Pb / Al co-doped quartz gain fiber at wave band of 1100-1200 nm and irradiation enhancement method

Abstract

The invention discloses a 1100-1200 nm waveband Pb / Al co-doped quartz gain optical fiber and an irradiation enhancement method, a fiber core comprises SiO2 loose layers at the outermost layer and the innermost layer and a doped layer in the middle of the fiber core, the SiO2 loose layers are made of high-purity SiO2 and materials doped with low-concentration and high-refractive-index GeO2, the doped layer is doped with one or more of Pb-containing compounds of PbO, PbS and PbSe, and the Pb / Al co-doped quartz gain optical fiber with the waveband of 1100-1200 nm is formed by doping one or more of the Pb-containing compounds of PbO, PbS and PbSe. And one or two of Al-containing compounds such as AlF3, Al2O3 and the like. The doping concentration range of Pb in the fiber core is controlled to be 0.01-1 mol%, and the doping concentration of Al is controlled to be 0.5-5 mol%. An irradiation source used in the irradiation post-treatment is gamma rays, the dosage is 100-2000 Gy, and the dosage rate is 50-2000 Gy / h. The crystal field environment of low-valence Pb ions responsible for near-infrared light emission is improved through Al doping, a new Pb / Al active center within the interval of 1100-1200 nm is formed, meanwhile, the forming probability of the Pb / Ge active center is reduced, harmful pumping competition and reabsorption are reduced, and the number of the Pb / Al active center in the optical fiber is further increased through gamma ray irradiation, so that the light emission intensity is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fibers. Background Art

[0002] Gain fibers based on the 1100-1200nm band and the fiber lasers with visible light wavelengths generated by frequency doubling have unique advantages in medical treatment, detection and imaging analysis, space environmental protection, and deep space exploration, and therefore have attracted much attention. Currently, active fibers in the 1100-1200nm band mainly include Yb-, Nd-, and Bi-doped fibers. Among them, the gain cross section of Yb- and Nd-doped fibers decreases with increasing wavelength, and will be affected by the spontaneous amplification radiation of their peak fluorescence at shorter wavelengths, so their gain in the 1100-1200nm range is relatively low. Bi-doped aluminosilicate fibers have begun to be used in fiber amplifiers and lasers in the 1100-1300nm band because of the presence of Bi / Al active centers at 1150nm, but there are also problems such as small emission cross section, long fiber length, and uncertain luminescence mechanism, which limit further improvement of their performance.

[0003] In addition to rare earth and Bi elements, Pb, as a main group metal element, has no shielding effect of outer electrons on its valence electrons, and its luminescence is also easily affected by the crystal field, and can produce near-infrared fluorescence in a wide range. Early studies have shown that Pb-doped alkaline earth metal fluoride crystals will form near-infrared luminescence centers around 1060nm after X-ray irradiation. Near-infrared fluorescence in the range of 1100 to 1240nm has also been found in Pb-doped aluminogermanate glass, with a fluorescence lifetime of about 400μs. Subsequently, near-infrared fluorescence at 1150nm was also found in Pb-doped quartz and germanosilicate optical fibers, but its luminescence efficiency is low, and the fluorescence lifetime is only tens of μs. At the same time, since the doping concentration of Pb is generally low, it is inevitable to dope a certain concentration of Ge elements in order to improve the refractive index of the core. This causes Pb to form additional new active centers at 1050 and 1240nm with Ge. Under the conventional 980nm pump, pump competition and reabsorption of the 1150nm fluorescence of the interstitial Pb+ center will occur, resulting in a further reduction in the luminous efficiency of the 1100-1200nm band, making it unsuitable for use as a gain fiber in the 1100-1200nm band. According to existing literature and analogy with Bi-doped fibers, it is speculated that there may be luminescent centers similar to Bi / Al active centers in the co-doped Al-doped Pb-doped fiber, which can be used as a gain medium in the 1100-1200nm band. At present, there is no report on the application of such gain fibers. Summary of the invention

[0004] The technical problem to be solved by the present invention is: in view of the low luminous efficiency of the current Pb-doped quartz optical fiber and germanosilicate optical fiber at 1150nm and the harmful competition of Pb / Ge active centers, a Pb / Al co-doped quartz gain optical fiber in the 1100-1200nm band and an irradiation enhancement method thereof are provided.

[0005] The technical solution of the present invention:

[0006] A 1100-1200nm band Pb / Al co-doped quartz gain optical fiber and an irradiation enhancement method thereof. The optical fiber comprises a core 1 and a cladding 2. The core 1 is doped with a small amount of Pb-containing compound and Al-containing compound. The cladding 2 is composed of a quartz optical fiber with a lower refractive index than the core 1.

[0007] The fiber core 1 includes an outer core layer 1-1 containing SiO2 and a small amount of GeO2, an intermediate doping layer 1-2 doped with Pb and Al elements, and an innermost core layer 1-3. The Pb compound contained in the intermediate doping layer 1-2 of the fiber core is one or more of PbO, PbS and PbSe, and the Al compound contained is one or two of AlF3 and Al2O3.

[0008] Preferably, the Pb ion doping concentration in the core is controlled within the range of 0.01-1 mol%, the Al doping concentration is controlled within the range of 0.5-5 mol%, and the Ge content is controlled within the range of 0.5-1%.

[0009] Preferably, the core diameter is 5-20 μm, the cladding diameter is 100-300 μm, and the refractive index difference between the core and the cladding is 0.2-2%.

[0010] The absorption wavelength range of the Pb / Al co-doped optical fiber with the above characteristics is 500-1050nm, the fluorescence spectrum range is 900-1400nm, and the gain in the range of 1100-1200nm is greater than 15dB. The optical fiber can be used as a gain optical fiber in the 1100-1200nm band, and the preferred pump is a 980nm and 1064nm pump source.

[0011] The Pb / Al co-doped quartz optical fiber is treated by post-irradiation with gamma rays. Preferably, the irradiation dose is 100-2000 Gy, the dose rate is 100-1500 Gy / h, and the gain of the optical fiber is increased by 5-10 dB in the range of 1100-1200 nm after irradiation.

[0012] The beneficial effects of the present invention are:

[0013] 1. By doping Al elements to regulate the crystal field coordination environment of Pb atoms, a new Pb / Al active center is formed at 1100nm. Compared with the interstitial Pb+ ion luminescence center responsible for 1150nm luminescence in conventional Pb-doped quartz fiber or germanosilicate fiber, it has a higher absorption cross section at conventional 980 and 1064nm pump sources and higher luminescence efficiency.

[0014] 2. By increasing the Al doping concentration to ensure the refractive index difference of the optical fiber, the dependence on co-doped Ge is reduced, and the probability of Pb and Ge coupling to form active centers is reduced, so as to reduce the competition of non-target active centers for 980 and 1064nm pumps and the reabsorption of fluorescence in the 1100-1200nm band.

[0015] 3. Utilize the interaction between radiation and materials in the optical fiber to cause the reduction of the valence state of Pb ions, changes in the coordination structure and Al-related defect structures, increase the number of Pb / Al defect active centers that are conducive to luminescence in the 1100-1200nm band, and further improve the optical fiber gain level. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the cross-sectional structure of the optical fiber of the present invention, wherein 1-1 is an outer core layer obtained from a loose layer, 1-2 is an intermediate doping layer, 1-3 is an inner core layer obtained from a loose layer, and 2 is a cladding layer.

[0017] Figure 2 The gain comparison between the optical fiber of the present invention and the Pb-doped quartz optical fiber under 980nm pumping is shown. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Embodiment 1:

[0020] See also Figure 1A 1100-1200nm band Pb / Al co-doped silica gain fiber and its irradiation enhancement method, after depositing SiO2 and GeO2 loose layers on the inner wall of a quartz substrate tube (1-1), on the basis of the loose layers, Al2O3 and PbO atomic layers are alternately deposited by ALD process to obtain a doping layer (1-2), and finally about 1500 layers of Al2O3 atomic layers are deposited on the outermost layer of the doping layer by ALD, and then SiO2 loose layers (1-3) are deposited, and finally the rod is drawn. The Pb / Al co-doped silica fiber is obtained. The Pb doping concentration is 0.02at%, the Al doping concentration is 0.5at%, the Ge doping concentration is 0.2at%, the core diameter is 10μm, the cladding diameter is 125μm, and the refractive index difference is 0.02%. The optical fiber absorption peaks are located at 700 and 1000nm. Under 980nm pumping, the fluorescence range is 900-1400nm, and the gain is 15dB in the 1100-1200nm range. The optical fiber is irradiated with gamma rays. The irradiation source is 60 Co, the dose is 1000Gy, the dose rate is 500Gy / h, and the gain is increased by 5dB in the range of 1100-1200nm after irradiation.

[0021] The present invention improves the crystal field environment of low-valent Pb ions responsible for near-infrared luminescence by Al doping, forming new Pb / Al active centers in the range of 1100-1200nm, while reducing the probability of forming Pb / Ge active centers, reducing harmful pump competition and reabsorption. The number of Pb / Al active centers in the optical fiber is further increased by gamma ray irradiation, thereby improving the luminescence intensity. Compared with the existing Pb-doped optical fiber, the present invention has a greatly improved luminescence efficiency, and the gain in the 1100-1200nm band is greater than 15dB, and can be applied to fields such as optical fiber amplifiers and lasers.

[0022] Embodiment 2:

[0023] See also Figure 1, a 1100-1200nm band Pb / Al co-doped quartz gain fiber and its irradiation enhancement method, after depositing SiO2 and GeO2 loose layers on the inner wall of a quartz substrate tube (1-1), Pb and Al elements are doped by solution immersion method. The quartz tube is immersed in a HNO3 solution doped with PbO and Al2O3 powder for 3 hours, and dried in a N2 atmosphere to obtain a doping layer (1-2), and then about 2000 layers of Al2O3 atomic layers are deposited in the dried substrate tube by ALD, and then a loose layer (1-3) is deposited by MCVD, and finally the rod is drawn. The obtained Pb / Al co-doped fiber has a Pb doping concentration of 0.05at%, an Al doping concentration of 1at%, and a Ge doping concentration of 0.3at%, a core diameter of 8μm, a cladding diameter of 125μm, and a refractive index difference of 0.03%. The optical fiber absorption peak is located at 700 and 1000nm. Under 1064nm pumping, the fluorescence range is 900-1400nm, and the gain is 15dB in the range of 1100-1200nm. The optical fiber is irradiated with gamma rays, and the irradiation source is 60 Co, the dose is 300Gy, the dose rate is 1200Gy / h, and the gain is increased by 7dB in the range of 1100-1200nm after irradiation.

Claims

1. A 1100-1200 nm band Pb / Al co-doped silica gain optical fiber, comprising a core (1) and a cladding (2), characterized in that: The core (1) is doped with a Pb-containing compound and an Al-containing compound, and the cladding (2) is made of quartz having a lower refractive index than the core (1).

2. The 1100-1200 nm band Pb / Al co-doped silica gain optical fiber according to claim 1, characterized in that: The fiber core comprises an outer core layer (1-1) containing SiO2 and GeO2, an intermediate doping layer (1-2) doped with Pb and Al compounds, and an innermost core layer (1-3) doped with SiO2 and GeO2.

3. The 1100-1200 nm Pb / Al co-doped silica gain optical fiber according to claim 2, characterized in that: The Pb-containing compound in the core intermediate doping layer (1-2) is one or more of PbO, PbS, and PbSe, and the Al-containing compound is one or two of AlF3 and Al2O3.

4. The 1100-1200 nm band Pb / Al co-doped silica gain optical fiber according to claim 3, characterized in that: The doping concentration range of Pb ions in the fiber core is controlled within 0.01-1 mol%, the doping concentration of Al is controlled within 0.5-5 mol%, and the content of Ge is controlled within 0.5-1%.

5. The 1100-1200 nm band Pb / Al co-doped silica gain optical fiber according to any one of claims 1 to 4, characterized in that: The core diameter is 5 to 20 μm, the cladding diameter is 100 to 300 μm, and the refractive index difference between the core and the cladding is 0.2 to 2%.

6. The 1100-1200 nm band Pb / Al co-doped silica gain optical fiber according to claim 5, characterized in that: By doping Al, the crystal field environment of low-valent Pb ions in the optical fiber is affected to form Pb / Al related active centers, which emit fluorescence in the range of 1100-1200nm. The absorption wavelength range of Pb / Al co-doped optical fiber is 500-1050nm, and its fluorescence spectrum range is 900-1400nm. The gain is greater than 15dB in the range of 1100-1200nm.

7. The Pb / Al co-doped silica gain optical fiber in the 1100-1200 nm band according to claim 5, characterized in that: The optical fiber is irradiated, wherein the irradiation source used in the irradiation is gamma rays, the dosage is 100 to 2000 Gy, and the dosage rate is 50 to 2000 Gy / h.

8. The Pb / Al co-doped silica gain optical fiber in the 1100-1200 nm band according to claim 7, characterized in that: After irradiation, the gain of the optical fiber in the range of 1100 to 1200 nm is increased by 5 to 10 dB.

Images