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CN-121499393-B - Optical cavity enhanced mid-infrared thermal vibration measurement system and method

CN121499393BCN 121499393 BCN121499393 BCN 121499393BCN-121499393-B

Abstract

The application provides an optical cavity enhanced mid-infrared photothermal vibration measurement system and method, relates to the field of material photothermal vibration spectrum detection, and aims to improve detection accuracy and sensitivity. The measuring system comprises an optical cavity enhanced substrate, a mid-infrared laser, a laser vibrometer and a lock-in amplifier. The optical cavity enhancement substrate comprises a substrate and an asymmetric Fabry-Perot resonant cavity, wherein the asymmetric Fabry-Perot resonant cavity comprises a reflecting layer, an intermediate medium layer and an object layer to be detected which are sequentially laminated on the substrate. The middle infrared laser acts on the object layer to be detected, so that the object layer to be detected generates a photo-thermal vibration signal. The laser vibration meter detects the photo-thermal vibration signal and converts the photo-thermal vibration signal into a detection electric signal. The phase-locked amplifier extracts the detection electric signal to determine the photo-thermal vibration spectrum of the object layer to be detected. The ratio of the thickness of the intermediate medium layer to the thickness of the object layer to be detected is 0.8-10. The refractive index of the material of the object layer to be detected is smaller than that of the material of the intermediate medium layer and larger than that of air.

Inventors

  • YU XIAOHAN
  • DENG BIWEI
  • JING ZE
  • XU KUN

Assignees

  • 甬江实验室

Dates

Publication Date
20260505
Application Date
20260114

Claims (12)

  1. 1. An optical cavity enhanced mid-infrared thermal vibration measurement system, comprising: the optical cavity enhancement substrate comprises a substrate, and a reflecting layer, an intermediate medium layer and a to-be-detected object layer which are sequentially laminated on the substrate, wherein the reflecting layer, the intermediate medium layer and the to-be-detected object layer form an asymmetric Fabry-Perot resonant cavity; The middle infrared laser is configured to act on the object layer to be detected, so that the object layer to be detected generates a photo-thermal vibration signal; The laser vibration meter is configured to transmit detection light to the object layer to be detected, generate reflected light under the action of the photo-thermal vibration signal, and convert beat frequency signals generated by interference of the reflected light and the detection light into detection electric signals, wherein the reflected light generates frequency shift compared with the detection light; the lock-in amplifier is electrically connected with the laser vibration meter and is configured to determine the photo-thermal vibration spectrum of the object layer to be detected according to the detection electric signal; the ratio of the thickness of the intermediate medium layer to the thickness of the object layer to be detected is 0.8-10 along the direction perpendicular to the substrate, the thickness of the intermediate medium layer is 400-1000 nm, and the thickness of the object layer to be detected is 100-500 nm; the refractive index of the material of the object layer to be detected is smaller than that of the material of the intermediate medium layer and larger than that of air, the material of the object layer to be detected comprises at least one of protein films, cells, viruses, organic matter films and organic matter microspheres, and the material of the intermediate medium layer comprises aluminum oxide or silicon nitride.
  2. 2. The measurement system of claim 1, wherein the extended surface of the object layer to be inspected, the extended surface of the intermediate dielectric layer, and the extended surface of the reflective layer are all parallel to the extended surface of the substrate.
  3. 3. The measurement system of claim 1, wherein a thermal conductivity of a material of the intermediate dielectric layer is less than a thermal conductivity of a material of the substrate.
  4. 4. The measurement system of claim 1, wherein the laser vibrometer comprises a laser doppler vibrometer having a sensitivity of greater than or equal to 1pm.
  5. 5. The measurement system according to claim 1, wherein the thickness of the intermediate medium layer is 560nm when the thickness of the object layer to be detected is 300nm in a direction perpendicular to the substrate.
  6. 6. The measurement system according to claim 1, wherein the absorbable wavelength of the material of the layer of the object to be detected is in the range of 5 μm to 8 μm.
  7. 7. The measurement system of claim 1, wherein a ratio of a thickness of the intermediate dielectric layer to a thickness of the reflective layer in a direction perpendicular to the substrate is in a range of 0.8-20.
  8. 8. The measurement system of claim 1, further comprising a first dichroic mirror, a second dichroic mirror, and a reflective objective; The measuring system further comprises a first light path, a second light path and a third light path, wherein the first light path comprises the second dichroic mirror and the reflective objective, the second light path comprises the first dichroic mirror, the second dichroic mirror and the reflective objective, and the third light path comprises the first dichroic mirror, the second dichroic mirror and the reflective objective; The first optical path is configured to transmit the mid-infrared laser light to the object layer to be detected through the second dichroic mirror and the reflective objective lens in sequence, the second optical path is configured to transmit the detection light to the object layer to be detected through the first dichroic mirror, the second dichroic mirror and the reflective objective lens in sequence, and the third optical path is configured to calibrate the first optical path and the second optical path.
  9. 9. The optical cavity enhanced mid-infrared thermal vibration measurement method is characterized by comprising the following steps of: Providing an optical cavity enhancement substrate, wherein the optical cavity enhancement substrate comprises a substrate, and a reflecting layer, an intermediate medium layer and a to-be-detected object layer which are sequentially laminated on the substrate, wherein the reflecting layer, the intermediate medium layer and the to-be-detected object layer form an asymmetric Fabry-Perot resonant cavity; the middle infrared laser acts on the object layer to be detected, so that the object layer to be detected generates a photo-thermal vibration signal; Transmitting detection light to the object layer to be detected, generating reflected light under the action of the photo-thermal vibration signal, and converting beat frequency signals generated by interference of the reflected light and the detection light into detection electric signals, wherein the reflected light generates frequency shift compared with the detection light; determining a photo-thermal vibration spectrum of the object layer to be detected according to the detection electric signal; the ratio of the thickness of the intermediate medium layer to the thickness of the object layer to be detected is 0.8-10 along the direction perpendicular to the substrate, the thickness of the intermediate medium layer is 400-1000 nm, and the thickness of the object layer to be detected is 100-500 nm; the refractive index of the material of the object layer to be detected is smaller than that of the material of the intermediate medium layer and larger than that of air, the material of the object layer to be detected comprises at least one of protein films, cells, viruses, organic matter films and organic matter microspheres, and the material of the intermediate medium layer comprises aluminum oxide or silicon nitride.
  10. 10. The measurement method according to claim 9, wherein causing the object layer to be detected to generate a photothermal vibration signal comprises: and enabling the middle infrared laser with the wavelength range of 5-8 mu m to act on the object layer to be detected, so that the object layer to be detected generates the photo-thermal vibration signal.
  11. 11. The measurement method according to claim 9, wherein the range of incidence angle of the mid-infrared laser is 0 ° to 20 °; The incidence angle is an included angle between the direction in which the mid-infrared laser is located and the direction perpendicular to the substrate.
  12. 12. The measurement method according to claim 9, wherein the variation range of the electric field of the object layer to be detected is 5 x 10 4 V/m~10 5 V/m, the variation range of the temperature field is 1k to 2k, and the variation range of the displacement field is 20pm to 30pm.

Description

Optical cavity enhanced mid-infrared thermal vibration measurement system and method Technical Field The application relates to the field of material photo-thermal vibration spectrum detection, in particular to an optical cavity enhanced mid-infrared photo-thermal vibration measurement system and method. Background The photo-thermal vibration spectrum detection technology is a molecular vibration spectrum analysis method based on photo-thermal effect, combines the vibration spectrum technology with the photo-thermal effect, and obtains vibration information of molecules by analyzing local temperature change caused by light of a specific frequency absorbed by a sample. The signal generated by the photo-thermal effect is usually relatively weak by the photo-thermal spectrum detection technology commonly used at present, and especially when the absorption capacity of a detection sample is low, the weak signal is difficult to capture by the measurement equipment. In addition, the weak signal is more sensitive to factors such as power fluctuation of the excitation light source and environmental temperature fluctuation, so that the detection accuracy and sensitivity are reduced. Disclosure of Invention The application provides an optical cavity enhanced mid-infrared thermal vibration measurement system and method, and aims to improve detection accuracy and sensitivity. In order to achieve the above object, the embodiments of the present application provide the following technical solutions: In one aspect, an optical cavity enhanced mid-infrared thermal vibration measurement system is provided that includes an optical cavity enhanced substrate, a mid-infrared laser, a laser vibrometer, and a lock-in amplifier. The optical cavity enhancement substrate comprises a substrate, and a reflecting layer, an intermediate medium layer and a layer of an object to be detected which are sequentially laminated on the substrate. The reflecting layer, the intermediate medium layer and the object layer to be detected form an asymmetric Fabry-Perot resonant cavity. The middle infrared laser is configured to act on the object layer to be detected, so that the object layer to be detected generates a photo-thermal vibration signal. The laser vibration meter is configured to transmit detection light to the object layer to be detected, generate reflected light under the action of a photo-thermal vibration signal, and convert a beat signal generated by interference of the reflected light and the detection light into a detection electric signal, wherein the reflected light generates a frequency shift compared with the detection light. The phase-locked amplifier is electrically connected with the laser vibration meter and is configured to determine the photo-thermal vibration spectrum of the object layer to be detected according to the detection electric signal. The ratio of the thickness of the intermediate dielectric layer to the thickness of the object layer to be detected is 0.8-10 along the direction perpendicular to the substrate. The refractive index of the material of the object layer to be detected is smaller than that of the material of the intermediate medium layer and larger than that of air. In an embodiment of the application, the optical cavity enhanced mid-infrared thermal vibration measurement system comprises an optical cavity enhanced substrate, a mid-infrared laser, a laser vibration meter and a lock-in amplifier. The optical cavity enhancement substrate comprises a substrate, and a reflecting layer, an intermediate medium layer and a layer of an object to be detected which are sequentially laminated on the substrate. The reflecting layer, the intermediate medium layer and the object layer to be detected form an asymmetric Fabry-Perot resonant cavity. It can be understood that the asymmetric fabry-perot resonant cavity is composed of the object layer to be detected and the reflecting layer, and the intermediate medium layer is clamped, so that non-target wavelength can be restrained through destructive interference, and the target wavelength is enhanced through constructive interference, so that a low-noise optical cavity is formed, and the accuracy of measurement of the measurement system is improved. And the middle infrared laser acts on the object layer to be detected, so that the object layer to be detected generates a photo-thermal vibration signal. The laser vibration meter transmits detection light to the object layer to be detected, generates reflected light under the action of a photo-thermal vibration signal, and converts beat frequency signals generated by interference of the reflected light and the detection light into detection electric signals. And the phase-locked amplifier is electrically connected with the laser vibration meter, and can determine the photo-thermal vibration spectrum of the object layer to be detected according to the beat frequency signal. The ratio of the thickness of the intermediate