A bismuth-doped silica fiber for O-band and E-band amplification and its preparation method

Abstract

This invention discloses a bismuth-doped silica optical fiber for O-band and E-band amplification. The fiber comprises, from the outside in, a cladding, a loose layer, and a core. The cladding is composed of pure silica with a lower refractive index than the core. The loose layer is a silica loose layer doped with GeO2 and P2O3. The core is doped with bismuth, with the outer layer doped with bismuth oxide and the inner layer doped with GeO2 and P2O3. 3. First, GeO2 and P2O3 are deposited on the inner wall of the base tube, then bismuth oxide is deposited. After the bismuth oxide is deposited, GeO2 and P2O3 are deposited again, and finally the rod is shrunk and drawn into wire.

Description

Technical fields:

[0001] This invention relates to a bismuth (Bi)-doped silica optical fiber based on atomic layer deposition technology, belonging to the field of optical fiber technology. Background technology:

[0002] The explosive growth of data transmission on the Internet has spurred the increased use and development of interconnected data centers for online multimedia applications and cloud computing. The global demand for higher data transmission rates is constantly increasing, which translates to a growing need for increased capacity in modern fiber optic communication systems. Developing high-efficiency amplifiers capable of operating outside the currently used C and L bands (1530nm-1625nm) will provide additional bandwidth capacity.

[0003] Currently, most commercially available amplifiers in the O-band region are semiconductor optical amplifiers (SOAs). However, SOAs are generally unsuitable for transmission due to their high noise figure (NF), fast dynamics, polarization sensitivity, and nonlinearity. Therefore, in recent years, bismuth (Bi) has emerged as a promising dopant for fiber amplifiers. Depending on the core composition (silicon dioxide, aluminum silicate, phosphate silicate, etc.), structure, and pump wavelength, BDFAs (Bi-doped fiber amplifiers) can be used to provide gain in the O and E bands.

[0004] Atomic layer deposition (ALD) is a chemical vapor deposition technique that involves pulsedly introducing a vapor precursor of a doped source into a heated reactor, followed by sequential chemisorption deposition onto the substrate surface until surface saturation, at which point the process automatically terminates. Its advantages primarily include: precise control of film thickness (atomic layer scale); ensuring conformal, uniform, and large-area films due to the saturated chemisorption of the precursor; and broad applicability to various matrix materials.

[0005] In 2015, Chinese patent 201510422447.2 proposed a near-infrared luminescent bismuth-doped multicomponent optical fiber, which uses a tube-rod method to fabricate the fiber. This method achieves high-concentration bismuth doping, but the fabrication process requires careful handling to prevent bubbles and interference, as the higher-refractive-index glass rod is inserted into a lower-refractive-index glass tube and heated together. This results in lower fiber fabrication efficiency and limitations on uniformity. Furthermore, strict temperature control is required during fiber drawing; otherwise, bismuth agglomeration and precipitation can cause the preform to blacken, leading to fiber devitrification, high loss, weakened luminescence, or even quenching. In 2019, Chinese patent 201910365061.0 proposed a method to improve the luminescence efficiency of bismuth-related doped active optical fibers by inducing irradiation and high-temperature annealing. This method is beneficial for improving the luminescence efficiency and fluorescence lifetime of bismuth-related doped active optical fibers, but its widespread application is limited by the conditions of post-processing. In 2020, Chinese patent 202010073619.0 proposed the preparation of Bi / Er / La / Al co-doped silica fiber based on a combination of high-temperature doping improved chemical vapor deposition (MCVD) and ALD or liquid phase doping processes, high-temperature evaporation doping process, and external vapor deposition process. This fiber exhibits broadband fluorescence in the range of 1530 to 1625 nm and can be used as an ultra-wideband light source or tunable laser in the C+L band. Summary of the Invention

[0006] This invention addresses the limitation of the limited amplification band in existing optical fibers. Leveraging the advantages of atomic layer deposition (ALD) technology, it combines bismuth oxide nanomaterials with optical fiber fabrication to provide a method for producing bismuth (Bi)-doped silica optical fibers based on ALD technology. This fiber exhibits characteristics such as wide gain spectrum, high amplification efficiency, simple structure, and ease of industrial production, making it suitable for fabricating lasers, optical amplifiers, sensors, broadband light sources, and more.

[0007] Technical principle of the invention:

[0008] Compared to rare earth (RE) ions, the optically active 4f electrons are shielded by the outermost 5s and 5p electrons, and the optical transitions in the BAC (Bi-associated active center) are related to the unshielded outer electron shell of bismuth atoms or ions. Therefore, the wavelength and energy level structure of the transitions largely depend on the matrix of the host glass. By changing the composition of the host glass, the emission wavelength range and optical amplification range of bismuth (Bi)-doped glass can be altered. This significantly improves the limitation of gain wavelength in erbium-doped fibers. Furthermore, compared to the preparation of O-band bismuth-doped fibers through tubular rod methods and post-processing, the ALD process can precisely control the film thickness, ensuring the formation of uniform, large-area films, solving the previous problems of low efficiency and non-uniformity in fiber preparation. Meanwhile, research shows that the BAC-P (bismuth-phosphorus active center) is located at the center of the O-band, at 1300 nm, playing a crucial role in the emission of bismuth-doped fibers in the O-band. Ge doping also greatly benefits the fluorescence and gain of bismuth-doped fibers at longer wavelengths. Therefore, this invention proposes to increase the doping of P and Ge elements in bismuth-doped optical fibers to further enhance the fluorescence efficiency of bismuth-doped optical fibers in the O and E bands, laying an important foundation for the construction of O and E band amplifiers.

[0009] The present invention adopts the following technical solution:

[0010] A bismuth-doped silica optical fiber for O-band and E-band amplification, comprising a cladding, a loose layer, and a core from the outside in. The cladding is composed of pure silica with a lower refractive index than the core. The loose layer is a silica loose layer doped with GeO2 and P2O3. The core is doped with bismuth.

[0011] The outer layer of the fiber core is doped with bismuth oxide, while the inner layer is doped with GeO2 and P2O3.

[0012] The core diameter and cladding diameter ranges are respectively d core =Φ8~10μm, d cladding =Φ120~125μm

[0013] The molar concentrations of doped silicon oxide, phosphorus oxide, and germanium oxide materials range from 0.1 mol% to 15 mol%.

[0014] The concentration of Bi ions was controlled within the range of 0.01-1.5 mol%; the concentration of P ions was controlled within the range of 0.5-15.0 mol%; and the concentration of Ge ions was controlled within the range of 0.1-5.0 mol%.

[0015] First, GeO2 and P2O3 are deposited on the inner wall of the base tube, then bismuth oxide is deposited. After the bismuth oxide is deposited, GeO2 and P2O3 are deposited again, and finally the rod is shrunk and drawn into wire.

[0016] Bismuth oxide materials doped using atomic layer deposition (ALD) technology are characterized in that the precursor is Bis(2,2,6,6-tetramethyl-3,5-heptanedionato)Bismuth(III)(Bi(tmhd)3), tris(2,2,6,6-tetramethyl-3,5-heptanedionate)bismuth(III) or (2,2,6,6-tetramethyl-3,5-heptanedionate)bismuth or tris(2,2,6,6-tetramethyl-3,5-heptanedionate)bismuth; or Bi(N(SiMe3)2)3(Me:CH3), tritrimethylsilamidobismuth; and the oxygen source precursor is O3, ozone or H2O, or deionized water.

[0017] By combining atomic layer deposition (ALD) with improved chemical vapor deposition (CVD), the precursor pulse time, heat source temperature, reaction temperature, and gas flow rate are precisely controlled to adjust the deposition thickness and doping concentration of bismuth oxide, phosphorus oxide, and germanium oxide.

[0018] The precursor pulse duration was 10-100 ms, the heat source temperature was 100-200℃, the reaction temperature was 180-300℃, and the gas flow rate was controlled at 200-500 sccm. The controlled parameters for bismuth oxide deposition were all achieved using micro-deposition at 100-2000 layers, with each deposition cycle at 0.01-0.25 nm. The Bi ion concentration was controlled at 0.01-1.5 mol%, the P ion concentration at 0.5-15.0 mol%, and the Ge ion concentration at 0.1-5.0 mol%.

[0019] The Bi source heating temperature is controlled at 100–300℃ with a pulse time of 200–400 ms; the oxygen source pulse time is 200–1000 ms; the temperature of the entire reaction chamber is uniform, and the reaction temperature is 200–400℃, with two deposition processes: forward and reverse.

[0020] Compared with the prior art, the present invention has the following obvious substantive features and significant advantages:

[0021] 1. Bismuth (Bi)-doped silica optical fiber can achieve broadband amplification of 1260nm-1360nm and 1400nm-1460nm;

[0022] 2. Atomic layer deposition technology is adopted, which has good uniformity, high doping concentration, and is convenient and feasible, thus obtaining higher quality bismuth (Bi) doped quartz optical fibers;

[0023] 3. It has a simple structure, low price, and is easy to industrialize. It can be used to build lasers, optical amplifiers, and sensors. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the optical fiber structure of the present invention.

[0025] Figure 2 This is a schematic diagram of doping in Embodiment 2 of the present invention.

[0026] Figure 3 This is a schematic diagram of doping in Embodiment 3 of the present invention.

[0027] Figure 4 This is a schematic diagram of doping in Embodiment 4 of the present invention.

[0028] Figure 5 This is a schematic diagram of the optical fiber spectral width of the present invention (the schematic diagrams of the gain spectra of the O-band and E-band of the bismuth-doped optical fiber are shown below). Figure 5 (As shown).

[0029] Figure 6 This is a schematic diagram of the doping distribution in an optical fiber. Detailed Implementation

[0030] A preferred embodiment of the present invention is described below in conjunction with the accompanying drawings:

[0031] Example 1:

[0032] See Figure 1 A bismuth (Bi)-doped silica optical fiber based on atomic layer deposition (ALD) technology includes a loose layer (structure 1), a core (structure 2), and a cladding (structure 3). From the outside in, the layers are cladding, loose layer, and core. The loose layer 1 is composed of silica loose layer doped with high-refractive-index GeO2 and P2O3. The cladding 3 is composed of pure silica with a lower refractive index than the core 2. The core is doped with Bi, and the core diameter ranges from d. core =Φ8~10μm, cladding diameter range d cladding =Φ120~125μm.

[0033] Example 2:

[0034] See Figure 2 First, Ge and P(60) were deposited on the surface of a quartz substrate to form a loose layer structure. The numbers in parentheses indicate the gas flow rate during doping, i.e., 60 sccm, and the same applies below. Next, bismuth oxide nanofilms were deposited alternately using atomic layer deposition (ALD). Bi(tmhd)3 and O3 are gaseous precursor materials for bismuth oxide, and the deposition temperature range is 250℃. During the bismuth deposition process, the number of cycles was 2000, and optical fibers with a certain concentration of bismuth doped were prepared. Finally, Ge and P(250) co-doping were further deposited on the oxide surface using MCVD to increase the refractive index of the optical fiber. When the concentration of P2O3 was 1.7 mol%, the luminous efficiency of the optical fiber was low, and the maximum fluorescence intensity in the O band was -45 dBm. The fiber was then wound up and drawn. The resulting optical fiber structure is as follows. Figure 6Three doped layers are formed within the cladding, with the bismuth-doped Bi layer located between the two P- and Ge-doped layers. This invention utilizes the advantages of thermal atomic layer deposition (T-ALD) or plasma-enhanced atomic layer deposition (PE-ALD) techniques to combine bismuth metal materials with optical fiber fabrication, providing a bismuth-doped silica amplifying optical fiber in a phosphorus-host environment and its fabrication method. By controlling the P / Ge doping levels and adjusting the optical basicity, Bi can better exist in a low-valence state, and this low-valence Bi is one of the sources of near-infrared emission. Because the low-valence Bi forms active centers in the 1300nm (O-band) near-infrared emission under the P-host environment, bismuth-doped optical fibers, compared to rare-earth-doped fibers such as praseodymium-doped fibers, can significantly increase spectral gain bandwidth, overcoming the bandwidth limitations imposed by the 4f-4f transitions in rare-earth elements. Furthermore, the formation of BAC-P active centers increases gain while decreasing the noise figure. Furthermore, the formation of multiple active centers in bismuth under different host environments can solve key scientific problems such as limited gain bandwidth and high noise figure in doped fiber amplification, significantly enhancing its luminescence intensity and showing potential application in the field of ultra-wideband, high-gain, low-loss, and low-noise quartz fiber amplifiers.

[0035] Table 1. Maximum fluorescence values ​​of optical fibers with different doping concentrations.

[0036] Ge / P (wt% / wt%) Bi / P (wt% / wt%) Fluorescence intensity (dBm) BPDF-1 8.76 / 1.10 0.03 / 1.10 -42 BPDF-2 8.85 / 0.01 0.03 / 0.01 -50 BPDF-3 8.62 / 2.17 0.03 / 2.17 -25 BPDF-4 8.61 / 1.51 0.03 / 1.51 -37 BPDF-5 8.72 / 1.92 0.03 / 1.92 -40 BPDF-6 8.66 / 1.89 0.06 / 1.90 -46

[0037] As shown in Table 1, changing the doping amount of P and Bi can adjust the fluorescence intensity. When the doping amounts of Ge and Bi remain unchanged, changing the doping amount of P can significantly change the fluorescence intensity.

[0038] Example 3:

[0039] See Figure 3 Ge and P(500) were deposited on a quartz substrate to form a loose layer structure. Then, bismuth oxide nanofilms were alternately deposited using atomic layer deposition (ALD), with Bi(tmhd)3 and O3 as vapor-phase precursors for bismuth oxide. The deposition temperature range was 180℃. During bismuth deposition, a bidirectional alternating deposition method of bismuth oxide was used, with 1500 cycles and 1000 cycles respectively, to prepare optical fibers with a certain concentration of bismuth doped with bismuth. Then, Ge and P(900) co-doping were further deposited on the oxide surface using MCVD. When the P2O3 concentration was 5 mol%, the optical fiber exhibited high luminous efficiency, with a maximum fluorescence intensity of -15 dBm in the O-band. The fiber was then wound and drawn into a wire.

[0040] Example 4:

[0041] See Figure 4A loose layer structure of P(300) and Ge was deposited on the surface of a quartz substrate. Then, bismuth oxide nanofilms were alternately deposited using atomic layer deposition (ALD), with Bi(tmhd)3 and O3 as vapor-phase precursors for bismuth oxide. The deposition temperature range was 220℃. During the bismuth deposition process, 1500 cycles were performed to prepare optical fibers with a certain concentration of bismuth doped with each element. Next, P(500) and Ge co-doping was further deposited on the oxide surface using MCVD. At this point, the doping efficiency of P2O3 was low; at a concentration of 2.1 mol%, the optical fiber luminous efficiency was low. The fiber was then wound and drawn into fibers.

Claims

1. A method for preparing bismuth-doped silica optical fiber for O-band and E-band amplification, characterized in that: First, GeO2 and P2O3 are deposited on the inner wall of the base tube, followed by bismuth oxide deposition. After bismuth oxide deposition, GeO2 and P2O3 are deposited again, and finally, the tube is shrunk and drawn into wire. Bismuth oxide is doped using atomic layer deposition (ALD). ALD combined with modified chemical vapor deposition (CVD) precisely controls the precursor pulse time, heat source temperature, reaction temperature, and gas flow rate to adjust the deposition thickness and doping concentration of bismuth oxide, phosphorus oxide, and germanium oxide. The precursor pulse time is 10-100 ms, the heat source temperature is 100-200℃, the reaction temperature is 180-300℃, and the gas flow rate is controlled at 200-500 sccm. The control parameters for bismuth oxide deposition are all based on micro-deposition of 100-2000 layers, with each deposition cycle at 0.01-0.25 nm. The Bi ion concentration is controlled in the range of 0.003-0.006 mol%; the P ion concentration is controlled in the range of 0.5-15.0 mol%; and the Ge ion concentration is controlled in the range of 0.1-5.0 mol%. %.

2. The method for preparing bismuth-doped silica optical fiber for O-band and E-band amplification according to claim 1, characterized in that... The precursors are as follows: bismuth source precursors are Bis(2,2,6,6-tetra-methyl-3,5-heptanedionato)Bismuth(III) (Bi(tmhd)3), tris(2,2,6,6-tetramethyl-3,5-heptanedionoic acid)bismuth(III), (2,2,6,6-tetramethyl-3,5-heptanedionoic acid)bismuth, tris(2,2,6,6-tetramethyl-3,5-heptanedionoic acid)bismuth, Bi(N(SiMe3)2)3 (Me: CH3) or tris(trimethylsilylamine)bismuth; oxygen source precursors are ozone (O3) or deionized water (H2O).

3. The method for fabricating bismuth-doped quartz O-band and E-band amplifying optical fibers according to claim 2, characterized in that: The Bi source heating temperature is controlled at 100–300℃ with a pulse time of 200–400 ms; the oxygen source pulse time is 200–1000 ms; the temperature of the entire reaction chamber is uniform, and the reaction temperature is 200–400℃, with two deposition processes: forward and reverse.

4. A bismuth-doped silica optical fiber for O-band and E-band amplification, wherein the optical fiber comprises, from the outside to the inside, a cladding layer, a loose layer, and a core, characterized in that... The fiber is prepared by the method described in claim 1, wherein the cladding is composed of pure quartz with a lower refractive index than the core; the porous layer is a porous quartz layer doped with GeO2 and P2O3; and the core is doped with bismuth.

5. The bismuth-doped silica optical fiber for O-band and E-band amplification according to claim 4, characterized in that: The outer layer of the fiber core is doped with bismuth oxide, while the inner layer is doped with GeO2 and P2O3.

6. The bismuth-doped silica optical fiber for O-band and E-band amplification according to claim 5, characterized in that: The core diameter and cladding diameter ranges are respectively d core =Φ 8~10 μm, d cladding =Φ 120~125 μm.

7. The bismuth-doped silica optical fiber for O-band and E-band amplification according to claim 5, characterized in that: The molar concentrations of doped bismuth oxide, phosphorus oxide, and germanium oxide materials range from 0.1 mol% to 15 mol%.

8. The bismuth-doped silica optical fiber for O-band and E-band amplification according to claim 7, characterized in that: The concentration of Bi ions was controlled in the range of 0.003-0.006 mol; the concentration of P ions was controlled in the range of 0.5-15.0 mol; and the concentration of Ge ions was controlled in the range of 0.1-5.0 mol.

Images