阅读说明：本技术 一种基于古斯-汉森位移的高灵敏度光波长传感器 (High-sensitivity optical wavelength sensor based on Gus-Hansen displacement ) 是由 刘芳梅 于 2021-07-26 设计创作，主要内容包括：本发明提供了一种基于古斯-汉森位移的高灵敏度光波长传感器,属于光学技术领域。高灵敏度光波长传感器的光子晶体包括石墨烯单层,石墨烯单层的入射侧设置有第一周期性晶体,石墨烯单层的出射侧设置有第二周期性晶体,石墨烯单层与第一周期性晶体之间、石墨烯单层与第二周期性晶体之间分别嵌入有一缺陷层；第一周期性晶体包括交替分布的若干第一电介质层和若干第二电介质层,第二周期性晶体包括交替分布的若干第三电介质层和若干第四电介质层。本发明能够探测入射光波长和同时实现拓扑边界态附近大的反射率和古斯-汉森位移。(The invention provides a high-sensitivity optical wavelength sensor based on Gus-Hansen displacement, and belongs to the technical field of optics. The photonic crystal of the high-sensitivity optical wavelength sensor comprises a graphene single layer, a first periodic crystal is arranged on the incident side of the graphene single layer, a second periodic crystal is arranged on the emergent side of the graphene single layer, and a defect layer is respectively embedded between the graphene single layer and the first periodic crystal and between the graphene single layer and the second periodic crystal; the first periodic crystals include a number of first dielectric layers and a number of second dielectric layers that are alternately distributed, and the second periodic crystals include a number of third dielectric layers and a number of fourth dielectric layers that are alternately distributed. The invention can detect the wavelength of incident light and simultaneously realize large reflectivity and Gus-Hansen displacement near the topological boundary state.)

1. The high-sensitivity optical wavelength sensor based on the Guss-Hansen shift is characterized in that a photonic crystal of the high-sensitivity optical wavelength sensor comprises a graphene single layer (G), a first periodic crystal is arranged on the incident side of the graphene single layer (G), a second periodic crystal is arranged on the emergent side of the graphene single layer (G), and a defect layer (E) is respectively embedded between the graphene single layer (G) and the first periodic crystal and between the graphene single layer (G) and the second periodic crystal; the first periodic crystals comprise a plurality of first dielectric layers (A) and a plurality of second dielectric layers (B) which are alternately distributed, and the second periodic crystals comprise a plurality of third dielectric layers (C) and a plurality of fourth dielectric layers (D) which are alternately distributed; the whole structure is (AB)^NEGE(CD)^NAnd N is the Bragg period number.

2. The highly sensitive optical wavelength sensor based on the goos-hansen shift according to claim 1, wherein the first dielectric layer (a) is magnesium fluoride.

3. The highly sensitive optical wavelength sensor based on the goos-hansen shift according to claim 2, wherein the defect layer (E) is magnesium fluoride.

4. The highly sensitive optical wavelength sensor based on the goos-hansen shift according to claim 2, wherein the second dielectric layer (B) is zinc sulfide.

5. The highly sensitive optical wavelength sensor based on the goos-hansen shift according to claim 2, wherein the third dielectric layer (C) is silicon.

6. The highly sensitive optical wavelength sensor based on the goos-hansen shift as claimed in claim 2, wherein the second dielectric layer (B) is silicon dioxide.

Technical Field

The invention belongs to the technical field of optics, and relates to a high-sensitivity optical wavelength sensor based on Gus-Hansen displacement.

Background

When light irradiates the two refractive indexes n₁And n₂If total reflection occurs at the dielectric interface, part of the optical field will penetrate into the underlying medium, which is equivalent to placing a virtual reflecting interface behind the actual interface, so that the reflected light will have a lateral shift, called the Goos-hansen shift, relative to the original geometrically optically predicted position, called the Goos-hansen phenomenon, which is earliest from Goos (Goos) and hansen (hansen)Observed experimentally. A schematic diagram of the formation of Gus-Hansen shifts is shown in FIG. 1Where the symbol Δ represents the lateral displacement of the reflected beam and the arrowed line represents the central axis of the beam.

The Gus-Hansen displacement can be widely applied to high-sensitivity sensors and optical switches. In particular, the goos-hansen shift is particularly sensitive to the wavelength of incident light, the angle of incidence, and the like, so high-brightness wavelength and angle sensors can be applied. However, in general, the goos-hansen shift is weak, typically in the range of a few wavelengths or a dozen wavelengths, and thus, it is very difficult to experimentally detect and apply the goos-hansen shift. Therefore, to obtain a highly sensitive wavelength and angle sensor based on the goos-hansen shift, the magnitude of the goos-hansen shift must be increased first.

Various approaches have been taken to enhance the goos-hansen shift, such as using the band gap edge states of photonic crystals, and weak loss of material to obtain larger goos-hansen shifts. In particular, the Guss-Hansen extrema occur near the outlier points (EPs) and coherent perfect-absorption-laser points (CPA-LP) in non-Hermite photonic systems (containing or containing both optical gain and optical loss), theoretically reaching infinity. However, the reflectance at and near EPs is very low, and CPA-LP is not a stable photon state. This therefore motivates us to explore stable, highly reflective photonic devices that can achieve large goos-hansen shifts.

The Gus-Hansen shift is proportional to the phase of the reflection coefficient, which changes dramatically near the band gap edge and defect mode of the photonic crystal, which inevitably results in a large Gus-Hansen shift. In order to further increase the change rate of the reflection coefficient phase, two different photonic crystals can be compounded to obtain a topological boundary state, and the reflection coefficient phase changes more severely near the topological boundary state. In addition, graphene is an emerging two-dimensional material with conductivity tunability, and its surface conductivity is a function of its chemical potential. Single layer graphene is transparent, however, there is a weak optical loss coefficient in graphene. Therefore, graphene can be compounded with photonic crystals to enhance the Gus-Hansen shift, thereby realizing a high-sensitivity wavelength or angle sensor.

Disclosure of Invention

The present invention is directed to provide a highly sensitive optical wavelength sensor based on the goos-hansen shift, which can detect the wavelength of incident light.

The purpose of the invention can be realized by the following technical scheme: the high-sensitivity optical wavelength sensor based on the Guss-Hansen displacement is characterized in that a photonic crystal of the high-sensitivity optical wavelength sensor comprises a graphene single layer, a first periodic crystal is arranged on the incident side of the graphene single layer, a second periodic crystal is arranged on the emergent side of the graphene single layer, and a defect layer is respectively embedded between the graphene single layer and the first periodic crystal and between the graphene single layer and the second periodic crystal; the first periodic crystals include a number of first dielectric layers and a number of second dielectric layers that are alternately distributed, and the second periodic crystals include a number of third dielectric layers and a number of fourth dielectric layers that are alternately distributed.

Further, the first dielectric layer is magnesium fluoride.

Further, the defect layer is magnesium fluoride.

Further, the second dielectric layer is zinc sulfide.

Further, the third dielectric layer is silicon.

Further, the second dielectric layer is silicon dioxide.

The energy bands in the photonic crystal have a band gap. When light is shone on the photonic crystal, if the frequency of the light is within the band gap, no light will be transmitted through the photonic crystal and the light beam will be totally reflected. However, if a defect layer is added to the photonic crystal, a defect mode exists in the band gap of the energy band. When the frequency of the incident light is equal to the frequency of the defect mode, the light beam will pass through the photonic crystal totally without reflection, with zero reflectivity, and the defect mode will be called a transmission mode as well. The energy of the defect mode is mainly distributed in the defect layer, and the energy distribution at the central point of the defect layer is strongest. Extending from the center of the defect layer to two sides of the photonic crystal, the energy distribution of the defect mode is exponentially attenuated.

The goss-hansen of the reflected light beam is located at a derivative of the phase of the wave vector proportional to the reflection coefficient, and the phase of the reflection coefficient of the defective mode is uncertain because the reflectivity of the defective mode is zero, so that the reflected light beam of the defective mode may have a large goss-hansen shift. However, for a photonic crystal without gain and loss, the reflectivity of the defect mode is zero, and even though there is a large goos-hansen shift, it is practically meaningless.

We can combine two different photonic crystals with a defect layer to obtain a topological boundary state (also a defect mode). And then embedding the graphene into a defect layer of the photonic crystal, and weakening the transmittance of the photonic crystal to a boundary state by using the weak loss of the graphene so as to improve the light reflectivity. Meanwhile, weak loss of graphene also causes a sharp change in reflection coefficient phase. According to the fact that the Gus-Hansen displacement of the reflected light beam is in direct proportion to the phase change rate of the reflection coefficient, the Gus-Hansen displacement of the reflected light beam is larger. The goos-hansen shift is a function of the angle of incidence, wavelength and refractive index, and therefore, when this dependence is relatively close, this effect can be applied to high sensitivity sensors. Meanwhile, the large reflectivity and the large Gus-Hansen displacement of the boundary state can be realized.

Drawings

FIG. 1 is a schematic representation of the Guss-Hansen shift.

Fig. 2 is a schematic diagram of the structure of a photonic crystal used as a high-sensitivity optical wavelength sensor.

FIG. 3(a) is the reflectance near the boundary state in a defective photonic crystal without graphene; fig. 3(b) is the reflection coefficient phase of the boundary state in the defect photonic crystal without the damascene graphene.

FIG. 4(a) is the reflectance of a photonic crystal in a defective photonic crystal with inlaid graphene; fig. 4(b) is a reflection coefficient phase of a photonic crystal in a defective photonic crystal in which graphene is inlaid.

FIG. 5 is a Guos-Hansen shift of a reflected light beam in a photonic crystal used as a photonic crystal for a high-sensitivity optical wavelength sensor.

Fig. 6 is a sensitivity coefficient of an optical wavelength sensor based on the goos-hansen shift.

In the figure, a first dielectric layer; B. a second dielectric layer; C. a third dielectric layer; D. a fourth dielectric layer; E. a defect layer; G. a graphene monolayer.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

As shown in fig. 2, a photonic crystal for an optical wavelength sensor is composed of a graphene monolayer G, two defect layers E, a first periodic crystal and a second periodic crystal, the first periodic crystal and the second periodic crystal are symmetrically distributed on two sides of the graphene monolayer G, one of the defect layers E is embedded between the first periodic crystal and the graphene monolayer G, the other defect layer E is embedded between the second periodic crystal and the graphene monolayer G, the first periodic crystal is located on an incident side, the second periodic crystal is located on an exit side, the first periodic crystal includes a plurality of first dielectric layers a and a plurality of second dielectric layers B which are alternately distributed, and the second periodic crystal includes a plurality of third dielectric layers C and a plurality of fourth dielectric layers D which are alternately distributed.

The graphene monolayer G is embedded in the center of the two defect layers E, as shown in fig. 2. The refractive indices of the first dielectric layer A, the second dielectric layer B, the third dielectric layer C, the fourth dielectric layer D and the defect layer E are n_a＝1.38，n_b＝2.35，n_c＝3.53，n_d1.46 and n_e2.35. The first dielectric layer A and the defect layer E are both magnesium fluoride, the second dielectric layer B is zinc sulfide, the third dielectric layer C is silicon, the fourth dielectric layer D is silicon dioxide, and the thickness of the first dielectric layer A is D_aThe thickness of the second dielectric layer B was d 0.281_b0.165, the thickness of the third dielectric layer C is d_cThe thickness of the fourth dielectric layer D is 0.11, D_d0.258, the thickness of the defect layer E is d_e0.165 μm. The incident ray is labeled 1, the reflected ray is labeled 2, and the transmitted ray is labeled 3.

Graphene is embedded in the middle of the two defect layers, i.e., at the 0 point position of the z-axis. Graphene is a two-dimensional material without thickness, the surface conductivity of which can be described by the formula of nine baugs (Kubo formula)

Wherein f is_d＝1/(1+exp[(ε-μ_c)/(k_BT)]) For Fermi-Dirac statistics, ε is the particle energy, μ_cIs the chemical potential of graphene (also called the Fermi level E)_F) T is ambient temperature, e is electron element charge, τ is momentum relaxation time, k_BIs the boltzmann constant.

Graphene can be considered as an equivalent dielectric with a thickness, and the effect of this equivalent method on calculating reflectance and transmittance is negligible when its equivalent thickness is below 1 nm. We now take the thickness of the graphene to be 0.34nm, i.e. the thickness corresponding to a monolayer of atoms. The equivalent dielectric constant of graphene is epsilon_g＝1+iσ_gη₀/(kd_g) Where k is the incident wave vector, η₀Is the vacuum impedance. The ambient temperature is 27 deg.C, the momentum relaxation time is 0.5ps, mu_c＝0.15eV。

The entire structure can be noted As (AB)^NEGE(CD)^NAnd the Bragg period number N is 5.

The incident light is a Transverse Magnetic (TM) wave, propagating along the z-axis. The electromagnetic fields across each layer of dielectric may be related by a transmission matrix. For example, the electromagnetic fields across the first layer dielectric may be related by

Wherein M is_lA transmission matrix called the l-th layer,wherein eta_l＝ε_l(ε₀/μ₀)^1/2/(ε_l-sin²θ)^1/2，θ is an incident angle of light, and is set to 20 °. The transmission matrix of the whole system is

Where n is the total number of layers of the structure. A reflection coefficient of

Wherein eta₁＝η_N+1＝(ε₀/μ₀)^1/2(1-sin²θ)^1/2The impedances of the incident end and the emergent end are respectively, and the reflectivity is equal to rr. The photonic crystal has a band gap of omega_gap＝4ω₀arcsin|(n_b-n_a)/(n_b+n_a)|²N,/z, where ω₀＝2πc/λ₀，λ₀＝1.55μm。

Fig. 3(a) is the reflectance of a defect mode in a defect photonic crystal without graphene. It can be seen that the reflectivity is a function of the frequency of the incident light. There is a band gap in the middle of the reflection spectrum within which light will be totally reflected. However, the reflectance of the topological boundary states (also a defect mode) at the position is zero, and the light of the topological boundary states will be totally transmitted, and thus is also called a transmission mode. Writing the reflection coefficient in the form of an indexWhereinIs the phase of the reflection coefficient. FIG. 3(b) is the reflection coefficient of the boundary state in a defective photonic crystal without graphene damascenePhase, it can be seen that there is a phase jump of pi at the boundary state position. Because the reflectivity of the boundary states is zero, there is uncertainty in the phase of the reflection coefficient. Meanwhile, the phase change of the reflection coefficient is severe near the boundary state. According to the relationship between the Gus-Hansen shift of the reflected light beam and the phase of the reflection coefficient

It can be seen that the goos-hansen shift of the reflected beam is large near the boundary states. However, since the reflectance is small, graphene is embedded in the defect layer, and a large reflectance is obtained.

Fig. 4(a) is the reflectance of a photonic crystal in a defective photonic crystal with graphene inlaid. It can be seen that the reflectance of the boundary state at the position is not zero, and R is 0.212. Fig. 4(b) is a reflection coefficient phase of a photonic crystal in a defective photonic crystal in which graphene is inlaid. It can be seen that the phase at the boundary state position does not jump, but changes more strongly, and therefore a reflected beam with a greater reflectivity and a greater goos-hansen shift can be obtained.

FIG. 5 is a Guss-Hansen shift of the reflected beam in a graphene-inlaid photonic crystal. It can be seen that the goos-hansen shift is a function of the wavelength of the incident light; when the wavelength of the incident light is at the boundary state, the goos-hansen shift of the reflected light beam is maximum, and the maximum value is 124 lambda.

The device is held in place by a sensor that detects the wavelength of the incident light using the goos-hansen shift of the reflected light beam. A section of the graph with better linearity can be selected as the working area. The sensitivity coefficient of the sensor can be calculated by formula

It was found that for such a reflected light beam Gus-Hansen shift-based optical wavelength sensor, FIG. 6 is a graph of the variation of its sensitivity coefficient with the wavelength of the incident lightAnd (4) relationship. At the center of the working area, the maximum sensitivity coefficient is 4.75 multiplied by 10⁴。

The invention has the advantages that: introducing defects into the two photonic crystals, and embedding graphene into a defect layer, so that a large reflectivity and a large Gus-Hansen displacement can be obtained at the same time, wherein the maximum reflectivity R is 0.212 and the maximum Gus-Hansen displacement delta is 124 lambda; the Gus-Hansen shift in the device is applied to the detection of incident light wavelength, and the sensitivity coefficient of the device is as high as 4.75 multiplied by 10⁴。

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.