CN110737047A - read-write controllable silicon-based integrated optical buffer - Google Patents

Abstract

The invention discloses a read-write controllable silicon-based integrated optical buffer, which comprises a non-reciprocal silicon-based rectangular waveguide and a graphene layer arranged in sequence on the left and right, wherein the graphene layer is integrated in the non-reciprocal silicon-based rectangular waveguide The output end face on the right side forms a read/write control end face; the read/write control end face regulates the graphene transmission coefficient by applying a voltage to determine whether the unidirectional transmission signal light entering the non-reciprocal silicon-based rectangular waveguide can transmit Through the graphene layer, the read/write control of the optical buffer is realized. The read-write controllable silicon-based integrated optical buffer of the present invention can realize the effect of convenient, adjustable and low-loss signal light writing and reading operations of the optical buffer.

Description

A read-write controllable silicon-based integrated optical buffer

technical field

The invention relates to the technical field of optoelectronic integration, in particular to a read-write controllable silicon-based integrated optical buffer.

Background technique

The research of all-optical caching technology has also received more and more attention as a key issue in the realization of optical quantum computers. The scheduling and control of data in the optical quantum computing technology is the basis of the optical quantum computer. Whether in the CPU or in the whole machine, various registers, memories, and buffers for accessing data are flooded. After the optical interconnection between chips is adopted, if the storage of data can be carried out in the optical domain without the need for multiple photoelectric conversions, it will be beneficial from various perspectives such as increasing the speed, improving the signal quality and reducing the energy consumption. of. For all-optical network node devices, such as all-optical switching routers, its node quantity, throughput, packet loss rate and other characteristics are directly related to its memory capacity, access speed and other characteristics. All-optical caching technology It can not only provide adjustable buffering time for nodes to process frame headers, but also solve the competition problem of the same port. Therefore, all-optical buffering technology is a key technology for all-optical routing control and solving channel competition. Its quality directly determines the Optical quantum computer information processing and storage performance. Therefore, the study of all-optical buffers is of great significance for the development of optical quantum computers in the future.

In all current researches, optical buffers of various structures have their own advantages and challenges: the slow optical buffers based on Electrically Induced Transparency (EIT) have high cost, complex system structure and manufacturing process, so it is difficult to realize; based on optical fiber delay Although the linear optical buffer can provide a large delay, its resolution is limited by the tuning step, and its size is large, so it is not easy to integrate into a microsystem; the optical buffer based on the slow light effect of photonic crystals exists and is limited by the The same problem of the slow light effect of laser Brillouin scattering (SBS), which has a small dynamic range of delay time and a total delay time of less than nanoseconds; optical microring resonator is a small and compact optical device, which is similar to Optical buffers of photonic crystal structure are comparable, but slightly inferior to optical buffers of photonic crystal structure in their optical performance, tunability, flexibility and reproducibility, and it is impossible to reduce the multi-ring resonant optical buffer simultaneously size and dispersion of the filter. Although the multi-stage cascade structure of optical switches and waveguide delay lines can realize a large-scale adjustment of the optical delay, it is not a cache in the true sense, but rather a temporary memory. In addition, these types of buffers are limited by bandwidth and delay time, that is, the product of storage time and system bandwidth is fixed. It is impossible to store large data for a long time in a resonator.

Although there are some research institutes studying non-reciprocal waveguides in the world, most of their researches focus on using non-reciprocal waveguides to realize non-reciprocal devices such as optical isolators and optical circulators. Cache related research reports. In addition, most of this research is concentrated in the terahertz band, and no relevant research reports in the optical communication band have been found. However, the terahertz frequency domain spectrum has defects such as low radiation power and narrow spectral range, and the size of terahertz devices is mostly digital. On the order of ten micrometers to millimeters, it is difficult to miniaturize the system size.

A very important aspect in evaluating the performance of an optical buffer is the ease of "write" and "read" operations of the signal light. In the traditional all-optical buffer based on the semiconductor SOA amplifier, since the optical signal needs to pass through the optical amplifier repeatedly, it is easy to cause the accumulation of noise, and the control technology is relatively complicated.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a silicon-based integrated optical buffer with controllable reading and writing, which is simple in structure, convenient and controllable, and can also realize buffering and reading and writing control of signal light in the C-band of optical communication.

In order to achieve the above object, the present invention provides a silicon-based integrated optical buffer with read-write controllable, comprising a non-reciprocal silicon-based rectangular waveguide and a graphene layer arranged in sequence on the left and right, and the graphene layer is integrated in the non-reciprocal silicon-based rectangular waveguide. The right output end face of the silicon-based rectangular waveguide forms the read/write control end face;

The read/write control end face regulates the graphene transmission coefficient by applying a voltage, and determines whether the unidirectional transmission signal light entering the non-reciprocal silicon-based rectangular waveguide can pass through the graphene layer to realize the optical buffer. read/write control.

Preferably, when a lower voltage is applied to the graphene layer, the graphene transmission coefficient is small, and the unidirectional transmission signal light entering the non-reciprocal silicon-based rectangular waveguide is reflected on the surface of the graphene layer for amplitude accumulation. , to realize write control to the optical buffer;

When a higher voltage is applied to the graphene layer, the graphene transmission coefficient becomes larger, and the optical pulse signal stored in the non-reciprocal silicon-based rectangular waveguide passes through the graphene layer to realize the control of reading the optical buffer. .

Preferably, the non-reciprocal silicon-based rectangular waveguide includes a metal nanolayer, a magneto-optical material layer, a silicon semiconductor layer and a metal nanolayer that are stacked sequentially from bottom to top.

Preferably, the size of the non-reciprocal silicon-based rectangular waveguide is in the order of nanometers.

Preferably, the metal nanolayer is an Ag metal nanolayer.

Preferably, the magneto-optical material layer is a Ce:YIG layer.

Preferably, the magneto-optical material layer breaks the symmetry of the dielectric constant under the action of an external magnetic field and the wavelength of the C-band of the optical communication to generate spinoelectric anisotropy, so that the light has the property of unidirectional transmission.

Preferably, the non-reciprocal frequency interval is regulated by the Faraday optical rotation coefficient of the magneto-optical material layer, and the Faraday optical rotation coefficient is proportional to the size of the non-reciprocal frequency interval.

Preferably, the wavelength range of the optical communication C-band is 1530-1565 nm.

Preferably, the chemical potential, electrical conductivity and dielectric constant of the graphene layer are adjusted by adjusting the external voltage loaded on the graphene layer, so that the graphene layer exhibits metallic properties and realizes the function of an optical switch .

Preferably, the loss of the surface wave of the graphene layer is reduced by increasing the chemical potential of the graphene layer.

Compared with the prior art, the read-write controllable silicon-based integrated optical buffer provided by the present invention has the following beneficial effects:

1. The magneto-optical material layer used in the present invention can break the limitation of "time-bandwidth" limit under the action of an external magnetic field, and the bandwidth range is adjustable, and it can also work in the C-band of optical communication.

2. The output control end face of the non-reciprocal silicon-based rectangular waveguide of the present invention adopts the read and write control scheme of graphene material, which can realize the operation of writing and reading the optical buffer with convenient adjustable and low loss signal light.

Description of drawings

The accompanying drawings used in the present application will be briefly described below. Obviously, these drawings are only used to explain the concept of the present invention.

1 is a schematic structural diagram of a read-write controllable silicon-based integrated optical buffer according to the present invention;

Fig. 2 is the dispersion curve diagram of the non-reciprocal silicon-based rectangular waveguide;

Fig. 3 is the group velocity diagram of the unidirectional transmission region of the non-reciprocal silicon-based rectangular waveguide;

Fig. 4 is a graph showing the change of the electrical conductivity of the graphene layer with the chemical potential in the optical communication 1550nm band;

FIG. 5 is a graph showing the change of the dielectric constant of the graphene layer with the chemical potential in the optical communication 1550 nm band.

Summary of reference numbers:

1. Metal nanolayer 2. Magneto-optical material layer 3. Silicon semiconductor layer

4. Metal nanolayer 5. Graphene layer

Detailed ways

Hereinafter, embodiments of a read-write controllable silicon-based integrated optical buffer of the present invention will be described with reference to the accompanying drawings.

The embodiments described herein are specific embodiments of the present invention, are used to illustrate the concept of the present invention, are illustrative and exemplary, and should not be construed as limiting the embodiments of the present invention and the scope of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims and the description of the present application, and these technical solutions include adopting any modifications made to the embodiments described herein. Obvious alternative and modified technical solutions.

The accompanying drawings in the present specification are schematic diagrams to assist in explaining the concept of the present invention, and schematically show the shapes of various parts and their mutual relationships. Please note that, in order to clearly represent the structure of each component of the embodiments of the present invention, the drawings are not necessarily drawn on the same scale. The same reference numerals are used to designate the same or similar parts.

Specific embodiments of the present invention will be explained below with reference to FIGS. 1 to 5 .

As shown in FIG. 1 , the present invention provides a silicon-based integrated optical buffer with read-write controllable, including a non-reciprocal silicon-based rectangular waveguide and a graphene layer 5 arranged in sequence on the left and right, wherein the graphene layer 5 is integrated in the The right output end face of the non-reciprocal silicon-based rectangular waveguide forms the read/write control end face. The read/write control end face regulates the graphene transmission coefficient by applying a voltage, and determines whether the unidirectional transmission signal light entering the non-reciprocal silicon-based rectangular waveguide can pass through the graphene layer 5 to realize the read/write of the optical buffer. control.

In a further embodiment of the present invention, the non-reciprocal silicon-based rectangular waveguide includes a metal nanolayer 1 , a magneto-optical material layer 2 , a silicon semiconductor layer 3 and a metal nanolayer 4 that are stacked sequentially from bottom to top. Preferably, the size of the non-reciprocal silicon-based rectangular waveguide is in nanometer order, the metal nanolayers 1 and 4 are Ag metal nanolayers, and the magneto-optical material layer 2 is a Ce:YIG layer.

The metal nano-layers 1 and 4 of the present invention select Ag metal nano-layers because metal Ag has lower loss compared with other metals.

The magneto-optical material layer 2 of the present invention is a Ce:YIG layer. Under the action of an external magnetic field, the magneto-optical material layer 2 (Ce:YIG layer) can break the symmetry of the dielectric constant under the condition of the C-band wavelength of optical communication, and generate spinoelectric anisotropy, that is, break the Lorentz reciprocity, realize The "time-bandwidth limit" is surpassed, and light has the property of unidirectional transmission. Among them, the wavelength range of the optical communication C-band is 1530-1565 nm. The dielectric constant of the magneto-optical material is expressed as:

The present invention regulates the non-reciprocal frequency interval by using the Faraday optical rotation coefficient of the magneto-optical material layer 2, and the Faraday optical rotation coefficient is proportional to the size of the non-reciprocal frequency interval. Among them, in order to calculate the non-reciprocal frequency range of the optical buffer, the dispersion curve of the non-reciprocal silicon-based rectangular waveguide structure as shown in Figure 2 can be obtained by calculating the dispersion equation. The above dispersion equation is:

为磁光材料的佛克脱介电常数；在非互易硅基矩形波导的外包层

ε_m为外层材料的介电常数，t为时间。由于对洛伦兹互易性的破坏，其色散曲线关于波矢k不对称，在不对称的频率(图中两水平虚线之间)区域内可以实现完全的单向传输，非互易硅基矩形波导表现出非互易性。其中法拉第旋光系数的大小决定了非互易频率区间的大小。由此使得非互易硅基矩形波导在外加磁场作用下可以打破“时间-带宽”极限的限制，最大非互易频率区间可达6.88×10¹³rad/s，信号光可在该宽频带上单向传输。因此，将信号光注入非互易硅基矩形波导，在外磁场的作用下可以实现非互易单向传输。Among them, in the above dispersion equation: k is the propagation constant, in the silicon semiconductor layer k ₀ =ω/c is the wave number in vacuum, the relative permittivity of silicon is ε _Si , and the thickness of the silicon semiconductor layer 3 is d;

is the Fokker's dielectric constant of magneto-optical materials; in the outer cladding of non-reciprocal silicon-based rectangular waveguides

ε _m is the dielectric constant of the outer layer material, and t is the time. Due to the destruction of Lorentz reciprocity, its dispersion curve is asymmetric about the wave vector k, and complete unidirectional transmission can be achieved in the asymmetric frequency (between the two horizontal dotted lines in the figure) region, non-reciprocal silicon-based Rectangular waveguides exhibit non-reciprocity. The size of the Faraday optical rotation coefficient determines the size of the non-reciprocal frequency interval. As a result, the non-reciprocal silicon-based rectangular waveguide can break the "time-bandwidth" limit under the action of an external magnetic field, and the maximum non-reciprocal frequency range can reach 6.88×10 ¹³ rad/s. One-way transmission. Therefore, when the signal light is injected into the non-reciprocal silicon-based rectangular waveguide, non-reciprocal unidirectional transmission can be achieved under the action of an external magnetic field.

通过计算可以得到图3所示非互易硅基矩形波导的缓存性能，图3计算了不同法拉第旋光系数Θ_f的非互易硅基矩形波导，其归一化群速度与归一化角频率ω/ω_p和归一化传播常数k/k_p的关系.可以看出不管是随着ω(虚线)增大还是随着k(实线)增大，均出现群速度减慢现象.并且当法拉第旋转系数为57deg/um时，慢光效应更明显，最小传输速度可达到1.25×10^-4c。For the non-reciprocal silicon-based rectangular waveguide, the slope of the dispersion curve corresponds to the normalized propagation velocity v _g /c in the non-reciprocal silicon-based rectangular waveguide. In order to calculate the buffer performance of the optical buffer, the dispersion curve is obtained by using the dispersion equation, and combined with the electromagnetic wave group velocity formula

The cache performance of the non-reciprocal silicon-based rectangular waveguide shown in Figure 3 can be obtained by calculation. Figure 3 calculates the normalized group velocity and normalized angular frequency of the non-reciprocal silicon-based rectangular waveguide with different Faraday optical rotation coefficients Θ _f . The relationship between ω/ω _p and the normalized propagation constant k/k _p . It can be seen that the group velocity slows down whether ω (dashed line) or k (solid line) increases. And When the Faraday rotation coefficient is 57deg/um, the slow light effect is more obvious, and the minimum transmission speed can reach 1.25×10 ^-4 c.

The read/write control end face of the non-reciprocal silicon-based rectangular waveguide of the present invention is composed of a graphene layer 5 integrated on the end face of the non-reciprocal silicon-based rectangular waveguide. By adjusting the external voltage loaded on the graphene layer 5, adjusting its chemical potential, changing the electrical conductivity and dielectric constant, the graphene layer 5 shows special metal properties and realizes the function of an optical switch; The chemical potential can reduce the loss of its surface wave.

Its surface conductivity can be calculated by the following Cooper formula:

为约化普朗克常数，ω表示角频率，为电子的费米-狄拉克分布，T为温度，μ_c为磁导率(可以通过改变掺杂和偏置电压改变)，Γ为弛豫时间。石墨烯层5的表面介电常数：

其中Δ为单层石墨烯厚度。以图4、5为例，为根据上述公式根据光通信1550nm波长条件下计算的石墨烯层5电导率随化学势的变化曲线，石墨烯层5的介电常数实部在0eV到0.4eV之间几乎没有变化，之后随着化学势的增加介电常数实部发生下降；介电常数的虚部在0.4eV之前随着化学势的增长而增长，随后下降，值得注意的是，石墨烯层5介电常数的实部下降区间是由正到负的，表明石墨烯层5开始由介质的特性向金属的特性转变。其中，化学势大概在0.515eV时候，石墨烯层5的介电常数绝对值最小，几乎为0，这个特殊的点成为ENZ(epsilon near zero)点，此时电磁波能几乎无损的穿过石墨烯层5。where e is the charge of the electron, ε is the energy,

To reduce Planck's constant, ω is the angular frequency, is the Fermi-Dirac distribution of electrons, T is the temperature, μ _c is the permeability (which can be changed by changing the doping and bias voltage), and Γ is the relaxation time. Surface dielectric constant of graphene layer 5:

where Δ is the thickness of single-layer graphene. Taking FIGS. 4 and 5 as an example, it is a curve of the change of the electrical conductivity of the graphene layer 5 with the chemical potential calculated according to the above formula according to the optical communication 1550nm wavelength condition, and the real part of the dielectric constant of the graphene layer 5 is between 0eV and 0.4eV. There is almost no change between the dielectric constants and then the real part of the dielectric constant decreases with the increase of the chemical potential; the imaginary part of the dielectric constant increases with the increase of the chemical potential before 0.4 eV, and then decreases. It is worth noting that the graphene layer 5 The real part of the dielectric constant decreases from positive to negative, indicating that the graphene layer 5 begins to transform from the characteristics of the dielectric to the characteristics of the metal. Among them, when the chemical potential is about 0.515eV, the absolute value of the dielectric constant of the graphene layer 5 is the smallest, which is almost 0. This special point becomes the ENZ (epsilon near zero) point. At this time, the electromagnetic wave can pass through the graphene almost losslessly. Layer 5.

Therefore, in the present invention, the control of the transmission coefficient of the graphene layer 5 can be used to determine whether the unidirectional transmission signal light entering the non-reciprocal silicon-based rectangular waveguide can pass through the graphene layer 5, so as to realize the read/write control of the optical buffer. . When the signal light is transmitted to the interface between the non-reciprocal silicon-based rectangular waveguide and the graphene layer 5, when a lower voltage is applied to the graphene layer 5, the graphene transmission coefficient is lower, and it enters the non-reciprocal silicon-based rectangular waveguide. The one-way transmission signal light is reflected on the graphene surface, and the amplitude is accumulated to control the writing of the optical buffer. When a higher voltage is applied to the graphene layer 5, the optical pulse signal stored in the non-reciprocal silicon-based rectangular waveguide can pass through the graphene to realize the control of reading the optical buffer.

The embodiment of a read-write controllable silicon-based integrated optical buffer of the present invention has been described above, and the purpose is to explain the spirit of the present invention. Please note that those skilled in the art can modify and combine the features of the above-described embodiments without departing from the spirit of the present invention, and thus, the present invention is not limited to the above-described embodiments. Moreover, the technical features disclosed above are not limited to the disclosed combination with other features, and those skilled in the art can also perform other combinations between the technical features according to the purpose of the invention, so as to achieve the purpose of the present invention.

Claims (10)

1. a controllable silicon-based integrated optical buffer for reading and writing, is characterized in that, comprises the non-reciprocal silicon-based rectangular waveguide and the graphene layer that are arranged successively from left to right, and the graphene layer is integrated in the described non-reciprocal silicon The right output end face of the basic rectangular waveguide forms the read/write control end face; The read/write control end face regulates the graphene transmission coefficient by applying a voltage, and determines whether the unidirectional transmission signal light entering the non-reciprocal silicon-based rectangular waveguide can pass through the graphene layer to realize the optical buffer. read/write control. 2. A kind of read-write controllable silicon-based integrated optical buffer as claimed in claim 1, it is characterized in that, when lower voltage is loaded to described graphene layer, graphene transmission coefficient is smaller, enters described non-volatile The unidirectional transmission signal light of the reciprocal silicon-based rectangular waveguide is reflected on the surface of the graphene layer, and the amplitude is accumulated to control the writing of the optical buffer; When a higher voltage is applied to the graphene layer, the graphene transmission coefficient becomes larger, and the optical pulse signal stored in the non-reciprocal silicon-based rectangular waveguide passes through the graphene layer to realize the control of reading the optical buffer. . 3 . The silicon-based integrated optical buffer with read-write controllable as claimed in claim 1 , wherein the non-reciprocal silicon-based rectangular waveguide comprises metal nano-layers stacked in sequence from bottom to top. 4 . , magneto-optical material layer, silicon semiconductor layer and metal nanolayer. 4 . The silicon-based integrated optical buffer with read-write controllable according to claim 1 , wherein the size of the non-reciprocal silicon-based rectangular waveguide is in nanometer order. 5 . 5 . The read-write controllable silicon-based integrated optical buffer according to claim 3 , wherein the metal nano-layer is Ag metal nano-layer. 6 . 6 . The read-write controllable silicon-based integrated optical buffer according to claim 3 , wherein the magneto-optical material layer is a Ce:YIG layer. 7 . 7. A read-write controllable silicon-based integrated optical buffer according to claim 6, wherein the magneto-optical material layer is under the action of an external magnetic field, and is broken under the condition of optical communication C-band wavelength. Dielectric constant symmetry, resulting in spin anisotropy, so that light has the property of unidirectional transmission. 8 . The read-write controllable silicon-based integrated optical buffer according to claim 6 , wherein the Faraday optical rotation coefficient of the magneto-optical material layer is used to regulate the non-reciprocal frequency interval, and the Faraday optical rotation coefficient is proportional to the size of the non-reciprocal frequency interval. 9 . The read-write controllable silicon-based integrated optical buffer according to claim 7 , wherein the wavelength range of the optical communication C-band is 1530-1565 nm. 10 . 10. A read-write controllable silicon-based integrated optical buffer according to claim 1, wherein the chemical potential of the graphene layer is adjusted by regulating the external voltage loaded on the graphene layer , electrical conductivity and dielectric constant, so that the graphene layer exhibits metallic properties and realizes the function of an optical switch.

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