A multilayer dielectric structure for liver pathology section detection

Abstract

The present invention provides a multilayer dielectric structure for liver pathological section detection, which belongs to the field of optical technology. It includes a defect layer, two second dielectric layers respectively located on both sides of the defect layer, and two first dielectric layers respectively located outside the two second dielectric layers. A prism-shaped coupling waveguide is arranged outside the first dielectric layer, and the cross section of the prism-shaped coupling waveguide is an isosceles right triangle; a liver pathological section to be detected is inserted between one of the prism-shaped coupling waveguides and the first dielectric layer. The present invention can accurately measure the refractive index of the liver pathological section by the spatial non-reciprocal Gus-Hansen shift of the reflected light beam, thereby realizing quantitative analysis of the liver pathological section.

Description

Technical Field

[0001] The invention belongs to the field of optical technology and relates to a multilayer dielectric structure for liver pathological section detection. Background Art

[0002] According to geometric optics, when light waves are at the interface of two different media, reflection and refraction will occur. Conversely, if the light beam is injected into the medium along the reflection or refraction light path, then at the interface, the original incident light path is the path of the reflected light or the refracted light. This is the principle of reversibility of the light path. In other words, when a beam of light passes through an optical device, the beam will form a light propagation path. If the positions of the light source and the light detector are interchanged, the light wave will return along the original path. This is the principle of spatial reciprocity of light waves. However, in a dielectric asymmetric structure with gain or loss, the reflection spectra of the left and right incident light, as well as the reflection coefficient phase spectrum, do not overlap, which is the spatial non-reciprocity phenomenon.

[0003] When the medium contains gain and loss, the light wave will form an evanescent wave on the medium interface, which is equivalent to the existence of a virtual reflection surface on the lower side of the interface. The reflected light beam will have a positive lateral displacement relative to the position predicted by the geometric light. This displacement is called the Goos-Hansen shift. The Goos-Hansen shift can also be negative, in which case the virtual reflection surface can be considered to be located on the upper side of the interface.

[0004] The Goos-Hansen shift is proportional to the rate of change of the phase of the reflection coefficient. Therefore, when light is irradiated into an asymmetric structure containing gain or loss, the Goos-Hansen shift curves of the left and right incident light waves must not overlap. This is the spatial non-reciprocity of the Goos-Hansen shift. The spatial Goos-Hansen shift is very sensitive to the refraction of dielectrics and is often used as a highly sensitive refractive index sensor. If the Goos-Hansen shift spatial non-reciprocity exists in the device and is used to measure the refractive index of the medium, the sensitivity of the sensor is doubled.

[0005] At the edge of the photonic band gap and near the defect mode of the defective photonic crystal, the phase of the reflection coefficient changes sharply with the change of the normalized frequency, which inevitably causes a considerable Goos-Hansen shift in the reflected beam. The photonic crystal is cut to form a photonic multilayer structure. In the photonic multilayer structure, there is also a similar Goos-Hansen effect.

[0006] Human tissues, such as liver slices, have large optical losses. When different tissues of the human body are diseased, the refractive index of the slices will also change. Traditionally, the detection of liver pathological slices is mostly done by microscopic observation, laboratory testing, and X-ray irradiation. There are disadvantages such as long detection cycle, high misjudgment rate and high cost. Summary of the invention

[0007] The purpose of the present invention is to provide a multilayer dielectric structure for liver pathological section detection in view of the above-mentioned problems existing in the prior art. The technical problem to be solved by the present invention is how to accurately measure the refractive index of liver pathological sections through the spatial non-reciprocal Goos-Hansen shift of the reflected light beam, thereby realizing quantitative analysis of liver pathological sections.

[0008] The objective of the present invention can be achieved through the following technical solutions: A multilayer dielectric structure for liver pathological section detection, characterized in that it comprises a defect layer, two second dielectric layers respectively located on both sides of the defect layer, and two first dielectric layers respectively located on the outsides of the two second dielectric layers, wherein a prismatic coupling waveguide is arranged on the outside of the first dielectric layer, and the cross-section of the prismatic coupling waveguide is an isosceles right triangle; a liver pathological section to be detected is inserted between one of the prismatic coupling waveguides and the first dielectric layer.

[0009] Furthermore, the second dielectric layer is zinc sulfide.

[0010] Furthermore, the dielectric layer 1 is silicon dioxide.

[0011] Furthermore, the prism-shaped coupling waveguide is made of silicon.

[0012] Furthermore, the defective layer is silicon.

[0013] The liver slices are compounded with photons to form an asymmetric dielectric multilayer structure. In addition, the optical loss of the liver slices is relatively large, which inevitably leads to large Goos-Hansen shifts of the left and right incident light and spatial non-reciprocity of the Goos-Hansen shifts. When the liver is diseased, the Goos-Hansen shifts of the left and right reflected light beams change, so as to accurately measure the refractive index of the liver pathological slices and quantitatively analyze the liver pathology.

[0014] The liver slice is compounded with a dielectric to form an asymmetrically distributed multilayer dielectric structure. Near the defect mode, the reflected light beam has a large Goos-Hansen shift and spatial non-reciprocity of the Goos-Hansen shift, that is, the positive and negative polarities of the Goos-Hansen shift of the left and right reflected light beams are exactly opposite. The wavelength position corresponding to the peak of the Goos-Hansen shift is extremely sensitive to the incident angle and the refractive index of the liver pathological slice. When the liver is diseased, its refractive index changes, and the obtained Goos-Hansen shift curve changes. Scan the incident wavelength and accurately measure the refractive index of the pathological slice through the wavelength position of the maximum Goos-Hansen shift of the left and right reflected light beams, thereby realizing quantitative analysis of the pathological slice. In addition, the non-reciprocity of the Goos-Hansen shift can double the measurement sensitivity of the refractive index of the liver slice. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1This is a schematic diagram of the structure of a photonic crystal used for pathological section detection.

[0016] Figure 2 Figure (a) shows the transmission spectrum of the light wave when it is incident on the left; Figure 2 Figure (b) shows the reflection spectrum of the light wave when it is incident on the left; Figure 2 Figure (c) shows the phase spectrum of the reflection coefficient at left incidence; Figure 2 Figure (d) shows the Goos-Hansen shift of the reflected beam at left incidence.

[0017] Figure 3 Figure (a) shows the phase spectrum of the reflection coefficient at right incidence; Figure 3 Figure (b) shows the Goos-Hansen shift of the reflected beam at right incidence.

[0018] Figure 4 (a) shows the effect of the real part of the refractive index of the liver pathological section on the Goos-Hansen shift of the left reflected beam; Figure 4 Figure (b) shows the effect of the real part of the refractive index of the liver pathological section on the Goos-Hansen shift of the right reflected light beam.

[0019] Figure 5 (a) shows the effect of the imaginary part of the refractive index of the liver pathological section on the Goos-Hansen shift of the left reflected beam; Figure 5 Figure (b) shows the effect of the imaginary part of the refractive index of the liver pathological section on the Goos-Hansen shift of the right reflected light beam.

[0020] In the figure, A, dielectric layer one; B, dielectric layer two; C, defect layer; D, prismatic coupled waveguide; E, liver pathological section to be examined. DETAILED DESCRIPTION

[0021] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0022] The first electrolyte layer A and the second electrolyte layer B are arranged on both sides of the defect layer C to form an axisymmetric distribution about the dielectric C. The liver pathological section E to be examined is placed on the right end of this structure, such as Figure 1 As shown, the symmetry of this structure is broken, but some characteristics of the photonic crystal, such as the photonic band structure, are still retained. This structure can also be recorded as EABCBA, where C is called the defect layer of the photonic crystal. Two prismatic coupling waveguides D with isosceles right triangle cross-sections are placed at the left and right ends of this multilayer structure to improve the coupling efficiency of light wave energy. Let the horizontal right be the positive direction of the Z axis in the Cartesian coordinate. The positive direction of the Y axis is perpendicular to the paper and the positive direction of the X axis is vertically upward.

[0023] When light is incident from the left, the symbol IL Represents the incident light, I′ L1 represents the reflected ray predicted by geometric optics, I′ L2 represents the reflected ray with a positive Goos-Hansen shift, I′ L3 represents a reflected ray with a negative Goos-Hansen shift.

[0024] When light is incident from the right, the symbol I R Represents the incident light, I′ R1 represents the reflected ray predicted by geometric optics, I′ R2 represents the reflected ray with a positive Goos-Hansen shift, I′ R3 represents a reflected ray with a negative Goos-Hansen shift.

[0025] The incident light is a transverse magnetic (TM) wave with an incident angle of θ. The dielectric A is silicon dioxide with a refractive index of n a =1.46, the thickness is 1 / 4 optical wavelength, that is, d a =λ0 / 4n a =0.2654μm (μm means micrometer), where λ0=1.55μm is the central wavelength; B is zinc sulfide, with a refractive index of n b =2.35, thickness is d b =λ0 / 4n b =0.1649μm; C is silicon, with a refractive index of n c =3.53; E is a liver pathological section with a thickness of d e =1μm. The material of the prismatic coupling waveguide D is silicon dioxide, with a refractive index of n d =1.46. Assuming the incident wavelength is around λ=1.55μm, the normal refractive index of the liver pathological section E to be examined is approximately n e =1.3624+0.0026964i, where i is the imaginary unit.

[0026] When light is incident from the left, change the input light frequency, Figure 2 (a) shows the transmission spectra corresponding to different incident angles. The vertical axis T represents the transmittance; the horizontal axis (ω-ω0) / ω gap represents the normalized angular frequency, where ω = 2πc / λ, ω0 = 2πc / λ0 and ω gap =4ω0arcsin│(n a -n b ) / (n a +n b )| 2 / π represents the angular frequency of the incident light, the central angular frequency of the incident light and the angular frequency band gap, c is the speed of light in a vacuum, and arcsin is the inverse sine function. Different incident angles correspond to different transmission spectra. In the normalized frequency range of [-1.8, 2.0], there are three transmission peaks on each spectrum line. The transmission peaks on both sides are the band gap edge states of the photonic multilayer, and the middle transmission peak (marked with an asterisk) is the defect mode in the photonic crystal. When the incident angle increases, the contour of the transmission spectrum will move to the right as a whole, that is, the frequency of the incident light wave corresponding to the central defect mode increases. When the incident angles are θ = [30°, 45°, 60°], the corresponding central normalized angular frequencies are (ω-ω0) / ω respectively. gap =[0.2977,0.5306,0.8144]. When the incident angle increases, the horizontal component of the wave vector decreases, while the thickness of the defect layer remains unchanged. Therefore, the frequency required to achieve the resonance of the defect layer increases, that is, the resonance wavelength blueshifts.

[0027] Figure 2 (b) shows the reflection spectrum of the left incident light wave, and the letter R on the ordinate represents the reflectivity. It can be seen that within the normalized angular frequency range of interest, there are three minimum reflectivity values ​​on each reflection spectrum line, and the positions of the minimum reflectivity are consistent with the positions of the peaks of the transmission spectrum. The reflectivity of the bandgap edge state is greater than that of the central defect mode, and when the incident angle increases, the reflection spectrum as a whole also shifts to the right, which is consistent with the right shift of the transmission spectrum.

[0028] The reflection coefficient can be written as modulus + argument: Where |r| represents the modulus, It represents the angle, which is the phase of the reflection coefficient. Figure 2 (c) shows the relationship between the reflection coefficient phase of the left incident light and the normalized frequency. When the incident light frequency is changed, the reflection coefficient phase changes sharply near the band gap edge and the defect mode. In particular, near the right edge of the band gap of each phase spectrum curve, there is a 2π phase jump in the reflection coefficient phase. However, the 2π phase jump is meaningless and can be removed. Therefore, the phase spectrum still changes continuously with the increase of the normalized frequency. Since the lateral displacement of the reflected light beam is proportional to the rate of change of the reflection coefficient angle: where k y =cosθλ / 2π, a larger Goos-Hansen shift of the reflected light beam can be obtained near the edge of the band gap and the central defect mode.

[0029] When the light is incident from the left, 2(d) provides the variation of the Goos-Hansen shift with the normalized frequency. When the incident angle is fixed, each specific incident angle corresponds to a different Goos-Hansen shift curve. When the incident light frequency is changed, two peaks and one trough appear in each curve. The positions of the peaks and troughs correspond exactly to the positions of the band gap edge and the central defect mode. When θ = 30°, the three extreme values ​​are Δ = 2.01λ, 42.17λ and -14.74λ from left to right. Obviously, it can be seen that the Goos-Hansen shift near the central defect mode is the largest compared to the other two extreme values. Although the reflectivity of the band gap edge is considerable, the corresponding Goos-Hansen shift is small, which is difficult to observe in practice considering that the beam has a certain width. Here we only focus on the Goos-Hansen shift of the central defect mode to perform pathological analysis on liver pathological sections. In addition, with increasing the incident angle, the Goos-Hansen shift curve shifts to the right as a whole, and the Goos-Hansen shift peak near the central defect mode decreases. Although increasing the angle of incidence can better separate the incident and reflected beams, that comes at the expense of the size of the Goos-Hansen shift.

[0030] When light is incident from the right, the transmission spectrum and reflection spectrum of the light wave are almost completely consistent with those when it is incident from the left. Therefore, only the phase spectrum of the reflection coefficient is discussed here, such as Figure 3 As shown in (a), it can be seen that when the incident light frequency is changed, there is a meaningless 2π phase jump in the reflection coefficient phase at the position of the left edge state of the band gap and the central defect mode; near the band gap edge and the defect mode, the reflection coefficient phase changes more dramatically, which means that there is a large Goos-Hansen shift near these positions; when the incident angle is increased, the reflection coefficient phase spectrum moves slightly to the right as a whole.

[0031] Figure 3 (b) shows the Goos-Hansen shift of the reflected beam at right incidence. The symbol Δ represents the Goos-Hansen shift, and λ represents the wavelength. It can be seen that different incident angles correspond to different Goos-Hansen shift curves; in each curve, there are two troughs and one peak, and the negative Goos-Hansen shift corresponding to the defect mode is the largest; when θ = 30°, the three extreme values ​​are Δ = -5.74λ, -52.13λ and 4.03λ from left to right; with increasing incident angle, the Goos-Hansen shift curve moves to the right as a whole, and the Goos-Hansen shift value near the central defect mode decreases. By comparing the Goos-Hansen shift generated by left incident light, we find that the positive and negative polarities of the Goos-Hansen shift near the band gap edge and the defect mode are exactly opposite. This phenomenon is the spatial non-reciprocity of the Goos-Hansen shift. This is caused by the asymmetry of the multilayer structure and the optical loss of the liver slice.

[0032] When the liver is diseased, the refractive index of its slice changes. Now only the real part of the refractive index of the liver pathological slice is changed, the incident angle θ is fixed to 30°, and other parameters are kept unchanged. Figure 4 (a) shows the Goos-Hansen shift near the central defect mode at left incidence. e ) represents the real part of the refraction of the liver pathological slice. It can be seen that the Goos-Hansen shift near the central defect mode is positive and has a peak; as the real part of the refractive index of the liver pathological slice increases, the Goos-Hansen shift curve moves to the right, which means that the peak value of the Goos-Hansen shift moves to the right.

[0033] When light is incident from the right, keeping other parameters unchanged, Figure 4 (b) shows the Goos-Hansen shift near the central defect mode. It can be seen that the Goos-Hansen shift near the central defect mode is negative and has a trough; as the real part of the refractive index of the liver pathological slice increases, the Goos-Hansen shift curve also moves to the right, which means that the trough of the Goos-Hansen shift moves to the right.

[0034] Therefore, the Goos-Hansen shift of the reflected light beam can be measured by the left and right incident light, and the frequency of the incident light corresponding to the extreme point of the Goos-Hansen shift can be found, so that the refractive index of the liver pathological slice can be accurately measured, thereby quantitatively analyzing the liver pathological slice. The positive and negative polarities of the Goos-Hansen shift of the left and right incident light are just opposite, which is the spatial non-reciprocity of the Goos-Hansen shift. The Goos-Hansen shift generated by the left and right incident light is also subtracted to detect the refractive index of the liver pathological slice, and the sensitivity is doubled.

[0035] Fix the incident angle θ = 30°, keep other parameters unchanged, and change the imaginary part of the refractive index of the liver pathological slice. Figure 5 (a) shows the Goos-Hansen shift near the central defect mode at left incidence. Im(n e ) represents the imaginary part of the refraction of the liver pathological slice. It can be seen that the Goos-Hansen shift near the central defect mode is positive and has a peak; as the imaginary part of the refractive index of the liver pathological slice increases, the peak position of the Goos-Hansen shift curve remains unchanged, while the peak value of the Goos-Hansen shift increases slightly.

[0036] When light is incident from the right, keeping other parameters unchanged, Figure 5(b) shows the Goos-Hansen shift near the central defect mode. It can be seen that the Goos-Hansen shift near the central defect mode is negative and has a trough. As the imaginary part of the refractive index of the liver pathological slice increases, the position of the trough of the Goos-Hansen shift curve remains unchanged, while the valley value of the Goos-Hansen shift decreases slightly. This shows that the imaginary part of the refractive index of the liver slice has little effect on the magnitude of the Goos-Hansen shift and can be ignored. However, the presence or absence of the imaginary part has a great influence on the magnitude of the Goos-Hansen shift.

[0037] In summary, in the asymmetric photonic multilayer structure containing liver pathological slices, there are band gap structures and central defect modes. Near the edge of the band gap and the defect, the phase of the reflection coefficient changes sharply with the change of the incident light frequency, thereby achieving a large Goos-Hansen shift of the reflected light beam. In particular, near the defect mode, the Goos-Hansen shift can reach the order of tens of wavelengths. The asymmetry of the structure and the optical loss of the liver pathological slices result in different positive and negative polarities of the Goos-Hansen shift of the left and right incident light, that is, the spatial non-reciprocity of the Goos-Hansen shift. The size and position of the peak Goos-Hansen shift are functions of the incident angle. As the incident angle increases, the peak value of the Goos-Hansen shift decreases, and the corresponding incident wavelength position blue-shifts. The light wave frequency position corresponding to the peak Goos-Hansen shift is a function of the refractive index of the liver pathological slice. Therefore, the wavelengths of the left and right incident light can be scanned respectively, and the wavelength positions of the corresponding peak Goos-Hansen shifts can be measured, and the refractive index of the liver pathological slices can be measured, so as to quantitatively analyze the liver slices. In addition, due to the spatial nonreciprocity of the Gus-Hansen shift in this device, its sensitivity in measuring the refractive index of liver pathological sections is doubled compared to that of a symmetrical structure.

[0038] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A multilayer dielectric structure for liver pathological section detection, characterized in that: The invention comprises a defect layer (C), two second dielectric layers (B) respectively located on both sides of the defect layer (C), and two first dielectric layers (A) respectively located on the outside of the two second dielectric layers (B), wherein a prism-shaped coupling waveguide (D) is arranged on the outside of the first dielectric layer (A), and the cross section of the prism-shaped coupling waveguide (D) is an isosceles right triangle; a liver pathological section (E) to be examined is inserted between one of the prism-shaped coupling waveguides (D) and the first dielectric layer (A), the second dielectric layer (B) is zinc sulfide, the first dielectric layer (A) is silicon dioxide, the prism-shaped coupling waveguide (D) is silicon, and the defect layer (C) is silicon.

2. A multilayer dielectric structure for liver pathological section detection according to claim 1, characterized in that: The refractive index of liver pathological sections is accurately measured by the spatial non-reciprocal Goos-Hansen shift of the reflected light beam, thereby achieving quantitative analysis of liver pathological sections.

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