Optical sensor based on cascaded Mach-Zehnder interference and testing method thereof
Through the cascaded Mach-Zehnder interferometer structure, the manufacturing complexity and cost problems of traditional Mach-Zehnder sensors are solved, a high-sensitivity multi-level phase superposition effect is achieved, and the flexible sensing needs of complex systems are met.
Patent Information
- Application Number
- CN202510796566.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-16
- Publication Date
- 2025-09-09
AI Technical Summary
Traditional Mach-Zehnder sensors have shortcomings in manufacturing process complexity and cost, and are difficult to meet flexible and changing application requirements, especially in complex systems that require multiple measurements and multiple sensors.
A cascaded Mach-Zehnder interferometer structure is adopted to connect a broadband light source, an input grating coupler, a 50% optical waveguide beam splitter, the first and second Mach-Zehnder interferometer structures, a 50% optical waveguide coupler, a 50% optical waveguide combiner and an output grating coupler to achieve multi-level phase superposition, reduce process complexity and improve sensitivity.
It achieves high-sensitivity sensing, reduces the complexity and cost of manufacturing processes, and meets the flexible application requirements of multiple measurements and multiple sensors.
Smart Images
Figure CN120609392A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of optical waveguide sensors, and in particular to an optical sensor based on cascaded Mach-Zehnder interference. Background Art
[0002] In the field of optical sensing, Mach-Zehnder interferometer sensors are renowned for their exceptional sensitivity and precision, and have been widely used in a variety of key areas, including optical measurement, optical modulation, and biosensing. Their core operating principle, based on the phenomenon of interference, enables precise detection of minute changes in the phase of light waves, enabling high-precision measurement of various physical quantities. In practical applications, precise information about the physical quantity being measured can be obtained by monitoring wavelength variations in the transmission spectrum.
[0003] However, traditional Mach-Zehnder sensors have certain limitations in practical applications. To achieve sensing functionality, they typically require a specially designed sensing window for optical signal input and output, which undoubtedly increases manufacturing complexity and production costs. Furthermore, for more complex sensing systems, such as those involving multiple different types of sensors or requiring multiple measurements at different locations, traditional Mach-Zehnder sensors often struggle to meet the flexible and diverse application requirements due to their structural limitations. Summary of the Invention
[0004] In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is: an optical sensor based on cascaded Mach-Zehnder interference, connected to a broadband light source and a spectrum analyzer, including: an input end connected to the broadband light source and an output end connected to the spectrum analyzer, and an input grating coupler, a 50% optical waveguide beam splitter, a first Mach-Zehnder interference structure, a 50% optical waveguide coupler, a second Mach-Zehnder interference structure, a 50% optical waveguide combiner and an output grating coupler are sequentially arranged between the input end and the output end.
[0005] Preferably, the broadband light source is used as an input light source, and the optical signal enters the Mach-Zehnder interference structure through the single-mode optical fiber, and then the optical signal carrying the sensing information enters the spectrum analyzer through the single-mode optical fiber.
[0006] Preferably, the first Mach-Zehnder interference structure is provided with reference arms of different lengths, and the upper cladding of the reference arms is water.
[0007] Preferably, the second Mach-Zehnder interference structure is provided with two sensing arms of different lengths, the upper cladding of the two sensing arms is the test agent; and the waveguides of the two sensing arms adopt a transverse magnetic mode for transmission.
[0008] Preferably, a testing method for an optical sensor based on cascaded Mach-Zehnder interferometry comprises: Light from a broadband light source is input into the first Mach-Zehnder interference structure through an input grating coupler; The two reference arms of the first Mach-Zehnder interferometer structure generate filtered spectra, which are input to the second Mach-Zehnder interferometer structure; The two sensing arms of the second Mach-Zehnder interferometer structure receive external refractive index changes, convert the sensing signals into optical signals, and generate sensing spectra; The superposition of the filtered spectrum and the sensed spectrum produces a new spectrum with an envelope and a higher degree of drift; The optical signal enters the spectrum analyzer through the output grating coupler, and the data is collected and processed by a computer.
[0009] Compared with the prior art, the present invention has the following beneficial effects: The cascaded Mach-Zehnder interference structure adopted in the present invention realizes a multi-level phase superposition effect through cascade interference, thereby improving sensitivity. The cascaded Mach-Zehnder interference structure does not require an additional sensing window, thereby reducing the complexity and cost of the manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 Schematic diagram of the overall structure of the sensor based on cascaded Mach-Zehnder interferometry in the present invention; Figure 2 is a graph showing the change of the free spectral range with different reference arm lengths in the present invention; Figure 3 FIG1 is a graph showing the variation of the free spectral range of the cascade output with the length of the two arms in the present invention; Figure 4 The output transmission spectrum of the present invention drifts with different concentrations of salt water In the figure: 1. Broad-spectrum light source; 2. Sensor chip; 3. Spectrum analyzer; 21. Input grating coupler; 22. 50% optical waveguide beam splitter; 23. First reference arm; 24. Second reference arm; 25. 50% optical waveguide coupler; 26. First sensing arm; 27. Second sensing arm; 28. 50% optical waveguide combiner; 29. Output grating coupler. DETAILED DESCRIPTION
[0011] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.
[0012] Example: like Figures 1 to 4The present invention provides a technical solution: an optical sensor based on cascaded Mach-Zehnder interferometry, comprising a sensor chip connected to a broadband light source and a spectrum analyzer. The broadband light source serves as the input light source for a sensor chip testing system. The sensor chip has an input terminal connected to the broadband light source and an output terminal connected to the spectrum analyzer.
[0013] An input grating coupler, a 50% optical waveguide beam splitter, a first Mach-Zehnder interference structure, a 50% optical waveguide coupler, a second Mach-Zehnder interference structure, a 50% optical waveguide combiner and an output grating coupler are arranged in sequence between the input end and the output end.
[0014] The first Mach-Zehnder interferometer structure is provided with reference arms of different lengths, namely a first reference arm and a second reference arm, and the upper cladding of the reference arms is water.
[0015] The second Mach-Zehnder interference structure is provided with two sensing arms of different lengths. The two sensors are respectively a first sensor and a second sensor. The upper cladding of the two sensing arms is a test agent. The waveguides of the two sensing arms adopt a transverse magnetic mode for transmission.
[0016] Spectrum analyzer, collects and detects the output transmission spectrum.
[0017] Among them, the polarized light of the transverse magnetic fundamental mode is allowed to enter from the grating coupler, enter the first reference arm and the second reference arm through the 50% optical waveguide beam splitter, and the generated optical signal with a filtered spectrum is then interfered and output by the 50% optical waveguide combiner. The optical signal then enters the first sensor arm and the second sensor arm through the 50% optical waveguide coupler. Finally, the cascade spectrum with the sensor signal is transmitted to the optical spectrum analyzer for detection via the 50% optical waveguide combiner and the output grating coupler.
[0018] The broadband light source and spectrum analyzer are controlled by a computer and collect and process the obtained data to extract the cascade spectrum changes with the sensing signals.
[0019] Furthermore, sensing information is obtained by observing and calculating the change in the central wavelength λ of the cascade spectrum.
[0020] Assuming that the waveguide type of the cascaded Mach-Zehnder interferometer on the sensor chip is a rectangular waveguide with a waveguide width of 550 nm and an upper cladding layer of aqueous solution, the effective refractive index is approximately 1.76 near a wavelength of 1550 nm, and the group refractive index ng1 is approximately 3.8 near a wavelength of 1550 nm.
[0021] The length of the second reference arm is set to 60 μm. When the length L1 of the first reference arm is different, such as Figure 2As shown in the figure, the free spectral range of the first Mach-Zehnder interference structure decreases as the length L1 increases. When L1 is set to 120 μm, the free spectral range of the first Mach-Zehnder interference structure is approximately 10.54 nm. The length of the second sensing arm is set to 60 μm. The length of the first sensing arm, L2, must be similar to L1 to produce a cascade spectrum with a large free spectral range.
[0022] like Figure 3 As shown, the free spectral range of the cascade output increases as the difference between the two arm lengths L1 and L2 decreases. In order to prevent the generation of a cascade spectrum with an excessively large free spectral range, L2 is set to 125 μm. At this time, the free spectral range of the cascade spectrum is about 115 nm.
[0023] When the refractive index of the test agent changes, the effective refractive index of the first sensor arm and the second sensor arm will also change. Figure 4 As shown, actual sensing is simulated by varying the concentration of the upper cladding salt solution. When the concentration is set to 0%, 1%, and 2%, the resulting cascade spectra are overlapping spectra, requiring envelope fitting of their minimum values to extract the central wavelength changes during the sensing process. The central wavelengths of the envelope lines corresponding to the three concentrations are 1534.55nm, 1539.74nm, and 1544.94nm, respectively, corresponding to a bulk refractive index sensitivity of 2888nm / RIU. Therefore, the sensor chip can achieve ultra-high sensitivity sensing.
[0024] A method for testing an optical sensor based on cascaded Mach-Zehnder interferometry, comprising: Light from a broadband light source is input into the first Mach-Zehnder interference structure through an input grating coupler; The two reference arms of the first Mach-Zehnder interferometer structure generate filtered spectra, which are input to the second Mach-Zehnder interferometer structure; The two sensing arms of the second Mach-Zehnder interferometer structure receive external refractive index changes, convert the sensing signals into optical signals, and generate sensing spectra; The superposition of the filtered spectrum and the sensed spectrum produces a new spectrum with an envelope and a higher degree of drift; The optical signal enters the spectrum analyzer through the output grating coupler, and the data is collected and processed by a computer.
[0025] When the refractive index of the test sample changes, the effective refractive index of both sensing arms also changes, causing changes in the propagation characteristics of light in the sensing arms. In the cascaded Mach-Zehnder interferometer structure, this change is amplified, making the change in the output light signal more significant. This cascade effect makes the entire structure more sensitive to refractive index changes, thereby improving the sensitivity of the sensor.
[0026] The embodiments disclosed in the present invention are preferred embodiments, but are not limited to them. Ordinary technicians in this field can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. As long as they do not deviate from the spirit of the present invention, they are all within the scope of protection of the present invention.
Claims
1. An optical sensor based on cascaded Mach-Zehnder interferometry, connected to a broadband light source and a spectrum analyzer, characterized in that: include: The input end is connected to the broadband light source and the output end is connected to the spectrum analyzer. An input grating coupler, a 50% optical waveguide beam splitter, a first Mach-Zehnder interference structure, a 50% optical waveguide coupler, a second Mach-Zehnder interference structure, a 50% optical waveguide combiner and an output grating coupler are arranged between the input end and the output end.
2. The optical sensor based on cascaded Mach-Zehnder interferometry according to claim 1, characterized in that: The broadband light source is used as an input light source, and the optical signal enters the Mach-Zehnder interference structure through the single-mode optical fiber. Then, the optical signal carrying the sensing information enters the spectrum analyzer through the single-mode optical fiber.
3. The optical sensor based on cascaded Mach-Zehnder interferometry according to claim 1, characterized in that: The first Mach-Zehnder interferometer structure is provided with reference arms of different lengths, and the upper cladding of the reference arms is water.
4. The optical sensor based on cascaded Mach-Zehnder interferometry according to claim 1, characterized in that: The second Mach-Zehnder interference structure is provided with two sensing arms of different lengths, the upper cladding of the two sensing arms is a test agent; the waveguides of the two sensing arms adopt a transverse magnetic mode for transmission.
5. A method for testing an optical sensor based on cascaded Mach-Zehnder interferometry according to any one of claims 1 to 4, characterized in that: include: Light from a broadband light source is input into the first Mach-Zehnder interference structure through an input grating coupler; The two reference arms of the first Mach-Zehnder interferometer structure generate filtered spectra, which are input to the second Mach-Zehnder interferometer structure; The two sensing arms of the second Mach-Zehnder interferometer structure receive external refractive index changes, convert the sensing signals into optical signals, and generate sensing spectra; The superposition of the filtered spectrum and the sensed spectrum produces a new spectrum with an envelope and a higher degree of drift; The optical signal enters the spectrum analyzer through the output grating coupler, and the data is collected and processed by a computer.