Mid-infrared integrated optical chip microfluidic multiphase detection device and on-chip spectrometer thereof

Abstract

An on-chip mid-infrared micro-ring resonant cavity microfluidic spectrometer is integrated on a substrate material and comprises a spot size converter, an optical coupler, a microfluidic module, a micro-ring resonant cavity, a miniature thin-film resistance heater, a sequential control power supply module, an optical filtering system and a photoelectric detector array. Selective filtering is performed on an input optical signal, and the flow and flow velocity of liquid or gas to be detected are controlled by using the microfluidic module, so that selective absorption of spectral components of the liquid or gas to be detected is realized. In addition, the invention also discloses a mid-infrared integrated optical chip micro-fluidic multiphase detection device comprising the spectrometer and a detection method thereof, the device also comprises a pumping and reference light source module and an on-chip mid-infrared frequency comb generation module, a broadband frequency comb is generated as a light source, a photoelectric detector array is used for collecting signals, and the detection precision is improved. The detection and inversion of the type and concentration of multi-component liquid or gas to be detected are realized, and the on-chip, real-time and micro detection of multi-component substances is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of mid-infrared analyte detection, and particularly relates to a mid-infrared integrated optical chip microfluidic multiphase detection device and an on-chip spectrometer thereof. Background Art

[0002] The wavelength band of 2 - 5 μm is often referred to as the "molecular fingerprint region", which covers the fundamental absorption bands of most organic and inorganic substances. Therefore, performing precise on-chip spectral measurement of multi-component substances in this wide spectral range and real-time monitoring of the composition of complex mixtures have great research and application value. Currently, most integrated optical chip sensing technologies focus on the visible and near-infrared bands, and there is still a large demand for application and research in on-chip sensing technologies in the mid-infrared band.

[0003] On-chip integrated Kerr frequency comb is an ideal broadband coherent light source, which can be applied to on-chip multi-component substance sensing. The existing on-chip integrated microcavity Kerr frequency comb infrared analyte detection technology requires the use of backend spectral analysis and processing to complete the inversion of the output spectrum. Therefore, it has deficiencies such as high system complexity and large data processing requirements.

[0004] The existing on-chip integrated spectral technology based on frequency comb is mainly applied to the field of gas sensing, and gas detection is carried out in an additional gas chamber or by using an optical waveguide sensing method. However, neither of the above methods can control parameters such as the flow rate and velocity of the detection target, and it is difficult to perform trace analyte detection. In addition, the precise detection of trace liquids has great application demand in the field of medical diagnosis. In the existing technology, no on-chip liquid sensing device based on frequency comb in the mid-infrared has been designed.

[0005] In view of the above problems, it is urgent to design a mid-infrared integrated optical chip microfluidic multiphase detection device to solve the problems of high system complexity, large data processing requirements, and inability to perform trace analyte detection existing in the above-mentioned existing technologies, and to realize on-chip, real-time, and micro-scale detection of multi-component substances. Summary of the Invention

[0006] In view of the above existing problems, the present invention aims to provide a mid-infrared integrated optical chip microfluidic multiphase detection device and an on-chip spectrometer thereof. Using the Kerr frequency comb formed in the microcavity as the light source and the single-frequency light output by the continuous-wave laser as the frequency reference light, through the micro-ring resonator array with tunable refractive index, the types and concentrations of multi-channel gases or liquids can be inversed in real time, which has the characteristics of direct frequency scanning, no subsequent data processing, high frequency stability, precise regulation of the target analyte, compact structure, and high detection accuracy.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides an on-chip mid-infrared micro-ring resonator microfluidic spectrometer, characterized in that it includes: integrated on a substrate material

[0009] Two mode spot converters are respectively arranged at the input ends of the input straight waveguide and the input bent waveguide to receive optical signals from different light sources or modules and couple them;

[0010] An optical coupler is respectively connected to the output ends of the input straight waveguide and the input bent waveguide, and is used to couple the optical field coupled into the input straight waveguide and the single-frequency light coupled into the input bent waveguide, and bundle them into a straight waveguide of the micro-ring resonator;

[0011] A microfluidic module is arranged at the output end of the optical coupler and is used to control the flow rate and velocity of the liquid or gas to be measured. The two ends of the microfluidic module are respectively connected to a straight waveguide of the micro-ring resonator, and the evanescent field is used to realize the selective absorption of the input spectral components by the liquid to be measured;

[0012] The micro-ring resonator is formed by coupling a ring waveguide and two straight waveguides, and the resonant wavelength and the free spectral range are changed by tuning the refractive index to perform selective filtering on the input optical signal;

[0013] A micro thin film resistor heater is integrated on the micro-ring resonator and is used to heat the micro-ring resonator, thereby changing the refractive index of the micro-ring resonator;

[0014] A timing control power supply module is connected to the micro thin film resistor heater and is used to provide heating power with timing control to control the heating process of the micro thin film resistor heater;

[0015] An optical filtering system is connected to the other straight waveguide of the micro-ring resonator and is used to separate the broad-spectrum components absorbed by the microfluidic module and filtered by the micro-ring resonator into frequency comb signals of different orders;

[0016] An optoelectronic detector array is composed of a plurality of optoelectronic detectors arranged at the output ends of each channel of the optical filtering system, and is used to receive the optical signals spectrally split by the optical filtering system and convert them into electrical signals.

[0017] Preferably, the transmission spectrum of the optical filtering system matches the working wavelength range of the micro-ring resonator, and the maximum tunable range of the resonant wavelength of the micro-ring resonator is equal to the full width at half maximum value of a single transmission peak of the optical filtering system.

[0018] Preferably, the microfluidic module includes a microfluidic chip and a controllable electroosmotic micropump, and the electroosmotic micropump drives the fluid to flow pulsation-free along a specified path by applying an electric field to achieve control.

[0019] Preferably, the on-chip mid-infrared microring resonator microfluidic spectrometer uses materials with high mid-infrared band transmissivity as the substrate and waveguide materials. Specifically, sapphire can be selected as the substrate material, and silicon can be selected as the waveguide material.

[0020] Preferably, the microfluidic module includes a microfluidic chip and a controllable electroosmotic micropump for precise control of trace liquid or gas to be measured.

[0021] Preferably, the microring resonator changes its resonant wavelength and free spectral range by tuning its refractive index, so as to perform time-resolved selective filtering on the spectral components of the input frequency comb using different-order cavity modes. The relationship between the transmission intensity of the microring resonator and the scanning time is the spectral convolution between the transmission function of the microring resonator and the input mid-infrared spectrum.

[0022] Preferably, the tunable range of the resonant wavelength of the microring resonator should be less than its free spectral range to prevent the crosstalk phenomenon between adjacent orders from affecting the detection results.

[0023] Preferably, the optical filtering system splits the broadband components absorbed by the microfluidic module and filtered by the microring resonator according to the transmission spectral lines of the optical filtering system, and outputs them through several waveguide channels to avoid spectral aliasing between adjacent resonant orders of the microring resonator.

[0024] Preferably, the transmission spectrum of the optical filtering system should match the working wavelength range of the microring resonator, and the maximum tunable range of the resonant wavelength of the microring resonator should be equal to the full width at half maximum value of a single transmission peak of the optical filtering system.

[0025] The optical coupler is used to couple the optical field coupled into the input straight waveguide and the single-frequency light coupled into the input bent waveguide, and bundle them into the subsequent waveguide structure. When in use, devices such as Y-type waveguide combiners can be used.

[0026] The chip used in the microfluidic module is a silicon-based microfluidic chip, integrated with the SOS material platform, and has high mid-infrared light transmissivity, which is used to precisely control the flow rate and velocity of the liquid or gas to be measured. The two ends of the microfluidic module are respectively connected to the waveguide structure, and the selective absorption of the input spectral components by the liquid to be measured is realized by using the intracavity absorption effect of the evanescent field.

[0027] The microfluidic module also includes an electroosmotic micropump for precisely controlling the flow rate and velocity of the liquid or gas to be measured. By applying an electric field in a tiny flow channel, the electroosmotic micropump can drive the fluid to flow pulsation-free along the specified path.

[0028] The micro-ring resonator uses an add-drop type micro-ring resonator. At a specific resonant wavelength, it selectively couples the optical signal input from the input end to the Drop port, while the un-resonated optical signal is output through the Through port, achieving selective filtering of different frequency spectral components.

[0029] A micro thin-film resistor heater is integrated above the micro-ring resonator to achieve time-resolved thermal tuning of the resonant wavelength of the micro-ring resonator. The heater can be made of nichrome or titanium metal. These two materials have excellent resistivity and high-temperature stability, and exhibit low optical absorption in the mid-infrared band, thus reducing interference with the transmission of optical signals.

[0030] The micro thin-film resistor heater is usually directly deposited above the micro-ring resonator through sputtering or lithography techniques to form a uniform resistive film. The heater is designed in a shape consistent with the micro-ring waveguide path and heats within the input end, through end, and the annular waveguide range to ensure efficient electro-thermal conversion within a small area. Heating is not performed at the drop port to avoid affecting the stability of the output signal. The thin-film resistor heater is supplied with current through an external power source. When current passes through, due to the resistance effect, Joule heat is generated in the film, causing the temperature of the film and the underlying waveguide structure to rise. The electrodes of the heater are usually wired with gold or aluminum and connected to the timing control power supply module.

[0031] The timing control power supply module is used to achieve time-resolved tuning of the micro thin-film resistor heater.

[0032] The timing control power supply module includes a low-resistance connector, a programmable current source, and a digital timing controller. The programmable current source is used to adjust and output a stable current to ensure that the micro thin-film resistor heater can operate stably at the set power. The low-resistance connector can connect the current source to the heater electrodes. The digital timing controller allows the user to set the working time interval of the heater to achieve time-resolved control of the heating process.

[0033] The optical filtering system should select a structure with strong wavelength dependence to separate frequency comb signals of different orders. Selectable spectral splitting structures include arrayed waveguide gratings, one-dimensional photonic crystal cavities, etc.

[0034] The photodetector array is used to receive the optical signal tuned by the micro-ring resonator array and convert it into an electrical signal to obtain the optical intensity, that is, to obtain the scanned spectral information of each channel.

[0035] Through the precise control of the micro thin-film resistor heater array by the timing control power module, each photodetector will collect optical signals of a specific wavelength within its corresponding time window. Subsequently, the acquisition signals of all channels are integrated in the time domain to generate a complete light intensity-time spectrum.

[0036] Second, the present invention also provides a mid-infrared integrated optical chip microfluidic multiphase detection device, which is characterized in that it includes the above-mentioned on-chip mid-infrared microring resonator microfluidic spectrometer.

[0037] Furthermore, it further includes:

[0038] A pump and reference light source module, which is composed of a pump light source system and a reference light source system. Among them, the pump light source system is used to provide mid-infrared band pump light as a pump source;

[0039] The reference light source system is used to provide a mid-infrared single-frequency continuous wave laser as an absolute frequency reference light and couple it into the on-chip mid-infrared microring resonator microfluidic spectrometer;

[0040] An on-chip mid-infrared frequency comb generation module, which is used to receive the pump source provided by the pump light source system and generate a broadband frequency comb, and couple it into the on-chip mid-infrared microring resonator microfluidic spectrometer.

[0041] Furthermore, the on-chip mid-infrared frequency comb generation module includes

[0042] A mode converter, which is used to couple the pump mid-infrared light output by the pump and reference light source module from the input optical fiber to the microcavity coupling input straight waveguide;

[0043] A microcavity coupling input straight waveguide, which is connected to the output end of the mode converter and is used to guide the coupled optical signal to the frequency comb microring resonator;

[0044] A frequency comb microring resonator, which is used to generate and maintain a standing wave field in the mid-infrared band and generate a broadband frequency comb by using the Kerr effect;

[0045] A microcavity waveguide constant temperature module, which is used to achieve constant temperature control and thermally lock the generated frequency comb in a thermal tuning manner;

[0046] A microcavity coupling output straight waveguide, which is connected to the output end of the frequency comb microring resonator and is used to extract the generated frequency comb signal from the microring resonator;

[0047] A waveguide grating coupler, which is connected to the output end of the microcavity coupling output straight waveguide and is used to couple the frequency comb signal into the on-chip mid-infrared microring resonator microfluidic spectrometer.

[0048] Preferably, the on-chip mid-infrared frequency comb generation module uses a material with high mid-infrared band transmissivity as the substrate and waveguide material for mid-infrared microcomb generation. Specifically, selectable material platforms include the Silicon-on-Sapphire (SOS) platform, nitride platforms (such as Si3N4 and AlN), halide platforms (such as MgF2 and CaF2), etc.

[0049] Preferably, the frequency comb micro-ring resonator adopts a ring waveguide structure with a high Q factor, which is used to generate and maintain a standing wave field within the mid-infrared band, and generate a broadband frequency comb by utilizing the Kerr effect.

[0050] Preferably, the microcavity waveguide constant temperature module realizes constant temperature through feedback control, so that the generated frequency comb realizes thermal locking under the action of thermal tuning.

[0051] Furthermore, the pump light source system includes a signal generator, a pump laser current controller, a pump semiconductor laser, an optical fiber amplifier, a frequency doubler, and a polarization controller; wherein, the pump semiconductor laser is a near-infrared band laser with a tunable wavelength, and the optical signal emitted by it is power-amplified by the optical fiber amplifier, and then the frequency of the optical signal is doubled to the required mid-infrared band by the frequency doubler, and is adjusted by the polarization controller to meet the quasi-phase matching condition; the reference light source system includes a constant current source, a single-frequency laser, and a thermoelectric cooling element, wherein the single-frequency laser is connected to the thermoelectric cooling element for real-time monitoring and stabilizing the frequency of the optical signal output by the single-frequency laser.

[0052] The signal generator is connected to the pump semiconductor laser through the pump laser current controller.

[0053] The output end of the frequency doubler is connected to the input end of the fiber-coupled input tapered mode spot converter.

[0054] Preferably, the reference light source system includes a constant current source, a single-frequency laser, and a thermoelectric cooling element.

[0055] The output end of the single-frequency laser is connected to the input end of the input bent waveguide.

[0056] Preferably, the frequency resolution of the single-frequency laser is higher than 1 / 2 times the frequency comb repetition frequency.

[0057] Preferably, the maximum adjustable range of the wavelength of the pump semiconductor laser is greater than one free spectral range of the micro-ring resonator.

[0058] Thirdly, the present invention also provides a method for detecting and inverting the types and concentrations of multi-component liquid or gas to be measured using the above-mentioned mid-infrared integrated optical chip microfluidic multiphase detection device, which is characterized by including the following steps:

[0059] S1. Adjust the alignment of the input and output coupling lens fibers in the pump light source system and the reference light source system;

[0060] S2. Set the drive current of the laser so that its output wavelength sweeps across a certain resonance peak of the microcavity;

[0061] S3. Adjust the heating power of the heater array from low to high, use the photodetector array to collect signals to reconstruct the frequency comb spectrum, and observe the repetition frequency of the output frequency comb;

[0062] S3. Introduce the gas or liquid to be measured into the microfluidic module at a certain flow rate and flow volume;

[0063] S4. According to the relationship between the pre-determined heater drive current and the change value of the micro-ring thermal tuning resonance frequency, regulate the heating power of the heater array, and use the photodetector array to collect signals to reconstruct the transmission spectrum;

[0064] S5. Invert the type and concentration of the gas or liquid by comparing with the standard database.

[0065] Specifically: Step 1. Connect all the optical and electrical equipment of the multiphase detection device;

[0066] Step 2. Fine-tune the input and output coupling lens fibers in the pump light source system to align them with the center of the tapered mode converter of the on-chip mid-infrared frequency comb generation module; fine-tune the input and output coupling lens fibers in the reference light source system to align them with the center of the input inverted taper mode spot converter of the on-chip mid-infrared micro-ring resonator microfluidic spectrometer

[0067] Step 3. Set the drive current of the laser so that its output wavelength sweeps across a certain resonance peak of the microcavity;

[0068] Step 4. Adjust the heating power of the heater array from low to high, use the photodetector array to collect signals to reconstruct the frequency comb spectrum, and observe the repetition frequency of the output frequency comb;

[0069] Step 5. Introduce the gas or liquid to be measured into the microfluidic module at a certain flow rate and flow volume;

[0070] Step 6. According to the relationship between the pre-determined heater drive current and the change value of the micro-ring thermal tuning resonance frequency, regulate the heating power of the heater array, and use the photodetector array to collect signals to reconstruct the transmission spectrum;

[0071] Step 7. Invert the type and concentration of the gas or liquid by comparing with the standard database.

[0072] The beneficial effects of the present invention are as follows: The present invention discloses a mid-infrared integrated optical chip microfluidic multiphase detection device and its application. Compared with the prior art, the improvements of the present invention are as follows:

[0073] 1. On-chip mid-infrared micro-ring resonator microfluidic spectrometer, including an input straight waveguide, a fiber-coupled input inverted tapered mode spot converter, an input curved waveguide, an optical coupler, a microfluidic module, a micro-ring resonator, a micro thin film resistor heater, an optical filtering system, a photodetector array, and a timing control power supply module. The on-chip mid-infrared micro-ring resonator microfluidic spectrometer designed by the present invention uses a micro-ring resonator with tunable refractive index for direct frequency scanning, without post-data processing. A single-frequency mid-infrared laser is used as a reference light source to obtain absolute frequency, with high frequency stability. The microfluidic module is used to precisely control the target analyte, enabling the detection of trace amounts of liquids or gases.

[0074] 2. Mid-infrared integrated optical chip microfluidic multiphase detection device, including an on-chip mid-infrared frequency comb generation module, an on-chip mid-infrared micro-ring resonator microfluidic spectrometer, and a pump and reference light source module. By using the high-conversion-efficiency broadband mid-infrared coherent Kerr frequency comb formed in the microcavity as a light source and integrating the micro-ring resonator microfluidic spectrometer, after the spectral signals are collected by the photodetector, the types and concentrations of multi-component liquids or gases can be inverted. The formed mid-infrared frequency comb can well cover the molecular fingerprint spectral region, and has great practical application value compared with the traditional on-chip frequency comb spectrometer with a central wavelength of about 1550 nm. Description of the Drawings

[0075] Figure 1 is a schematic structural diagram of an embodiment of the on-chip mid-infrared micro-ring resonator microfluidic spectrometer of the present invention

[0076] Figure 2 is a schematic diagram of an embodiment of the mid-infrared integrated optical chip microfluidic multiphase detection device of the present invention

[0077] Figure 3 is an operation flow chart of using the mid-infrared integrated optical chip microfluidic multiphase detection device of the present invention to measure a liquid or gas to be detected.

[0078] Wherein:

[0079] 1. On-chip mid-infrared frequency comb generation module, 101. Mode converter, 102. Microcavity-coupled input straight waveguide, 103. Frequency comb micro-ring resonator, 104. Microcavity waveguide constant temperature module, 105. Microcavity-coupled output straight waveguide, 106. Waveguide grating coupler;

[0080] 2. On-chip mid-infrared micro-ring resonator microfluidic spectrometer, 201. Mode spot converter, 202. Input straight waveguide, 203. Input curved waveguide, 204. Optical coupler, 205. Microfluidic module, 206. Micro-ring resonator, 207. Micro thin-film resistor heater, 208. Optical filtering system, 209. Photoelectric detector array, 210. Timing control power supply module; 3. Pumping and reference light source module, 31. Pumping light source system, 311. Signal generator, 312. Pumping laser current controller, 313. Pumping semiconductor laser, 314. Fiber amplifier, 315. Frequency doubler, 316. Polarization controller; 32. Reference light source system, 321. Constant current source, 322. Single-frequency laser, 323. Thermoelectric cooling element. Detailed implementation manners

[0081] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention should not be limited thereby.

[0082] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of an embodiment of the on-chip mid-infrared micro-ring resonator microfluidic spectrometer of the present invention. As shown in the figure, the on-chip mid-infrared micro-ring resonator microfluidic spectrometer includes:

[0083] Two mode spot converters 201 are respectively arranged at the input ends of the input straight waveguide 202 and the input curved waveguide 203 to receive optical signals from different light sources or modules. The mode spot converter 201 adopts an inverted cone design and is used to couple the optical signal from the optical fiber into the waveguide structure.

[0084] The optical coupler 204 couples the optical field coupled into the input straight waveguide 202 and the single-frequency light coupled into the input curved waveguide 203 and bundles them into the subsequent waveguide structure. It is usually realized by devices such as a Y-type waveguide combiner.

[0085] The microfluidic module 205 is used to control the flow rate and velocity of the liquid or gas to be measured. This embodiment includes a microfluidic chip and a controllable electroosmotic micropump. The microfluidic chip is integrated with the SOS material platform and has high mid-infrared light transmittance. The electroosmotic micropump drives the fluid to flow pulsation-free along the specified path by applying an electric field to achieve precise control. When the liquid or gas to be measured flows in the microfluidic module, it will selectively absorb the input spectral components by using the evanescent field cavity absorption effect.

[0086] The microring resonator 206 is used to selectively filter the input optical signal. It adopts an add-drop type design, coupling the optical signal to the Drop port at a specific resonance wavelength, while the un-resonated optical signal is output through the Through port. By tuning the refractive index of the microring resonator, its resonance wavelength and free spectral range can be changed, thereby achieving selective filtering of different frequency spectral components. This is achieved through the integrated micro thin-film resistor heater 207 above the microring resonator 206.

[0087] The micro thin-film resistor heater 207 is used for time-resolved thermal tuning of the microring resonator 206. In this embodiment, it is made of nickel-chromium alloy or titanium metal, having excellent resistivity and high-temperature stability, and showing low light absorption rate in the mid-infrared band. The micro thin-film resistor heater 207 is usually directly deposited above the microring resonator through sputtering or lithography techniques to form a uniform resistive film. The heater adopts a shape design consistent with the microring waveguide path, heating within the input end, through end, and the range of the ring waveguide to ensure efficient electro-thermal conversion within a small area, without heating at the drop port to avoid affecting the stability of the output signal. The thin-film resistor heater is supplied with current through an external power supply. When the current passes through, due to the resistance effect, Joule heat will be generated in the film, causing the temperature of the film and the underlying waveguide structure to rise. The electrodes of the heater are usually wired with gold or aluminum and connected to the timing control power module 210.

[0088] The timing control power module 210 is used to control the heating process of the micro thin-film resistor heater 207. It includes a low-resistance connector, a programmable current source, and a digital timing controller. The programmable current source is used to adjust and output a stable current to ensure the heater operates stably at the set power. The digital timing controller allows the user to set the working time interval of the heater to achieve time-resolved control of the heating process.

[0089] The optical filtering system 208 is used to split the broad-spectrum components that have been absorbed by the microfluidic module 205 and filtered by the microring resonator 206. In this embodiment, it is an arrayed waveguide grating, a one-dimensional photonic crystal cavity, etc., separating the frequency comb signals of different orders into several waveguide channels for output to avoid spectral aliasing between adjacent resonance orders of the microring resonator.

[0090] The optoelectronic detector array 209 is used to receive the optical signals spectrally separated by the optical filtering system and convert them into electrical signals. Each detector is arranged at the output end of each channel of the optical filtering system for collecting optical signals of a specific wavelength. Through the control of the micro thin-film resistor heater 207 by the timing control power supply module 210, each optoelectronic detector will collect optical signals of a specific wavelength within its corresponding time window. Subsequently, the collected signals of all channels are integrated in the time domain to generate a complete light intensity-time spectral line.

[0091] Each of the above-mentioned on-chip sensors is fabricated on a sapphire substrate to form an integrated chip, and the waveguide structure has a single-crystalline silicon core with a silicon nitride cladding material. The high transmittance of single-crystalline silicon in the mid-infrared band is utilized to ensure the efficient transmission of optical signals in the waveguide. At the same time, the silicon nitride cladding provides good optical isolation, reducing losses and cross-interference.

[0092] The input straight waveguide 202 serves to connect the on-chip mid-infrared frequency comb generation module 1 and the on-chip mid-infrared micro-ring resonator microfluidic spectrometer 2.

[0093] The mode spot converter 201 serves to couple and connect the pump and reference light source module 3 and the on-chip mid-infrared micro-ring resonator microfluidic spectrometer 2. At the same time, during the coupling process, the multi-dimensional adjustment frame can be finely adjusted to change the position and angle of the large numerical aperture tapered lens optical fiber to align it with the center of the inverted tapered waveguide mode spot converter, achieving the maximum coupling efficiency.

[0094] An on-chip mid-infrared micro-ring resonator microfluidic spectrometer includes a mode spot converter 201, an input straight waveguide 202, an input bent waveguide 203, an optical coupler 204, a microfluidic module 205, a micro-ring resonator 206, a micro thin-film resistor heater 207, an optical filtering system 208, an optoelectronic detector array 209, and a timing control power supply module 210 integrated on a substrate material.

[0095] The two fiber-coupled input inverted tapered mode spot converters 201 are respectively arranged at the input ends of the input straight waveguide 202 and the input bent waveguide 203. The optical coupler 204 is arranged at the output ends of the input straight waveguide 202 and the input bent waveguide 203. The microfluidic module 205 is arranged at the output end of the optical coupler 204. The micro-ring resonator 206 is arranged at the output end of the microfluidic module 205. The micro thin-film resistor heater 207 is integrated above the micro-ring resonator 206. The optical filtering system 208 is arranged at the output end of the micro-ring resonator 206, outputting multiple parallel detection channels. Each detector of the optoelectronic detector array 209 is arranged at the output end of each channel of the optical filtering system 208. The timing control power supply module 210 is arranged at both ends of the electrodes of the micro thin-film resistor heater 207.

[0096] The single-frequency mid-infrared reference light generated by the pump and reference light source module 3 enters the mode field converter 201 and is finally detected in the photodetector array 209. According to the known absolute frequency of the single-frequency light, its position in the intensity-time spectrum, the repetition frequency of the frequency comb, the carrier-envelope phase shift, and the free spectral range and resonant mode order information of the microring resonator, the absolute frequencies of all the transmitted frequency comb teeth can be calculated, thereby converting the intensity-time spectrum from the time domain to the frequency domain to obtain complete transmitted spectral information.

[0097] Example 2: Refer to Figures 2-3 As shown, the on-chip mid-infrared microring resonator microfluidic spectrometer described in Example 1 is applied to the mid-infrared integrated optical chip microfluidic multiphase detection device to obtain a multiphase detection device of the on-chip mid-infrared microring resonator microfluidic spectrometer based on absolute frequency reference that can be applied to the detection of various liquids or gases. The detection device includes an on-chip mid-infrared frequency comb generation module 1, an on-chip mid-infrared microring resonator microfluidic spectrometer 2, and a pump and reference light source module 3; among them

[0098] The output end of the on-chip mid-infrared frequency comb generation module 1 is coupled to the input end of the on-chip mid-infrared microring resonator microfluidic spectrometer 2, and is used to input the generated mid-infrared frequency comb broadband signal into the on-chip mid-infrared microring resonator microfluidic spectrometer 2 for subsequent evanescent field absorption and detection work;

[0099] The pump and reference light source module 3 provides a pump light source and a single-frequency mid-infrared reference light for the on-chip mid-infrared frequency comb generation module 1 and the on-chip mid-infrared microring resonator microfluidic spectrometer 2 respectively.

[0100] The coupling between the output end of the mid-infrared frequency comb generation module 1 and the input end of the on-chip mid-infrared microring resonator microfluidic spectrometer 2 is realized through a microcavity-coupled input straight waveguide.

[0101] The bandwidth of the frequency comb output by the mid-infrared frequency comb generation module 1 is less than the free spectral range of the optical filtering system 208 to avoid the aliasing phenomenon caused by the transmission of spectral components of different orders in the same output channel.

[0102] The pump and reference light source system 3 includes two main parts: a pump light source system 31 and a reference light source system 32, both of which include their respective driving and control devices to ensure the stable output of the two light sources.

[0103] The coupling between the pump light source system 31 and the on-chip mid-infrared frequency comb generation module 1, and the coupling between the reference light source system 32 and the on-chip mid-infrared microring resonator microfluidic spectrometer 2 are both realized by fiber optic coupling. The input ends of the on-chip mid-infrared frequency comb generation module 1 and the on-chip mid-infrared microring resonator microfluidic spectrometer 2 are respectively equipped with a fiber optic coupling input tapered mode spot converter 101 and a fiber optic coupling input tapered mode spot converter 201 for receiving pump laser and reference optical signals.

[0104] The output end of the pump light source system 31 is coupled to the input end of the on-chip mid-infrared microring resonator microfluidic spectrometer 2, which is used to generate pump laser with specific polarization characteristics and output quasi-TE mode laser that meets the optical parametric oscillation threshold power.

[0105] Specifically, the drive circuit of the pump light source system 31 consists of a signal generator 311 and a pump laser current controller 312. The drive current is input into the pump semiconductor laser 313. The optical signal emitted by the pump semiconductor laser 313 is first power-amplified by a fiber optic amplifier 314, and then the frequency of the optical signal is doubled to the required mid-infrared band by a frequency doubler 315. After making it meet the quasi-phase matching condition through a polarization controller 316, the optical signal is fiber-coupled to the fiber optic coupling input tapered mode spot converter 11 to provide sufficient pump energy for the generation of the frequency comb.

[0106] The pump semiconductor laser 313 is a near-infrared band laser with a tunable wavelength for emitting laser. Specifically, devices such as a distributed feedback laser or an external cavity semiconductor laser can be used, and its wavelength can be precisely tuned by adjusting the internal parameters (such as current) of the laser.

[0107] The fiber optic amplifier 314 has the function of increasing the optical power and is used to increase the power of the laser output by the pump semiconductor laser 313. When in use, this fiber optic amplifier can be made of a fiber doped with rare earth ions. Specifically, erbium-doped fiber or ytterbium-doped fiber can be used.

[0108] The frequency doubler 315 has the function of converting a near-infrared optical signal into a mid-infrared optical signal. When in use, this frequency doubler can be composed of a nonlinear optical crystal device, such as periodically poled lithium niobate or zinc telluride crystal.

[0109] Specifically, the reference light source system 32 is driven by a constant current source 321. The drive current is input into a single-frequency laser 322. The single-frequency laser 322 is connected to a thermoelectric cooling element 323, which is used to monitor the frequency of the optical signal output by the single-frequency laser in real time, and maintain the precise stability of the frequency by adjusting the current and temperature parameters.

[0110] The single-frequency laser 322 is a laser that generates stable single-frequency mid-infrared light, and has the function of highly stable output light frequency and extremely narrow spectral linewidth. Specifically, devices such as external cavity lasers or quantum cascade lasers are used. These lasers achieve the output of light with a single frequency through precise intracavity feedback control.

[0111] Specifically, the thermoelectric cooling element 323 controls the direction and magnitude of the current through the Peltier effect to effectively absorb or release heat, maintaining the laser within a precise temperature range to avoid frequency drift caused by temperature fluctuations.

[0112] The on-chip mid-infrared frequency comb generation module 1 includes a mode converter 101, a microcavity-coupled input straight waveguide 102, a frequency comb micro-ring resonator 103, a microcavity waveguide constant temperature module 104, a microcavity-coupled output straight waveguide 105, and a waveguide grating coupler 106.

[0113] The mode converter 101 is used to efficiently couple the pump mid-infrared light from the input optical fiber into the SOS waveguide. Using a tapered mode converter can reduce mode mismatch and improve coupling efficiency.

[0114] The microcavity-coupled input straight waveguide 102 is used to guide the coupled optical signal to the micro-ring resonator 103 to ensure the mode stability of the optical signal before entering the resonator.

[0115] The frequency comb micro-ring resonator 103 adopts a high-Q-factor ring waveguide structure based on the Silicon-on-Sapphire (SOS) platform. The cross-section of the waveguide is designed as a rectangle to achieve single-mode transmission and good anomalous dispersion characteristics.

[0116] The microcavity waveguide constant temperature module 104 is divided into three parts: a power supply, a thin-film heater, and a high-precision servo PID controller. The thin-film heater covers the waveguide and is used to heat the micro-ring resonator 103. Through the feedback control of the high-precision servo PID controller, constant temperature is achieved, enabling the generated frequency comb to achieve thermal locking under the action of thermal tuning.

[0117] Specifically, the microcavity-coupled output straight waveguide 105 is used to extract the generated frequency comb signal from the micro-ring resonator, maintaining the spectral integrity of the signal.

[0118] Specifically, the waveguide grating coupler 106 is used to efficiently couple the frequency comb signal from the on-chip mid-infrared frequency comb generation module 1 into the on-chip mid-infrared micro-ring resonator microfluidic spectrometer 2, ensuring low loss during signal transmission.

[0119] Embodiment 3: Different from the above embodiments, the mid-infrared integrated optical chip microfluidic multiphase detection device described in Embodiment 2 is applied to the inversion and detection process of the types and concentrations of multi-component liquids or gases to be measured. The application process includes:

[0120] Step 1: Adjust the laser emitted by the pump semiconductor laser 313, and adjust the optical fiber amplifier 314, frequency doubler 315, and polarization controller 316 so that the output light meets the power requirements and quasi-phase matching conditions of four-wave mixing, serving as the seed light source for frequency comb generation.

[0121] Step 2: Couple the quasi-TE light that meets the optical parametric oscillation threshold power into the inverted conical mode converter 101 through a tapered lens optical fiber with a large numerical aperture. Adjust the coupling lens optical fiber to align it with the center of the tapered mode converter.

[0122] Step 3: Generate a frequency comb signal. By adjusting the constant temperature module, make the generated frequency comb complete thermal locking, and directly input it into the spectrometer system through the input straight waveguide 202.

[0123] Step 4: Adjust the laser emitted by the single-frequency laser 322, output it through a tapered lens optical fiber with a large numerical aperture, and adjust the multi-dimensional adjustment frame to change the position and angle of the tapered lens optical fiber with a large numerical aperture to align it with the center of the inverted conical mode spot converter 201 to optimize the coupling efficiency.

[0124] Step 5: According to the relationship between the heater drive current and the change value of the micro-ring thermal tuning resonance frequency measured in advance, set the current magnitude of the timing control power supply module 210 to ensure that the thermal tuning range covers the working range of the micro-ring.

[0125] Step 6: Obtain a complete intensity-time spectrum line at the output end of the photodetector array 209, calculate it using the absolute frequency reference of the single-frequency reference light, and convert this spectrum line into a complete frequency comb spectrogram.

[0126] Step 7: Introduce the liquid or gas to be measured into the microfluidic module 205, and precisely control its flow rate and velocity.

[0127] Step 8: Obtain a complete transmission spectrum after evanescent field absorption by the liquid or gas to be measured through calculation at the output end of the photodetector array 209.

[0128] Step 9: Compare and analyze the obtained transmission spectrum with the pre-calibrated frequency comb spectrogram and the standard absorption spectra of known compounds in the NIST spectral database, and finally determine information such as the types and concentrations of the multi-component liquid or gas to be measured through an inversion algorithm.

Claims

1. A mid-infrared micro-ring resonator microfluidic spectrometer on a chip, characterized in that Including integrated on a substrate material: Two mode spot converters (201), respectively arranged at the input ends of the input straight waveguide (202) and the input bent waveguide (203) to receive optical signals from different light sources or modules and couple them; An optical coupler (204), respectively connected to the output ends of the input straight waveguide (202) and the input bent waveguide (203), for coupling the optical field coupled into the input straight waveguide (202) and the single-frequency light coupled into the input bent waveguide (203), and bundling them into a straight waveguide of the micro-ring resonator (206); A microfluidic module (205), arranged at the output end of the optical coupler (204), for controlling the flow rate and velocity of the liquid or gas to be measured. The two ends of the microfluidic module (205) are respectively connected to a straight waveguide of the micro-ring resonator (206), and the evanescent field is used to realize the selective absorption of the input spectral components by the liquid to be measured; A micro-ring resonator (206), formed by coupling a ring waveguide and two straight waveguides, and selectively filtering the input optical signal by tuning the refractive index to change the resonant wavelength and the free spectral range; A micro thin-film resistor heater (207), integrated on the micro-ring resonator (206), for heating the micro-ring resonator (206) to change the refractive index of the micro-ring resonator (206); A timing control power supply module (210), connected to the micro thin-film resistor heater (207), for providing heating power with timing control to control the heating process of the micro thin-film resistor heater (207); An optical filtering system (208), connected to the other straight waveguide of the micro-ring resonator (206), for separating the broadband spectral components absorbed by the microfluidic module (205) and filtered by the micro-ring resonator (206) into frequency comb signals of different orders; An optoelectronic detector array (209), composed of a plurality of optoelectronic detectors arranged at the output ends of each channel of the optical filtering system (208), for receiving the optical signals split by the optical filtering system (208) and converting them into electrical signals.

2. The on-chip mid-infrared micro-ring resonator microfluidic spectrometer according to claim 1, wherein The transmission spectrum of the optical filtering system (208) matches the operating wavelength range of the micro-ring resonator (206), and the maximum tunable range of the resonant wavelength of the micro-ring resonator (206) is equal to the full width at half maximum value of a single transmission peak of the optical filtering system (208).

3. The on-chip mid-infrared microring resonator microfluidic spectrometer according to claim 1, characterized in that, The microfluidic module (205) includes a microfluidic chip and a controllable electroosmotic micropump. The electroosmotic micropump drives the fluid to flow pulsation-free along a specified path by applying an electric field to achieve control.

4. A mid-infrared integrated optical chip microfluidic multiphase detection device, characterized in that, Including the on-chip mid-infrared micro-ring resonator microfluidic spectrometer according to any one of claims 1 to 3.

5. The mid-infrared integrated optical chip microfluidic multiphase detection device according to claim 4, characterized in that Further including: The pump and reference light source module (3) is composed of a pump light source system (31) and a reference light source system (32). Among them, the pump light source system (31) is used to provide pump light in the mid-infrared band as a pump source; the reference light source system (32) is used to provide a mid-infrared single-frequency continuous-wave laser as an absolute frequency reference light and couple it into the on-chip mid-infrared micro-ring resonator microfluidic spectrometer. The on-chip mid-infrared frequency comb generation module (1) is used to receive the pump source provided by the pump light source system (31) and generate a broadband frequency comb, which is coupled into the on-chip mid-infrared micro-ring resonator microfluidic spectrometer.

6. The mid-infrared integrated optical chip microfluidic multiphase detection device according to claim 5, wherein The on-chip mid-infrared frequency comb generation module (1) includes a mode converter (101) for coupling the pump mid-infrared light output by the pump and reference light source module (3) from the input optical fiber into the microcavity coupling input straight waveguide (102); the microcavity coupling input straight waveguide (102) is connected to the output end of the mode converter (101) and is used to guide the coupled optical signal to the frequency comb micro-ring resonator (103); the frequency comb micro-ring resonator (103) is used to generate and maintain a standing wave field in the mid-infrared band and generate a broadband frequency comb by using the Kerr effect; a microcavity waveguide constant temperature module (104) for realizing constant temperature control and thermally locking the generated frequency comb in a thermal tuning manner; the microcavity coupling output straight waveguide (105) is connected to the output end of the frequency comb micro-ring resonator (103) and is used to extract the generated frequency comb signal from the micro-ring resonator; a waveguide grating coupler (106) is connected to the output end of the microcavity coupling output straight waveguide (105) and is used to couple the frequency comb signal into the on-chip mid-infrared micro-ring resonator microfluidic spectrometer.

7. The mid-infrared integrated optical chip microfluidic multiphase detection device according to claim 5, characterized in that, The pump light source system (31) includes a signal generator (311), a pump laser current controller (312), a pump semiconductor laser (313), an optical fiber amplifier (314), a frequency doubler (315) and a polarization controller (316); among them, the pump semiconductor laser (313) is a wavelength-tunable near-infrared band laser, and the optical signal emitted by it is power-amplified by the optical fiber amplifier (314), and then the frequency of the optical signal is doubled to the required mid-infrared band by the frequency doubler (315), and is adjusted by the polarization controller (316) to meet the quasi-phase matching condition; the reference light source system (32) includes a constant current source (321), a single-frequency laser (322) and a thermoelectric cooling element (323), where the single-frequency laser (322) is connected to the thermoelectric cooling element (323) and is used to monitor and stabilize the frequency of the optical signal output by the single-frequency laser (322) in real time.

8. A method for detecting and inverting the types and concentrations of multi-component liquid or gas to be measured using the mid-infrared integrated optical chip microfluidic multiphase detection device according to any one of claims 4-7, characterized in that, It includes the following steps: S1. Adjust the alignment of the input and output coupling lens optical fibers in the pump light source system and the reference light source system; S2. Set the drive current of the laser so that its output wavelength sweeps across a certain resonance peak of the microcavity; S3. Adjust the heating power of the heater array from low to high, use the photodetector array to collect signals to reconstruct the frequency comb spectrum, and observe the repetition frequency of the output frequency comb. S3 introduces the gas or liquid to be measured into the microfluidic module at a certain flow rate and flow volume; S4. According to the relationship between the heater drive current and the change value of the micro-ring thermal tuning resonance frequency measured in advance, the heating power of the heater array is regulated, and the photodetector array is used to collect signals to reconstruct the transmission spectrum; S5. The type and concentration of the gas or liquid are inverted by comparing with the standard database.

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