A double-layer optical encryption fluorescent polymer waveguide chip based on optical pulse coding modulation technology

Abstract

A dual-layer optical encryption fluorescent polymer waveguide chip based on optical pulse code modulation technology belongs to the field of functional photonic chip technology. It consists of a substrate layer, a buffer layer, a cladding layer, a bottom waveguide layer, and a top waveguide layer. The cladding layer is divided into three parts: a lower cladding layer, a middle cladding layer, and an upper cladding layer. The bottom waveguide is located within the middle cladding layer, and the top waveguide is located within the upper cladding layer. The bottom and top waveguides do not overlap in the chip's top-view plane. The waveguide layer material is obtained by doping fluorescent small-molecule oligomer chromophores into a polymer material. This invention achieves signal optical pulse coding by modulating the pump light power intensity. By detecting changes in optical transmission loss in the fiber optic system, it determines whether eavesdropping has occurred. Eavesdropping is indicated by optical transmission loss exceeding a threshold. False information is displayed in the bottom waveguide for disguise, while the modulated information is transmitted encrypted through the top waveguide, thus solving the problems of limited controllability and insufficient security in traditional encryption technologies.

Description

Technical Field

[0001] This invention belongs to the field of functional photonic chip technology, specifically relating to a dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology. Background Technology

[0002] In recent years, with the rapid development of information technology and the internet, and the deep integration of various aspects of society, information security issues have occurred frequently, and optical information security has received increasing attention. Optical systems possess the inherent ability to process complex 2D data at high speed and in parallel, and optical encryption has formulated a unique strategy to promote the development of information security, ensuring the multidimensionality, complexity, artistry, and integrity of information. Currently, optical encryption technology mainly relies on monochromatic photoluminescence modes, but with the rapid development of science and technology, monochromatic light is often easily deciphered, making it increasingly unable to meet people's needs for high security and large data volumes, greatly limiting the application of optical encryption technology in information security. In contrast, polymer waveguide devices made by combining optical coding modulation technology with traditional encryption technology have irreplaceable advantages such as variable light emission modes, fast response time, miniaturization, versatility, and strong integration capabilities. Furthermore, by modulating the wavelength, amplitude, phase, and frequency of the integrated beam, the data processing range can be extended to three dimensions (3D), paving a new path for high-security optical encryption technology. Summary of the Invention

[0003] This invention proposes a dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology, fabricated using ultraviolet lithography direct writing process. The principle is to achieve signal optical pulse coding function (e.g., by modulating the pump light power intensity). Figure 6 As shown, the input signal light is amplified by the gain of the pump light containing pulse modulation information, and the output signal light, converted into a voltage signal, exhibits pulse modulation information containing voltage amplitude changes in the time domain. Furthermore, by detecting changes in optical transmission loss in the fiber optic system, the presence of eavesdropping is determined; if the optical transmission loss exceeds a threshold, eavesdropping is detected. The device can disguise itself by transmitting false information through the bottom waveguide and encrypt the transmission of real modulation information through the top waveguide, thus solving the problems of limited control and insufficient security in traditional encryption technologies.

[0004] The present invention discloses a dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology, as shown in the attached figure. Figure 1 As shown in (a), the cross-sections at points a and c are as shown in the attached figure. Figure 1 As shown in (b), the cross-section at point b is as shown in the attached figure. Figure 1As shown in (c), from bottom to top, it consists of a substrate layer 1, a buffer layer 2, a cladding layer 3, a bottom waveguide 4, and a top waveguide 6. The cladding layer 3 is divided into three parts: a lower cladding layer, a middle cladding layer, and an upper cladding layer. The bottom waveguide 4 is located in the middle cladding layer, and the top waveguide 6 is located in the upper cladding layer. The bottom waveguide 4 and the top waveguide 6 are separated by the cladding layer 3 and do not overlap in the top view plane. The bottom waveguide 4 and the top waveguide 6 are respectively composed of an input curved waveguide, a coupling region waveguide, and an output curved waveguide. The coupling region waveguides of the bottom waveguide 4 and the top waveguide 6 are arranged in parallel, and the input curved waveguides and the output curved waveguides of the bottom waveguide 4 and the top waveguide 6 are arranged symmetrically facing each other.

[0005] The substrate layer 1 material described in this invention is any one of indium phosphide, gallium arsenide, and silicon.

[0006] The material of the buffer layer 2 described in this invention is any one of SU-8, PMMA, P(MMA-co-GMA), and silicon dioxide.

[0007] The coating layer 3 described in this invention is made of any one of SU-8, PMMA, P (MMA-co-GMA), or silicon dioxide. In the same device, the materials of the buffer layer 2 and the coating layer 3 can be the same or different.

[0008] The bottom waveguide 4 material of the present invention is obtained by doping a TCBzC fluorescent small molecule oligomer chromophore into a polymer material. The polymer material is any one of SU-8, PMMA, and P(MMA-co-GMA), and the mass fraction of the TCBzC fluorescent small molecule oligomer chromophore doping ranges from 3 to 8 wt‰.

[0009] The top waveguide 6 material of this invention is obtained by doping a TCNzC fluorescent small molecule oligomer chromophore into a polymer material. The polymer material is any one of SU-8, PMMA, or P(MMA-co-GMA), and the mass fraction of the TCNzC fluorescent small molecule oligomer chromophore doping ranges from 3 to 8 wt‰. The refractive indices of the bottom waveguide 4 and top waveguide 6 materials are greater than the refractive indices of the buffer layer 2 and the cladding layer 3.

[0010] The structural formulas of TCBzC and TCNzC are shown in (a) and (b), respectively.

[0011]

[0012]

[0013] The optical encryption working principle of the dual-layer optical encryption fluorescent polymer waveguide chip based on optical pulse code modulation technology described in this invention is as follows: Figure 2 As shown in the attached document. Figure 2As shown in (a), in the initial state, the signal light I λ1 Input from the input end of the bottom waveguide 4, a pump light B containing modulation information of a certain power is applied. λ3 Pulse modulation gain effect is generated under vertical illumination, signal light I λ1 Light intensity due to pump light B λ3 Enhanced by photoluminescence and due to pump light B λ3 The modulation information carried by the light exhibits pulsed changes in intensity, which are output from the bottom waveguide 4 and interact with the pump light B. λ3 Output optical signal O with the same modulation information λ1 As a bright state transmission path; signal light I λ2 Input from the input end of the top waveguide 6, in the same pump light B λ3 Under the action of the top waveguide 6, the output of the pump light B is generated. λ3 The output optical signal O with the same modulation information and light intensity gain amplification λ2 This serves as a backup for the encrypted transmission path. When eavesdropping occurs on the open-state transmission path, the signal light O output from the open-state transmission path will be interrupted due to the eavesdropping path stealing light intensity. λ1 The light intensity decreased significantly, as shown in the attached image. Figure 2 As shown in (b), the threshold for eavesdropping is set to the output signal light O in the initial state. λ1 The light intensity is set to 5%. If the decrease in light intensity exceeds a threshold, eavesdropping is considered to have occurred. Once eavesdropping has occurred, see attached... Figure 2 As shown in (c), the carrier of modulation information (after determining that there was eavesdropping behavior, the pump light B containing modulation information) λ3 Replace with pump light B containing modulation information λ4 Under photoluminescence, the modulation information carrier will exhibit pulsed changes in light intensity according to the modulation information (due to pump light B). λ3 Manually switch to pump light B λ4 Pump light B containing modulation information λ3 Switch to B λ4 During the process, in order for the terminal receiver to determine the switch between open and closed state transmission paths, the pump light B should be guaranteed to function properly. λ4 The light power intensity is higher than that of the pump light B. λ3 Pump light B λ4 Only for I λ2 It has a gain amplification effect, for I λ1 Without gain amplification, the signal light O output from the bright state transmission path at this time λ1 Without gain amplification and pulse modulation, the light will contain no modulation information and its intensity will decrease, thus achieving anti-eavesdropping functionality. The modulation information will be transmitted via the signal light O output from the dense transmission path. λ2 It can be carried to achieve optical encryption.

[0014] Based on the principle of photoluminescence, the TCBzC fluorescent small molecule oligomer chromophore in the bottom waveguide 4 absorbs the pump light B. λ3 The signal light I is emitted and covers the bottom waveguide 4. λ1 Photons of a specific wavelength are used to enhance the signal light transmitted in the bottom waveguide 4, and the power intensity of the signal light output from the bottom waveguide 4 increases with the gradual increase of the pump light power. The TCNzC fluorescent small molecule oligomer chromophore in the top waveguide 6 absorbs the pump light B. λ3 Or B λ4 The signal light I is emitted and covers the top waveguide 6. λ2 Photons of a specific wavelength are used to achieve a gain function for the signal light transmitted in the top waveguide 6, and the power intensity of the signal light output from the top waveguide 6 also increases as the pump light power gradually increases. When the pump light is from B... λ3 Switch to B λ4 Signal light I is transmitted in the bottom waveguide 4. λ1 The gain effect will disappear, while the signal light I transmitted in the top waveguide 6 will... λ2 The buff effect will not disappear.

[0015] The signal light I used in the dual-layer optical encryption fluorescent polymer waveguide chip based on optical pulse code modulation technology described in this invention λ1 I λ2 and pump light B λ3 B λ4 All originate from lasers. Signal light I λ1 and I λ2 The wavelength range is 500–700 nm, the power range is 0.2–2 mW, and the pump light B... λ3 The wavelength range is 400–600 nm, and the pump light B λ4 wavelength and signal light I λ1 The wavelength ranges are similar or the same, ranging from 500 to 700 nm; signal light I λ1 The wavelength is less than the signal light I λ2 wavelength, pump light B λ3 The wavelength is less than the signal light I λ1 wavelength, pump light B λ4 The wavelength is greater than or equal to the signal light I λ1 The wavelength is smaller than that of the signal light I λ2 wavelength, pump light B λ3 and B λ4 The power range is 10 to 100 mW.

[0016] Compared with existing device structures and fabrication techniques, the advantages of this invention are:

[0017] (1) Compared with existing encryption devices, the polymer material of the present invention can be easily doped and the refractive index can be flexibly adjusted to meet different needs.

[0018] (2) Compared with existing encryption devices, the device made by the present invention has a simple manufacturing process and can usually be mass-produced using ultraviolet lithography direct writing process, which improves production efficiency and saves costs.

[0019] (3) Compared with existing encryption devices, the present invention has no restrictions on the substrate. Both inorganic crystals and polymer films can be used as substrates for waveguide devices. The cross-linked structure of polymer materials is beneficial to improving mechanical strength. The related technologies are mature enough to facilitate the fabrication of integrated photonic encryption chips. Attached Figure Description

[0020] Figure 1 (a) is a schematic diagram of the three-dimensional structure of a dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology; Figure 1 (b) is Figure 1 Figure (a) shows the cross-sectional view at positions a and c; Figure (c) shows the cross-sectional view at position b in Figure (a).

[0021] Figure 2 (a) is a schematic diagram of the working principle of a dual-layer optical encryption fluorescent polymer waveguide chip based on optical pulse code modulation technology transmitting information in the initial state; Figure 2 (b) is a schematic diagram of the working principle of a dual-layer optical encryption fluorescent polymer waveguide chip based on optical pulse code modulation technology to determine whether there is eavesdropping behavior. Figure 2 (c) is a schematic diagram of the working principle of a dual-layer optical encryption fluorescent polymer waveguide chip based on optical pulse code modulation technology to realize optical encryption function.

[0022] Figure 3 (a) Corresponding Figure 1 Schematic diagram of the cross-sectional dimensions at positions a and c; Figure 3 (b) Corresponding Figure 1 Schematic diagram of the cross-sectional dimensions at position b; Figure 3 (c) is a top view of the device in Example 1.

[0023] Figure 4 In Embodiment 1 of the present invention, in the pump light B λ3 The curve showing the relationship between the output signal power of the bottom waveguide 3 in its initial state and the output signal optical power when eavesdropping occurs.

[0024] Figure 5 (a) is the pump light B λ3 The relationship curve of average gain when applied to the bottom waveguide 4; Figure 5 (b) is the pump light B λ3The relationship curve of average gain generated when applied to the top waveguide 6; Figure 5 (c) is the pump light B λ4 The relationship curve of average gain when applied to the bottom waveguide 4; Figure 5 (d) is the pump light B λ4 The relationship curve of average gain when applied to the top waveguide 6;

[0025] Figure 6 (a) is a graph showing the change of switching voltage over time during the open / closed path switching process without eavesdropping. Figure 6 (b) is a graph showing the change of switching voltage over time during the open / closed path switching process under eavesdropping behavior.

[0026] Figure 7 This is a flowchart illustrating the fabrication process of the device in Embodiment 1 of the present invention. Detailed Implementation

[0027] The present invention will now be described more clearly and comprehensively with reference to the accompanying drawings. Those skilled in the art will gain a deeper understanding of the advantages and functions of the present invention from this description. However, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Example 1:

[0029] In this embodiment, the substrate layer 1 is a silicon substrate with a thickness of 730 μm.

[0030] In this embodiment, the buffer layer 2 is silicon dioxide with a thickness of 5μm.

[0031] In this embodiment, the material used for the coating layer 3 is P(MMA-co-GMA).

[0032] In this embodiment, the fluorescent small molecule oligomer chromophore used in the bottom waveguide 4 is TCBzC, and the fluorescent small molecule oligomer chromophore used in the top waveguide 6 is TCNzC. For detailed experimental spectra, please refer to the reference (Zhang M, Xue SF, Dong WY, et al. Highly-efficient solution-processed OLEDs based on new bipolar emitters[J]. Chemical Communications, 2010, 46: 3923-3925). The polymer material used in the bottom waveguide 4 and the top waveguide 6 is SU-8 2005.

[0033] In this embodiment, the mass fraction of the fluorescent small molecule oligomer chromophore TCBzC or TCNzC in the bottom waveguide 4 and top waveguide 6 is 5 wt‰.

[0034] As attached Figure 3 As shown, in this embodiment, the bottom waveguide 4 and the top waveguide 6 both have a thickness of 5μm and a width of 7μm, and are both located within the cladding layer 3, separated by the cladding layer 3. The total thickness of the cladding layer 3 is 28μm, and the cladding layer 3 is divided into three parts: lower, middle, and upper cladding layers, with thicknesses of 10μm, 9μm, and 9μm, respectively. The bottom waveguide 4 is located within the middle cladding layer, and the top waveguide 6 is located within the upper cladding layer. The vertical distance between the top surface of the bottom waveguide 4 and the bottom surface of the top waveguide 6 is 4μm. The spacing between the input curved waveguides of the bottom waveguide 4 and the output curved waveguides of the top waveguide 6 is 127μm, the length of the curved waveguide is 1500μm, and the length of the coupling region waveguide is 1150μm.

[0035] The basic synthesis method of the SU-8 core material doped with fluorescent small molecule oligomers used in this embodiment is as follows:

[0036] 1. Take 5g of SU-8 2005 photoresist and place it in a clean weighing bottle, then add 0.025g of TCBzC or TCNzC (mass fraction of 5wt‰);

[0037] 2. Wrap the weighing bottle in tin foil and place it on the stirring table in a light-proof environment. Stir at 45°C for 30 minutes to completely dissolve the fluorescent small molecule oligomer chromophore powder in the SU-8 2005 solution, and you can obtain the SU-8 2005 core material doped with fluorescent small molecule oligomer chromophores.

[0038] In this embodiment, pump light B is selected. λ3 and B λ4 The wavelengths are 405nm and 532nm.

[0039] In this embodiment, signal light I is selected. λ1 and I λ2 The wavelengths are 532nm and 655nm.

[0040] In this embodiment, the buffer layer 2 has a refractive index of 1.45 at wavelengths of 405 nm and 532 nm, the cladding layer 3 has a refractive index of 1.48 at wavelengths of 405 nm and 532 nm, the bottom waveguide 4 has a refractive index of 1.601 at wavelength of 405 nm and 1.597 at wavelength of 532 nm, and the top waveguide 6 has a refractive index of 1.589 at wavelength of 532 nm and 1.587 at wavelength of 655 nm.

[0041] B λ3The pump light is absorbed by the fluorescent small-molecule oligomer TCBzC in the bottom waveguide 4, generating photons whose wavelengths cover the signal light I. λ1 Wavelength. B λ3 The pump light is absorbed by the fluorescent small molecule oligomer in the top waveguide 6, and the resulting photon wavelength covers the signal light I. λ2 Wavelength. B λ4 The pump light is absorbed by the fluorescent small-molecule oligomer TCNzC in the top waveguide 6, and the resulting photon wavelength can only cover the signal light I. λ2 Wavelength. For details of its PL spectrum, please refer to the reference (Wang CX, Zhang DM, Yue J, et al. On-chip optical sources of 3D photonic integration based on active fluorescent polymer waveguide microdisks for light display application[J]. PhotoniX, 2023, 4(1): 1-15).

[0042] To steal information, an intruder must extract a portion of the optical signal from the output, causing a rapid decrease in the output optical power intensity. This reduces the ratio of the output signal power to the initial output signal power. Continuous detection of this ratio immediately indicates eavesdropping and switches the transmission path from open to closed states. According to existing reports, the threshold for determining eavesdropping is a 5% power loss; see reference (Shaneman, K. et al. Optical network security: technical analysis of fiber tapping mechanisms and methods for detection & prevention. IEEE Military Communications Conference, Monterey, Canada, 2004: 711-716). The detection of the eavesdropping signal in this embodiment is shown in the attached figure. Figure 4 As shown. In pump light B λ3 Under the influence of the signal, the output power of the bottom waveguide 4 is measured at the output terminal in the initial state; when eavesdropping occurs, the eavesdropper steals a portion of the modulation information from the output terminal, causing the output signal power to decrease.

[0043] In this embodiment, the average gain of the bottom waveguide 4 and the top waveguide 6 was measured, and the calculation formula used was as follows: In the formula P out The optical power intensity of the output signal when no pump light is applied. The optical power intensity of the output signal when the pump light is applied. Figure 5 It can be observed that signal light I λ1 and I λ2 The average gain varies with the pump light B λ3 The optical power intensity gradually increases, and the signal light I... λ2 The average gain varies with the pump light B λ4 The power of the pump light B increases gradually with the increase of the light intensity. λ4 For signal light I λ1 There is no gain amplification effect. The output signal light power when the pump light is applied is stronger than the output signal light power intensity when the pump light is not applied. Therefore, the smaller output signal light power when the pump light is not applied is used as the 0 signal in the optical pulse coding, and the larger output signal light power when the pump light is applied is used as the 1 signal in the optical pulse coding, so that the modulation information carried by the output signal light is the same as the modulation information carried by the pump light.

[0044] In this embodiment, a photodetector is used to convert the output optical signal into an electrical signal, which is then sent to an oscilloscope for testing. The process of switching between overt and covert paths when there is no eavesdropping is shown in the attached figure. Figure 6 As shown in (a), within the range of 0–20s, the signal light I in the bright-state transmission path... λ1 and signal light I in dense state transmission path λ2 Pump light B with an optical power intensity of 80mW λ3 The converted electrical signals all contain modulation information; within the range of 20–40 seconds, the signal light I in the bright state transmission path λ1 Unaffected by pump light B λ4 The gain effect causes the converted electrical signal voltage to decrease and contains no modulation information; the signal light I in the dense state transmission path... λ2 Pump light B with an optical power intensity of 100mW λ4 The converted electrical signal voltage is enhanced and contains modulation information. Pump light B λ3 Switch to pump light B λ4 Signal light I in bright state transmission path λ1 To achieve demodulation-state transmission, the signal light I in the dense-state transmission path λ2 By maintaining the modulation state during transmission, path switching functionality is achieved. Compared to the attached... Figure 6 In (a), the process of switching between overt and covert paths when eavesdropping occurs is shown in the appendix. Figure 6 As shown in (b), the signal light I in the bright-state transmission path λ12 Pump light B with an optical power intensity of 80mW λ3 The voltage of the converted electrical signal under the action is lower than the voltage of the converted electrical signal when there is no eavesdropping, which can be used to determine whether there is eavesdropping. Pump light B λ3 Switch to pump light B λ4The path switching function is the same when there is eavesdropping activity as when there is no eavesdropping activity. The aforementioned dual-layer optical encryption fluorescent polymer waveguide chip based on optical pulse code modulation technology achieves encryption and anti-eavesdropping functions based on the above-mentioned path switching scheme.

[0045] The fabrication method of the dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology in this embodiment is as follows: Figure 7 As shown, the specific description is as follows:

[0046] A. Using monocrystalline silicon as substrate layer 1 and the silicon dioxide layer on substrate layer 1 as buffer layer 2, immerse it in a beaker containing acetone solution and clean it with an ultrasonic cleaner for 5 minutes, then remove it; then place it in a beaker containing isopropanol (IPA) solution and sonicate for 5 minutes to remove organic solvents, then clean it with deionized water, and use a nitrogen gun to blow dry the deionized water on the surface of buffer layer 2, and finally place it in a glass container and place it in an oven at 120°C for 30 minutes to dry it, which can remove surface moisture and organic impurities;

[0047] B. Spin-coating P(MMA-co-GMA) onto the cleaned buffer layer 2 surface to form a 10 μm lower coating layer 31. Then spin-coating SU-8 2005 doped with the fluorescent small molecule oligomer TCBzC (rotation speed: 3000 rpm, time: 20 seconds) is performed, followed immediately by thermosetting on a hot plate (pre-baking: 60°C, 10 minutes; post-baking: 90°C, 20 minutes) to obtain a 5 μm thick coating 4a doped with the fluorescent small molecule oligomer TCBzC.

[0048] C. After cooling the device coated with coating 4a to room temperature at 25°C, it is exposed to ultraviolet light using photomask 5 (exposure time 7s). The exposed part of photomask 5 is the bottom waveguide 4 structure. Then, after post-baking (65°C for 10 minutes, 95°C for 20 minutes), the epoxy groups in SU-8 2005 crosslink at the exposed sites, improving thermal stability.

[0049] D. Immerse the waveguide chip obtained in step C in photoresist developer (propylene glycol methyl ether acetate (PGMEA)) for 15 seconds to dissolve the non-epoxy crosslinked polymer film region. Then place it on a hot plate and heat at 120°C for 30 minutes. Spin-coat P(MMA-co-GMA) as the middle cladding layer 32 of the bottom waveguide 4, with a thickness of 9 μm.

[0050] E. The fabrication process of the top waveguide 6 is similar to that of the bottom waveguide 4. SU-8 2005 spin-coating (3000 rpm, 20 seconds) of the fluorescent small molecule oligomer TCNzC was applied to the P(MMA-co-GMA) coating layer 3, and then immediately thermo-cured on a hot plate (pre-bake: 60°C, 10 minutes; post-bake: 90°C, 20 minutes) to obtain a 5 μm thick coating 6a of the fluorescent small molecule oligomer TCNzC.

[0051] F. After cooling the device coated with coating 6a to room temperature at 25°C, it is exposed to ultraviolet light using photomask 7 (exposure time 7s). The exposed portion of photomask 7 is the top waveguide 6 structure. It is particularly important that during the exposure process, the position of photomask 7 is adjusted so that the bottom waveguide 4 and top waveguide 6 do not overlap in the top view. After post-baking (65°C for 10 minutes, 95°C for 20 minutes), the epoxy groups in SU-8 2005 crosslink at the exposed sites. P(MMA-co-GMA) is spin-coated onto the top waveguide 6 to form a 9μm thick upper cladding layer 33, thus fabricating a dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology. The lower cladding layer 31, middle cladding layer 32, and upper cladding layer 33 are collectively referred to as cladding layer 3.

Claims

1. A dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology, characterized in that: From bottom to top, the waveguide consists of a substrate layer (1), a buffer layer (2), a cladding layer (3), a bottom waveguide (4), and a top waveguide (6). The cladding layer (3) is divided into three parts: a lower cladding layer, a middle cladding layer, and an upper cladding layer. The bottom waveguide (4) is located in the middle cladding layer, and the top waveguide (6) is located in the upper cladding layer. The bottom waveguide (4) and the top waveguide (6) are separated by the cladding layer (3) and do not overlap in the top view plane of the waveguide chip. The bottom waveguide (4) and the top waveguide (6) are composed of an input-end curved waveguide, a coupling region waveguide, and an output-end curved waveguide, respectively. The coupling region waveguides of the bottom waveguide (4) and the top waveguide (6) are arranged in parallel, and the input-end curved waveguides and the output-end curved waveguides of the bottom waveguide (4) and the top waveguide (6) are arranged symmetrically facing each other. The refractive index of the bottom waveguide (4) and the top waveguide (6) is greater than that of the buffer layer (2) and the cladding layer (3).

2. The dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology as described in claim 1, characterized in that: The substrate (1) material is one of indium phosphide, gallium arsenide, and silicon.

3. The dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology as described in claim 1, characterized in that: The material of the buffer layer (2) is one of SU-8, PMMA, P (MMA-co-GMA), and silicon dioxide.

4. The dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology as described in claim 1, characterized in that: The coating layer (3) is made of one of the following materials: SU-8, PMMA, P (MMA-co-GMA), or silicon dioxide.

5. The dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology as described in claim 1, characterized in that: The bottom waveguide (4) material is obtained by doping a TCBzC fluorescent small molecule oligomer chromophore into a polymer material. The polymer material is one of SU-8, PMMA, and P(MMA-co-GMA). The mass fraction of the TCBzC fluorescent small molecule oligomer chromophore doping ranges from 3 to 8 wt%. The TCBzC structural formula is shown below.

6. The dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology as described in claim 1, characterized in that: The top waveguide (6) material is obtained by doping a TCNzC fluorescent small molecule oligomer chromophore into a polymer material. The polymer material is any one of SU-8, PMMA, and P(MMA-co-GMA). The mass fraction of the TCNzC fluorescent small molecule oligomer chromophore doping ranges from 3 to 8 wt%. The structural formula of TCNzC is shown below.

7. The dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology as described in claim 1, characterized in that: Signal light I λ1 and I λ2 The wavelength range is 500–700 nm, and the power range is 0.2–2 mW; pump light B λ3 The wavelength range is 400–600 nm, and the pump light B λ4 The wavelength range is 500–700 nm, and the pump light B λ3 and B λ4 Power range is 10–100 mW; signal light I λ1 The wavelength is less than the signal light I λ2 wavelength, pump light B λ3 The wavelength is less than the signal light I λ1 wavelength, pump light B λ4 The wavelength is greater than or equal to the signal light I λ1 The wavelength is smaller than that of the signal light I λ2 The wavelength.

8. The dual-layer optically encrypted fluorescent polymer waveguide chip based on optical pulse code modulation technology as described in claim 1, characterized in that: The bottom waveguide (4) and the top waveguide (6) are both 5 μm thick and 7 μm wide. The total thickness of the cladding layer (3) is 28 μm, and the thicknesses of the lower, middle and upper cladding layers are 10 μm, 9 μm and 9 μm, respectively. The vertical distance between the top surface of the bottom waveguide (4) and the bottom surface of the top waveguide (6) is 4 μm. The spacing between the bent waveguides at the input end of the bottom waveguide (4) and the bent waveguides at the output end of the top waveguide (6) is 127 μm, the length of the bent waveguide is 1500 μm, and the length of the waveguide in the coupling region is 1150 μm.

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