Manufacturing method of photo-thermal refractive glass gradient refractive index optical fiber
By using ion exchange method to form Ag+ concentration and refractive index gradients in photothermal folded glass fibers, the scattering problem caused by interface defects of the fiber core layer and cladding is solved, and lower transmission loss and better optical performance are achieved.
Patent Information
- Application Number
- CN202310829463.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-07
- Publication Date
- 2025-01-07
AI Technical Summary
The existing photothermal folded glass fibers have micro-holes and micro-cracks at the interface between the fiber core and the cladding, resulting in large scattering losses of the light guide waves and it is difficult to effectively reduce the transmission loss of the optical fiber.
Ag+ concentration gradient is formed in the radial direction of the photothermal folding glass homogeneous fiber preform rod by ion exchange method, resulting in a refractive index gradient, forming a core layer and a cladding layer, reducing interface defects, and photothermal folding is made by optical fiber drawing method to make photothermal folding Glass gradient refractive index fiber.
It reduces the transmission loss of the optical fiber, reduces the scattering of the light guide wave, and improves the optical performance of the optical fiber.
Smart Images
Figure CN119263621A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to an optical fiber device, and in particular to a gradient refractive index optical fiber made of a photothermal refracting glass material. Background Art
[0002] Photo-Thermo-Refractive Glass (PTRG) is a new type of photosensitive glass material. This material can precipitate sodium fluoride crystals in the glass body after ultraviolet irradiation and heat treatment. The crystallization process is accompanied by permanent negative refractive index modulation (the refractive index modulation amplitude can be as high as 1000ppm). By utilizing the photosensitive properties of this material, the glass material is exposed to ultraviolet light holographically and heat treated at a reasonable temperature, so that periodic refractive index modulation can be formed on the glass substrate. In addition, this glass material also has a series of excellent properties such as good optical uniformity, good transmittance, and good chemical uniformity. This material can be used in the manufacture of a variety of optical components, and is particularly suitable for the manufacture of volume phase gratings. This volume phase grating has excellent frequency selectivity and can be used for frequency selection and frequency stabilization of lasers. It is called the "stabilizing force" of lasers and is an indispensable device for the manufacture of high-performance lasers. In addition, this device can also achieve angle selection, spectral beam combining, pulse compression, etc., and can be used in augmented reality display devices.
[0003] The most widely used photothermal refractory glass is mainly composed of Na2O-ZnO-Al2O3-SiO2, doped with Ag. + 、Ce 4+ and F - The reason for the change in refractive index is the precipitation of nano-sized NaF crystals after UV exposure and heat treatment.
[0004] In recent years, the application of photothermorefractive glass materials in optical fiber and optical waveguide devices has received more and more attention. Researchers have tried to use various methods to make optical waveguide and optical fiber devices based on this material. In 2013, P. Hofmann et al. used photothermorefractive glass to make unclad optical fiber. Their production method was to pull the photothermorefractive glass preform into a fiber with a diameter of 60-135μm (P. Hofmann et al., "Strong Bragg Gratings in Highly Photosensitive Photo-Thermo-Refractive-Glass Optical Fiber," IEEE Photonics Technology Letters, vol. 25, (1), pp. 25-28, 2013). In 2014, K. Al Yahyaei et al. from the same research group as P. Hofmann published a paper using rod-in-tube PTR materials to achieve the production of step-refractive index optical fiber (K. Al Yahyaei et al., "Highly photosensitive fiber fabricated from photo-thermo-refractive glass," in 2014). The first type of cladding-free optical thermorefractive glass fiber has a uniform refractive index distribution inside, and in fact uses air as the cladding. This type of optical fiber is difficult to avoid the loss caused by the scattering of light-guided waves on the surface of the optical fiber. The second type of optical thermorefractive glass fiber produced by the casing method has a cladding, but because the optical fiber produced by this casing method is a step-refractive index optical fiber, the light field is strong at the interface between the optical fiber core and the cladding, so the scattering loss caused by micro holes and micro cracks at this interface is also large, making it difficult to effectively reduce the transmission loss of the optical fiber. Summary of the invention
[0005] The object of the present invention is to provide a method for manufacturing a photothermorefractive glass gradient refractive index optical fiber.
[0006] The technical solution adopted by the present invention to solve its technical problem is:
[0007] The photothermorefractive glass gradient refractive index optical fiber of the present invention has a refractive index on the central axis of the optical fiber higher than that on the surface of the optical fiber, and the refractive index from the central axis of the optical fiber to the surface of the optical fiber shows a gradual change. The production process of this optical fiber is carried out in four steps (see attached Figure 1As shown in the figure): the first step is to make a photothermorefractive glass substrate to obtain an optical grade homogeneous photothermorefractive glass material block; the second step is to make a cylindrical photothermorefractive glass homogeneous optical fiber preform, and use a mechanical processing method to obtain a cylindrical photothermorefractive glass homogeneous optical fiber preform; the third step is ion exchange of the optical fiber preform to form a photothermorefractive glass gradient refractive index optical fiber preform; the fourth step is to draw a photothermorefractive glass gradient refractive index optical fiber, and draw the photothermorefractive glass gradient refractive index optical fiber preform into a photothermorefractive glass gradient refractive index optical fiber. This optical fiber manufacturing method is characterized in that the optical fiber is drawn after the photothermorefractive glass homogeneous optical fiber preform is converted into a photothermorefractive glass gradient refractive index optical fiber preform by ion exchange.
[0008] The photothermal refractive glass substrate is doped with Ag + 、Ce 4+ and F - of silicate glass.
[0009] The molten salt used in the ion exchange contains Na + ; K can be added to the molten salt selectively + , Li + , or Ag + .
[0010] The shape of the photothermorefractive glass homogeneous optical fiber preform is as follows: Figure 2 As shown, its radius is R and its length is L.
[0011] The Ag in the photothermorefractive glass homogeneous optical fiber preform + The concentration is evenly distributed along the radius, such as Figure 3 As shown in the figure, Ag in each part of the photothermorefractive glass homogeneous optical fiber preform + The concentration is N0.
[0012] The medium refractive index of the photothermorefractive glass homogeneous optical fiber preform is uniformly distributed along the radial direction, such as Figure 4 As shown, the refractive index of each part in the photothermorefractive glass homogeneous optical fiber preform is N0.
[0013] The Ag in the photothermorefractive glass gradient refractive index optical fiber preform + The concentration shows a gradient distribution in the radial direction of the optical fiber preform. + The concentration is the highest, along the radius of the cylinder toward the surface of the optical fiber preform Ag + The concentration gradually decreases. Figure 5 As shown, on the central axis of the photothermorefractive glass gradient refractive index optical fiber preform, Ag + The concentration is N0; on the surface of the photothermal refractory glass gradient refractive index optical fiber preform, Ag + The concentration is N1.
[0014] The refractive index of the photothermorefractive glass gradient refractive index optical fiber preform presents a gradient distribution characteristic in the radial direction of the optical fiber preform, with the highest refractive index on the central axis of the optical fiber preform and gradually decreasing along the cylindrical radius toward the surface of the optical fiber preform. Figure 6 As shown, on the central axis of the photothermorefractive glass gradient refractive index optical fiber preform, the refractive index is n0; on the surface of the photothermorefractive glass gradient refractive index optical fiber preform, the refractive index is n1.
[0015] The shape of the photothermorefractive glass gradient refractive index optical fiber is as follows: Figure 7 As shown, its radius is r and its length is l.
[0016] The Ag in the photothermal refractory glass gradient refractive index optical fiber + The concentration shows a gradient distribution in the radial direction of the optical fiber. + The concentration is highest along the radius of the cylinder toward the surface of the optical fiber. + The concentration gradually decreases. Figure 8 As shown, on the central axis of the photothermal refracting glass gradient refractive index fiber, Ag + The concentration is N0; on the surface of the photothermal refracting glass gradient refractive index fiber, Ag + The concentration is N1.
[0017] The refractive index of the photothermorefractive glass gradient refractive index optical fiber presents a gradient distribution characteristic in the radial direction of the optical fiber, with the highest refractive index on the central axis of the optical fiber and gradually decreasing along the cylindrical radius toward the surface of the optical fiber. Fig. 9 As shown, on the central axis of the photothermorefractive glass gradient refractive index optical fiber, the refractive index is n0; on the surface of the photothermorefractive glass gradient refractive index optical fiber, the refractive index is n1.
[0018] The present invention has the following beneficial effects:
[0019] The method for manufacturing the photothermorefractive glass optical fiber of the present invention adopts an ion exchange method to form Ag in the radial direction of a cylindrical photothermorefractive glass material optical fiber preform rod. + The concentration gradient also produces a refractive index gradient along the radial direction of the photothermorefractive glass fiber preform. After the fiber is drawn, the Ag concentration gradient in the radial direction of the fiber is correspondingly formed. + Concentration gradient and refractive index gradient. Ag in the inner layer of optical fiber + High concentration, high refractive index, used as the core; Ag in the outer layer of the optical fiber +The optical fiber produced by this optical fiber production method has the advantages that the produced optical fiber has a core layer and a cladding layer made of glass material, and the core layer and the cladding layer are derived from the same piece of glass material, so there is no defect between the interface of the core layer and the cladding layer, which reduces the scattering of the optical waveguide and reduces the transmission loss of the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a schematic diagram of the process flow of photothermorefractive glass gradient refractive index optical fiber production.
[0021] Figure 2 It is a schematic diagram of the structure of a cylindrical photothermorefractive glass homogeneous optical fiber preform.
[0022] Figure 3 It is the Ag in the cylindrical photothermorefractive glass homogeneous optical fiber preform. + Radial distribution of concentration.
[0023] Figure 4 It is the radial distribution diagram of the refractive index in the cylindrical photothermorefractive glass homogeneous optical fiber preform.
[0024] Figure 5 Ag in the photothermorefractive glass gradient refractive index optical fiber preform + Radial distribution of concentration.
[0025] Figure 6 It is the radial distribution diagram of the refractive index in the photothermorefractive glass gradient refractive index optical fiber preform.
[0026] Figure 7 It is a schematic diagram of the structure of photothermorefractive glass gradient refractive index optical fiber.
[0027] Figure 8 Ag in the photothermorefractive glass gradient refractive index fiber + Radial distribution of concentration.
[0028] Fig. 9 It is the radial distribution diagram of the refractive index in the photothermorefractive glass gradient refractive index optical fiber. DETAILED DESCRIPTION
[0029] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.
[0030] The production process of photothermorefractive glass fiber is divided into four steps:
[0031] The first step is to make the photothermal refractive glass substrate. The glass material is melted in a platinum crucible. The material composition is: 68.5wt% SiO2, 4.8wt% Al2O3, 12.9wt% Na2O, 6.6wt% ZnO, 4.3wt% NaF, 2.5wt% KBr, 0.02wt% Ag2O, 0.02wt% CeO2, 0.08wt% Sb2O3, 0.02wt% SnO2, and the melting temperature is 1480-1500°C. Obtain an optical grade homogeneous photothermal refractive glass material block.
[0032] The second step is to make a cylindrical photothermorefractive glass homogeneous optical fiber preform rod. The cylindrical photothermorefractive glass homogeneous optical fiber preform rod is obtained by mechanical processing and the surface is polished. The radius of the optical fiber preform rod is 1 to 8 mm and the length is 50 to 300 cm.
[0033] The third step is the ion exchange of the optical fiber preform. The cylindrical photothermorefractive glass homogeneous optical fiber preform is placed in a mixed molten salt of NaNO3 and KNO3 molten at 300-400°C (the weight ratio of NaNO3 to KNO3 is 3:1-10:1), and kept warm for 3-72 hours to form a photothermorefractive glass gradient refractive index optical fiber preform.
[0034] The fourth step is to draw the photothermorefractive glass gradient refractive index optical fiber. The optical fiber drawing equipment is used to draw the photothermorefractive glass gradient refractive index optical fiber preform into a photothermorefractive glass gradient refractive index optical fiber. The diameter of the optical fiber is 50 to 200 microns.
[0035] The above specific implementation modes are used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.
Claims
1. A method for manufacturing a photothermorefractive glass gradient refractive index optical fiber, the manufacturing process is divided into four steps: the first step is to manufacture a photothermorefractive glass substrate to obtain an optical grade homogeneous photothermorefractive glass material block; the second step is to manufacture a cylindrical photothermorefractive glass homogeneous optical fiber preform rod, and obtain a cylindrical photothermorefractive glass homogeneous optical fiber preform rod by mechanical processing; the third step is ion exchange of the optical fiber preform rod to form a photothermorefractive glass gradient refractive index optical fiber preform rod; the fourth step is to draw the photothermorefractive glass gradient refractive index optical fiber, and draw the photothermorefractive glass gradient refractive index optical fiber preform rod into a photothermorefractive glass gradient refractive index optical fiber. The optical fiber manufacturing method is characterized in that the optical fiber is drawn after the photothermorefractive glass homogeneous optical fiber preform rod is processed into a photothermorefractive glass gradient refractive index optical fiber preform rod by ion exchange.
2. The method for manufacturing a photothermorefractive glass gradient refractive index optical fiber according to claim 1, characterized in that: The photothermal refractive glass substrate is doped with Ag + 、Ce 4+ and F - of silicate glass.
3. The method for manufacturing a photothermorefractive glass gradient refractive index optical fiber according to claim 1, characterized in that: The molten salt used in the ion exchange contains Na + ; K can be added to the molten salt selectively + , Li + , or Ag + .
4. The method for manufacturing a photothermorefractive glass gradient refractive index optical fiber according to claim 1, characterized in that: The Ag in the photothermorefractive glass homogeneous optical fiber preform + The concentration is evenly distributed along the radius.
5. The method for manufacturing a photothermorefractive glass gradient refractive index optical fiber according to claim 1, characterized in that: The refractive index of the photothermorefractive glass homogeneous optical fiber preform is uniformly distributed along the radial direction.
6. The method for manufacturing a photothermorefractive glass gradient refractive index optical fiber according to claim 1, characterized in that: The Ag in the photothermorefractive glass gradient refractive index optical fiber preform + The concentration shows a gradient distribution in the radial direction of the optical fiber preform. + The concentration is the highest, along the radius of the cylinder toward the surface of the optical fiber preform Ag + The concentration gradually decreases.
7. The method for manufacturing a photothermorefractive glass gradient refractive index optical fiber according to claim 1, characterized in that: The refractive index of the photothermorefractive glass gradient refractive index optical fiber preform presents a gradient distribution characteristic in the radial direction of the optical fiber preform, the refractive index is highest on the central axis of the optical fiber preform, and the refractive index gradually decreases along the cylindrical radius toward the surface of the optical fiber preform.
8. The method for manufacturing a photothermorefractive glass gradient refractive index optical fiber according to claim 1, characterized in that: The Ag in the photothermal refractory glass gradient refractive index optical fiber + The concentration shows a gradient distribution in the radial direction of the optical fiber. + The concentration is highest along the radius of the cylinder toward the surface of the optical fiber. + The concentration gradually decreases.
9. The method for manufacturing a photothermorefractive glass gradient refractive index optical fiber according to claim 1, characterized in that: The refractive index of the photothermorefractive glass gradient refractive index optical fiber presents a gradient distribution characteristic in the radial direction of the optical fiber, the refractive index is highest on the central axis of the optical fiber, and the refractive index gradually decreases along the cylindrical radius toward the surface of the optical fiber.