CN117233128A - Inversion calculation method for infrared material high-temperature broadband optical constants - Google Patents
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Abstract
The application provides an inversion calculation method of an infrared material high-temperature broadband optical constant, which comprises the following steps: selecting an infrared material, and determining a spectrum segment calculated by inversion; at a preset temperature, testing the actual transmittance of the infrared material to each wavelength in the spectrum band by a spectrometer; establishing an optical constant calculation model of the infrared material based on a phonon absorption theory, wherein the optical constant calculation model comprises a plurality of model parameters, and calculating to obtain the theoretical transmittance of the infrared material to each wavelength in a spectrum section at a preset temperature through the optical constant calculation model; performing iterative optimization on the parameter of the multi-phonon absorption model within a preset range by using a numerical optimization method with the error of the theoretical transmittance and the actual transmittance as a target, so as to obtain an optimized parameter; and (5) bringing the optimized parameters into an optical constant calculation model to calculate the actual optical constant of the infrared material. The calculation model has the advantages of practicability and more accurate calculation of the optical constants.
Description
Technical Field
The application relates to an infrared material optical characteristic analysis technology, in particular to an infrared material high-temperature broadband optical constant inversion calculation method.
Background
The infrared material is mainly applied to optical windows and elements in an infrared detection system, and the optical characteristics of the infrared material determine the performance of the system. At present, the infrared detection system has increasingly increased application requirements in various high-temperature special environments, and in order to realize the works such as accurate and effective infrared optical system design, infrared optical film design, infrared emissivity characterization, infrared imaging analysis and the like under high-temperature conditions, the broadband optical constant of the infrared material under high temperature must have high accuracy. The optical constants of a material refer to the refractive index and extinction coefficient of the material. In general, the refractive index and extinction coefficient of a material are only wavelength dependent. However, under the condition of changing temperature, the refractive index and extinction coefficient of the same material are changed along with the temperature at a certain wavelength. The conventional classical vibrator infrared material optical constant model established based on a Cauchy model, a Sellmeier model, a Gaussian model and the like does not contain temperature parameters, and the model is difficult to correspond to accurate physical significance for the characterization of the material optical constant under the temperature changing condition.
Disclosure of Invention
In view of the foregoing drawbacks or shortcomings in the prior art, it is desirable to provide an infrared material high temperature broadband optical constant inversion calculation method, comprising:
selecting an infrared material, and determining a spectrum segment calculated by inversion; testing the actual transmittance of the infrared material to each wavelength in the spectrum section through a spectrometer at a preset temperature;
based on phonon absorption theory and Kramers-Transforming, namely establishing an optical constant calculation model of the infrared material, wherein the optical constant calculation model comprises a plurality of model parameters, the model parameters are related to temperature, and calculating to obtain the theoretical transmittance of the infrared material to each wavelength in the spectrum section at the preset temperature through the optical constant calculation model;
performing iterative optimization on the model parameters within a preset range by using a numerical optimization method with the aim of reducing errors of the theoretical transmittance and the actual transmittance to obtain optimized parameters;
and carrying the optimized parameters into the optical constant calculation model to calculate the actual optical constant of the infrared material.
The optical constant calculation model according to the technical scheme provided by the embodiment of the application comprises the following steps: a multi-phonon absorption coefficient model, a multi-phonon refractive index model, a single-phonon absorption coefficient model and a single-phonon refractive index model.
According to the technical scheme provided by the embodiment of the application, the calculation process of the theoretical transmittance of the infrared material to each wavelength in the spectrum segment at the preset temperature comprises the following steps:
calculating a multi-phonon absorption coefficient of the infrared material to the wavelength through the multi-phonon absorption model; calculating a single phonon absorption coefficient of the infrared material to the wavelength through the single phonon absorption model;
summing the single phonon absorption coefficient and the multi-phonon absorption coefficient to obtain a theoretical absorption coefficient of the infrared material for the wavelength;
calculating the multi-phonon refractive index of the infrared material to the wavelength through the multi-phonon refractive index model; calculating the single phonon refractive index of the infrared material to the wavelength through the single phonon refractive index model;
summing the multi-phonon refractive index and the single-phonon refractive index to obtain a theoretical refractive index of the infrared material for the wavelength;
based on the theoretical absorption coefficient and the theoretical refractive index, the theoretical transmittance is obtained through the Fresnel law and the light transmission theory.
The establishment of the multi-phonon absorption coefficient model according to the technical scheme provided by the embodiment of the application comprises the following steps:
establishing an n-order phonon state intensity function S n (ν,T)；
Establishing an n-order phonon state density function rho n (ν,T)；
Based on the S n (v, T) and said ρ n (v, T) establishing the model of the multi-phonon absorption coefficient according to the multi-phonon absorption theory
Where v is the wavenumber and T is the temperature.
The establishment of the multi-phonon refractive index model according to the technical scheme provided by the embodiment of the application comprises the following steps:
-applying said n-order phonon state density function ρ n (v, T) Kramers-Transforming to obtain delta n (ν)；
Based on the n-order phonon state intensity function S n (v, T) and delta n (v) obtaining a multi-phonon refractive index model
Wherein,
δ n (v) is through Kramers-A transformed n-order phonon state density function;
ν max is the maximum longitudinal vibration frequency of the crystal lattice, pi is the circumference rate, T 0 Is at room temperature;
α (a/o)11 、α (a/o)12 、α (a/o)13 are empirical parameters containing phonon information of optical mode and acoustic mode,is the frequency associated with the optical mode and the acoustic mode in the n-order phonon state intensity function.
The technical proposal provided by the embodiment of the application obtains the dielectric function epsilon based on the single-phonon vibrator model r Based on the dielectric function epsilon r Establishing the single phonon absorption coefficient modelBased on the dielectric function epsilon r Establishing the single phonon refractive index model +.>
The calculation process of the theoretical transmittance according to the technical scheme provided by the embodiment of the application comprises the following steps:
calculating an extinction coefficient based on the theoretical absorption coefficient;
calculating a complex refractive index based on the extinction coefficient and the actual refractive index;
calculating a first reflectivity of light from air to the surface of the infrared material based on the complex refractive index, and further calculating a first transmittance, and a second reflectivity of light from the surface of the infrared material to air, and further calculating a second transmittance;
calculating an internal transmittance based on the thickness of the infrared material and the theoretical absorption coefficient;
and calculating the theoretical transmittance based on the first transmittance, the second transmittance and the inner transmittance.
According to the technical scheme provided by the embodiment of the application, the actual optical constant comprises the actual absorption coefficient and the actual refractive index of the infrared material for the wavelength.
According to the technical scheme provided by the embodiment of the application, the numerical optimization method adopts a particle swarm algorithm or a genetic algorithm.
The steps of the particle swarm algorithm according to the technical scheme provided by the embodiment of the application comprise:
initializing a particle swarm and setting parameters;
calculating an objective function value;
updating the individual optimal value and the group optimal value;
judging whether convergence data are met; if yes, outputting an optimal result and iteration times; otherwise, the position vector and the velocity vector of each particle are updated and the iterative process is repeated.
The beneficial effects are as follows:
based on phonon absorption theory and Kramers-And transforming to establish an optical constant calculation model of the infrared material, wherein the optical constant calculation model comprises a plurality of model parameters, and the model parameters are related to temperature, so that an optical constant calculation model related to temperature is established, the calculation model can calculate the optical constant at the preset temperature, and the calculation model has higher practicability.
And carrying out iterative optimization on the model parameters within a preset range by a numerical optimization method to obtain optimized parameters, and carrying the optimized parameters into the optical constant calculation model to calculate the actual optical constant of the infrared material, so that the calculation of the optical constant is more accurate.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the accompanying drawings in which:
FIG. 1 shows the multi-phonon refractive index of ZnS at 300 ℃ in the spectral band of 2-16 μm in the example of the present application;
FIG. 2 shows the multi-phonon refractive index of ZnS at 300 ℃ in the spectral band of 2-16 μm in the example of the present application;
FIG. 3 shows the single phonon absorption coefficient of ZnS at 300℃in the spectral band of 2-16 μm in the example of the present application;
FIG. 4 shows the single phonon refractive index of ZnS at 300℃in the spectral band of 2-16 μm in the example of the present application;
FIG. 5 shows the theoretical absorption coefficient of ZnS at 300℃for a spectral band of 2-16 μm in the examples of the present application;
FIG. 6 shows the theoretical refractive index of ZnS at 300℃for a spectral band of 2-16 μm in the examples of the present application;
FIG. 7 shows theoretical transmittance, actual transmittance and transmittance calculated after inversion of ZnS having a spectral band of 2-16 μm and a thickness of 5mm at 300℃in the examples of the present application;
FIG. 8 shows the optical constants (refractive index and extinction coefficient) of ZnS material 2-16 μm and 300 ℃ after inversion calculation at 300 ℃ in the spectral band 2-16 μm in the example of the application;
fig. 9 is a flowchart of a particle swarm algorithm according to an embodiment of the application.
Detailed Description
The application is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. It should be noted that, for convenience of description, only the portions related to the application are shown in the drawings.
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
Referring to fig. 1 to 8, an inversion calculation method for an infrared material high-temperature broadband optical constant includes:
selecting an infrared material, and determining a spectrum segment calculated by inversion; testing the actual transmittance of the infrared material to each wavelength in the spectrum section through a spectrometer at a preset temperature;
based on phonon absorption theory and Kramers-Transforming to build an optical constant calculation model of the infrared material, the optical constant calculation model comprising a plurality of model parameters, the model parameters and a temperatureThe theoretical transmittance of the infrared material to each wavelength in the spectrum section at the preset temperature is calculated through the optical constant calculation model;
performing iterative optimization on the model parameters within a preset range by using a numerical optimization method with the aim of reducing errors of the theoretical transmittance and the actual transmittance to obtain optimized parameters;
and carrying the optimized parameters into the optical constant calculation model to calculate the actual optical constant of the infrared material.
Specifically, the infrared material includes transparent and semitransparent fluoride, oxide, sulfide, oxynitride material, and the like.
In this example, the infrared material selected was ZnS (zinc sulfide) with a thickness of d=5 mm.
In this example, a spectral band in the wavelength range of 2-16 μm was selected, and the preset temperature was 300 ℃.
In this embodiment, the spectrometer is an infrared fourier analysis spectrometer with a sample high temperature heating function.
Specifically, a ZnS material sample with a thickness of d=5mm was tested by infrared fourier analysis spectrometer to have a transmittance T in the 2-16 μm spectral band at a temperature of t=300℃ b (v) the test results are shown as curve 2 in fig. 7.
In particular, in the phonon absorption theory, the mechanism of phonon absorption can be described as a discrete quantum process, in which lattice vibrations are excited into an acoustic mode of a high energy state, then absorb the energy of a photon or other particle, and finally be excited into an acoustic mode of another low energy state.
Specifically, the Kramers-The transformation is a cremer-kroneich transformation for relating the real and imaginary parts of the refractive index of the material.
Further, the Kramers-The transformation is to convert the imaginary parts of the reflected and transmitted spectra to the real part of the refractive index or to calculate the imaginary part by means of the known real part.
In a preferred embodiment, the optical constant calculation model includes: a multi-phonon absorption coefficient model, a multi-phonon refractive index model, a single-phonon absorption coefficient model and a single-phonon refractive index model.
In a preferred embodiment, the establishing of the multi-phonon absorption coefficient model includes:
establishing an n-order phonon state intensity function S n (ν,T)；
Establishing an n-order phonon state density function rho n (ν,T)；
Based on the S n (v, T) and said ρ n (v, T) establishing the model of the multi-phonon absorption coefficient according to the multi-phonon absorption theory
Where v is the wavenumber and T is the temperature.
Further, the method comprises the steps of,
n-order phonon state intensity function S n The expression of (v, T) is:
n-order phonon state density function ρ n The expression of (v, T) is:
wherein k is b Is the boltzmann constant, c is the speed of light, m=0, 1,2,3, …, m max ≤(J-1)/2，
Where h is the pramk constant, D is the dissociation energy, J is the phonon state, and Q (T) is the partitioning function.
Wherein,
wherein,
wherein,
Φ(nν max -v) is a step function, T 0 Take 293K
Wherein a, K, alpha (a/o)11 、α (a/o)12 、α (a/o)13 、α (a/o)21 、α (a/o)22 、α (a/o)23 、α 3 For empirical parameters, refer to table 1.
TABLE 1
In a preferred embodiment, the establishing of the multi-phonon refractive index model includes:
-applying said n-order phonon state density function ρ n (v, T) Kramers-Transforming to obtain delta n (ν)；
Based on the n-order phonon state intensity function S n (v, T) and delta n (v) obtaining a multi-phonon refractive index model:
wherein,
δ n (v) is through Kramers-A transformed n-order phonon state density function;
ν max is the maximum longitudinal vibration frequency of the crystal lattice, pi is the circumference rate, T 0 Is at room temperature;
α (a/o)11 、α (a/o)12 、α (a/o)13 are empirical parameters containing phonon information of optical mode and acoustic mode,is the frequency associated with the optical mode and the acoustic mode in the n-order phonon state intensity function.
Specifically, the n-order phonon state density function ρ n (v, T) KramersTransforming to obtain delta n The specific process of (v) is as follows:
n-order phonon state density function ρ n (v, T) Kramers-And (3) transforming to obtain:
through multi-step approximation, delta n (v) can be obtained by solving and calculating the integral of the ballast:
wherein D is the pearson integration process.
In a preferred embodiment, the dielectric function ε is obtained based on a model of a single phonon vibrator r Based on the dielectric function epsilon r Establishing the single phonon absorption coefficient modelBased on the dielectric function epsilon r Establishing the single phonon refractive index model +.>
Specifically, in the single phonon vibrator model, the dielectric function ε r The expression of (2) is:
wherein,
wherein v cutoff Is the highest infrared optical longitudinal mode frequency, v cutoff ＝333(cm -1 )；
ν i Refers to the center vibration frequency of each vibrator in the single phonon model with temperature dependence,
ν i (T)＝ν i (T 0 )+a1 i ·(T-T 0 )+a2 i ·(T-T 0 ) 2 。
Δε i refers to the vibration intensity corresponding to each vibrator with temperature dependence,
Δε i (T)＝Δε i (T 0 )+b1 i ·(T-T 0 )+b2 i ·(T-T 0 ) 2 。
wherein Γ is i Is the long wave optical transverse mode frequency v i The corresponding linewidth temperature-dependent linewidth expression is:
wherein a1 i 、b1 i 、c1 i 、c2 i The parameters of the model are referred to in Table 2.
TABLE 2
In a preferred embodiment, the process for calculating the theoretical transmittance of the infrared material for each wavelength in the spectrum segment at a predetermined temperature includes:
calculating a multi-phonon absorption coefficient of the infrared material to the wavelength through the multi-phonon absorption model; calculating a single phonon absorption coefficient of the infrared material to the wavelength through the single phonon absorption model;
summing the single phonon absorption coefficient and the multi-phonon absorption coefficient to obtain a theoretical absorption coefficient of the infrared material for the wavelength;
calculating the multi-phonon refractive index of the infrared material to the wavelength through the multi-phonon refractive index model; calculating the single phonon refractive index of the infrared material to the wavelength through the single phonon refractive index model;
summing the multi-phonon refractive index and the single-phonon refractive index to obtain a theoretical refractive index of the infrared material for the wavelength;
based on the theoretical absorption coefficient and the theoretical refractive index, the theoretical transmittance is obtained through the Fresnel law and the light transmission theory.
Specifically, the expression of the theoretical absorption coefficient is: beta (v, T) =beta onephonon (ν,T)+β multiphonon (ν,T)。
Specifically, the expression of the theoretical refractive index is: n (v, T) =n osc (v,T)+n multiphonon (ν,T)。
Specifically, v is in cm -1 Thus, the wavelength range of 2-16 μm corresponds to 5000-625cm -1 Wave number range of v is 5000-625cm -1 Inside every 1cm -1 Taking a value once, and calculating once by utilizing a multi-phonon absorption coefficient model under each wave number v to finish 5000-625cm -1 After substitution calculation of all wave numbers in the range, znS multi-phonon absorption coefficients of each wavelength in the spectrum band 2-16 μm at the temperature of 300 ℃ can be obtained, as shown in FIG. 1.
Further, a single calculation is performed by using a single phonon absorption coefficient model under each wave number v to finish 5000-625cm -1 After substitution calculation of all wavenumbers in the range, znS single phonon absorption coefficients of each wavelength in the spectrum band 2-16 μm at the temperature of 300 ℃ can be obtained, as shown in FIG. 3.
Further, the theoretical absorption coefficient of ZnS material at 300℃for each wavelength of 2-16 μm in the spectral band was calculated based on the expression of the theoretical absorption coefficient, as shown in FIG. 5.
Specifically, v is set to 5000-625cm -1 Inside every 1cm -1 Taking a value once, and calculating once by utilizing a multi-phonon refractive index model under each wave number v to finish 5000-625cm -1 After substitution calculation of all wavenumbers in the range, znS multi-phonon refractive index of each wavelength in the spectrum band 2-16 μm at 300 ℃ can be obtained, as shown in FIG. 2.
Further, a single calculation is performed by using a single phonon refractive index model under each wave number v to finish 5000-625cm -1 After substituting all wave numbers in the range, the spectrum band of 2-16 mu m can be obtainedZnS single phonon refractive index at temperature 300 ℃ for each wavelength within, as shown in fig. 4.
Further, based on the expression of the theoretical refractive index, the theoretical refractive index of ZnS material at 300℃for each wavelength of 2-16 μm in the spectrum was calculated as shown in FIG. 6.
In a preferred embodiment, the calculation process of the theoretical transmittance includes:
calculating an extinction coefficient based on the theoretical absorption coefficient;
calculating a complex refractive index based on the extinction coefficient and the actual refractive index;
calculating a first reflectivity of light from air to the surface of the infrared material based on the complex refractive index, and further calculating a first transmittance, and a second reflectivity of light from the surface of the infrared material to air, and further calculating a second transmittance;
calculating an internal transmittance based on the thickness of the infrared material and the theoretical absorption coefficient;
and calculating the theoretical transmittance based on the first transmittance, the second transmittance and the inner transmittance.
Specifically, the extinction coefficient expression is: k=βλ/4pi.
Where λ is the wavelength and pi is the circumference ratio.
Specifically, according to snell's law: angle of complex refraction in ZnS materialSatisfy->
Wherein N is A Is the complex refractive index of ZnS material, N 0 Is the complex refractive index of air, theta 0 Is the angle of incidence of the light.
Wherein N is 0 ＝1，N A ＝n+ik，
Further, let θ in the present embodiment 0 For 0, according to fresnel's law, a first reflectivity is obtained:
and a second reflectivity:
further, a first transmittance is obtained: t (T) 1 ＝1-R 1 And a second transmittance T 2 ＝1-R 2 。
Specifically, the internal transmittance expression of ZnS material obtained according to the light transmission theory is as follows:
u＝exp(-βd)；
wherein d is the thickness of ZnS.
Further, the expression for obtaining the theoretical transmittance is:
further, a calculation is performed at each wave number v by using the expression of the theoretical transmittance to finish 5000-625cm -1 After substitution calculation of all wavenumbers in the range, the theoretical transmittance of ZnS at 300 ℃ for each wavelength in the spectrum band of 2-16 μm can be obtained as shown in curve 1 in FIG. 7
In a preferred embodiment, the actual optical constants include an actual absorption coefficient and an actual refractive index of the infrared material for the wavelength.
In a preferred embodiment, the numerical optimization method is a particle swarm algorithm or a genetic algorithm.
In a preferred embodiment, as shown in fig. 9, the steps of the particle swarm algorithm include:
initializing a particle swarm and setting parameters;
calculating an objective function value;
updating the individual optimal value and the group optimal value;
judging whether convergence data are met; if yes, outputting an optimal result and iteration times; otherwise, the position vector and the velocity vector of each particle are updated and the iterative process is repeated.
Specifically, in the particle swarm algorithm, the solution of each optimization problem is a bird of the search space, called "particle". All particles have an adaptive value determined by an optimized function, and each particle has a velocity that determines the direction and distance they fly toward. The particles then search in the solution space following the current optimal particle.
Specifically, a population of random particles (random solutions) is initialized, then an optimal solution is found by iteration, in each iteration, the particles update themselves by tracking two "extrema", the first being the optimal solution found by the particles themselves, this solution being called the individual extremum. The other extremum is the optimal solution currently found for the whole population, and this extremum is the global extremum. Alternatively, instead of using the whole population, only a part of it may be used as a neighbor of the particle, and the extremum in all is the local extremum.
Specifically, in this embodiment, the iteration number is used as the ending criterion, the iteration number is set to 20, and the population size is set to 50.
Specifically, for the parameters D, K, alpha in the optical constant calculation model (a/o)11 、α (a/o)12 、α (a/o)13 、α (a/o)21 、α (a/o)22 、α (a/o)23 、α 3 Iterative optimization is carried out in the vicinity of the theoretical value to obtain optimization parameters, and the optimization range and the optimization result of each parameter are shown in table 3:
TABLE 3 Table 3
Further, the optimization parameters are brought into the optical constant calculation model, and an optimized optical constant calculation model is obtained.
Further, v is set to 5000-625cm -1 Inside every 1cm -1 Take a value once, inCalculating once by using the optimized optical constant calculation model under each wave number v to finish 5000-625cm -1 After substituting all wave numbers in the range into calculation, the optimized optical constants of ZnS with the temperature of 300 ℃ at each wavelength in the spectrum of 2-16 μm can be obtained, and the optimized transmittance after optimizing parameters is calculated.
Specifically, the optimized optical constants include an optimized refractive index and an optimized extinction coefficient, as shown in fig. 8, in which curve 11 represents the optimized refractive index and curve 22 represents the optimized transmittance in fig. 8. As shown in curve 3 in fig. 7, it can be seen from fig. 7 that the optimized transmittance is closer to the actual transmittance than the theoretical transmittance, so that the optical constant calculation model has more practicability, and the calculation accuracy of the optical constant is higher after the empirical parameters are optimized.
The above description is only illustrative of the preferred embodiments of the present application and of the principles of the technology employed. It will be appreciated by persons skilled in the art that the scope of the application referred to in the present application is not limited to the specific combinations of the technical features described above, but also covers other technical features formed by any combination of the technical features described above or their equivalents without departing from the inventive concept. Such as the above-mentioned features and the technical features disclosed in the present application (but not limited to) having similar functions are replaced with each other.
Claims (10)
1. The inversion calculation method of the infrared material high-temperature broadband optical constant is characterized by comprising the following steps of:
selecting an infrared material, and determining a spectrum segment calculated by inversion; testing the actual transmittance of the infrared material to each wavelength in the spectrum section through a spectrometer at a preset temperature;
based on phonon absorption theory and Kramers-Transforming to build an optical constant calculation model of the infrared material, the optical constant calculation model comprising a plurality of model parameters, anThe model parameters are related to the temperature, and the theoretical transmittance of the infrared material to each wavelength in the spectrum section at the preset temperature is calculated through the optical constant calculation model;
performing iterative optimization on the model parameters within a preset range by using a numerical optimization method with the aim of reducing errors of the theoretical transmittance and the actual transmittance to obtain optimized parameters;
and carrying the optimized parameters into the optical constant calculation model to calculate the actual optical constant of the infrared material.
2. The method for inversion calculation of a high-temperature broadband constant of an infrared material according to claim 1, wherein the optical constant calculation model comprises: a multi-phonon absorption coefficient model, a multi-phonon refractive index model, a single-phonon absorption coefficient model and a single-phonon refractive index model.
3. The method for calculating the inversion of the high-temperature broadband constant of the infrared material according to claim 2, wherein the calculation process of the theoretical transmittance of the infrared material for each wavelength in the spectrum segment at the preset temperature comprises the following steps:
calculating a multi-phonon absorption coefficient of the infrared material to the wavelength through the multi-phonon absorption model; calculating a single phonon absorption coefficient of the infrared material to the wavelength through the single phonon absorption model;
summing the single phonon absorption coefficient and the multi-phonon absorption coefficient to obtain a theoretical absorption coefficient of the infrared material for the wavelength;
calculating the multi-phonon refractive index of the infrared material to the wavelength through the multi-phonon refractive index model; calculating the single phonon refractive index of the infrared material to the wavelength through the single phonon refractive index model;
summing the multi-phonon refractive index and the single-phonon refractive index to obtain a theoretical refractive index of the infrared material for the wavelength;
based on the theoretical absorption coefficient and the theoretical refractive index, the theoretical transmittance is obtained through the Fresnel law and the light transmission theory.
4. The method for inverting and calculating the high-temperature broadband constant of the infrared material according to claim 2, wherein the establishing of the multi-phonon absorption coefficient model comprises the following steps:
establishing an n-order phonon state intensity function S n (ν,T)；
Establishing an n-order phonon state density function rho n (ν,T)；
Based on the S n (v, T) and said ρ n (v, T) establishing the model of the multi-phonon absorption coefficient according to the multi-phonon absorption theory
Where v is the wavenumber and T is the temperature.
5. The method for inverting the high-temperature broadband constant of the infrared material according to claim 4, wherein the establishing of the multi-phonon refractive index model comprises:
-applying said n-order phonon state density function ρ n (v, T)Transforming to obtain delta n (ν)；
Based on the n-order phonon state intensity function S n (v, T) and delta n (v) obtaining a multi-phonon refractive index model
Wherein,
δ n (v) is the pass throughA transformed n-order phonon state density function;
ν max is the maximum longitudinal vibration frequency of the crystal lattice, pi is the circumference rate, T 0 Is at room temperature;
α (a/o)11 、α (a/o)12 、α (a/o)13 are empirical parameters containing phonon information of optical mode and acoustic mode,is the frequency associated with the optical mode and the acoustic mode in the n-order phonon state intensity function.
6. The method for inversion calculation of high temperature broadband constant of infrared material according to claim 5, wherein dielectric function epsilon is obtained based on single phonon vibrator model r Based on the dielectric function epsilon r Establishing the single phonon absorption coefficient modelBased on the dielectric function epsilon r Establishing the single phonon refractive index model
7. The method for calculating the inversion of the high-temperature broadband constant of the infrared material according to claim 3, wherein the calculating process of the theoretical transmittance comprises the following steps:
calculating an extinction coefficient based on the theoretical absorption coefficient;
calculating a complex refractive index based on the extinction coefficient and the actual refractive index;
calculating a first reflectivity of light from air to the surface of the infrared material based on the complex refractive index, and further calculating a first transmittance, and a second reflectivity of light from the surface of the infrared material to air, and further calculating a second transmittance;
calculating an internal transmittance based on the thickness of the infrared material and the theoretical absorption coefficient;
and calculating the theoretical transmittance based on the first transmittance, the second transmittance and the inner transmittance.
8. The method of claim 1, wherein the actual optical constants include an actual absorption coefficient and an actual refractive index of the infrared material for the wavelength.
9. The method for inverting and calculating the high-temperature broadband constant of the infrared material according to claim 1, wherein the numerical optimization method is a particle swarm algorithm or a genetic algorithm.
10. The method for calculating the inversion of the high-temperature broadband constant of the infrared material according to claim 9, wherein the step of the particle swarm algorithm comprises the following steps:
initializing a particle swarm and setting parameters;
calculating an objective function value;
updating the individual optimal value and the group optimal value;
judging whether convergence data are met; if yes, outputting an optimal result and iteration times; otherwise, the position vector and the velocity vector of each particle are updated and the iterative process is repeated.
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