A flexible planar lightwave circuit device and a method for fabricating the same

Abstract

The application discloses a flexible planar light waveguide device and a preparation method thereof, and relates to the technical field of optoelectronic materials and devices. Technical points are as follows: the device provided by the application comprises a flexible substrate, a core layer and an upper cladding layer, and the core layer is a CuI film; a waveguide topological structure for optical signal transmission is formed on the substrate; the CuI film has a cubic zinc blende crystal structure; the average absorption rate of the CuI film in a 0.4-30 mu m wide spectral range is less than 10%; and the refractive index of the CuI film is 2.2-2.5. The transmittance attenuation of the CuI film is less than 2% after the CuI film is bent at a bending radius of 5 mm and is bent 5000 times, and the CuI film exhibits excellent flexibility and optical performance. The method is simple in process, low in cost and suitable for large-scale production. The application solves the problems of narrow light transmission range and poor flexibility of traditional optical waveguide materials, is suitable for flexible optoelectronic device applications in the visible light to mid-infrared waveband, and has a wide market prospect.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials and devices, specifically to a flexible planar optical waveguide device based on cuprous iodide (CuI), which is particularly suitable for flexible optoelectronic device applications in the visible to mid-far-infrared bands. Background Technology

[0002] In the design of flexible optical waveguide devices (such as flexible optical fibers), flexible materials with high refractive index and low optical loss characteristics over a wide spectral range are crucial for forming the core optical transmission channel (core layer). This type of core layer material needs to be integrated with a low-refractive-index flexible polymer cladding material to form an optical waveguide structure, enabling sensitive detection of changes in external environmental parameters (such as refractive index and temperature).

[0003] Current mainstream optical waveguide materials (such as single-crystal silicon, silicon dioxide, and lithium niobate) generally exhibit intrinsic brittleness and poor bending resistance, making them unsuitable for flexible applications. Known flexible optical waveguide materials include SU-8 photoresist (n=1.59), polymethyl methacrylate (PMMA) (n=1.49), polydimethylsiloxane (PDMS) (n=1.43), and polyimide (PI) (n=1.7). While possessing good flexibility, their refractive indices are generally low (n<1.8), making them unsuitable for use as high-refractive-index core layers. Therefore, core layer materials possessing excellent mechanical flexibility, a wide-spectrum high refractive index, and low absorption characteristics are extremely scarce, which has become a key bottleneck restricting the development and application expansion of flexible integrated photonic device technology. Summary of the Invention

[0004] The purpose of this invention is to address the problems of narrow light transmission range and poor flexibility of existing optical waveguide materials by providing a flexible planar optical waveguide device based on a CuI core layer and its fabrication method.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A flexible planar optical waveguide device is characterized by having a sandwich-like stacked structure, consisting of a flexible substrate, a core layer, and an upper cladding layer from bottom to top; the flexible substrate serves as the lower cladding layer, together with the upper cladding layer, enclosing the core layer; the flexible substrate, core layer, and upper cladding layer are all made of transparent flexible materials; the core layer material is a CuI thin film, prepared by magnetron sputtering and annealing, forming a waveguide topology for optical signal transmission on the substrate.

[0007] Furthermore, the CuI film has a cubic zincblende crystalline structure, with an average absorption rate of <10% in a wide spectral range of 0.4-30 μm and a refractive index of 2.2-2.5.

[0008] Furthermore, the transmittance of the CuI film decreases by less than 2% after bending 5000 times with a bending radius ≤5mm.

[0009] A method for fabricating the above-mentioned flexible planar optical waveguide device specifically includes the following steps:

[0010] Step 1: Select a flexible substrate and perform a cleaning pretreatment on it;

[0011] Step 2: Core layer preparation; using magnetron sputtering, CuI ceramic is used as the sputtering target to deposit a CuI thin film on a substrate covering the mask as the core layer of the optical waveguide device; the sputtering power is 50-100 W, the argon flow rate is 100-150 mL / min, the deposition time is 20-40 minutes, and the core layer thickness is 100-300 nm.

[0012] Step 3: Preparation of the upper cladding layer; A flexible transparent organic layer is spin-coated onto the core layer as the upper cladding layer;

[0013] Step 4: Post-processing; Annealing at 60-90℃ for 0.5-2 hours to obtain the flexible planar optical waveguide device; wherein:

[0014] The flexible substrate is one of thermoplastic polyurethane (TPU), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyimide (PI), and polyethylene dinaphthalate (PEN).

[0015] The flexible transparent organic layer is one of the following: polydimethylsiloxane (PDMS), sodium alginate, SU-8 epoxy resin, thermoplastic polyurethane (TPU), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyimide (PI), and polyethylene dinaphthalate (PEN).

[0016] Compared with existing technologies, the beneficial effects of this solution are:

[0017] 1) Broad spectrum transparency: This planar optical waveguide device covers the visible light to mid-far infrared band (0.4-30 μm) with an average absorption rate of <10%, solving the problem of narrow light transmission range of traditional materials;

[0018] 2) High refractive index core layer: The core layer has a refractive index of 2.2-2.5, which forms a good optical waveguide structure with the low refractive index cladding material (n=1.4-1.7);

[0019] 3) Excellent flexibility: After bending radius ≤5mm and 5000 bending cycles, the transmittance of CuI film decreases by <2%, making it suitable for flexible electronic devices;

[0020] 4) Low cost and easy preparation: The raw materials are inexpensive and the preparation process is simple, making it suitable for large-scale production. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of the device of the present invention;

[0022] Figure 2 This is a flowchart illustrating the fabrication process of the device of the present invention;

[0023] Figure 3 This is a schematic diagram of the linear CuI optical waveguide structure in Embodiment 1 of the present invention;

[0024] Figure 4 This is an absorptivity curve of the CuI thin film in the core layer of the optical waveguide device in Embodiment 1 of the present invention;

[0025] Figure 5 This is a schematic diagram of the micro-ring resonator type CuI optical waveguide structure in Embodiment 2 of the present invention;

[0026] Figure 6 This is a graph showing the refractive index of the CuI thin film in the core layer of the optical waveguide device in Embodiment 2 of the present invention.

[0027] Figure 7 This is a schematic diagram of the bifurcated CuI optical waveguide structure in Embodiment 3 of the present invention;

[0028] Figure 8 This is a schematic diagram showing the degree of transmittance attenuation of the CuI thin film in the core layer of the optical waveguide device in Embodiment 3 of the present invention after bending 5000 times with a bending radius of 5 mm. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be described in further detail below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are merely 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 should fall within the scope of protection of the present invention.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0031] Example 1

[0032] (a) PET was selected as the flexible substrate 1, and ultrasonically cleaned with acetone and isopropanol for 15 minutes in sequence, and then dried with nitrogen.

[0033] (b) CuI core layer deposition by magnetron sputtering: CuI target with a purity of 99.9% was used, working pressure was 1 Pa, and sputtering power was 70 W. A linear mask 4 was fixed above the substrate, and sputtering was performed for 30 minutes to obtain a linear CuI waveguide core layer 2 with a thickness of 150 nm;

[0034] (c) PDMS is spin-coated as the upper cladding layer 3 on top of the CuI thin film layer in step (b), with a thickness of 100-200 nm, and annealed at 80°C for 1 hour. The schematic diagram of the obtained optical waveguide structure is shown below. Figure 3 As shown;

[0035] The CuI thin film in the core layer of the optical waveguide device prepared by this method has an average absorption rate of <10% in the wavelength range of 0.4-30 μm, such as Figure 4 As shown, it has excellent light transmittance in the visible light and mid-to-far infrared regions.

[0036] Example 2

[0037] The difference between this embodiment and Embodiment 1 is that in step (b), the mask 4 has both ring and linear patterns, the magnetron sputtering time is 40 minutes, and a micro-ring resonator-type CuI optical waveguide core layer 2 is fabricated. The other steps are the same, and the schematic diagram of the obtained optical waveguide structure is shown below. Figure 5 As shown;

[0038] The CuI thin film in the core layer of the optical waveguide device prepared by this method has a refractive index of 2.2-2.5 in the wavelength range of 0.4-30 μm, such as... Figure 6 As shown, it can form a good refractive index match with the upper and lower cladding layers.

[0039] Example 3

[0040] The difference between this embodiment and Embodiment 1 is that in step (b), the mask 4 has a bifurcation pattern; and in step (c), spin-coated PVA is used as the upper cladding layer. The other steps are the same, and the resulting optical waveguide structure is shown in the schematic diagram below. Figure 7 As shown.

[0041] The CuI thin film in the core layer of the optical waveguide device prepared by this method exhibits a transmittance decrease of less than 2% after 5000 bends with a bending radius of 5 mm. Figure 8 As shown, it exhibits excellent flexibility and optical transmittance.

[0042] The above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A flexible planar optical waveguide device, characterized in that, The device is a sandwich stacked structure, consisting of a flexible substrate, a core layer, and an upper cladding layer from bottom to top. The flexible substrate serves as the lower cladding layer, which, together with the upper cladding layer, encloses the core layer. The flexible substrate, core layer, and upper cladding layer are all made of transparent flexible materials. The core layer material is a CuI thin film, which is prepared by magnetron sputtering and annealing to form a waveguide topology for optical signal transmission on the substrate.

2. The flexible planar optical waveguide device according to claim 1, characterized in that, The CuI film has a cubic zincblende crystalline structure, with an average absorption rate of <10% in a wide spectral range of 0.4-30 μm and a refractive index of 2.2-2.

5.

3. The flexible planar optical waveguide device according to claim 1, characterized in that, The CuI film has a bending radius ≤5mm and a transmittance decrease of <2% after 5000 bends.

4. A method for fabricating the flexible planar optical waveguide device according to claim 1, characterized in that, Specifically, it includes the following steps: Step 1: Select a flexible substrate and perform a cleaning pretreatment on it; Step 2: Core layer preparation; using magnetron sputtering, CuI ceramic is used as the sputtering target to deposit a CuI thin film on a substrate covering the mask as the core layer of the optical waveguide device; the sputtering power is 50-100 W, the argon flow rate is 100-150 mL / min, the deposition time is 20-40 minutes, and the core layer thickness is 100-300 nm. Step 3: Preparation of the upper cladding layer; A flexible transparent organic layer is spin-coated onto the core layer as the upper cladding layer; Step 4: Post-processing; Annealing at 60-90℃ for 0.5-2 hours to obtain the flexible planar optical waveguide device; wherein: The flexible substrate is one of thermoplastic polyurethane, polymethyl methacrylate, polyvinyl alcohol, polyethylene terephthalate, polyimide, and polyethylene naphthalate. The flexible transparent organic layer is one of the following: polydimethylsiloxane, sodium alginate, SU-8 epoxy resin, thermoplastic polyurethane, polymethyl methacrylate, polyvinyl alcohol, polyethylene terephthalate, polyimide, and polyethylene naphthalate.

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