CN102798764B - Method for measuring medium loss by using phase change of electromagnetic evanescent wave - Google Patents
Method for measuring medium loss by using phase change of electromagnetic evanescent wave Download PDFInfo
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- CN102798764B CN102798764B CN201110139419.1A CN201110139419A CN102798764B CN 102798764 B CN102798764 B CN 102798764B CN 201110139419 A CN201110139419 A CN 201110139419A CN 102798764 B CN102798764 B CN 102798764B
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Abstract
The invention provides a method for measuring the medium loss by using the phase change of an electromagnetic evanescent wave. The method comprises the following steps of: 1) determining a refractive ratio real part of a medium to be measured in an electromagnetic wave with preset frequency, and defining the medium to be measured as an optically thinner medium; 2) searching an optically denser medium with a known refractive ratio, wherein the refractive ratio real part of the optically denser medium is greater than that of the medium to be measured, and forming a full-reflection system by the optically denser medium and the medium to be measured; 3) radiating the medium to be measured by the electromagnetic wave with the preset frequency from the optically denser medium, adjusting an incidence angle, making the electromagnetic wave be fully reflected at an interface of the optically denser medium and the medium to be measured, and generating the evanescent wave in the medium to be measured; and 4) selecting a measurement point in the medium to be measured, measuring change of a phase of the evanescent wave, and calculating a refractive ratio virtual part of the medium to be measured according to the phase change of the evanescent wave. The measurement method can be losslessly and repeatedly executed; and ultrahigh-precision measurement can be realized.
Description
Technical field
The present invention relates to a kind of method of the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave, particularly utilize the method for the weak loss of the phase place measure of the change low density gas of electromagnetism evanescent wave.
Background technology
If the refractive index of a certain medium is n=n '+n ", wherein n ' and n " be respectively real part and the imaginary part of medium refraction index, our target is to measure n ' and n ".
We know, for transmission wave, n ' and n " determine respectively real part and the imaginary part of transmission wave wave vector, so when transmission wave is after Propagation one segment distance, " phase place that has determined respectively transmission wave changes and the variation of amplitude for n ' and n.Because phase place variation is obvious and easily accurately measures by instruments such as interferometers, so the method for many measurement n ' all utilizes transmission wave to carry out.But very faint when the absorption of medium, i.e. " when very small, the variation of transmission wave amplitude also will be very small to n, " have very large difficulty, not even possible accuracy measurement so utilize transmission wave to measure n.So we need new method to measure n ".
With transmission wave difference, evanescent wave is to n " is very sensitive.N ' and n " are antipodal with them to the effect of transmission wave to the effect of evanescent wave.For evanescent wave, n " determined the real part of evanescent wave wave vector, n ' decision be the imaginary part of evanescent wave wave vector.So " variation and the phase place that have determined respectively the amplitude of evanescent wave change for n ' and n.We because changing more easily, phase place accurately measure, so can change and carry out measuring media loss by the phase place of evanescent wave.
Lay special stress on herein, the method method different from the past of the phase place measure of the change dielectric loss of electromagnetism evanescent wave that what we provided utilize, such as the method described in document (C.Carniglia and L.Mandel, J.Opt.Soc.Am.61,1035 (1971) .).Utilizing in the method that evanescent wave surveys in the past, its system has two interfaces at least, and evanescent wave is between these two interfaces.In such system, due to the tunneling effect of evanescent wave, its phase place changes and is determined by interface completely, and does not consider the loss of medium.In fact,, in such system, even without the loss of medium, after evanescent wave tunnelling, still there is the variation of phase place.And in the method providing at us, testing medium and optically denser medium are " single interfaces ".If testing medium is the desirable lossy medium that do not have, the evanescent wave in testing medium does not have phase place to change so; If testing medium is lossy, evanescent wave will have phase transformation variation so, and its variable quantity " is directly proportional with the imaginary part n of testing medium refractive index.
Summary of the invention
The present invention relates to a kind of method of the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave, for realize harmless repeatedly, the measurement of superhigh precision.
In order to achieve the above object and other objects, the present invention adopts following technical scheme: a kind of method of the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave, and it comprises step:
1) in the electromagnetic wave of frequency given in advance, determine the real part of testing medium refractive index, and this testing medium is defined as to optically thinner medium;
2) find the optically denser medium that the known and refractive index real part of refractive index is greater than the refractive index real part of testing medium, and the positional alignment of optically denser medium and testing medium formation " optically denser medium-optically thinner medium " full reflected system;
3) with the electromagnetic wave of frequency given in advance from optically denser medium to testing medium incident, and regulate incident angle, make electromagnetic wave, in the interface of optically denser medium and testing medium, total reflection occur, and at the inner evanescent wave that produces of testing medium;
4) in testing medium, select a measurement point, measure the variation of evanescent wave phase place; And calculate the imaginary part of testing medium refractive index according to the variation of evanescent wave phase place, obtain dielectric loss.
Preferably, described step 4) calculating testing medium refractive index imaginary part n
2" expression formula be:
wherein, the phase place that Δ φ is evanescent wave changes, and L is that measurement point is to the distance at " optically denser medium-testing medium " interface in testing medium, and c is the light velocity in vacuum, the circular frequency that ω is incident electromagnetic wave, n
1and n '
2be respectively the refractive index real part of optically denser medium and testing medium, θ is electromagnetic incident angle.
Preferably, described electromagnetic incident angle θ meets total reflection condition: θ > arcsin (n '
2/ n
1).
Preferably, described testing medium is non-dispersive medium or dispersive medium.
Preferably, described testing medium has the medium of weak loss.
The medium preferably, with weak loss is included as the one in gas, liquid or colloid.
Preferably, the electromagnetic wave of described frequency range given in advance comprises the one in visible ray, infrared light and microwave.
Preferably, described step 4) adopt and include but not limited to the variation of phase difference measuring apparatus, network analyzer, interferometer measurement evanescent wave phase place.
The method of utilizing the loss of electromagnetism evanescent wave measuring media of the present invention, press specific positional alignment by a known optically denser medium and testing medium, form " optically denser medium-optically thinner medium " full reflected system, and the phase place variation of measuring the inner evanescent wave of testing medium, realize the measurement of dielectric loss (refractive index imaginary part).The advantage of this regulate and control method comprises: (1) this measuring method can be adjusted and adjustment repeatedly easily; (2) can measure the refractive index imaginary part of dispersive medium under different frequency, and needn't again change the experiment structure of measuring system; (3) because the phase place of evanescent wave is very sensitive to dielectric loss, simultaneously more convenient and accurate to the measurement of electromagnetic wave phase place, so measuring method of the present invention can have high precision.
Brief description of the drawings
Fig. 1 is the operating process schematic diagram of the method for the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave of the present invention.
Fig. 2 is the empirical model schematic diagram of the phase place changing method measuring media loss that utilizes electromagnetism evanescent wave of the present invention.
Fig. 3 a-3c is the schematic diagram that utilizes the phase place changing method of electromagnetism evanescent wave to measure the weak loss of two kinds of representative gases (dispersive medium) of the present invention.
Embodiment
Refer to shown in Fig. 1, the method for the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave of the present invention at least comprises the following steps:
First, under wave frequency given in advance, determine the real part n ' of testing medium refractive index
2, and this testing medium is defined as to optically thinner medium.That we need to measure is the refractive index imaginary part n of this testing medium "
2.If testing medium is dispersive medium, so n '
2and n "
2relevant with electromagnetic frequency.Conventionally, predefined wave frequency scope can be visible ray, infrared light or microwave etc.
Then, find an optically denser medium (refractive index real part n for this medium
1for known, and be greater than the refractive index real part n ' of testing medium
2), and optically denser medium and testing medium are pressed to specific positional alignment, form " optically denser medium-optically thinner medium " full reflected system.As shown in Figure 2.
Then, with electromagnetic incident angle θ in predefined adjusting optically denser medium, make it the boundary generation total reflection at optically denser medium and testing medium, thereby at the inner evanescent wave that produces of testing medium.
While there is total reflection, in testing medium inside, the wave vector perpendicular to interface direction of evanescent wave is:
wherein, the circular frequency that ω is incident electromagnetic wave, c is the light velocity in vacuum.So, at L place, testing medium middle distance interface, evanescent wave will have phase place changes delta φ, and it meets:
Subsequently, at L place, testing medium middle distance interface, include but not limited to the apparatus measures such as phase difference measuring apparatus, network analyzer, interferometer by employing, we can obtain the phase place changes delta φ of evanescent wave.By (1) formula, we can be in the hope of n "
2, it meets:
wherein, the phase place that Δ φ is evanescent wave changes, and L is that measurement point is to the distance at " optically denser medium-testing medium " interface in testing medium, and c is the light velocity in vacuum, the circular frequency that ω is incident electromagnetic wave, n
1and n '
2be respectively the refractive index real part of optically denser medium and testing medium, θ is electromagnetic incident angle.
Adopting the phase place changes delta φ of the apparatus measures evanescent waves such as phase difference measuring apparatus, network analyzer, interferometer is general knowledge known in this field, does not repeat them here.
Like this, we just, by measuring the variation of evanescent wave phase place, calculate the value that has obtained the refractive index imaginary part of testing medium under certain frequency.
Finally, change the frequency of incident electromagnetic wave, repeat aforesaid operations step, can be in the hope of under different frequency, the value of testing medium refractive index imaginary part.As an example, the relation of two kinds of gas medium refractive index imaginary parts and frequency as shown in Figure 3, wherein, Fig. 3 (a) is the relation of testing medium refractive index real part with frequency change, Fig. 3 (b) is for the variation of evanescent wave phase place is with the relation of frequency change, and the refractive index imaginary part that Fig. 3 (c) is testing medium is with the relation of frequency.
In sum, the method of utilizing the loss of electromagnetism evanescent wave measuring media of the present invention, press specific positional alignment by a known optically denser medium and testing medium, form " optically denser medium-optically thinner medium " full reflected system, and the phase place variation of measuring the inner evanescent wave of testing medium, realize the measurement of dielectric loss (refractive index imaginary part).The advantage of this regulate and control method comprises: (1) this measuring method can be adjusted and adjustment repeatedly easily; (2) can measure the refractive index imaginary part of dispersive medium under different frequency, and needn't again change the experiment structure of measuring system; (3) because the phase place of evanescent wave is very sensitive to dielectric loss, simultaneously more convenient and accurate to the measurement of electromagnetic wave phase place, so measuring method of the present invention can have high precision.
Be understandable that, although the present invention discloses as above with preferred embodiment, but above-described embodiment is not in order to limit the present invention.For any those of ordinary skill in the art, do not departing from technical solution of the present invention scope situation, all can utilize the technology contents of above-mentioned announcement to make many possible variations and modification to technical solution of the present invention, or be revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not depart from technical solution of the present invention,, all still belongs in the scope of technical solution of the present invention protection any simple modification made for any of the above embodiments, equivalent variations and modification according to technical spirit of the present invention.
Claims (7)
1. a method of utilizing the phase place measure of the change dielectric loss of electromagnetism evanescent wave, is characterized in that comprising step:
1) in the electromagnetic wave of frequency given in advance, determine the real part of testing medium refractive index, and this testing medium is defined as to optically thinner medium;
2) find the optically denser medium that the known and refractive index real part of refractive index is greater than the refractive index real part of testing medium, and the positional alignment of optically denser medium and testing medium formation " optically denser medium-optically thinner medium " full reflected system;
3) with the electromagnetic wave of frequency given in advance from optically denser medium to testing medium incident, and regulate incident angle, make electromagnetic wave, in the interface of optically denser medium and testing medium, total reflection occur, and at the inner evanescent wave that produces of testing medium;
4) in testing medium, select a measurement point, measure the variation of evanescent wave phase place; And calculate the imaginary part of testing medium refractive index according to the variation of evanescent wave phase place, obtain dielectric loss;
Described step 4) is calculated testing medium refractive index imaginary part n
2' ' expression formula be:
wherein, the phase place that △ φ is evanescent wave changes, and L is that measurement point is to the distance at " optically denser medium-testing medium " interface in testing medium, and c is the light velocity in vacuum, the circular frequency that ω is incident electromagnetic wave, n
1and n'
2be respectively the refractive index real part of optically denser medium and testing medium, θ is electromagnetic incident angle.
2. the method for the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave as claimed in claim 1, is characterized in that: described electromagnetic incident angle θ meets total reflection condition: θ >arcsin (n'
2/ n
1).
3. the method for the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave as claimed in claim 1, is characterized in that: described testing medium is non-dispersive medium or dispersive medium.
4. the method for the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave as claimed in claim 1, is characterized in that: described testing medium has the medium of weak loss.
5. the method for the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave as claimed in claim 4, is characterized in that: described in there is weak loss medium be included as the one in gas, liquid or colloid.
6. the method for the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave as claimed in claim 1, is characterized in that: the electromagnetic wave of described frequency range given in advance comprises the one in visible ray, infrared light and microwave.
7. the method for the phase place measure of the change dielectric loss of utilizing electromagnetism evanescent wave as claimed in claim 1, is characterized in that: described step 4) adopts the variation that includes but not limited to phase difference measuring apparatus, network analyzer, interferometer measurement evanescent wave phase place.
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| CN107064062B (en) * | 2017-04-13 | 2019-08-27 | 云南电网有限责任公司电力科学研究院 | A kind of method and device based on total reflection principle measurement soil refractive index |
| CN113758877B (en) * | 2021-08-30 | 2023-08-18 | 清华大学深圳国际研究生院 | Frequency domain quantum weak measurement biomolecular sensor and measurement method thereof |
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| JP2007271412A (en) * | 2006-03-31 | 2007-10-18 | Yamato Scale Co Ltd | Method and device for measuring lipid content |
| CN101821606A (en) * | 2007-07-26 | 2010-09-01 | 皇家飞利浦电子股份有限公司 | Microelectronic sensor device for optical examinations with total internal reflection |
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| US7550963B1 (en) * | 1996-09-20 | 2009-06-23 | The Regents Of The University Of California | Analytical scanning evanescent microwave microscope and control stage |
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| JP2007271412A (en) * | 2006-03-31 | 2007-10-18 | Yamato Scale Co Ltd | Method and device for measuring lipid content |
| CN101821606A (en) * | 2007-07-26 | 2010-09-01 | 皇家飞利浦电子股份有限公司 | Microelectronic sensor device for optical examinations with total internal reflection |
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| Phase-Shift Measurement of Evanescent Electromagnetic Waves;C.K.CARNIGLIA et.;《JOURNAL OF THE OPTICAL SOCIETY OF AMERICA》;19710831;第61卷(第8期);1035-1043 * |
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