Encrypted optical communication system and method based on electric control second harmonic circular dichroism

Abstract

The invention discloses an encrypted optical communication system based on electric control second harmonic circular dichroism. The encrypted optical communication system realized by utilizing the second harmonic circular dichroism is mainly composed of a light source modulation module, a signal processing module and a signal processing module, wherein the light source modulation module is responsible for polarization initialization and regulation of incident fundamental frequency light and stray light filtering; the device comprises a laser used for generating incident fundamental frequency light with a specific wavelength; comprising a polarization adjusting assembly. According to the encrypted optical communication system disclosed by the invention, the complete process from light source preparation, signal encryption generation to receiving decryption is realized through the designed four modules. Particularly, the encryption optical communication system is designed by utilizing the combination of the electronic control second harmonic circular dichroism characteristic and the exclusive-OR gate logic, and the system not only improves the security of information transmission, but also shows the huge potential of the optical communication technology in the encryption field.

Description

Technical Field

[0001] The present application relates to the technical field of encrypted optical communication, and in particular to an encrypted optical communication system and method based on electrically controlled second harmonic circular dichroism. Background Art

[0002] Traditional optical communication encryption methods are usually too simple and pose huge security risks. All-optical encryption communication technology can greatly improve the security and confidentiality of information transmission and effectively prevent information from being stolen and tampered with. Among them, all-optical XOR encryption communication schemes, such as those based on highly nonlinear optical fibers and those based on semiconductor amplifiers, achieve XOR operations by utilizing the nonlinear effects of optical signals, and have the advantages of high speed, high security, and high reliability. However, the scheme based on highly nonlinear optical fibers has problems such as relatively large XOR gate size, complex structure, difficulty in integration, and sensitivity to the environment. The scheme based on semiconductor amplifiers has chirp characteristics due to cross-gain modulation, which makes it difficult to obtain encryption operation results with high extinction ratios.

[0003] Electronic control technology plays a key role in optical communications. The precise control and regulation of the second harmonic circular dichroism achieved by electronic control technology can accurately adjust the polarization characteristics of the second harmonic, and can be used to accurately control the generation and transformation of keys, thereby achieving more efficient, flexible, and more compatible information transmission, and enhancing the security and reliability of encryption. In addition, electronic control technology can also optimize the performance of optical communication systems, such as improving the transmission quality of signals, reducing noise and interference, etc.

[0004] In summary, the present invention proposes an encrypted optical communication system based on electrodynamic second harmonic circular dichroism. The system can achieve precise control of key generation through bias voltage and effectively regulate the second harmonic circular dichroism, thereby successfully generating encrypted communication and providing a strong guarantee for the security of information transmission. Summary of the invention

[0005] In order to solve the problems mentioned in the above background technology, the present invention provides an encrypted optical communication system based on electrically controlled second harmonic circular dichroism.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The system is based on the principle of electrically controlled second harmonic circular dichroism and uses bias control to achieve efficient encryption and transmission of information. The core is to use bias to control the second harmonic circular dichroism of the material, encode the encryption key into a specific bias sequence, modulate the second harmonic circular dichroism through this sequence, and encrypt the information into the second harmonic signal. The basic principle is:

[0008] When a laser beam with an electric field large enough to affect the relative positions of atoms and the motion state of electrons in the medium is irradiated onto the surface of the sample, a nonlinear optical effect will occur. Among them, the second harmonic is a second-order nonlinear optical phenomenon, which means that when a beam of fundamental frequency light with high electric field intensity is irradiated onto a medium with central inversion symmetry breaking, an optical signal with a frequency twice that of the fundamental frequency light will be generated in the medium - the second harmonic signal.

[0009] Second harmonic circular dichroism is a unique manifestation of this nonlinear phenomenon, which refers to the significant difference in the second harmonic signal intensity under the excitation of left-handed circularly polarized and right-handed circularly polarized fundamental frequency light. Compared with traditional linear circular dichroism (there is a difference in the absorption or scattering of left-handed and right-handed circularly polarized light by the medium), second harmonic circular dichroism has higher optical sensitivity and therefore has higher potential application value. By applying an external electric field, the changes in the structure and properties of the material can be precisely controlled, thereby affecting the response of the second harmonic intensity to circularly polarized light, and realizing precise control of the second harmonic circular dichroism.

[0010] XOR gates are used in digital logic to implement logical XOR operations. Their characteristic is that the output is 1 only when the two input logic values ​​are different (i.e. one is 1 and the other is 0); if the inputs are the same (i.e. both are 1 or 0), the output is 0. This logical characteristic provides a basis for the realization of complex information processing and information encryption. The optical data sequence is XORed by the encryption key sequence to generate an encrypted ciphertext sequence. The decryption process is to XOR the ciphertext sequence again with the same encryption key sequence to restore the original plaintext data sequence. The reversibility of the XOR operation ensures the correctness of the encryption and decryption process.

[0011] For electrically controlled second harmonic circular dichroism, the key operating variables - positive voltage and negative voltage, left-handed circularly polarized light and right-handed circularly polarized light, can be mapped to the binary states of A and B of the input logic (i.e., 1 and 0). This design enables the system to generate second harmonic signals with different intensities when these variables are used as inputs, and the high and low intensities directly correspond to the binary outputs (i.e., 1 and 0) in the output logic C. Based on the above logic, an XOR gate logic model can be constructed, such as Figure 2 As shown. Further using the XOR gate, the corresponding encrypted optical communication system can be designed, and its system architecture diagram is shown as follows Figure 1As shown. The system can encrypt information by precisely controlling the circular dichroism and bias state of the optical signal, and then transmit the encrypted information. The input information is converted into the polarization state of the baseband optical signal through the encoding method, and the bias is encoded to form an encryption key. The information is processed by forming an XOR gate through the combination of the polarization state of the baseband optical signal and the bias, forming an encrypted second harmonic signal. The receiving end detects the strength changes of the corresponding second harmonic signal and uses the key to reversely parse the original information to complete the encrypted optical communication process.

[0012] The encrypted optical communication system realized by using second harmonic circular dichroism proposed in the present invention mainly consists of the following modules:

[0013] Light source modulation module: This module is responsible for polarization initialization, regulation and stray light filtering of incident fundamental frequency light. It includes a laser for generating incident fundamental frequency light of a specific wavelength; a polarization adjustment component for modulating the polarization state of the incident fundamental frequency light through a combination of a linear polarizer and a quarter-wave plate; and a bandpass filter for filtering stray light incident on the sample, allowing only fundamental frequency light of a specific polarization to pass through.

[0014] Bias modulation module: This module is responsible for controlling the sensitivity of the second harmonic circular dichroism. It contains an electrical source meter, which is used to apply bias to the device and control the sensitivity of the second harmonic circular dichroism through the bias.

[0015] Electrically controlled second harmonic signal generation module: This module integrates materials (such as chiral ferroelectrics) and devices that can realize second harmonic circular dichroism through electrical control, and is used to realize the generation and modulation of second harmonic circular dichroism signals. It contains materials that can generate second harmonic circular dichroism, which is used to generate second harmonics with circular dichroism characteristics; at the same time, it contains devices prepared based on this material, which are closely connected with the bias modulation module, and are used to realize real-time response and modulation of the bias, ensuring the dynamic regulation of the second harmonic circular dichroism.

[0016] Second harmonic signal receiving module: This module is responsible for receiving and analyzing the encrypted second harmonic signal. It is used for receiving the second harmonic signal. It contains a filter to filter the stray light generated by the system, filter out the encrypted second harmonic signal, and remove background noise interference; it contains a highly sensitive detector to realize the reception of the second harmonic signal and convert it into a processable electrical signal.

[0017] The encryption process of the encrypted optical communication system based on electrically controlled second harmonic circular dichroism:

[0018] The specific encryption process of the encrypted optical communication system of the present invention is mainly divided into the following stages:

[0019] Encryption stage: First, the information to be transmitted is converted into a sequence of 1 and 0 through a specific protocol and encoding method. The light source modulation module generates fundamental frequency light of a specific wavelength and polarization state, and the left-handed circular polarization and right-handed circular polarization of the fundamental frequency light are used as 1 and 0 respectively to encode the information. Subsequently, the bias adjustment module is used to encode the pre-designed encryption key by using positive and negative biases to represent 1 and 0 respectively. These voltages are then combined with the incident fundamental frequency light and applied to the material in the electrically controlled second harmonic signal generation module in sequence. According to the preset encryption key (i.e., the bias applied to the material), the second harmonic circular dichroism of the material will be modulated, which is specifically manifested in that the material will change the second harmonic signal intensity under the excitation of fundamental frequency light of different polarizations. This process can generate an encrypted optical signal from the information carried by the left-handed circular polarization and right-handed circular polarization of the fundamental frequency light.

[0020] Transmission stage: The encrypted optical signal is transmitted to the receiving end via optical fiber or other optical transmission media. During this process, if eavesdropping occurs, the eavesdropper will only receive a series of stray signals and the encrypted second harmonic signal.

[0021] Decryption stage: The receiving end captures the encrypted optical signal through the second harmonic signal receiving module. According to the known decryption key (i.e., the voltage-coded encryption key), the encrypted optical signal is decrypted to restore the original information and complete the optical communication process.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The encrypted optical communication system proposed by the present invention can be seamlessly connected with the existing optical communication network and has good compatibility. Whether it is a traditional optical fiber communication network or an emerging all-optical communication network, the encryption mechanism of the present invention can be used to improve the security of communication.

[0024] 2. Since the encryption process is dynamically adjusted by electronic control means, the present invention can flexibly adjust the encryption strategy according to actual needs. For example, during the communication process, the encryption strength can be dynamically adjusted according to factors such as the importance of the signal, the transmission distance, and the transmission time; at the same time, security elements such as random numbers and timestamps can be added to the encryption process to further enhance the encryption effect.

[0025] 3. The system realizes the complete process from light source preparation, signal encryption generation to reception and decryption through the design of four major modules.

[0026] 4. The system designs an encrypted optical communication system by utilizing the combination of electrically controlled second harmonic circular dichroism characteristics and XOR gate logic, which improves the security of information transmission and demonstrates the great potential of optical communication technology in the field of encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the system of the present invention;

[0029] Figure 2 It is a schematic diagram of the XOR gate logic model in the present invention;

[0030] Figure 3 A schematic diagram of a device for realizing electrically controlled second harmonic circular dichroism in the present invention;

[0031] Figure 4 A schematic diagram of electrically controlled second harmonic circular dichroism based on chiral organic-inorganic hybrid perovskite ferroelectrics in the present invention;

[0032] Figure 5 A schematic diagram of an encrypted optical communication transmission configuration based on electrically controlled second harmonic circular dichroism in the present invention;

[0033] Figure 6 It is a schematic diagram of the structure, XRD and circular dichroism signals of the synthesized crystal sample;

[0034] In the figure: 1 light source modulation module, 11 laser, 12 polarization adjustment component, 13 bandpass filter, 2 bias modulation module, 21 electrical source meter, 3 electronically controlled second harmonic signal generation module, 4 second harmonic signal receiving module, 41 filter, 42 detector. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] Reference Figure 1, an encrypted optical communication system based on electrically controlled second harmonic circular dichroism, comprising a light source modulation module 1, a bias modulation module 2, an electrically controlled second harmonic signal generation module 3 and a second harmonic signal receiving module 4, wherein the light source modulation module 1 is responsible for polarization initialization, regulation and stray light filtering of incident fundamental frequency light, and comprises a laser 11 for generating incident fundamental frequency light of a specific wavelength, and the laser 11 is connected to a polarization adjustment component 12 for providing fundamental frequency light thereto;

[0038] The polarization adjustment component 12 is used to modulate the polarization state of the incident fundamental frequency light. The polarization adjustment component 12 is composed of a linear polarizer and a quarter wave plate, and is connected to the laser 11 and the bandpass filter 13 through an optical path to modulate the polarization state of the incident fundamental frequency light; and the bandpass filter 13 is used to filter stray light. The bandpass filter 13 is located on the optical path after the polarization adjustment component 12 and only allows fundamental frequency light of a specific polarization to pass.

[0039] The bias modulation module 2 comprises an electrical source meter 21 for applying a bias voltage to the device to control the sensitivity of the second harmonic circular dichroism.

[0040] The electrically controlled second harmonic signal generating module 3 integrates materials and devices that can realize second harmonic circular dichroism through electrical control, and is used to realize the generation and modulation of second harmonic circular dichroism signals.

[0041] The second harmonic signal receiving module 4 is used to receive and analyze the encrypted second harmonic signal, and includes a filter 41 for filtering stray light and a high-sensitivity detector 42 for receiving the second harmonic signal and converting it into an electrical signal.

[0042] The encryption process of the encrypted optical communication system includes an encryption stage. In the encryption stage, the information to be transmitted is converted into a sequence through a specific protocol and encoding method, the light source modulation module 1 is used to generate a fundamental frequency light of a specific wavelength and polarization state to encode the information, and the bias modulation module 2 is used to encode the encryption key. The bias and the incident fundamental frequency light are combined and applied to the material in the electrically controlled second harmonic signal generation module 3 to modulate the second harmonic circular dichroism of the material to generate an encrypted optical signal.

[0043] The specific encryption process includes a transmission stage. During the transmission stage, the encrypted optical signal is transmitted to the receiving end through an optical transmission medium.

[0044] The specific encryption process includes a decryption stage. In the decryption stage, the receiving end captures the encrypted optical signal through the second harmonic signal receiving module 4, decrypts the optical signal according to the predicted decryption key, and restores the original information.

[0045] The material that can realize the second harmonic circular dichroism by electrical control is a chiral ferroelectric, a chiral ferroelectric film or any medium that can realize the electrically controllable second harmonic circular dichroism.

[0046] Example 2

[0047] Embodiment of a device for realizing electrically controlled second harmonic circular dichroism:

[0048] In order to realize the electrically controlled second harmonic circular dichroism, the key is to prepare a device that can apply a bias voltage. Figure 3 An embodiment of device preparation is shown. First, a suitable insulating substrate is selected, such as silicon or sapphire. These materials are often used in the preparation of electronic devices due to their good insulating properties and stability. The sample to be studied (a thin film or nanostructure with potential second harmonic circular dichroism) is transferred to an insulating substrate. The designed electrode pattern is transferred to the photoresist using photolithography technology, and the exposed photoresist portion is removed through development treatment, leaving the electrode pattern, and then a layer of metal is deposited as an electrode. The electrode structure as shown in the figure can realize the application of bias in the horizontal and vertical directions, allowing the second harmonic circular dichroism of the sample to be regulated in multiple directions by bias, achieving a more refined regulation effect.

[0049] Embodiment 3:

[0050] Embodiment of realizing electric control method to modulate second harmonic circular dichroism based on organic-inorganic hybrid perovskite ferroelectrics:

[0051] In this embodiment, hydrochloric acid, fluorobutane and diamine hydrochloride are used as precursors to synthesize and prepare organic trans-fluorobutane diamine hydrochloride and trans-fluorobutane diamine. Subsequently, 0.5mmol of cadmium chloride and an equal molar amount of organic trans-fluorobutane diamine hydrochloride and trans-fluorobutane diamine are added together in 3ml of hydrochloric acid (concentration 37%) solution. The solution is heated in an 80°C oil bath for 2 hours to ensure that the dissolved compounds react completely. Finally, the solution is slowly cooled to room temperature to obtain crystals after crystallization, completing the preparation of a chiral organic-inorganic hybrid perovskite ferroelectric (trans-fluorobutane diamine cadmium chloride compound).

[0052] This chiral hybrid perovskite ferroelectric has a unique structure, which not only exhibits the spontaneous polarization characteristics of ferroelectrics, but also has a multi-level effect due to the introduction of its unique chiral structure. When the fundamental frequency light with circular polarization characteristics is irradiated onto the surface of the sample, the multi-level effect will make the second harmonic signal response of the material show different sensitivities to the left-handed circular polarization and right-handed circular polarization of the fundamental frequency light, that is, it exhibits second harmonic circular dichroism.

[0053] In addition, the ferroelectricity contained in the material allows its polarization direction to be regulated by applying voltage. This electrically controlled change in polarization direction directly affects the charge distribution inside the material, thereby regulating the multi-level effects within the material. This regulation mechanism further affects the response of the material's second harmonic signal to different polarization states of fundamental frequency light. Therefore, based on this unique chiral perovskite ferroelectric, electrically controlled second harmonic circular dichroism can be achieved.

[0054] Figure 4 The test structure schematic diagram and measurement data results of voltage-controlled second harmonic circular dichroism based on chiral perovskite ferroelectrics are intuitively displayed. Figure 4 (a) is a schematic diagram of the test structure for measuring the pressure-controlled second harmonic circular dichroism, in which the incident fundamental frequency light uses a femtosecond laser with a wavelength of 800nm, the linear polarizer is used to initialize the polarization of the fundamental frequency light to horizontal polarization, and the quarter-wave plate is used to control the polarization of the fundamental frequency light. Filter 1 is a bandpass filter with a central wavelength of 800nm ​​and a passband of 10nm, which filters stray light and allows only the fundamental frequency light to pass. The dichroic mirror is used to reflect the 800nm ​​fundamental frequency light and transmit the 400nm signal light. Filter 2 is a bandpass filter with a central wavelength of 400nm and a passband of 10nm, which again filters stray light to ensure that only the second harmonic signal light passes. The polarization state of the fundamental frequency light can be controlled from linear polarization → elliptical polarization → circular polarization by rotating the quarter-wave plate, and the application and control of the bias voltage can be achieved through the electrode.

[0055] Figure 4 (b)-(c) show the data results of voltage-controlled second harmonic circular dichroism based on s-FCC. The angle of the horizontal axis represents the change in the polarization state of the fundamental frequency light (from linear polarization (0) to elliptically polarized left-handed circular polarization (45) to elliptically polarized linear polarization (90) to elliptically polarized right-handed circular polarization (135) to elliptically polarized linear polarization (180)), and the vertical axis represents the second harmonic signal intensity of the sample. Figure 4 In (b), when a forward bias is applied, the intensity of the second harmonic signal of the material under the excitation of the fundamental frequency light of right circular polarization is significantly higher than that under the excitation of the fundamental frequency light of left circular polarization, indicating that the second harmonic response of the material is more sensitive to right circular polarization. Figure 4 In (c), when the bias direction is negative, the second harmonic signal of the material is more intense under the excitation of left-handed circularly polarized light, indicating that the second harmonic signal response of the material under negative bias is more sensitive to left-handed light. This second harmonic circular dichroism that reverses with the change of bias direction is a favorable proof of the electrically controlled second harmonic circular dichroism.

[0056] Embodiment 4:

[0057] Embodiments of realizing encrypted optical communication based on electrically controlled second harmonic circular dichroism:

[0058] Figure 5 The operational process of information transmission achieved by an encrypted optical communication system based on electrically controlled second harmonic circular dichroism technology is intuitively demonstrated. The entire process is mainly divided into information encryption process, information transmission process and signal reception process.

[0059] Signal encryption process: In the information encryption stage, the sender first encodes the information to be transmitted "BAQIS" in binary using the ASCII standard, converting the information into a series of 1s and 0s. Subsequently, the polarization properties of the fundamental frequency light are used: the left-handed circular polarization state represents 1, and the right-handed circular polarization state represents 0, and the polarization state of the fundamental frequency light is set according to the binary encoding order of the information. At the same time, the forward bias and negative bias are used as 1 and 0 respectively to encode the preset key to generate the encryption key. Under the combined effect of different polarization states of the fundamental frequency light and bias in different directions, the transmitted information "BAQIS" is encrypted into the second harmonic signal intensity, and the strength of the second harmonic signal is used as the carrier of 1 and 0 to encrypt the information.

[0060] Information transmission process: During the information transmission process, the encrypted second harmonic signal is sent to the receiving end. It is worth noting that even if an eavesdropper tries to intercept these signals, they cannot identify the encryption logic behind the bias and polarization state due to the lack of correct key information, and therefore cannot effectively decrypt the original information, ensuring the security of the communication process.

[0061] Signal receiving process: At the receiving end, the system first collects and processes the transmitted second harmonic signal. Then, using the previously shared key, the receiver decrypts the original information hidden in the second harmonic signal and recovers the real information "BAQIS" transmitted by the sender, thus completing the entire encrypted optical communication process.

[0062] This encryption method based on electrically controlled second harmonic circular dichroism not only improves the security of data transmission, but also demonstrates the great potential of optical communication technology in the field of information security.

[0063] Embodiment 5:

[0064] A sample synthesis that can achieve electrically controlled second harmonic circular dichroism.

[0065] An equimolar amount (0.5 mmol) of an organic precursor ((2S)-2-fluorobutane-1,4-diamine dihydrochloride [*2HCl]) was added to 2 ml of HCl (37%). The solution was heated (80°C) until all compounds dissolved to obtain a clear solution. After cooling the saturated solution to room temperature, millimeter-sized crystals of (2S)-2-fluorobutane-1,4-diamine (s-FBDA)]CdCl4 (s-FCC, chemical formula: CdCl4C4H13FN2) were obtained.

[0066] Figure 6 The structure, XRD and circular dichroism signals of the synthesized crystal sample are shown in Figure 1. The crystal is a Dion-Jacobson (DJ) phase layered perovskite, in which adjacent perovskite layers are connected by interlayer s-FBDA cations, showing <100> The s-FBDA cations present an ordered arrangement along the crystallographic b-axis, which is manifested by all F atoms located on the same side of the s-FBDA cations along this direction. Therefore, spontaneous polarization is triggered along the b-axis, such as Figure 6 Its XRD pattern ( Figure 6 b) shows its monoclinic P21 space group characteristics. In addition, the circular dichroism (CD) ( Figure 6 c) The spectrum proves the chiral properties of the sample, that is, an obvious CD response is observed in the absorption region, indicating that it can be used to achieve circular dichroism regulation.

[0067] Example 6: Theoretical prediction of ferroelectrically switchable SHG-CD

[0068] In addition to the traditional electric dipole contribution, the intrinsic chirality introduces an additional magnetic dipole contribution in the nonlinear process, the so-called multipole effect. The multipole effect leads to the SHG pattern excited by asymmetric circularly polarized light (CPL), which exhibits different SHG responses under left and right CPL excitation, which is called SHG circular dichroism (SHG-CD).

[0069] For the SHG response excited by z-axis incident light in chiral s-FCC, the intensity is written as:

[0070]

[0071] where f, g, and h are parameters consisting of the corresponding electric and magnetic second-order tensors.

[0072] Taking the +P ferroelectric state as an example, the electric and magnetic tensor elements can be represented and assigned by the following equations:

[0073]

[0074] Wherein equation (2) and equation (3) are the expressions of the second-order nonlinear polarization and magnetization, respectively. Equation (4) is the Maxwell equation describing the mutual electric and magnetic interactions in the nonlinear process. According to the above equations, the second-order tensor elements are assigned as shown in Table 1.

[0075] Table 1 Combination of SHG tensor components in two ferroelectric states

[0076]

[0077] Consider further the -P ferroelectric state, which is mirror-symmetric to the +P ferroelectric state along the polar axis (crystallographic b-axis / laboratory y-axis). According to the following magnetoelectric relationship,

[0078] E(2ω)~P(2ω)+k 2ω ×M(2ω), (5)

[0079] Due to mirror symmetry, the polarization and wave vector are reversed along the y-axis (b-axis). This reversal will cause the tensor elements with odd superscript "y" to change their signs. Therefore, the second-order tensor assignment in the -P state is obtained, as shown in Table 1.

[0080] For the incident CPL along the z-axis, the electric field component of the incident light is the QWP rotation angle Function:

[0081]

[0082] It is obvious that the third term of Eq. (6) / Eq. (1) is the CPL sensitivity term since its sign oscillates between positive and negative as the CPL angle changes.

[0083] As shown in Table 1, as long as the magnitudes of the two magnetic second tensors are large enough, the h parameter has the potential to change sign between the two ferroelectric states. Mathematically, it is assumed that the change in sign may have an effect on the third term of equation (1), which will lead to a 90-degree phase difference in the CPL-excited SHG mode, resulting in a switching of the CPL sensitivity of the SHG response. Therefore, we can observe electrically switchable SHG-CD behavior by switching the ferroelectric dipole.

[0084] Based on theoretical analysis, we fabricated a two-terminal electrically controlled device on a SiO2 substrate, where the electrode pattern was connected to a source meter via wires to apply bias. The fabricated device was installed in an electro-optical system to explore encrypted optical communications.

[0085] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0086] In the present invention, unless otherwise clearly specified and limited, the terms "set", "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0087] The control method of the present invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by technicians in this field. The provision of power is also common knowledge in this field. The present invention is mainly used to protect mechanical devices, so the present invention will no longer explain the control method and circuit connection in detail.

[0088] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An encrypted optical communication system based on electrically controlled second harmonic circular dichroism, comprising: A light source modulation module is used to encode the information sequence to be transmitted to generate incident fundamental frequency light of corresponding wavelength and polarization state; A bias modulation module, used for applying a bias voltage to encode a preset encryption key to generate a bias voltage sequence; as well as The electrically controlled second harmonic signal generating module is used to modulate the second harmonic circular dichroism of the material according to the incident fundamental frequency light and the bias sequence to generate an encrypted optical signal.

2. The system according to claim 1, characterized in that The light source modulation module comprises: A laser for generating incident fundamental frequency light of a desired wavelength and polarization state; a polarization adjustment component, connected to the laser, and used to modulate the polarization state of the incident fundamental frequency light; and The bandpass filter is located on the optical path after the polarization adjustment component and is used to perform bandpass filtering on the modulated incident fundamental frequency light to allow the incident fundamental frequency light with the desired polarization to pass through.

3. The system according to claim 1, characterized in that The bias modulation module comprises: A source meter is used to bias the device to control the sensitivity of the second harmonic circular dichroism.

4. The system according to claim 1, characterized in that The electrically controlled second harmonic signal generating module includes a material capable of realizing second harmonic circular dichroism through electrical control, and is used to realize the generation and modulation of a second harmonic circular dichroism signal.

5. The system according to claim 4, characterized in that The materials capable of realizing second harmonic circular dichroism through electrical control include chiral ferroelectrics and ferroelectric thin films.

6. The system according to any one of claims 1 to 5, characterized in that: Also includes: The second harmonic signal receiving module is used to receive the encrypted optical signal and decrypt the optical signal according to a known decryption key.

7. The system according to claim 6, characterized in that The second harmonic signal receiving module comprises: A filter, used for filtering stray light in the received encrypted optical signal; and A high-sensitivity detector is used to decrypt the filtered encrypted optical signal according to the predicted decryption key and convert the filtered encrypted optical signal into an electrical signal.

8. An encrypted optical communication method based on electrically controlled second harmonic circular dichroism, characterized in that: include: The information sequence to be transmitted is encoded by the light source modulation module to generate incident fundamental frequency light of corresponding wavelength and polarization state; Applying a bias voltage through a bias modulation module to encode a preset encryption key to generate a bias voltage sequence; as well as The second harmonic circular dichroism of the material is modulated according to the incident fundamental frequency light and the bias sequence by an electrically controlled second harmonic signal generating module to generate an encrypted optical signal.

9. The method according to claim 8, characterized in that The generating of incident fundamental frequency light of corresponding wavelength and polarization state comprises: Producing incident fundamental frequency light of a desired wavelength; modulating the polarization state of the incident fundamental frequency light; and The modulated incident fundamental frequency light is bandpass filtered to allow incident fundamental frequency light of a desired polarization to pass.

10. The method according to claim 8, characterized in that The step of applying a bias voltage by a bias modulation module to encode a preset encryption key to generate a bias voltage sequence includes: The preset encryption key is encoded by a positive bias voltage and a negative bias voltage respectively to generate the bias voltage sequence.

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