阅读说明：本技术 一种基于非对称超表面的载流子色散型全光开关 (Carrier dispersion type all-optical switch based on asymmetric super surface ) 是由 文永正 路亚峰 郎光辉 周济 范本勇 吴经欧 于 2021-09-03 设计创作，主要内容包括：本发明公开了一种基于非对称超表面的载流子色散型全光开关。该全光开关的基本结构为周期排列的二维非对称半导体颗粒结构单元组成的超表面阵列。在泵浦光的照射下,半导体颗粒材料内部发生载流子色散效应,光生载流子密度的大幅增加使全光开关器件的谐振波长发生偏移,在信号光工作波长附近发生特征频谱的峰-谷(或谷-峰)转换。通过该过程,泵浦光束完成了对信号光束的通/断操控,实现了以光控光的全光开关。同时,本发明还提供了一种有效降低全光开关泵浦光强的方法。(The invention discloses a carrier dispersion type all-optical switch based on an asymmetric super surface. The basic structure of the all-optical switch is a super-surface array consisting of periodically arranged two-dimensional asymmetric semiconductor grain structure units. Under the irradiation of pumping light, a carrier dispersion effect occurs inside the semiconductor particle material, the resonance wavelength of the all-optical switching device is shifted due to the great increase of the density of photon-generated carriers, and the peak-to-valley (or valley-to-peak) conversion of a characteristic spectrum occurs near the working wavelength of signal light. Through the process, the pumping light beam completes on/off control of the signal light beam, and the all-optical switch of light control light is realized. Meanwhile, the invention also provides a method for effectively reducing the pumping light intensity of the all-optical switch.)

1. A carrier dispersion type all-optical switch based on an asymmetric super surface is structurally a super surface array formed by two-dimensional asymmetric semiconductor particle structure units which are arranged periodically.

2. The asymmetric super-surface based carrier dispersion all-optical switch of claim 1, wherein: the two-dimensional asymmetric semiconductor grain structure unit has asymmetry under single or multiple symmetry standards and has sub-wavelength dimensions.

3. The asymmetric super-surface based carrier dispersion all-optical switch according to claim 1 or 2, wherein: the material of the semiconductor particles has stronger carrier dispersion effect at the wavelength of the pump light and has higher refractive index and lower loss at the wavelength of the signal light; the semiconductor material used for the semiconductor particles includes but is not limited to: si, Ge, GaAs.

4. The asymmetric, super-surface based, carrier-dispersive all-optical switch according to any of claims 1-3, wherein: the array of super-surfaces is arranged on the surface of the substrate or is arranged inside the substrate.

5. The asymmetric super-surface based carrier dispersion all-optical switch according to claim 4, wherein: the substrate is made of a material with high transmission and low loss on incident light; the incident light comprises signal light and pump light; the materials of the substrate include, but are not limited to: polymeric materials, dielectric materials, and other solid materials.

6. The asymmetric super-surface based carrier dispersion all-optical switch according to claim 4 or 5, wherein: the dielectric constants of the semiconductor particle constituent material and the substrate constituent material are different from each other so as to satisfy bound-state resonance mode excitation.

7. The asymmetric, super-surface based, carrier-dispersive all-optical switch according to any of claims 1-6, wherein: the structural units are designed into two-dimensional asymmetric semiconductor particles, and the purpose of the structural units is to realize the multi-pole mode coupling between different particles inside the structural units or between the structural units when external electromagnetic waves irradiate the super-surface, so as to excite the bound mode of the asymmetric super-surface, wherein the mode corresponds to a sharp characteristic spectrum in a spectrum.

8. The asymmetric, super-surface based, carrier-dispersive all-optical switch according to any of claims 1-7, wherein: the characteristic frequency spectrum of the all-optical switch corresponds to a resonance peak (or valley) at the working wavelength of the signal light;

when the pump light with photon energy larger than the forbidden band width of the semiconductor material irradiates the super surface, a large number of photon-generated carriers are generated in the semiconductor particles, so that the dielectric constant or refractive index of the semiconductor particles is reduced, the resonant wavelength of the super surface is shifted, and through the process, the pump light beam can complete on/off control of the signal light beam, and the all-optical switch for controlling light is realized.

9. The asymmetric, super-surface based, carrier-dispersive all-optical switch according to any of claims 1-8, wherein: adjusting the sharpness of the characteristic spectrum of the all-optical switch by adjusting the asymmetry of the semiconductor particles in the super-surface; by adjusting the size of the semiconductor particles in the super-surface and tuning the resonance wavelength of the super-surface to the expected signal light working wavelength, the tunable range can cover the optical band between the radio frequency and the photon wavelength corresponding to the forbidden bandwidth of the used semiconductor particle material.

10. The asymmetric, super-surface based, carrier-dispersive all-optical switch according to any of claims 1-9, wherein: the sharper the characteristic frequency spectrum of the super surface is, the smaller the pumping light intensity required by the all-optical switch is, and the sharpness degree of the characteristic frequency spectrum is customized by adjusting the asymmetry degree of the particle structure unit to reduce or customize reasonable pumping light intensity.

Technical Field

The invention belongs to the technical field of all-optical information, and particularly relates to a carrier dispersion type all-optical switch based on an asymmetric super-surface.

Background

Emerging technologies of the modern information society, such as the internet, the internet of things, big data, cloud computing and the like, are established on the basis of information technologies of data storage, transmission, processing and the like. The dramatic increase of data volume has enabled the volume of information to be transferred and processed to increase, the bottleneck limitations of the conventional electronic devices in terms of power consumption, delay, bandwidth, crosstalk, noise, etc. become more and more prominent, and the transmission and processing of information face a serious challenge. At present, all-optical information technology with photons as information carrier is considered as a major approach to break the physical limits of electronic devices. The most important and essential all-optical devices in all-optical information technology are all-optical switches. The working process of the all-optical switch is similar to that of an electronic switch, and the key difference is that the all-optical switch realizes on/off control of a signal light transmission process by using control light, and is a basic device for constructing an ultra-fast all-optical switching network and an all-optical processor. The use of the all-optical switch device can enable optical communication to avoid photoelectric conversion and electronic exchange links, and really realize optical speed transmission of information; photon devices such as an all-optical switch and the like are used for forming various optical logic gates to replace the current electronic logic gates, and data are coded in an optical mode to realize all-optical calculation.

Disclosure of Invention

The invention aims to provide a carrier dispersion type all-optical switch based on an asymmetric super surface.

The invention combines the Mie scattering theory of the super surface of the semiconductor particles with the carrier dispersion effect of the semiconductor material, and utilizes the resonance wavelength shift of the super surface characteristic frequency spectrum to complete the on/off control of the signal light transmission process, thereby realizing the all-optical switch of light control.

The principle on which the invention is based is as follows:

the structural units constituting the super-surface all-optical switch have asymmetry under a single or multiple symmetry standards, and according to the Mie scattering theory, when external electromagnetic waves irradiate the super-surface, a bound mode with broken symmetry is excited in the structural units, wherein the bound mode corresponds to a sharp characteristic spectrum in a spectrum.

The resonance wavelength shift of the characteristic spectrum of the super-surface all-optical switch is realized by the carrier dispersion effect of the semiconductor particle material. The specific process is that the carrier concentration in the semiconductor material is changed through the irradiation of the pump light to cause the change of the complex refractive index of the material, thereby achieving the purpose of dynamically regulating and controlling the resonance wavelength of the semiconductor particle material by utilizing the pump light.

Large refractive index changes require large pump intensities according to the carrier dispersion equation. In order to reduce the pump intensity, the refractive index change required for the resonant wavelength shift of the device characteristic spectrum must be reduced. The sharper the characteristic spectrum of the device, the smaller the shift of the resonant wavelength required to realize the switching function of the device, and the smaller the corresponding change in refractive index. The invention realizes the super surface with sharp characteristic frequency spectrum by adjusting the asymmetry of the semiconductor particle structure unit, realizes the dynamic frequency shift required by the all-optical switch by using lower pumping light intensity, and effectively reduces the driving power consumption of the all-optical switch. The reduction of the pump light power is the key for the practicality of the all-optical switch and is an important innovation point of the patent.

In order to achieve the purpose, the invention adopts the following technical scheme:

a carrier dispersion type all-optical switch based on an asymmetric super surface is a super surface array which is composed of two-dimensional asymmetric semiconductor particle structure units which are arranged periodically.

The array of super-surfaces may be arranged on the surface of the substrate or may be placed inside the substrate. The specific manner depends on the requirements.

The two-dimensional asymmetric semiconductor grain structure unit has asymmetry under single or multiple symmetry standards and has sub-wavelength dimensions. The structural unit structure is designed to be an asymmetric structure, so that when external electromagnetic waves (namely signal light) irradiate the super-surface, multipole mode coupling between different particles inside the structural unit or between the structural units is realized, and a bound mode of the asymmetric super-surface is excited. The mode has a sharp characteristic spectrum, and the signal light working wavelength corresponds to a resonance peak (or valley), i.e. high (or low) transmission intensity (or reflection intensity, diffuse reflection intensity, etc.). When the pump light with photon energy larger than the forbidden band width of the semiconductor material irradiates the super surface, a large number of photon-generated carriers are generated in the semiconductor particles, so that the dielectric constant (or refractive index) of the semiconductor particles is reduced, and the resonant wavelength of the super surface is shifted. At this time the operating wavelength corresponds to a resonance valley (or peak), i.e. a low (or high) transmission intensity (or reflection intensity, diffuse reflection intensity, etc.). Through the process, the pumping light beam can complete on/off control of the signal light beam, and the all-optical switch of light control light is realized.

The semiconductor particles should be made of a material having a strong carrier dispersion effect at the pump light wavelength and a high refractive index and low loss at the signal light wavelength. Materials that may be employed include, but are not limited to: various semiconductor materials such as Si, Ge, GaAs, and the like.

According to one embodiment of the invention, square units composed of polysilicon asymmetric (different lengths) double-rod structures are selected as structural units and are periodically arranged on a two-dimensional plane to form a super surface. The super surface and the structural unit are schematically shown in the attached figure 1.

The material of the substrate should be a material with high transmission and low loss for incident light (including signal light and pump light), including but not limited to: various high molecular materials (such as Teflon and polyimide), and dielectric materials (such as SiO)₂、CaF₂、Al₂O₃Etc.) and other solid materials.

The dielectric constants (or refractive indexes) of the semiconductor particles and the constituent materials of the substrate should be different (the difference is that the dielectric constants cannot be the same, and the dielectric constants of the substrate materials can be smaller than that of the semiconductor particle materials, or can be interchanged but cannot be equal) so as to satisfy the bound state resonance mode excitation.

By adjusting the asymmetry of the semiconductor particles in the super-surface (e.g. by adjusting the difference in length between the two rods, the asymmetry is achieved in the example), the sharpness of the resonance spectrum can be adjusted. By adjusting the size of the semiconductor particles in the super-surface, the resonance wavelength of the super-surface can be tuned to the expected signal light working wavelength, and the adjustable range can cover the optical band between the radio frequency and the photon wavelength corresponding to the forbidden bandwidth of the used semiconductor particle material.

The polarization direction of incident signal light of the carrier dispersion type all-optical switch based on the asymmetric super-surface is related to the asymmetric direction of particles. Since the particles are asymmetric, the incident signal light of the asymmetric super-surface based carrier dispersion type all-optical switch must be polarized light.

The invention has the following advantages:

1) according to the invention, symmetry defects are introduced into the super-surface structure unit, so that bound mode excitation is realized, and the mode has a sharp characteristic transmission spectrum. The smaller the asymmetry of the structural element, the sharper the characteristic spectrum of the super-surface, and the smaller the required pump intensity. The degree of sharpness of the characteristic spectrum can be tailored by adjusting the asymmetry of the grain structure elements to reduce or tailor the reasonable pump intensity.

2) The dynamic mechanism of the all-optical switching device is derived from the carrier dispersion effect of a semiconductor material, and the response speed of the all-optical switching device is high. For example, the response speed of silicon materials is on the order of picoseconds.

3) The super surface can be prepared by adopting a micro-nano processing technology, and is easy to integrate with electronic and optoelectronic systems.

Drawings

Fig. 1 is a schematic structural diagram of the present invention, in which 1 is a substrate of an all-optical switching device, 2 is an asymmetric semiconductor particle, and 3 is a structural unit, i.e., a partition of a unit cell;

FIG. 2 is a schematic diagram of a super-surface all-optical switching device irradiated by pump light and linearly polarized (in the x-axis direction in the figure) signal light;

fig. 3 is a transmission characteristic curve of the all-optical switching device irradiated by signal light near an operating wavelength in the present invention, in which the abscissa is a free space wavelength, the ordinate is a transmittance, the solid line is a transmission characteristic curve of the device in the case of no pump, and the dotted line is a transmission characteristic frequency shift curve of the device when pumping.

Detailed Description

The present invention will be further illustrated with reference to the following specific examples, but the present invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The starting materials are commercially available from the open literature unless otherwise specified.

Example 1 preparation of asymmetric Supersurface-based Carrier Dispersion all-optical switch

1. And selecting the working wavelength of the signal light of the all-optical switch device. The operating wavelength of the signal light selected in this embodiment is 1550nm, which is widely used in optical communication, according to practical requirements.

2. And selecting materials of the all-optical switch device. Polysilicon with stronger carrier dispersion effect and higher refractive index at the working wavelength of signal light is selected as the material of semiconductor particles. The fused quartz plate with lower refractive index and absorption coefficient in the signal light working waveband is selected as the substrate.

3. The wavelength of pump light (control light) of the all-optical switch device is selected. In order to excite the photon-generated carriers with high density, light with photon energy larger than the forbidden band width of the semiconductor material is selected as a pumping light source. The wavelength of light corresponding to the polysilicon forbidden band at room temperature is 1107nm, and light with the wavelength smaller than that is selected as pump light. Here we select the 808nm semiconductor laser with wide application as the pump light source.

4. And (3) designing an all-optical switch device. In this embodiment, square units composed of polysilicon asymmetric double-rod structures are used as structural units, and periodically arranged as a super surface on a two-dimensional plane, and a schematic diagram of the super surface and the structural units is shown in fig. 1. The lengths of the asymmetric polycrystalline silicon rods are 584nm and 616nm respectively, the widths and the heights of the double rods are 200nm, the spacing between the double rods is 358nm, the arrangement period of the structural units is 1000nm, and the thickness of the quartz substrate is 0.5 mm. The orientation of the dual rods is aligned with the polarization direction of the incident signal light. The working mode of the device is schematically shown in figure 2, and the transmission characteristic and the switching principle of the all-optical switching device are schematically shown in figure 3. The device in this example operates at a wavelength of 1550 nm. When the control light/pump light irradiates the device, the transmission characteristic of the device is shown by a solid line, signal light with the wavelength of 1550nm is transmitted without attenuation, and the device is in an 'on' state of the optical switch; when the control light/pump light irradiates the device, the transmission characteristic of the device is shown by dotted lines, and the 1550nm wavelength signal light is greatly attenuated and cannot penetrate through, so that the device is in an off state of the optical switch.

And (3) regulating and controlling the resonance wavelength position of the resonant peak of the super-surface all-optical switch by regulating the parameters such as the size, the period and the like of the polycrystalline silicon rod by adopting a numerical simulation method, so that the wavelength of the resonant peak is coincided with the working wavelength of the selected signal light, such as the position of a solid line resonant peak in the attached figure 3. When the pumping light irradiates the polysilicon rod with a certain light intensity, a carrier dispersion effect is generated inside the polysilicon rod, the carrier density is greatly increased, the refractive index of the polysilicon rod is reduced, the transmission spectrum of the super surface is shifted to a short wavelength direction, the shifted spectrum is shown as a dotted line in figure 3, and the resonance valley of the dotted line corresponds to the working wavelength of the signal light. Therefore, the pump light irradiates the super surface of the polysilicon asymmetric double-rod structure, so that on/off operation of a signal beam can be completed, and the all-optical switch for controlling light is realized.

5. And (4) processing an all-optical switch device. According to design, an asymmetric dual-rod array of polysilicon is arranged on a substrate, as shown in FIG. 1. The device can be fabricated by depositing 200nm thick polysilicon on a 0.5mm fused silica substrate using a Low Pressure Chemical Vapor Deposition (LPCVD) process, and then fabricating a polysilicon dual bar array pattern on the substrate using a Focused Ion Beam (FIB) process or an Electron Beam Lithography (EBL) + Reactive Ion Etching (RIE) process.

The above embodiments are only used to illustrate the working principle and technical solution of the present invention, and all the implementation steps and the like may be changed, and all the equivalent changes and improvements based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.