CN102944519A - Optical system and method for measuring thermal physical property parameters of solid - Google Patents
Optical system and method for measuring thermal physical property parameters of solid Download PDFInfo
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Abstract
The invention provides an optical system and a method for measuring thermal physical property parameters of a solid. The optical system comprises a heating laser production assembly, a detection laser production assembly, a beam combining element, a beam split element, a heating laser receiving assembly, a sample test assembly and a detection laser receiving assembly. The method uses a signal modulating photo-thermal reflection method and belongs to a frequency domain method, and compared with time domain methods of ultrashort pulse laser pumping detection methods and the like, the method has the advantages that mechanical moving components are absent, the measuring system is relatively simple, and light path adjustment is more convenient.
Description
Technical Field
The invention relates to a photothermal reflection measurement technology utilizing periodic modulation heating and continuous laser detection, in particular to an optical system and a method for measuring thermophysical parameters of a solid.
Background
Thin film materials are widely used in the fields of microelectronics, optoelectronics, micro-fabrication and the like, and these micro/nano devices generate extremely high heat flux density during operation, and the heat accumulation directly affects the operating efficiency and reliability of the devices. The solution to the problem of heat dissipation of the micro/nano device is very urgent, and accurate characterization of the thermal physical properties, especially the thermal conductivity, the interface thermal resistance and the like of the thin film material composing the micro/nano device is required so as to reveal the thermal transport mechanism of the micro/nano device. The 3 omega method is a commonly used method for measuring the thermophysical properties of thin film materials, but the method needs to weld metal sheets/wires on a sample to be measured, and belongs to a destructive detection technology.
The ultrashort pulse laser pumping detection method is a new solid thermophysical parameter measuring method. FIG. 1 is a schematic optical path diagram of an optical system for measuring thermophysical parameters of a solid in the prior art. As shown in fig. 1, the optical system includes: the laser 1 outputs pulse laser; the first wave plate 2 (half wave plate) rotates the polarization direction of the laser light; the first light splitting device 3 splits the laser beam into two beams whose polarization directions are perpendicular to each other; the electro-optical modulator 4 modulates the laser beam; the electro-optical modulator driver 5 sends a modulation signal to the electro-optical modulator 4; the first reflecting mirror 6 receives and reflects the laser beam; the laser beam passes through a first focusing lens 7, a frequency doubling crystal 8 and a second focusing lens 9 to generate second harmonic; the first filter 10 filters out incoherent light; the beam expander 11 expands the diameter of the laser beam; the second mirror 12 receives and reflects the laser beam; the electric control displacement platform 14 moves back and forth; the laser beam is reflected by the parallel light reflector 13 and then passes through a second wave plate 15 (a half wave plate), and the polarization direction of the laser beam rotates; the second beam splitter 16 splits the laser beam into two beams whose polarization directions are perpendicular to each other; the laser beam vertically enters the surface of the sample through the third wave plate 17 (quarter wave plate), and returns to pass through the third wave plate 17 again in the original path, so that the polarization direction is changed by 90 degrees; the cold light mirror 18 combines the laser beams with different wavelengths; the focusing lens 19 irradiates laser light on the surface of the sample on the fixed adjusting frame 20; the electro-optical detector 23 receives the laser beam transmitted through the second filter 21 and the third focusing lens 22; the signal of the electro-optical detector 23 is input to a filter amplifier 24. The pumping light and the detection light use femtosecond pulse lasers with different wavelengths, the femtosecond pulse lasers are combined into a laser beam through a cold light mirror, and an optical filter with high selective permeability is used for filtering the pumping light after frequency multiplication before the pumping light and the detection light reach a detector, so that the interference of the pumping light on signals is avoided, and accurate and efficient measurement is realized; the filter amplifier can effectively filter the influence of high-frequency harmonic waves and effectively improve the accuracy of signals.
Different moving distances of the electric control displacement platform correspond to different delay times between the detection light and the pumping light, an output signal of the filter amplifier is compared with a modulation signal given by the driver of the electro-optical modulator to obtain a phase difference signal, and the phase difference signal under different delay times is measurement data obtained by experiments.
However, for the optical path system for measuring the thermophysical parameters of the solid shown in fig. 1, the electrically controlled displacement platform belongs to a mechanical motion part, and the precise control is difficult; and the frequency doubling module consisting of the first focusing lens, the frequency doubling crystal and the second focusing lens has difficult collinear focusing and low frequency doubling efficiency.
Disclosure of Invention
Technical problem to be solved
In order to solve one or more of the problems, the invention provides an optical system and a method for measuring the thermophysical property parameters of the solid, which are accurately controlled and conveniently adjusted.
(II) technical scheme
According to one aspect of the present invention, an optical system for measuring a thermophysical parameter of a solid is provided. The system comprises: the device comprises a heating laser generating assembly, a detection laser generating assembly, a beam combining element, a light splitting element, a heating laser receiving assembly, a sample testing assembly and a detection laser receiving assembly; wherein, the heating laser generating assembly generates heating laser with continuous polarization and frequency modulation, and the detection laser generating assembly generates detection laser with continuous polarization; the heating laser and the detection laser are combined into a combined laser positioned on the plane A after passing through a beam combining element; the beam-combined laser is incident to the light splitting element, the component with the polarization direction in the plane A is transmitted to the sample testing component, and the component with the polarization direction vertical to the horizontal plane is reflected to the heating laser receiving component; the beam combination light component with the polarization direction in the plane A is irradiated to the surface of the tested sample after passing through the sample testing assembly; heating the detected sample by the heating laser in the beam combination optical component with the polarization direction in the plane A, and modulating the detection laser by the heated detected sample; the combined laser of the heating laser reflected by the surface of the tested sample and the modulated detection laser passes through the sample testing component again and then is reflected to the detection laser receiving component by the light splitting element; the detection laser receiving assembly filters out heating laser components in the incident combined laser to obtain a detection laser signal; and the heating laser receiving assembly filters out detection laser components in the incident combined laser to obtain a signal of the heating laser.
According to another aspect of the present invention, there is also provided a method for measuring a thermophysical parameter of a solid by using the optical system described above, including: step A, acquiring a detection laser signal generated by a detection laser receiving assembly and a heating laser signal generated by a heating laser receiving assembly under different heating laser modulation frequencies by using an optical system, wherein the detection laser signal and the heating laser signal both comprise power information and phase information; b, performing phase difference processing on the detection laser signal and the heating laser signal under different heating laser modulation frequencies to obtain a phase difference experimental value; step C, assigning an initial value to the thermophysical property parameter of the solid to be fitted; step D, calculating a phase difference theoretical value under the frequency corresponding to the phase difference experimental value according to a theoretical model formula under different heating laser modulation frequencies; step E, performing least square calculation on the phase difference experimental values and the corresponding phase difference theoretical values under all the heating laser modulation frequencies, wherein the least square calculation value is used as a current iteration result; step F, recording a thermal conductivity value and an interface thermal conductivity value corresponding to the current iteration result; g, judging whether the result of the current iteration is smaller than the result of the previous iteration, if so, executing the step H, otherwise, executing the step I; step H, taking the solid thermophysical property parameter value corresponding to the iteration result as change detection output data, and executing step J; step I, taking the solid thermophysical property parameter value corresponding to the previous iteration result as change detection output data, and executing step J; step J, judging whether the iteration result of 3 times is less than the control precision, if so, executing the step K, otherwise, executing the step L; step K, stopping iteration, outputting the solid thermophysical property parameter value obtained in the step H or the step I, and ending the process; and step L, increasing or decreasing the solid thermophysical property parameter value obtained in the step H or the step I according to a preset step length, determining a numerical value change path by a preset optimization function, and executing the step D.
(III) advantageous effects
According to the technical scheme, the optical system and the method for measuring the thermophysical parameters of the solid have the following beneficial effects: the photothermal reflection method using signal modulation belongs to a frequency domain method, and compared with the time domain method such as an ultrashort pulse laser pumping detection method, the photothermal reflection method has the advantages of no mechanical moving part, relatively simple measuring system and more convenient light path adjustment.
Drawings
FIG. 1 is a schematic optical path diagram of an optical system for measuring thermophysical parameters of a solid in the prior art;
FIG. 2 is a schematic optical path diagram of an optical system for measuring a thermophysical parameter of a solid according to an embodiment of the invention;
FIG. 3 is a flow chart of a method of measuring a thermophysical parameter of a solid according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
It should be noted that in the drawings or description, the same drawing reference numerals are used for similar or identical parts. Implementations not depicted or described in the drawings are of a form known to those of ordinary skill in the art. Additionally, while exemplifications of parameters including particular values may be provided herein, it is to be understood that the parameters need not be exactly equal to the respective values, but may be approximated to the respective values within acceptable error margins or design constraints. In addition, directional terms such as "upper", "lower", "front", "rear", "left", "right", and the like, referred to in the following embodiments, are directions only referring to the drawings. Accordingly, the directional terminology is used for purposes of illustration and is in no way limiting.
Referring to fig. 1, a drawing of a prior art optical system for measuring thermophysical properties of a solid is shown, wherein the reference numbers are for reference and are not included in the present invention. To facilitate understanding of the present invention, the main elements involved in the present invention will be first numbered by those skilled in the art, and will be specifically shown as follows:
10-heating the laser assembly; 20-a detection laser assembly;
30-a beam combining element; 40-a light splitting element;
50-heating the laser receiving assembly; 60-a sample testing assembly;
70-a sample holding element; 80-probe laser receiving assembly;
11-a signal modulator; 12-a first laser;
13-a first wave plate; 14-a first mirror;
21-a second laser; 22-a second wave plate;
23-a second mirror; 51-a first filter;
52-a first photodetector; 61-a third wave plate;
62-objective lens; 81-a focusing lens;
82-a second optical filter; 83-second photodetector.
In one exemplary embodiment of the present invention, an optical system for measuring a thermophysical parameter of a solid is provided. As shown in fig. 2, the system includes: a heating laser generating assembly 10, a detection laser generating assembly 20, a beam combining element 30, a light splitting element 40, a heating laser receiving assembly 50, a sample testing assembly 60, a sample fixing element 70, a detection laser receiving assembly 80 and a data processing assembly (not shown). The heating laser generating assembly 10 generates continuously polarized heating laser with frequency modulation, and the detection laser generating assembly 20 generates continuously polarized detection laser; the heating laser and the detection laser are combined into a combined beam laser which is positioned on the horizontal plane after passing through the beam combining element 30; the combined laser beam is incident on the light splitting element 40, the component with the polarization direction in the horizontal plane is transmitted to the sample testing assembly 60, and the component with the polarization direction vertical to the horizontal plane is reflected to the heating laser receiving assembly 50; the beam-combining light component with the polarization direction on the horizontal plane irradiates the surface of the tested sample on the sample fixing element 70 after passing through the sample testing component 60, the tested sample is heated by the heating laser, and the heated tested sample generates a modulation effect on the detection laser; the combined laser of the heating laser reflected by the surface of the tested sample on the sample fixing element 70 and the modulated detection laser is reflected to the detection laser receiving assembly 80 by the light splitting element 40 after passing through the sample testing assembly 60 again; the detection laser receiving assembly 80 filters the heating laser component in the incident heating laser and the detection laser to obtain a signal of the detection laser; the heating laser receiving assembly 50 filters out the detection laser components in the incident heating laser and detection laser to obtain a signal of the heating laser; the data processing component reversely deduces the thermophysical property parameters of the tested sample according to a theoretical model by using the modulation frequency of the heating laser, the detection laser signal generated by the detection laser receiving component 50 and the signal of the heating laser generated by the heating laser receiving component 80.
Each component/element is described in detail below.
Heating laser generating assembly 10
The heating laser generating assembly 10 is used to generate a signal modulated continuously polarized heating laser. As shown in fig. 1, the heating laser generating assembly includes: the signal modulator 11, which can be a digital signal generator, is used for modulating the first laser, the modulation frequency of the signal modulator 11 is controlled by an external computer, the modulation frequency range is determined by the signal modulator 11 and the data processing component, and can be 50kHz to 20 MHz; a first laser 12, which is a semiconductor laser, and is configured to output continuous polarized laser with a wavelength of 830nm under the modulation of the signal modulator 11, and the power of the continuous polarized laser is 170 mW; a first wave plate 13, which is a half wave plate, for adjusting the ratio of the horizontal polarization component and the vertical polarization component of the continuous polarization laser output by the first laser 12; the first laser mirror 14 has a reflectivity of more than 99%, and a reflection surface thereof forms an angle of 45 ° with the heating laser transmitted through the first wave plate 13, and is configured to deflect the incident add laser by 90 ° and then to enter the beam combining element 30 at an angle of 45 °.
Detection laser generation assembly 20
The detection laser generation assembly 20 is used to generate a continuously polarized detection laser having a wavelength different from the heating laser and a power much less than the heating laser power. As shown in fig. 1, the heating laser generating assembly 20 includes: the second laser 21 is a semiconductor laser and is used for outputting detection laser with the wavelength of 635nm, and the power of the detection laser is 6 mW; a second wave plate 22, which is a half wave plate, for adjusting the ratio of the horizontal polarization component and the vertical polarization component of the continuous polarization laser output by the second laser 21; the reflectivity of the second laser reflector 23 is greater than 99%, and the reflecting surface of the second laser reflector forms an angle of 45 ° with the detection laser transmitted through the second wave plate 22, and is used for deflecting the incident detection laser by 90 ° and then entering the beam combining element 30 at an angle of 45 °.
Beam combining element 30
The beam combining element 30 is a cold light mirror and transmits heating laser with the wavelength of 830nm incident at an angle of 45 degrees with the plane where the beam combining element is located; the detection laser with the wavelength of 635nm incident at an angle of 45 degrees with the plane where the laser is located is totally reflected, so that the heating laser and the detection laser are combined, and collinear heating detection is realized.
Light splitting element 40
The light splitting element 40 is a light splitting prism. Through the beam splitting prism, in the combined heating laser and detection laser, the components with the polarization directions on the horizontal plane are transmitted to the sample testing component, and the components with the polarization directions vertical to the horizontal plane are reflected to the heating laser receiving component; the heating laser light and the detection laser light reflected by the sample surface are reflected to the detection laser receiving assembly.
Heating laser receiver assembly 50
And the heating laser receiving assembly 50 is used for filtering out the detection laser components in the incident heating laser and the detection laser to obtain a signal of the heating laser. The heating laser receiving assembly 50 includes: a first filter 51 and a first photodetector 52. Wherein:
a first filter 51 for filtering out the detection laser component in the incident combined beam laser, wherein the transmittance of the first filter to the detection laser with the wavelength of 635nm is 10-7To 10-9。
The first photodetector 52 is used to detect the heating laser signal in the combined laser beam, and may be a high speed PIN diode, an avalanche diode, a photomultiplier, or a charge coupled device, with a response time of less than 10 ns. Wherein, the signal can include: power (amplitude), phase, etc.
The combined laser of the heating laser and the detection laser transmitted by the spectroscopic element 40 passes through the sample test assembly 60 and then reacts with the surface of the sample to be tested on the sample fixing element, and the heating laser and the detection laser reflected by the surface of the sample are re-incident to the spectroscopic element 40 through the sample test assembly 60.
The sample testing assembly 60 includes: a quarter-wave plate 61 and an objective lens 62. The objective lens 62 is an achromatic objective lens with a magnification of 100 times and a focal length of 2 mm. After the incident combined laser beam passes through the quarter-wave plate 61 twice, the polarization direction changes by 90 °.
Sample holding member 70
The sample fixing element 70 is a fixing and adjusting frame for adjusting and fixing the orientation of the tested sample, so as to ensure that the combined laser beam is vertically incident on the surface of the tested sample, and the reflected combined laser beam returns to the original path and is incident on the sample testing component 60.
Heating the detected sample by the heating laser, and modulating the detection laser by the heated detected sample; the combined laser beam of the heating laser beam reflected by the surface of the sample to be tested on the sample fixing element 70 and the modulated detection laser beam is reflected by the beam splitting element 40 to the detection laser receiving assembly 80 after passing through the sample testing assembly 60 again.
Detection laser receiving assembly 80
And the detection laser receiving assembly 80 is used for filtering out the heating laser components in the incident heating laser and the detection laser to obtain a signal of the detection laser. The detection laser receiving assembly 80 includes: a focusing lens 81, a second filter 82 and a second photodetector 83. Wherein:
the focusing lens 81 is used for focusing the incident combined laser beam. The focal length of the focusing lens 81 may be 10mm to 300mm, depending on the requirements.
A second filter 82 for filtering out heating laser component in the focused combined beam laser, wherein the transmittance of the second filter to the heating laser with 830nm wavelength is 10-7To 10-9。
And a second photodetector 83 for detecting the signal of the detection laser in the combined laser, which may be a high-speed PIN diode, an avalanche diode, a photomultiplier, or a charge-coupled device, with a response time of less than 10 ns. Wherein, the signal can include: power (amplitude), phase, etc.
And calculating to obtain the thermophysical property parameters of the solid by using the signals obtained by the heating laser receiving assembly and the detection laser receiving assembly. Compared with time domain methods such as an ultrashort pulse laser pumping detection method and the like, the optical system for measuring the thermophysical parameters of the solid has no mechanical moving part, the measuring system is relatively simple, and the light path is more convenient to adjust.
Based on the optical system, the invention also provides a method for measuring the thermophysical parameters of the solid, which is to fit the thermophysical parameters of the tested sample, including thermal conductivity, interface thermal conductivity between materials and the like, according to the phase difference between the signal of the detection laser generated by the detection laser receiving component and the signal of the heating laser generated by the heating laser receiving component under different angular frequencies of the signal modulator.
In an exemplary embodiment of the present invention, as shown in fig. 3, the method includes:
step A, acquiring a detection laser signal generated by a detection laser receiving assembly and a signal generated by a heating laser receiving assembly under different heating laser modulation frequencies by using the optical system, wherein the detection laser signal and the heating laser signal both contain power information and phase information;
b, performing phase difference processing on the detection laser signal and the heating laser signal under different heating laser modulation frequencies to obtain a phase difference experimental value;
step C, giving initial values to the thermal conductivity to be fitted and the interface thermal conductivity;
step D, calculating a phase difference theoretical value under the frequency corresponding to the phase difference experimental value according to a theoretical model formula under different heating laser modulation frequencies;
wherein Q is0、Q1Power of heating laser and detection laser, gamma is light reflection coefficient of tested sample surface, l is integral variable, R is0、R1The beam waist radii when the heating laser and the detection laser are generated are respectively, and omega is the angular frequency of the modulation signal; phi is a phase difference theoretical value between the detection laser received by the detection laser receiving assembly and the heating laser received by the heating laser receiving assembly. C. Material thermophysical property parameter matrix with D of 2 x 2 The respective parameters of (a):
in the case of a certain layer, the layer is,
in the case of an interface, the interface is,
wherein,
rho, c, k and d are respectively the density, mass heat capacity, heat conductivity and thickness of a certain layer, G is interface heat conductivity, i is an imaginary number unit, and j is the number of layers counted from the incident end of the laser.
Further, with respect to specific meanings of the above-mentioned thermophysical parameters of the material, see reference 1 [ j.zhuet al.j.appl.phys.108, 094315(2010) ].
Step E, performing least square calculation on the phase difference experimental values and the corresponding phase difference theoretical values under all the heating laser modulation frequencies, wherein the least square calculation value is used as a current iteration result;
step F, recording a thermal conductivity value and an interface thermal conductivity value corresponding to the current iteration result, namely current optimal data;
g, judging whether the result of the current iteration is smaller than the result of the previous iteration, if so, executing the step H, otherwise, executing the step I;
step H, taking the thermal conductivity value and the interface thermal conductivity value corresponding to the iteration result as change detection output data, and executing step J;
step I, taking a thermal conductivity value and an interface thermal conductivity value corresponding to the previous iteration result as change detection output data, and executing step J;
step J, judging whether the iteration result for 3 times is less than the control precision (such as 10)-6) If yes, executing the step K, otherwise, executing the step L;
step K, stopping iteration, outputting the thermal conductivity value and the interface thermal conductivity value obtained in the step H or the step I, and ending the process;
and step L, increasing or decreasing the thermal conductivity value and the interface thermal conductivity value obtained in the step H or the step I according to a preset step length, determining a numerical value change path by a preset optimization function, and executing the step D.
In this step, the preset step length may be 0.5-5% of the current thermal conductivity value and the interface thermal conductivity value; the optimization function may be an lsqcurvefit function, fmisearch function, or other functions known in the art.
It should be noted that the thermal conductivity value and the interface thermal conductivity value are obtained simultaneously by using the two-parameter fitting method, and of course, a specific numerical value of the other one may also be obtained by using a single-parameter fitting method on the premise that one of the values is determined to be a fixed value. The related calculation methods are easily conceivable by those skilled in the art from the above description, and will not be repeated here.
It should be noted that the above definitions of the elements are not limited to the specific structures or shapes mentioned in the embodiments, and those skilled in the art can easily substitute them, for example:
(1) the heating laser or the detection laser can also be incident into the laser reflector at other angles;
(2) the light path of the system may not be in a horizontal plane, and the horizontal plane is selected only for convenience of adjustment in the embodiment;
(3) the focusing lens only has the function of concentrating the light beam and enabling the light beam to be incident to the photosensitive area of the photoelectric detector, and in the heating laser receiving assembly, the focusing lens is added or removed, so that the measuring result is not influenced;
(4) the first and second photodetectors may be high speed PIN diodes, avalanche diodes, photomultiplier tubes, or charge coupled devices.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (14)
1. An optical system for measuring a thermophysical parameter of a solid, comprising: the device comprises a heating laser generating assembly, a detection laser generating assembly, a beam combining element, a light splitting element, a heating laser receiving assembly, a sample testing assembly and a detection laser receiving assembly; wherein,
generating continuously polarized heating laser with frequency modulation by the heating laser generating assembly, and generating continuously polarized detection laser by the detection laser generating assembly; the heating laser and the detection laser are combined into a combined laser positioned on the plane A after passing through a beam combining element;
the beam-combined laser is incident to the light splitting element, the component with the polarization direction in the plane A is transmitted to the sample testing component, and the component with the polarization direction vertical to the horizontal plane is reflected to the heating laser receiving component; the beam combination light component with the polarization direction in the plane A is irradiated to the surface of the tested sample after passing through the sample testing assembly;
heating the detected sample by the heating laser in the beam combination optical component with the polarization direction in the plane A, and modulating the detection laser by the heated detected sample; the combined laser of the heating laser reflected by the surface of the tested sample and the modulated detection laser passes through the sample testing component again and then is reflected to the detection laser receiving component by the light splitting element;
the detection laser receiving assembly filters out heating laser components in the incident combined laser to obtain a detection laser signal; and the heating laser receiving assembly filters out detection laser components in the incident combined laser to obtain a signal of the heating laser.
2. The optical system of claim 1, wherein the beam combining element is a cold mirror;
the cold mirror is fully transmitted to the heating laser which is incident at an angle of 45 degrees with the plane where the cold mirror is located; and totally reflecting the incident detection laser forming an angle of 45 degrees with the plane where the laser is positioned, so that the combination of the heating laser and the detection laser is realized to be combined laser positioned on the plane A.
3. The optical system of claim 2, wherein the heated laser generating assembly comprises:
a signal modulator;
the first laser is a semiconductor laser and is used for outputting continuous polarized laser under the modulation of the signal modulator;
the first wave plate is a half wave plate and is used for adjusting the proportion of the horizontal polarization component and the vertical polarization component of the continuous polarization laser output by the first laser; and
and the reflecting surface of the first laser reflector forms a 45-degree angle with the heating laser which is transmitted through the first wave plate, and the first laser reflector is used for deflecting the incident added laser by 90 degrees and then irradiating the beam combining element at the 45-degree angle.
4. The optical system of claim 2, wherein the modulation frequency of the signal modulator is between 50kHz and 20 MHz.
5. The optical system of claim 2, wherein the probe laser generating assembly comprises:
the second laser is a semiconductor laser and is used for outputting continuously polarized detection laser;
the second wave plate is a half wave plate and is used for adjusting the proportion of the horizontal polarization component and the vertical polarization component of the continuous polarization laser output by the second laser; and
and the reflecting surface of the second laser reflector forms a 45-degree angle with the detection laser which is transmitted through the second wave plate, and the second laser reflector is used for deflecting the incident detection laser by 90 degrees and then irradiating the beam combination element at the 45-degree angle.
6. The optical system of claim 1, wherein the beam splitting element is a beam splitting prism.
7. The optical system of claim 1, wherein the sample testing assembly comprises:
a quarter-wave plate for changing the polarization direction of the combined laser beam passing through the quarter-wave plate by 45 degrees each time; and
and the objective lens is used for focusing the combined beam light component of the polarization direction of the quarter-wave plate on the plane A to the tested sample and re-transmitting the combined beam laser of the heating laser reflected by the surface of the tested sample and the modulated detection laser to the quarter-wave plate.
8. The optical system of claim 1, wherein the heated laser receiving assembly comprises:
the first optical filter is used for filtering detection laser components in the incident combined beam laser; and
a first photodetector for detecting a signal of the heating laser light in the combined laser light, wherein the signal includes: power and/or phase information.
9. The optical system of claim 1, wherein the detection laser receiving assembly comprises:
the second optical filter is used for filtering heating laser components in the incident combined beam laser; and
a second photodetector for detecting a signal of the detection laser in the combined laser, wherein the signal includes: power and/or phase information.
10. The optical system of claim 9, wherein the detection laser receiving assembly further comprises:
and the focusing mirror is positioned in front of the optical path of the second optical filter and used for focusing the incident combined laser, and the focused combined laser enters the second optical filter.
11. A method of measuring a thermophysical parameter of a solid using the optical system of any one of claims 1 to 10, comprising:
step A, acquiring a detection laser signal generated by a detection laser receiving assembly and a heating laser signal generated by a heating laser receiving assembly under different heating laser modulation frequencies by using the optical system, wherein the detection laser signal and the heating laser signal both contain power information and phase information;
b, performing phase difference processing on the detection laser signal and the heating laser signal under different heating laser modulation frequencies to obtain a phase difference experimental value;
step C, assigning an initial value to the thermophysical property parameter of the solid to be fitted;
step D, calculating a phase difference theoretical value under the frequency corresponding to the phase difference experimental value according to a theoretical model formula under different heating laser modulation frequencies;
step E, performing least square calculation on the phase difference experimental values and the corresponding phase difference theoretical values under all the heating laser modulation frequencies, wherein the least square calculation value is used as a current iteration result;
step F, recording a thermal conductivity value and an interface thermal conductivity value corresponding to the current iteration result;
g, judging whether the result of the current iteration is smaller than the result of the previous iteration, if so, executing the step H, otherwise, executing the step I;
step H, taking the solid thermophysical property parameter value corresponding to the iteration result as change detection output data, and executing step J;
step I, taking the solid thermophysical property parameter value corresponding to the previous iteration result as change detection output data, and executing step J;
step J, judging whether the iteration result of 3 times is less than the control precision, if so, executing the step K, otherwise, executing the step L;
step K, stopping iteration, outputting the solid thermophysical property parameter value obtained in the step H or the step I, and ending the process; and
and step L, increasing or decreasing the solid thermophysical property parameter value obtained in the step H or the step I according to a preset step length, determining a numerical value change path by a preset optimization function, and executing the step D.
12. The method of claim 11, wherein the theoretical model formula in step D is:
wherein Q is0、Q1Power of heating laser and detection laser, gamma is light reflection coefficient of tested sample surface, l is integral variable, R is0、R1The beam waist radii of the heating laser and the detection laser are respectively, Z represents a signal obtained by the data processing assembly, and omega is the angular frequency of a modulation signal; phi is the phase difference between the detection laser received by the detection laser receiving assembly and the heating laser received by the heating laser receiving assemblyTheoretical value, C, D is a 2 x 2 material thermophysical property parameter matrix Of the corresponding parameter.
13. The method according to claim 11, wherein in the step L, the preset step length is 0.5-5% of the current solid thermophysical property parameter value; the optimization function is an lsqcurvefit function or an fmisearch function.
14. The method of any one of claims 11 to 13, wherein the solid thermophysical parameter is thermal conductivity, and/or interfacial thermal conductivity.
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