Rare-earth doped phosphate glass double-clad optical fiber with emission wavelength at 1.3 μm band, its preparation method and application

Abstract

The application discloses a rare earth doped phosphate glass double-clad optical fiber with a wavelength of 1.3 microns, a preparation method and application thereof. The double-clad optical fiber comprises a core, an inner cladding and an outer cladding. The core is doped with Nd 3+ phosphate glass, the inner cladding is doped with Yb 3+ phosphate glass, and the outer cladding is undoped oxide glass. The rare earth doped phosphate glass double-clad optical fiber utilizes the absorption of Yb 3+ ions in the inner cladding to make the transmission loss of the core in the range of 0.9 microns to 1.05 microns greater than or equal to 2 dB / cm, so that the spontaneous radiation of Nd 3+ ions in the core in the two wavelength ranges of 0.9 microns and 1.05 microns is effectively inhibited, and the optical signal-to-noise ratio during 1.3-micron laser operation is improved. The application also provides a full-fiber type 1.3-micron Q-switched fiber laser built by using the double-clad optical fiber.

Description

Technical Field

[0001] The present invention relates to the field of glass optical fibers and optical fiber lasers, and in particular to a rare earth-doped phosphate glass double-clad optical fiber with an emission wavelength in the 1.3 μm band, and a preparation method and application thereof. Background Art

[0002] Rare earth ion doped active optical fiber plays an important role in many fields such as optical fiber communication, laser, sensing and detection. Although its types have been rapidly expanded in the past few decades, the development of rare earth doped optical fiber with ideal properties has always been the pursuit of the optical fiber material community. Among them, Nd 3+ Doped glass optical fibers have attracted wide attention due to their applications in quantum information, laser processing, and medical fields. However, the Nd doped fibers suitable for 1.3 μm laser operation are currently 3+ The doping matrix material is mainly crystal, such as Nd:YAG, Nd:YVO4, etc., which is suitable for Nd-doped CMOS working at 1.3 microns. 3+ Glass fiber optic materials remain a huge challenge.

[0003] Different from the strong emission peak at 1.3 μm in the crystal, 3+ The 1.3 micron emission in the doped glass material shows a significant non-uniform broadening, and its fluorescence branching ratio is only about 0.1, which is much smaller than the fluorescence branching ratios of 0.9 micron and 1.06 micron from the same upper energy level. This puts the 1.3 micron at a serious disadvantage in the fierce gain competition with 0.9 and 1.06 micron. In addition, the 1.3 micron also faces the problem of excited state absorption, that is, Nd 3+ ion 4 F 3 / 2 Excited state energy level to 4 G 7 / 2 Energy level transitions will also absorb 1.3-micron photons, further weakening the fiber gain.

[0004] How to suppress and solve Nd 3+ The gain competition and excited state absorption issues in doped glass fibers have become the research focus of scholars at home and abroad. 3+ Microstructured quartz fiber improves the loss at 0.9 and 1.06 microns, thereby suppressing the competing transition and achieving wide spectrum amplification from 1376nm to 1466nm (Opt. Express, 25, 6524, 2017). However, microstructured fiber has a complex preparation process. 3+The 1.3 micron excited state absorption of ions is relatively weak in matrices such as fluoride glass and phosphate glass, which can achieve 1.3 micron laser output. However, fluoride glass faces the disadvantages of poor physical and chemical properties, short material quality, and difficulty in fiber drawing. On the contrary, phosphate glass has the advantages of high rare earth ion doping, large stimulated emission cross section, mature preparation process and easy fiber drawing, making it an excellent gain material matrix. However, at present, the Nd doped 3+ The 1.3-micron laser operation obtained in phosphate optical fiber has problems such as low laser signal-to-noise ratio and low efficiency due to the failure to suppress competing transitions at 0.9 and 1.06 microns. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the above scheme, the purpose of the present invention is to provide a rare earth doped phosphate glass double clad optical fiber with an emission wavelength in the 1.3 μm band and its preparation method and application. 3+ Yb-doped phosphate glass core 3+ The inner envelope of the ion, using Yb 3+ Ion absorption orientation increases the transmission loss of the fiber core from 900nm to 1050nm (≥2dB / cm), thereby suppressing the Nd 3+ ions spontaneously emit light at 0.9 and 1.0 μm. This fiber combines the advantages of competitive transition suppression and stimulated absorption attenuation; it has the advantages of simple structure and easy preparation. Furthermore, a 1.3 μm Q-switched fiber laser device with high laser signal-to-noise ratio based on this phosphate double-clad fiber is provided.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention provides a rare earth doped phosphate glass double clad optical fiber with an emission wavelength in the 1.3 μm band, the double clad optical fiber is composed of a core, an inner cladding and an outer cladding, and is characterized in that the core is made of Nd 3+ doped phosphate glass, the inner cladding is composed of Yb 3+ The fiber is composed of doped phosphate glass, the outer cladding is composed of undoped oxide glass, and the transmission loss of the fiber core in the range of 0.9μm to 1.05μm is greater than or equal to 2dB / cm.

[0008] The optical fiber is a single-mode optical fiber.

[0009] The refractive index difference between the core glass and the inner cladding glass is 0.02 to 0.10.

[0010] The fiber core has a diameter of 4 to 10 μm, the inner cladding has a diameter of 20 to 125 μm, and the outer cladding has a diameter of 125 μm.

[0011] Nd in the fiber core 3+The doping concentration of Yb in the inner cladding is ≥0.1wt%. 3+ Doping concentration ≥ 0.1wt%.

[0012] By mass percentage, the Nd 3+ The composition of doped phosphate glass is (70-78.8)P2O5-(5-8)Al2O3-(3-7)La2O3-(0.1-4.5)Nd2O3-(0-12)BxOy, wherein B is one or more of Mg, Ca, Ba or Y; the Yb 3+ The doped phosphate glass composition is (62.5-78.8)P2O5-(0-10)SiO2-(0-10)BaO-(5-7)Al2O3-(2-4)La2O3-(0-4)Y2O3-(0.1-8)Yb2O3-(3-10)CxOy, wherein C is one or both of Na or K; the oxide glass is phosphate, germanate or silicate glass.

[0013] The second aspect of the present invention provides a method for preparing the rare earth doped phosphate glass double clad optical fiber with an emission wavelength in the 1.3 μm band, wherein the method is characterized in that the Nd 3+ Doped phosphate glass is processed into glass rods, and Yb 3+ Doped phosphate glass and undoped oxide glass are processed into glass tubes respectively, which are then combined into optical fiber preforms after acid treatment, cleaning and drying, and then drawn to obtain the double-clad optical fiber.

[0014] A third aspect of the present invention provides an all-fiber 1.3 μm Q-switched fiber laser, which is characterized in that it includes the rare-earth-doped phosphate glass double-clad fiber with an emission wavelength in the 1.3 μm band.

[0015] The 1.3 micron Q-switched laser has a laser optical signal-to-noise ratio of >50dB, a repetition frequency of >200kHz, and a pulse width of >150ns.

[0016] Compared with the prior art, the technology of the present invention has significant effects:

[0017] The present invention is to dope Nd 3+ In the phosphate fiber structure, a layer of Yb-doped 3+ Phosphate inner cladding, using Yb in the inner cladding 3+ The absorption direction of ions increases the transmission loss of the fiber core from 900nm to 1050nm (≥2dB / cm), thereby suppressing the Nd 3+ The 0.9 and 1.0 micron spontaneous radiation of ions was finally obtained, which can be used to generate high signal-to-noise ratio 1.3 micron rare earth doped phosphate double-clad optical fiber.

[0018] Nd-doped 3+ Phosphate fiber has three bands of ASE spectrum, with the center wavelengths at 0.9μm, 1.05μm and 1.3μm. Since the upper energy levels of the three bands are Nd 3+ : 4 F 3 / 2 , which makes the three bands compete fiercely and the 1.3μm ASE is the weakest, suppressing the Nd-doped 3+ The ASE intensity of phosphate fiber at 0.9μm and 1.05μm can obtain high signal-to-noise ratio 1.3μm laser output. 3 + It has strong absorption in the range of 0.85μm to 1.05μm, but no absorption at 1.3μm. 3+ : 4 F 3 / 2 Energy levels and Yb 3 + : 2 F 5 / 2 Cross relaxation occurs between energy levels, which will reduce Nd 3+ : 4 F 3 / 2 energy level lifetime, thereby reducing Nd 3+ The gain at 1.3 μm is such that Nd cannot be doped directly into the fiber core. 3+ ions and Yb 3+ In addition, the quenching concentration of rare earth ions in phosphate glass is high. Using phosphate glass as a doping matrix can increase the rare earth ion doping concentration and thus increase the optical fiber gain.

[0019] At the same time, an all-fiber 1.3-micron Q-switched laser was constructed using this rare-earth-doped phosphate double-clad fiber, with a direct output optical signal-to-noise ratio of >50dB, a repetition frequency of >200kHz, and a pulse width of >150ns. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the end face diagram of the optical fiber in Example 1# of the present invention.

[0021] Figure 2 This is the optical path diagram in Example 1# of the present invention.

[0022] Figure 3 This is the laser spectrum diagram in Example 1# of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0024] The embodiment of the present invention provides a rare earth doped phosphate glass double cladding optical fiber with an emission wavelength in the 1.3 μm band, the core of which is Nd 3+ Doped phosphate glass with Yb as inner cladding 3+ Doped phosphate glass, the outer cladding is undoped oxide glass, prepared by the tube-rod method, the transmission loss of the optical fiber core in the range of 0.9μm to 1.05μm is ≥2dB / cm.

[0025] According to the mass percentage, Nd in the fiber core 3+ The doping concentration is ≥0.1%. Furthermore, by mass percentage, the Nd 3+ The doping concentration is 0.1% to 4.5%. 3+ Can produce high gain at 1.3μm.

[0026] According to the mass percentage, the Yb 3+ The doping concentration of Yb in the inner cladding is ≥0.1%. Furthermore, by mass percentage, 3+ The doping concentration is 0.1% to 8%. 3+ Able to suppress Nd in the fiber core to a limited extent 3+ ASE at 0.9μm and 1.05μm, thus achieving high signal-to-noise ratio 1.3μm laser.

[0027] The optical fiber is a single-mode optical fiber and is prepared by a tube-rod method.

[0028] The refractive index difference between the core glass and the inner cladding glass is 0.02 to 0.10.

[0029] The fiber core has a diameter of 4 to 10 μm, the inner cladding has a diameter of 20 to 125 μm, and the outer cladding has a diameter of 125 μm.

[0030] The present invention also provides an all-fiber 1.3 μm Q-switched fiber laser based on the rare-earth-doped phosphate double-clad fiber. The components of the all-fiber 1.3 μm Q-switched fiber laser include the rare-earth-doped phosphate glass double-clad fiber, a dichroic film, a saturable absorber, and a wavelength division multiplexer.

[0031] One end of the rare earth doped phosphate glass double cladding optical fiber is closely attached to the saturable absorber, and the other end is closely attached to the dichroic film to form a resonant cavity.

[0032] The pump light passes through the common end of the wavelength division multiplexer and enters the resonant cavity from the dichroic film. The 1.3μm photons generated by stimulated radiation are reflected back and forth in the resonant cavity and amplified to form Q-switched lasers which are output through the signal port of the wavelength division multiplexer.

[0033] The all-fiber 1.3-micron Q-switched laser has a laser signal-to-noise ratio of >50dB, a repetition frequency of >200kHz, and a pulse width of >150ns.

[0034] The following are specific examples.

[0035] Example 1

[0036] This embodiment is a rare earth doped phosphate glass double clad optical fiber with an emission wavelength in the 1.3 μm band. The optical fiber end face is as follows: Figure 1 As shown, it includes a core 1, an inner cladding 2 and an outer cladding 3. The core 1 is doped with Nd 3+ Multi-component phosphate glass, by mass percentage, its oxide formula is 78.8P2O5-5Al2O3-10BaO-5La2O3-1.2Nd2O3, the inner cladding 2 is doped with Yb 3+ The multi-component phosphate glass has an oxide composition of 78.8P2O5-5Al2O3-10BaO-2La2O3-3Na2O-0.1Yb2O3 by mass. The outer cladding 3 is an undoped multi-component phosphate glass with an oxide composition of 70P2O5-4Al2O3-10BaO-2La2O3-7Na2O-7K2CO3 by mass. The multi-component phosphate glass is produced using a melt-quenching method. The core, inner cladding, and outer cladding are mechanically processed, acid-treated, cleaned, and dried before being assembled into an optical fiber preform. The double-clad optical fiber is then drawn using a tube-and-rod method. The optical fiber has a core diameter of 4μm, an inner cladding diameter of 35μm, and an outer cladding diameter of 125μm. The refractive index difference between the core and inner cladding is 0.10, and the transmission loss of the optical fiber core in the 0.9μm to 1.05μm range is 2dB / cm.

[0037] Based on the above optical fiber, an all-fiber 1.3-micron Q-switched laser is constructed. The optical path diagram is shown in the attached figure. Figure 2 As shown, an 808 nm pump source 4, an 808 / 1360 nm wavelength division multiplexer 5, a dichroic film 6, a saturable absorber 7, a prepared double-clad optical fiber 8, and a wavelength division multiplexer signal end 9; one end of the prepared rare earth-doped phosphate glass double-clad optical fiber is placed close to the saturable absorber (modulation depth 1.6%, recovery time 1 ps, saturation flux 50 μJ / cm 2, 1360nm unsaturated reflectivity is 97%), and the other end is closely attached to the dichroic film (808nm transmittance is 99.8%, 1360nm reflectivity is 96.5%) to form a resonant cavity. The 808nm pump light enters the resonant cavity from the dichroic film after passing through the 808 / 1360nm WDM. The 1.3μm photons generated by stimulated radiation are reflected back and forth in the resonant cavity, oscillated and amplified, forming a Q-switched laser that is output through the signal port 9 of the wavelength division multiplexer. The directly output 1.3μm Q-switched laser spectrum is shown in the attached figure. Figure 3 As shown, the optical signal-to-noise ratio is 51dB; the repetition frequency is 220kHz, and the pulse width is 150ns.

[0038] Example 2

[0039] This embodiment is a rare earth doped phosphate glass double cladding optical fiber with an emission wavelength in the 1.3 μm band. The optical fiber includes a core, an inner cladding and an outer cladding. The core is doped with Nd 3+ Multi-component phosphate glass, by mass percentage, its oxide formula is 74.9P2O5-6Al2O3-12BaO-7La2O3-0.1Nd2O3, the inner cladding is doped with Yb 3+ The multi-component phosphate glass has an oxide composition of 64P2O5-7Al2O3-2BaO-4La2O3-7Na2O-8K2O-8Yb2O3 by mass. The outer cladding is an undoped multi-component silicate glass with an oxide composition of 70SiO2-10CaO-10K2O-10Na2O by mass. The multi-component phosphate glass is produced using a melt-quenching method. The core, inner cladding, and outer cladding are mechanically processed, acid-treated, cleaned, and dried before being assembled into an optical fiber preform. The double-clad optical fiber is then drawn using a tube-and-rod method. The optical fiber has a core diameter of 5μm, an inner cladding diameter of 20μm, and an outer cladding diameter of 125μm. The refractive index difference between the core and inner cladding is 0.08, and the transmission loss of the optical fiber core in the 0.9μm to 1.05μm range is 12dB / cm.

[0040] Based on the above fiber, an all-fiber 1.3 μm Q-switched laser was constructed. One end of the prepared rare earth-doped phosphate glass double-clad fiber was placed close to a saturable absorber (modulation depth 4%, recovery time 1 ps, saturation flux 45 μJ / cm 2The resonant cavity is formed by a laser beam with a wavelength division multiplexer (WDM) at one end (with an unsaturated reflectivity of 94% at 1360nm) and a dichroic film at the other end (with a transmittance of 99.8% at 808nm and a reflectivity of 96.5% at 1360nm). 808nm pump light passes through the 808 / 1360nm WDM and enters the resonant cavity from the dichroic film. 1.3μm photons generated by stimulated emission are reflected and amplified back and forth within the resonant cavity, forming Q-switched laser light that is output through the signal port of the wavelength division multiplexer. The directly output 1.3μm Q-switched laser has a signal-to-noise ratio of 60dB, a repetition rate of 300kHz, and a pulse width of 220ns.

[0041] Example 3

[0042] This embodiment is a rare earth doped phosphate glass double cladding optical fiber with an emission wavelength in the 1.3 μm band. The optical fiber includes a core, an inner cladding and an outer cladding. The core is doped with Nd 3+ Multi-component phosphate glass, by mass percentage, its oxide formula is 76.9P2O5-8Al2O3-10MgO-5La2O3-0.1Nd2O3, the inner cladding is doped with Yb 3+ The multi-component phosphate glass has an oxide composition of 60.5P2O5-5SiO2-7Al2O3-4Y2O3-8K2O-5.5Yb2O3 by mass. The outer cladding is an undoped multi-component silicate glass with an oxide composition of 65GeO2-10Al2O3-10CaO-7K2O-8Na2O by mass. The multi-component phosphate glass is produced using a melt-quenching method. The core, inner cladding, and outer cladding are mechanically processed, acid-treated, cleaned, and dried before being assembled into an optical fiber preform. The double-clad optical fiber is then drawn using a tube-and-rod method. The optical fiber has a core diameter of 8μm, an inner cladding diameter of 60μm, and an outer cladding diameter of 125μm. The refractive index difference between the core and inner cladding is 0.05, and the transmission loss of the optical fiber core in the 0.9μm to 1.05μm range is 7dB / cm.

[0043] Based on the above fiber, an all-fiber 1.3 μm Q-switched laser was constructed. One end of the prepared rare earth-doped phosphate glass double-clad fiber was placed close to a saturable absorber (modulation depth 1.6%, recovery time 1 ps, saturation flux 50 μJ / cm 2The resonant cavity is formed by a laser beam with a wavelength division multiplexer (WDM) at one end (with an unsaturated reflectivity of 97% at 1360nm) and a dichroic film at the other end (with a transmittance of 99.8% at 808nm and a reflectivity of 96.5% at 1360nm). 808nm pump light passes through the 808 / 1360nm WDM and enters the resonant cavity from the dichroic film. 1.3μm photons generated by stimulated emission are reflected and amplified in the resonant cavity, forming Q-switched laser light that is output through the signal port of the wavelength division multiplexer. The directly output 1.3μm Q-switched laser has a signal-to-noise ratio of 55dB, a repetition rate of 280kHz, and a pulse width of 400ns.

[0044] Example 4

[0045] This embodiment is a rare earth doped phosphate glass double cladding optical fiber with an emission wavelength in the 1.3 μm band. The optical fiber includes a core, an inner cladding and an outer cladding. The core is doped with Nd 3+ Multi-component phosphate glass, by mass percentage, its oxide formula is 70P2O5-6Al2O3-12CaO-3.5La2O3-4Y2O3-4.5Nd2O3, the inner cladding is doped with Yb 3+ The multi-component phosphate glass has an oxide formula of 62.5P2O5-10SiO2-7Al2O3-4Y2O3-10Na2O-6.5Yb2O3 by mass. The multi-component phosphate glass is prepared using a melt-quenching method. The fiber core and inner cladding are mechanically processed, acid-treated, cleaned, and dried before being combined into an optical fiber preform. The double-clad optical fiber is then drawn using the tube-and-rod method. The optical fiber has a core diameter of 10μm, an inner cladding diameter of 125μm, a refractive index difference between the core and cladding of 0.02, and a transmission loss of 8dB / cm in the 0.9μm to 1.05μm range.

[0046] Based on the above fiber, an all-fiber 1.3 μm Q-switched laser was constructed. One end of the prepared rare earth-doped phosphate glass double-clad fiber was placed close to a saturable absorber (modulation depth 4%, recovery time 1 ps, saturation flux 45 μJ / cm 2 The resonant cavity is formed by a laser diode (1 / 4" x 240 nm) with a 1 / 4" optical fiber (with an unsaturated reflectivity of 94% at 1360nm) and a dichroic film (with a transmittance of 99.8% at 808nm and a reflectivity of 96.5% at 1360nm) on the other end. 808nm pump light passes through the 808 / 1360nm WDM and enters the resonant cavity from the dichroic film. 1.3μm photons generated by stimulated emission are reflected and amplified in the resonant cavity, forming Q-switched laser light that is output through the signal port of the wavelength division multiplexer. The directly output 1.3μm Q-switched laser has an optical signal-to-noise ratio of 54dB, a repetition rate of 435kHz, and a pulse width of 340ns.

Claims

1. A rare earth-doped phosphate glass double-clad optical fiber with an emission wavelength in the 1.3 μm band, the double-clad optical fiber comprising a core, an inner cladding, and an outer cladding, characterized in that: The core is made of Nd 3+ Doped phosphate glass, Nd 3+ Doping concentration ≥0.1wt% The inner cladding is composed of Yb 3+ Doped phosphate glass, Yb 3+ The doping concentration is 0.1%~8%; it is used to directionally absorb light in the 0.9 mm~1.05 mm band, so that the transmission loss of the fiber core in the 0.9 mm~1.05 mm range is ≥2dB / cm; The outer cladding is composed of undoped oxide glass.

2. The rare earth-doped phosphate glass double-clad optical fiber with an emission wavelength in the 1.3 μm band according to claim 1, characterized in that: The core Nd 3+ doped phosphate glass with the inner cladding Yb 3+ The refractive index difference of doped phosphate glass is 0.02~0.

10.

3. The rare earth-doped phosphate glass double-clad optical fiber with an emission wavelength in the 1.3 μm band according to claim 1, characterized in that: The diameter of the fiber core is 4-10 mm, the diameter of the inner cladding is 20-125 mm, and the diameter of the outer cladding is 125-400 mm.

4. The rare earth-doped phosphate glass double-clad optical fiber with an emission wavelength in the 1.3 μm band according to claim 1, characterized in that: By mass percentage, the Nd 3+ The composition of doped phosphate glass is (70~78.8)P2O5-(5~8)Al2O3-(3~7)La2O3-(0.1~4.5)Nd2O3-(0~12)BxOy, wherein B is one or more of Mg, Ca, Ba or Y; the Yb 3+ The doped phosphate glass composition is (62.5~78.8)P2O5-(0~10)SiO2-(0~10)BaO-(5~7)Al2O3-(2~4)La2O3-(0~4)Y2O3-(0.1~8)Yb2O3-(3~10)CxOy, wherein C is one or both of Na or K; the oxide glass is phosphate, germanate or silicate glass.

5. The rare earth-doped phosphate glass double-clad optical fiber with an emission wavelength in the 1.3 μm band according to any one of claims 1 to 4, characterized in that: The optical fiber is a single-mode optical fiber.

6. A method for preparing the rare earth-doped phosphate glass double-clad optical fiber with an emission wavelength in the 1.3 μm band according to any one of claims 1 to 5, characterized in that: The Nd 3+ Doped phosphate glass is processed into glass rods, and Yb 3+ Doped phosphate glass and undoped oxide glass are processed into glass tubes respectively, which are then combined into optical fiber preforms after acid treatment, cleaning and drying, and then drawn to obtain the double-clad optical fiber.

7. An all-fiber 1.3-micron Q-switched fiber laser, characterized in that: The rare-earth-doped phosphate glass double-clad optical fiber having an emission wavelength in the 1.3 μm band as claimed in any one of claims 1 to 5.

8. The all-fiber 1.3-micron Q-switched fiber laser according to claim 7, characterized in that: The laser has a laser signal-to-noise ratio of >50dB, a repetition frequency of >200kHz, and a pulse width of >150ns.

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