unit 34, respectively. The coupling coefficients of the fifth directional coupler 341, the sixth directional coupler 343, and the seventh directional coupler 345 are 0.5, 0.29, and 0.08, respectively. The fourth flat-top MZI filter unit 34, the fifth flat-top MZI filter unit 35, and the sixth flat-top MZI filter unit 36 ​​have the same parameters, as do the seventh flat-top MZI filter unit 37, the eighth flat-top MZI filter unit 38, and the ninth flat-top MZI filter unit 39.

[0036] The arm length difference of each phase shifter consists of the basic arm length difference ΔL1 and the additional arm length difference ΔL. shift It is a linear combination of the two, where the arm length difference refers to the difference in length between the upper arm and the lower arm; the basic arm length difference ΔL1 and the additional arm length difference ΔL shift It can be calculated using the following formula:

[0037]

[0038] Where λ is the wavelength of light, specifically 1550nm in this embodiment, and FSR ringn represents the free spectral range of the thermally tuned microring resonator. g Let n be the group refractive index of the waveguide arms of the phase shifter. eff The effective refractive index of the waveguides in both arms of the phase shifter;

[0039] The theoretical length formula and actual length of the arm length difference of each phase shifter are shown in Table 1.

[0040] Table 1. Arm length difference data for each phase shifter

[0041]

[0042] Except for the arm length difference of the phase shifters, the design parameters of the second flat-top cascaded MZI unit structure filter 4 are the same as those of the first flat-top cascaded MZI unit structure filter 3; the arm length difference of each phase shifter in the second flat-top cascaded MZI unit structure filter 4 is equal to the arm length difference of the corresponding phase shifter in the first flat-top cascaded MZI unit structure filter 3 and a preset arm length interpolation value ΔL. E The sum, ΔL E =ΔL shift / 2.

[0043] In this invention, the working process of the spectrometer based on the thermally tunable microring cascaded flat-top MZI unit structure filter is as follows: Light enters from the input end of the thermally tunable microring resonator 1, resonates in the microring waveguide, and generates a transmission peak with high resolution; as shown... Figure 5 As shown, changing the voltage of the metal heater in the thermally tunable microring resonator 1 can change the transmission spectrum of the thermally tunable microring resonator 1; the transmitted light from the thermally tunable microring resonator 1, after passing through the directional coupler 2, enters the first flat-top cascaded MZI unit structure filter 3 and the second flat-top cascaded MZI unit structure filter 4 in a 50:50 ratio; as... Figure 6 As shown, the first flat-topped cascaded MZI unit structure filter 3 and the second flat-topped cascaded MZI unit structure filter 4 each generate four flat-topped filter channels, and the passbands of the corresponding flat-topped filter channels of the two filters are complementary, avoiding the influence of channel overlap and reducing crosstalk between channels; as Figure 7 As shown, under different heating voltages, the outputs of the first flat-top cascaded MZI unit structure filter 3 and the second flat-top cascaded MZI unit structure filter 4 with less crosstalk can be selected to combine the outputs of the spectrometer based on the thermally tuned micro-ring cascaded flat-top MZI unit structure filter. In this specific embodiment, the spectrometer based on the thermally tuned micro-ring cascaded flat-top MZI unit structure filter can achieve a high resolution of 0.2 nm while maintaining a large operating bandwidth of 1537 nm to 1567 nm for the dispersive wavelength range.

[0044] It should be understood that the embodiments and descriptions above are only the principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope of the invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A spectrometer based on a thermally tunable microring cascaded flat-top MZI unit filter, characterized in that: The system includes a thermally tuned microring resonator, a directional coupler, a first flat-topped cascaded MZI unit structure filter, and a second flat-topped cascaded MZI unit structure filter. Both the first and second flat-topped cascaded MZI unit structure filters have input terminals and multiple output terminals. The output terminal of the thermally tuned microring resonator is connected to any input terminal of the directional coupler. The first output terminal of the directional coupler is connected to the input terminal of the first flat-topped cascaded MZI unit structure filter, and the second output terminal of the directional coupler is connected to the input terminal of the second flat-topped cascaded MZI unit structure filter. At the input end, the first flat-top cascaded MZI unit structure filter includes several cascaded flat-top MZI filter units, each of which includes several connected phase shifters. The second flat-top cascaded MZI unit structure filter has the same structure and parameters as the first flat-top cascaded MZI unit structure filter, except for the arm length difference of the phase shifters. The arm length difference of each phase shifter in the second flat-top cascaded MZI unit structure filter is equal to the sum of the arm length difference of the corresponding phase shifter in the first flat-top cascaded MZI unit structure filter and a preset arm length interpolation value.

2. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 1, characterized in that: The thermally tuned microring resonator includes a first straight waveguide, a second straight waveguide, a microring waveguide, and a metal heater. The first and second straight waveguides are placed in parallel, and the microring waveguide is placed between the first and second straight waveguides. The two ports on the same side of the first and second straight waveguides are the input and output terminals of the thermally tuned microring resonator, respectively. The metal heater covers the microring waveguide.

3. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 1, characterized in that: The first flat-top cascaded MZI unit structure filter includes a first flat-top MZI filter unit, a second flat-top MZI filter unit, a third flat-top MZI filter unit, a fourth flat-top MZI filter unit, a fifth flat-top MZI filter unit, a sixth flat-top MZI filter unit, a seventh flat-top MZI filter unit, an eighth flat-top MZI filter unit, and a ninth flat-top MZI filter unit; Any input terminal of the first flat-top MZI filter unit serves as the input terminal of the first flat-top cascaded MZI unit structure filter. Any input terminal of the second and third flat-top MZI filter units is connected to the first and second output terminals of the first flat-top MZI filter unit, respectively. Any input terminal of the fourth flat-top MZI filter unit is connected to the first output terminal of the second flat-top MZI filter unit. Any input terminal of the fifth flat-top MZI filter unit is connected to the second output terminal of the third flat-top MZI filter unit. Any input terminal of the sixth and seventh flat-top MZI filter units is connected to the first and second output terminals of the fourth flat-top MZI filter unit, respectively. Any input terminal of the eighth and ninth flat-top MZI filter units is connected to the first and second output terminals of the fourth flat-top MZI filter unit, respectively. The first output terminal of the sixth flat-top MZI filter unit, the second output terminal of the seventh flat-top MZI filter unit, the first output terminal of the eighth flat-top MZI filter unit, and the second output terminal of the ninth flat-top MZI filter unit serve as the four output terminals of the first flat-top cascaded MZI unit structure filter.

4. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 3, characterized in that: The remaining input terminals of each flat-top MZI filter unit are left unused.

5. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 3, characterized in that: The first, second, and third flat-top MZI filter units have the same structure and parameters, and each includes a first directional coupler, a first phase shifter, a second directional coupler, a second phase shifter, a third directional coupler, a third phase shifter, and a fourth directional coupler connected in sequence. The first and second input terminals of the first directional coupler serve as the first and second input terminals of the corresponding flat-top MZI filter unit, respectively, and the first and second output terminals of the fourth directional coupler serve as the first and second output terminals of the corresponding flat-top MZI filter unit, respectively.

6. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 3, characterized in that: The fourth, fifth, sixth, seventh, eighth, and ninth flat-top MZI filter units have the same structure, each including a fifth directional coupler, a fourth phase shifter, a sixth directional coupler, a fifth phase shifter, and a seventh directional coupler connected in sequence. The first and second input terminals of the fifth directional coupler serve as the first and second input terminals of the corresponding flat-top MZI filter unit, respectively, and the first and second output terminals of the seventh directional coupler serve as the first and second output terminals of the corresponding flat-top MZI filter unit, respectively.

7. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 6, characterized in that: The fourth, fifth, and sixth flat-top MZI filter units have the same parameters, as do the seventh, eighth, and ninth flat-top MZI filter units.

8. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 5, characterized in that: The coupling coefficients of the first directional coupler, the second directional coupler, the third directional coupler, and the fourth directional coupler are 0.5, 0.2, 0.2, and 0.04, respectively.

9. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 6, characterized in that: The coupling coefficients of the fifth, sixth, and seventh directional couplers are 0.5, 0.29, and 0.08, respectively.

10. The spectrometer based on a thermally tuned microring cascaded flat-top MZI unit filter according to claim 1, characterized in that: The preset arm length interpolation value is specifically: ΔL E =ΔL shift / 2 In the formula, ΔL E For the preset arm length interpolation value, ΔL shift The difference in arm length is λ, where λ is the wavelength of light, and n is the wavelength of light. eff The effective refractive index of the waveguides in both arms of the phase shifter.

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