阅读说明：本技术 一种基于鲁丁-夏皮诺光子晶体的光存储器 (Optical memory based on rutin-Xiapino photonic crystal ) 是由 方明 于 2021-09-29 设计创作，主要内容包括：本发明提供了一种基于鲁丁-夏皮诺光子晶体的光存储器,属于全光通讯技术领域。包括若干第一电介质层、若干第二电介质层和两个石墨烯单层,第一电介质层记为H,第二电介质层记为L,石墨烯单层记为G,光存储器的层状结构表示为：HHHLHHL-(1)GL-(2)HHL-(2)GL-(1)HHLHHH,其中L-(1)GL-(2)和L-(2)GL-(1)均表示石墨烯单层嵌入第二电介质层内形成的三层结构,第一电介质层和第二电介质层的厚度分别为各自光学波长的1/4,第一电介质层和第二电介质层分别为折射率高、低不同的两种均匀电介质薄片；所述基于鲁丁-夏皮诺的光子晶体的光存储器可实现低阈值光学双稳态,双稳态的上、下阈值分别对应着光存储器的写入和读取判决阈值。本发明具有能够运用于光存储器等优点。(The invention provides an optical memory based on a rutin-Xiapino photonic crystal, and belongs to the technical field of all-optical communication. The optical memory comprises a plurality of first dielectric layers, a plurality of second dielectric layers and two graphene single layers, wherein the first dielectric layers are marked as H, the second dielectric layers are marked as L, the graphene single layers are marked as G, and the layered structure of the optical memory is represented as follows: HHHLHHL 1 GL 2 HHL 2 GL 1 HHLHHH, wherein L 1 GL 2 And L 2 GL 1 Both represent a three-layer structure formed by embedding a graphene monolayer into a second dielectric layer, the thicknesses of the first dielectric layer and the second dielectric layer are 1/4 of the optical wavelength of each dielectric layer, and the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indexes; the photonics crystal optical memory based on the Lutin-Charcinod can realize low-threshold optical bistable state, and the upper threshold and the lower threshold of the bistable state respectively correspond to the optical memoryWrite and read decision thresholds for the memory. The invention has the advantages of being applicable to optical memories and the like.)

1. An optical memory based on a luding-schpino photonic crystal is characterized by comprising a plurality of first dielectric layers, a plurality of second dielectric layers and two graphene single layers, wherein the first dielectric layers are marked as H, the second dielectric layers are marked as L, the graphene single layers are marked as G, and the layered structure of the optical memory is represented as: HHHLHHL₁GL₂HHL₂GL₁HHLHHH, wherein L₁GL₂And L₂GL₁Both represent a three-layer structure formed by embedding a graphene monolayer into a second dielectric layer, the thicknesses of the first dielectric layer and the second dielectric layer are 1/4 of the optical wavelength of each dielectric layer, and the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indexes; the photonics crystal based on the rutin-Charcot optical memory can realize low-threshold optical bistable state, and the upper threshold and the lower threshold of the bistable state respectively correspond to the writing-in judgment threshold and the reading-out judgment threshold of the photonics crystal based on the rutin-Charcot optical memory.

2. The ludin-xiapino photonic crystal-based optical memory of claim 1, wherein the first dielectric layer is a high refractive index material of lead telluride, and the second dielectric layer is a low refractive index material of cryolite.

3. The optical storage device based on the rutin-Prunellano photonic crystal as claimed in claim 1 or 2, wherein the writing decision threshold, the reading decision threshold and the interval between the writing decision threshold and the reading decision threshold of the optical storage device are regulated and controlled by the chemical potential of the graphene monolayer.

4. The optical storage device based on the rutin-Prunellano photonic crystal as claimed in claim 1 or 2, wherein the writing decision threshold, the reading decision threshold and the interval between the writing decision threshold and the reading decision threshold of the optical storage device are regulated and controlled by incident wavelength.

Technical Field

The invention belongs to the technical field of all-optical communication, and relates to an optical memory based on a rutin-Xiapino photonic crystal.

Background

In all-optical communication, information needs to be stored, transmitted, relayed, timed, amplified, shaped, etc. in the optical domain, which leads to the great development of all-optical devices for optical control of light, and optical memories based on optical bistable state are an important class. Optical bistability is a nonlinear optical effect based on the optical kerr effect of a material. When the incident light is sufficiently strong, one input intensity value may correspond to two different output intensity values, i.e. one input intensity value may induce two stable output resonance states.

When the optical bistable state is applied to the optical memory, the upper threshold value and the lower threshold value of the bistable state respectively correspond to the decision threshold values of writing and reading of the optical memory; the larger the decision threshold, the stronger the light intensity required to trigger writing and reading of the optical memory. However, as the power of the device increases, the stability of the device during operation deteriorates and the requirements for heat dissipation conditions also increase. In addition, the smaller the interval between the upper and lower bistable thresholds, the less discriminative the corresponding optical memory is between writing and reading, which may result in an increased probability of malfunction. Therefore, current research on optical bistable devices focuses on reducing the threshold of optical bistable states and increasing the interval between upper and lower thresholds by new materials and new structures.

In order to achieve low threshold optical bistable effects, on the one hand, materials with large third-order nonlinear coefficients are sought; on the other hand, the local electric field is enhanced by optimizing the system structure. The optical Kerr effect is proportional to the local electric field intensity, so that the strong local electric field can improve the third-order nonlinear effect of the material, thereby reducing the bistable threshold value.

Graphene is a new two-dimensional material, and has ultrathin property and excellent conductivity. The surface conductivity of graphene can be flexibly controlled by its chemical potential. Importantly, graphene has a considerable third-order nonlinear optical coefficient, which makes graphene a popular material in optical bistable studies. In addition, in order to further reduce the threshold value of bistable state, the local electric field intensity of graphene can be enhanced by using the surface plasmon polariton of the graphene; graphene can also be embedded into a defective photonic crystal to enhance its nonlinear effects. In the defect photonic crystal, the energy of a defect mode is mainly distributed in a defect layer, so that the third-order nonlinear optical effect of graphene can be greatly enhanced by embedding the graphene in the defect layer.

Two dielectric sheets with different refractive indexes are arranged alternately in space to form the photonic crystal with a periodic structure. In the wave vector space, a photonic crystal has a photonic band structure similar to an electron band in a semiconductor. Light waves within the band gap will be totally reflected. If defects are introduced into the photonic crystal, a transmission mode appears in the transmission spectrum. The transmission mode is a defect mode, has local property to electric field, and is often used to enhance the third-order nonlinear effect of the material.

Quasi-photonic crystals or aperiodic photonic crystals are often used to enhance the electric field localization because of the natural defect layer and the geometric progression of the number of defect modes with the increasing sequence number.

The Thue-Morse (TM) sequence is mathematically a quasi-periodic sequence, and its corresponding photonic crystal is a quasi-periodic photonic crystal. The graphene is embedded into the TM photonic crystal, so that optical bistable state can be realized, and the threshold value of the optical bistable state is about 100GW/cm²(gigawatts per square centimeter). The TM photonic crystal is provided with a plurality of defect cavities, and a plurality of defect modes, namely resonant transmission modes, exist in the same defect cavity. As the serial number increases, the transmission mode in the TM photonic crystal is split in a geometric series, so the effect is called optical fractal. The locality of the optical fractal to the electric field allows for low threshold optical bistability. Whether quasi-periodic photonic crystals with stronger electric field locality can be found or not and then the composite structure of the quasi-periodic photonic crystals and graphene is obtained, so that the nonlinear effect of the graphene is further enhanced, and the threshold value of optical bistable state is reduced; the optical bistable state is then applied to an optical memory to obtain a decision threshold for writing and reading, and an optical logic with an adjustable threshold is the research focus in the field.

Disclosure of Invention

The invention aims to provide an optical memory based on a rutin-Xiapino photonic crystal aiming at the problems in the prior art, and the technical problem to be solved by the invention is how to enhance the nonlinear effect of graphene and reduce the threshold value of optical bistable state, so that the optical memory can be applied to the optical memory.

The purpose of the invention can be realized by the following technical scheme: the optical memory based on the Lutin-Charcinod photonic crystal is characterized by comprising a plurality of first dielectric layers and a plurality of second dielectric layersThe optical memory comprises a dielectric layer and two graphene single layers, wherein the first dielectric layer is marked as H, the second dielectric layer is marked as L, the graphene single layer is marked as G, and the layered structure of the optical memory is represented as: HHHLHHL₁GL₂HHL₂GL₁HHLHHH, wherein L₁GL₂And L₂GL₁Both represent a three-layer structure formed by embedding a graphene monolayer into a second dielectric layer, the thicknesses of the first dielectric layer and the second dielectric layer are 1/4 of the optical wavelength of each dielectric layer, and the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indexes; the photonics crystal based on the rutin-Charcot optical memory can realize low-threshold optical bistable state, and the upper threshold and the lower threshold of the bistable state respectively correspond to the writing-in judgment threshold and the reading-out judgment threshold of the photonics crystal based on the rutin-Charcot optical memory.

Further, the first dielectric layer is made of lead telluride which is a high-refractive-index material, and the second dielectric layer is made of cryolite which is a low-refractive-index material.

Further, the writing decision threshold, the reading decision threshold, and the interval between the writing decision threshold and the reading decision threshold of the optical memory are regulated and controlled by the chemical potential of the graphene monolayer.

Further, the writing decision threshold, the reading decision threshold, and the interval between the writing decision threshold and the reading decision threshold of the optical memory are regulated and controlled by incident wavelength.

Two dielectric sheets A and B with different refractive indexes are sequentially arranged according to a Rudin-Shapiro (RS) sequence with the sequence number N being 3 to form an RS photonic crystal pair symmetrical about an origin; embedding the two graphene single layers into the RS photonic crystal pair to form a composite structure; the RS photonic crystal pair has an optical fractal which has a local effect on an electric field; the two graphene single layers are just positioned at the position with the strongest local electric field corresponding to one of the optical fractal states respectively, so that the third-order nonlinear optical effect of the graphene is greatly enhanced, and further the low-threshold optical bistable state is realized; the threshold value of the optical bistable state in the structure can be as low as 10MW/cm²This is compared to Thue-Morse lightThe optical bistable threshold in the composite structure of the sub-crystal and the graphene is lower by 4 orders of magnitude.

The upper and lower thresholds of the optical bistable state in the Luding-Charcinod photonic crystal structure and the interval between the upper and lower thresholds are increased along with the increase of the chemical potential and the incident wavelength of the graphene. Therefore, when the optical bistable effect is applied to an optical memory, the writing and reading decision thresholds of the optical memory and the interval between the writing and reading decision thresholds can be flexibly regulated and controlled through the chemical potential and the incident wavelength of the graphene.

Drawings

Fig. 1 is a schematic diagram of a composite structure of two RS photonic crystals with sequence number N-3 and graphene.

Fig. 2 is a linear transmission spectrum of light waves in a composite structure of two RS photonic crystals with sequence number N-3.

FIG. 3 shows the wavelength λ₁A normalized electric field distribution corresponding to an optical fractal of 1.7271 μm.

In FIG. 4, (a) is a graph showing the input-output intensity relationship corresponding to different chemical potentials of graphene; the graph (b) in fig. 4 shows the variation of the upper and lower bistable thresholds with the chemical potential of graphene.

FIG. 5 is a graph (a) showing the input-output intensity relationship for different incident wavelengths; the graph (b) in fig. 5 shows the variation of the upper and lower thresholds of the bistable state with the incident wavelength.

Fig. 6 is a schematic diagram of an optical memory based on optical bistability.

In the figure, H, a first dielectric layer; l, a second dielectric 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.

Mathematically, the iterative rule for the rutin-Charcinod (Rudin-Shapiro: RS) sequence is: s₀＝H，S₁＝HH，S₂＝HHHL，S₃＝HHHLHHLH，……，S_N＝S_N-1(HH→HHHL，HL→HHLH，LH→LLHL，LL→LLLH) … … where N (0, 1, 2, 3, … …) denotes the sequence number, S_NThe Nth item representing the sequence, HH → HHHL representing S_N-1HH in (1) is replaced by HHHL.

Fig. 1 shows a schematic diagram of a composite structure of two binary RS photonic crystals with sequence number N ═ 3 and graphene. Two binary RS photonic crystals are symmetrically distributed about the origin and can be represented as: HHHLHHLHHLHHGHHH, wherein the letters H, L denote two homogeneous dielectric sheets with different high and low refractive indices, respectively; and then respectively embedding the two graphene single layers into the position with the strongest local electric field corresponding to one fractal state to form a composite structure, wherein the composite structure can be expressed as: HHHLHHL₁GL₂HHL₂GL₁HHLHHH, wherein G represents a graphene monolayer. The composite structure is centrosymmetrically distributed about the origin, similar to a distributed feedback bragg grating. The horizontal direction to the right is the positive direction of the coordinate axis Z direction.

In the RS photonic crystal pair, H is a high-refractive-index material lead telluride, and the refractive index of the material is n_H＝4.1；L、L₁And L₂Is a low refractive index material cryolite having a refractive index n_L1.35. Both H and L have a thickness of 1/4 optical wavelengths, i.e., H has a thickness d_H＝λ₀/4/n_H0.0945 μm (μm denotes μm), where λ₀1.55 μm as the center wavelength and L as the thickness d_L＝λ₀/4/n_L＝0.287μm。L₁Has a thickness of d_L1＝0.1933μm，L₂Has a thickness of d_L20.0937 μm, satisfies the condition d_L1+d_L2＝d_L. The incident light is transverse magnetic wave and is vertically incident from the left.

Single layer graphene has a thickness of about 0.33nm (nm means nanometers), which corresponds to the size of one atom. With respect to the dielectric sheet H, L, L₁And L₂The thickness of graphene is negligible. Here, the ambient temperature is set to 300K (K denotes kelvin), and the relaxation time τ of the electrons in the graphene is 0.5ps (ps denotes picosecond).

Changing the incident light frequency, when the effect of graphene is not considered, as given in FIG. 2The linear transmission spectrum of the light wave in the composite structure of the two RS photonic crystals with the sequence number N being 3. The ordinate T represents the transmittance of light waves; abscissa (ω - ω)₀)/ω_gapDenotes a normalized angular frequency, where ω is 2 π c/λ, ω₀＝2πc/λ₀And ω_gap＝4ω₀arcsin│(n_H-n_L)/(n_H+n_L)|²And/pi respectively represents incident light angular frequency, incident light central angular frequency and angular frequency band gap, c is light speed in vacuum, and arcsin is an inverse sine function. At normalized frequency of [ -0.25,0.25]Within the interval, there are 3 transmission formants corresponding to 3 resonance optical partial forms. They are independent of each other and are separated by a suitable distance. The 3 transmittance peaks are all 1, and the corresponding medium wavelengths are respectively: lambda [ alpha ]₁＝1.7271μm、λ₂1.55 μm and λ₃1.4058 μm. The 3 optical sub-morphologies all have a local effect on the electric field, and only the 1 st resonance state (marked with a star) is selected here to obtain the corresponding mode field distribution. And then the graphene single layer is embedded at the position with the strongest local electric field intensity in the structure, so that the nonlinear effect of the graphene is enhanced, and the low-threshold optical bistable state is realized. In addition, to achieve low threshold optical bistability near the 1 st formant, the incident wavelength must be relative to the 1 st resonance wavelength λ₁Suitably red detuned at 1.7271 μm.

FIG. 3 shows the electric field distribution of the 1 st resonant optical fractal in the composite structure of FIG. 2, corresponding to the resonant wavelength λ₁1.7271 μm. The dotted line represents the interface of two adjacent dielectric sheets, and two graphene monolayers G are respectively embedded at two positions with the strongest local electric field strength in the structure. The ordinate represents the normalized Z-component electric field strength. It can be seen that the distribution of the electric field energy in the structure is not uniform and localized. The two graphene monolayers are located at two positions with the strongest local electric field. The optical third-order nonlinear effect of the graphene is in direct proportion to the local electric field intensity, so that the nonlinear effect of the graphite is greatly enhanced.

The fixed incident wavelength λ is 1.748 μm relative to the first optical fractal resonance wavelength λ₁＝1.727There is some red detuning at 1 μm. When the input light intensity is strong enough, the nonlinear effect of the graphene is considered, other parameters are kept unchanged, and the input-output light intensity relation corresponding to different graphene chemical potentials mu is shown in fig. 4 (a). Abscissa I_iRepresenting input light intensity, ordinate I_oRepresenting the output light intensity; unit MW/cm²Representing megawatts per square centimeter. It can be seen that: when mu is 0.4eV and 0.5eV, the input-output light intensity relation curves have a section of S-shaped curve section corresponding to the bistable state relation; and when μ ═ 0.3eV, the input-output light intensity relationship is non-bistable.

Increasing the input light intensity, and enabling the output light intensity to jump upwards at the right turning point of the S curve section, wherein the corresponding input light intensity value at the moment is called as an upper threshold value of the optical bistable state; when the input light intensity is gradually reduced from a relatively large value, the output light intensity jumps downwards at the left turning point of the S curve section, and the corresponding input light intensity value at the moment is called as a lower threshold value of the optical bistable state; the difference between the upper and lower thresholds is called the threshold interval.

When the input intensity is between the upper and lower threshold values, one input intensity value corresponds to two output intensity values, which is called optical bistability. The S-shaped curve segment in the input-output light intensity relation outline is the typical characteristic of the optical bistable state, and the effect can be used for the optical storage.

Increasing the mu value, wherein bistable curves corresponding to different graphene chemical potentials are different, and the upper threshold value, the lower threshold value and the threshold interval of the bistable state are also different; as the chemical potential of graphene increases, both upper and lower bistable thresholds increase, and the interval between bistable thresholds increases, as shown in fig. 4 (b). Ordinate I_thA threshold value indicative of bistability; symbol I_uAnd I_dRepresenting bistable upper and lower thresholds, respectively. When mu is more than or equal to 0.36eV, the input-output light intensity relation is bistable; the bistable upper and lower thresholds, and the threshold interval, both increase with increasing chemical potential of the graphene. Therefore, the upper and lower thresholds and the threshold interval of the bistable state can be regulated by the chemical potential of graphene.

Optical bistable threshold in a composite system of Thue-Morse photonic crystals and grapheneThe value is 100GW/cm²Magnitude, while in the composite structure of two RS photonic crystals and graphene, the optical bistable threshold is reduced to 10MW/cm²Magnitude.

In addition, the corresponding bistable curves and thresholds are different for different incident wavelengths.

The fixed graphene chemical potential μ is 0.4eV, other parameters are kept unchanged, and fig. 5(a) shows the input-output light intensity relationship corresponding to different incident wavelengths. It can be seen that: when λ is 1.57 μm to 1.58 μm, input-output optics are bistable; the bistable curves corresponding to different incident wavelengths are different, namely the upper threshold value, the lower threshold value and the threshold value interval of the bistable state are different; as the incident wavelength increases, i.e., the amount of wavelength detuning increases, the bistable upper and lower threshold values increase, and the bistable upper and lower threshold intervals also increase, as shown in fig. 5 (b). The larger the detuning amount of the wavelength, the more the difference needs to be made up by the nonlinear effect to achieve resonance, and the stronger the incident light energy needed to satisfy resonance. Thus, the upper and lower thresholds and threshold spacing of the bistable states can be tuned by the incident wavelength.

In a word, two graphene monolayers are embedded into an RS photonic crystal pair to form a composite structure, a resonant optical fractal state exists in the composite structure, and the optical fractal state has a strong local effect on an electric field; the two graphene single layers are just positioned at the strongest position of the local electric field corresponding to one optical fractal state respectively, so that the nonlinear effect of the graphene is greatly enhanced, and the low-threshold optical bistable state is realized; threshold of optical bistability as low as 10MW/cm²The magnitude is 4 magnitudes smaller than the optical bistable state in the compounding of the Thue-Morse photonic crystal and the graphene; the optical bistable state can be applied to an optical memory, and the writing and reading judgment threshold values of the optical memory and the interval between the writing and reading judgment threshold values can be flexibly regulated and controlled through the chemical potential and the incident wavelength of the graphene.

The wavelength of incident light is set to λ 1.748 μm, the chemical potential is set to μ 0.4eV, and an optical bistable phenomenon appears in the input-output light intensity relationship, and the principle of the optical bistable phenomenon is applied to an optical memory as shown in fig. 6. When the input light intensity is changed from a lower valueWhen the light intensity is gradually increased, an upward jump occurs in the output light intensity at the right turning point of the S curve section, and the input light intensity I_i＝I_uAn upper threshold called optical bistable, which corresponds to the writing process of the optical memory, and_i＝I_ucalled the write decision threshold of the optical memory; when the input light intensity is gradually reduced from a higher value, the output light intensity generates a downward jump at the left turning point of the S curve section, and the input light intensity I_i＝I_dLower threshold called optical bistable, which corresponds to the reading process of the optical memory, and I_i＝I_dCalled the read decision threshold of the optical memory. When the corresponding write-in decision threshold is I_u＝44.4985MW/cm²Read decision threshold of I_d＝31.9573MW/cm²The interval between the write and read decision thresholds is I_u-I_d＝12.5412MW/cm²。

Fig. 4(b) and 5(b) show that the input-output curve of the optical bistable state is affected by the graphene chemical potential and the incident wavelength. The chemical potential and the input wavelength of the graphene are different, and the positions of two inflection points in the corresponding S curve section are also changed. The two inflection points of the S-curve segment correspond to the upper and lower thresholds of the optical bistable state, i.e., the read and write decision thresholds of the optical memory, respectively. Therefore, the read and write decision thresholds of the optical memory, and the interval between the read and write decision thresholds, can be adjusted by the chemical potential and input wavelength of the graphene. It can be seen that as the chemical potential and input wavelength increase, the read and write decision thresholds of the optical storage, and the interval between the read and write decision thresholds, both increase.

The larger the decision threshold interval of the optical memory is, the greater the discrimination between write and read operations is, and the smaller the probability of erroneous operation is. To reduce the mishandling rate of the optical storage, the chemical potential or wavelength detuning amount of the graphene needs to be increased, and meanwhile, the write-in and read-out decision thresholds of the optical storage are increased, so that the reduction of the mishandling rate of the optical storage is achieved at the cost of increasing the decision threshold of the optical storage.

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.