WO2022052077A1 - Rare earth doped bismuth germanate single crystal optical fiber and cladding method - Google Patents

Abstract

The present invention provides a rare earth doped bismuth germanate single crystal optical fiber, comprising two parts: an external cladding and an internal fiber core. The fiber core has a Bi₄Ge₃O₁₂ single crystal structure doped with a certain concentration of rare earth ions. The cladding has a Bi₄Ge₃O₁₂ structure. The raw materials used for preparing the fiber core include rare earth ion oxides, Bi₂O₃ and GeO₂, wherein the molar ratio of Bi₂O₃ to GeO₂ is 1-2: 3-4. Provided in the present invention is a two-layer structure, comprising two parts: an external cladding and an internal fiber core. The external cladding uses a glass structure prepared by Bi₄Ge₃O₁₂, and the internal fiber core is a Bi₄Ge₃O₁₂ single crystal structure doped with rare earth ions. Further provided is a preparation method for said optical fiber. Compared with the prior art, the prepared optical fiber has a more efficient laser output and a higher power.

Description

Rare earth doped bismuth germanate single crystal fiber and cladding method technical field

The invention belongs to the field of optical fiber materials, in particular to a method for cladding rare earth doped bismuth germanate single crystal optical fibers.

Background technique

At present, the widely used material for crystal cladding is quartz (SiO ₂ ). The basic function of the silica fiber is to confine and propagate the light beam, that is, to confine the light energy of a certain wavelength in the radial range of several to tens of micrometers and propagate along the length of the silica fiber with low loss. Due to the wide transmission wavelength range of silica fiber (from near-ultraviolet to near-infrared, wavelength from 0.38-2.1um), silica fiber is suitable for the transmission of signals and energy of various wavelengths from ultraviolet to infrared. It has the advantages of high mechanical strength, good bending performance and easy coupling with the light source, so it is used in sensing, spectral analysis, process control and laser transmission (especially the ideal medium for transmitting He-Ne, Ar ⁺ ions and YAG lasers), laser The applications in the fields of medical treatment, measurement technology, criminal investigation, information transmission and lighting are extremely extensive. It has been widely used in various fields such as electronics, medical treatment, bioengineering, material processing, sensing technology, national defense and military. Silica fiber is the abbreviation of optical fiber, which is a fibrous waveguide structure made of silica glass with particularly high purity (with _SiO2 as the main component). The basic function of the silica fiber is to confine and propagate the light beam, that is, to confine the light energy of a certain wavelength in the radial range of several to tens of micrometers and propagate along the length of the silica fiber with low loss.

technical problem

However, quartz is not suitable for the cladding of lower melting point crystals, BGO has been widely used in scintillation research, but its excellent physical properties, stable chemical properties and thermal properties make it an excellent rare earth ion dopant to achieve Potential host material for laser output. Among them, LD-pumped Nd:BGO single crystal rods have achieved watt-level laser output. Rare earth ion doped optical fiber has the characteristics of optical amplification, which can meet the requirements of optical communication, and the rare earth ion is rich in energy levels, and can emit light in different wavelength bands in different matrix environments. Therefore, rare earth doped crystal fiber has broad prospects. .

technical solutions

In order to solve the defects of the prior art, the present invention utilizes two powder raw materials, bismuth oxide and germanium oxide, to grow into single crystal and to prepare glass, and use BGO glass to realize the cladding of BGO single crystal, making it a high-efficiency and high-power laser The output single crystal fiber specifically provides a rare earth doped bismuth germanate single crystal fiber, which includes two parts: an outer cladding and an inner core, the core is made of Bi ₄ Ge ₃ doped with a certain concentration of rare earth ions O ₁₂ single crystal structure, the cladding layer is a Bi ₄ Ge ₃ O ₁₂ structure, and the raw materials used in the preparation of the core are rare earth ion oxides, Bi ₂ O ₃ and GeO ₂ , wherein Bi ₂ O ₃ and GeO ₂ are The molar ratio is 1~2:3~4.

Further, the rare earth ion is any one of Yb ³⁺ , Nd ³⁺ and Tm ³⁺ , wherein when the raw material is Yb ³⁺ ion oxide, the Yb ³⁺ ion concentration accounts for 0.5~0.75 mol of the fiber core. %; when the raw material is Nd ³⁺ ion oxide, the Nd ³⁺ ion concentration accounts for 0.2~0.35 mol.% of the fiber core; when the raw material is Tm ³⁺ ion oxide, the Tm ³⁺ ion concentration accounts for 3% of the fiber core -5.5 mol.%.

At the same time, a preparation method of rare earth doped bismuth germanate single crystal optical fiber is also provided, and the specific preparation steps are as follows.

(1) Ingredients: take rare earth ion oxide, Bi ₂ O ₃ , GeO ₂ as raw materials, weigh the raw materials according to the molar percentage and molar ratio of each component in claim 2, and put them in an agate mortar and grind for 40-60min , mix the raw materials evenly.

(2) Pressing: the raw materials prepared in step (1) are pressed under the water pressure of 48-75MPa to form a rod.

(3) Sintering material: put the bar material in step (2) into the muffle furnace, according to the heating rate of 80-150 °C/h, the temperature is increased to 650-800 °C, the constant temperature is 20-30 h, and the cooling rate is 60-120℃/h.

(4) Growth of the fiber core: Prepare a silicate fiber core doped with rare earth ions with a diameter of 1-2mm by using the micro-pull-down method or the laser heating pedestal method.

(5) Core annealing treatment: put the fiber into a muffle furnace for annealing.

(6) Processing of cladding tube: Using Bi ₄ Ge ₃ O ₁₂ structure as raw material, a hollow tube structure with a certain length and an inner diameter of 1.1-2.1 mm is prepared.

(7) Preform: insert the fiber core in step (5) into the hollow tube structure in step (6) to obtain a preform.

(8) Optical fiber drawing: fix the preform in step (7) on the drawing tower, and draw the preform into an optical fiber at a temperature of 900-1050 degrees Celsius.

Further, in step (4), the pulling speed of the micro-pull-down method is: 0.2-0.5mm/min; the pulling rate of the laser heating pedestal method is 3-20mm/h.

Further, in step (7), the initial length of the fiber core and the length of the hollow tube structure is the same.

beneficial effect

_The rare earth doped bismuth _germanate single crystal optical fiber provided by the present invention is provided with a two _- layer structure, including an outer cladding layer and an inner core. The Bi ₄ Ge ₃ O ₁₂ single crystal structure doped with rare earth ions also provides a preparation method of the above-mentioned optical fiber. Compared with the prior art, the prepared optical fiber outputs a more efficient and higher power laser.

Description of drawings

FIG. 1 is a schematic diagram of the growth process of the present invention in a micro-pull-down furnace.

FIG. 2 is a schematic diagram of the growth process of the present invention in a laser heating furnace.

Figure 3 shows the resulting fiber and cladding.

In the drawings: 21, the first cladding tube; 22, the first fiber core; 1, the thermal insulation layer of the side wall of the furnace body; 2, the induction coil; 3, the preform; 5, the seed rod; 6, the observation window; 7 , zirconia base; 8, quartz support column; 9, seed rod; 11, second cladding tube; 12, second fiber core; 13, laser beam.

BEST MODE FOR CARRYING OUT THE INVENTION

A rare-earth-doped bismuth germanate single-crystal optical fiber, comprising an outer cladding and an inner core, the core is a single-crystal structure of Bi ₄ Ge ₃ O ₁₂ doped with rare earth ions of a certain concentration, the cladding The layer is a Bi ₄ Ge ₃ O ₁₂ structure, and the raw materials used in the preparation of the core are rare earth ion oxides, Bi ₂ O ₃ and GeO ₂ , wherein the molar ratio of Bi ₂ O ₃ and GeO ₂ is 1~2:3~ 4. Preferably, the molar ratio is set to 2:3.

The above-mentioned rare earth ions are any one of Yb ³⁺ , Nd ³⁺ , and Tm ³⁺ , wherein when the raw material is Yb ³⁺ ion oxide, the Yb ³⁺ ion concentration accounts for 0.5~0.75 mol.% of the fiber core, preferably is 0.5 mol.%; when the raw material is Nd ³⁺ ion oxide, the Nd ³⁺ ion concentration accounts for 0.2~0.35 mol.% of the core, preferably 0.3 mol.%; when the raw material is Tm ³⁺ ion oxide , the Tm ³⁺ ion concentration is 3-5.5 mol.% of the core, preferably 4 mol.%.

As a specific embodiment of the present invention, when preparing the core of the above-mentioned optical fiber, the growth device in the micro-pull furnace shown in FIG. 1 can be optionally used to obtain the first core 22, and then the first core 22 is prepared by preparing the Bi ₄ Ge ₃ O ₁₂ structure. A cladding tube 21 is placed, the first fiber core 22 is placed inside the first cladding tube 21, the preform 3 is prepared, and the optical fiber is drawn to obtain the final optical fiber.

Alternatively, the laser heating pedestal method in FIG. 2 can be used to obtain the second core 12, and then the second core 12 is placed in the second cladding tube 11 by preparing the hollow second cladding tube 11 of the Bi ₄ Ge ₃ O ₁₂ structure. Inside the layer tube 11, a preform is prepared, and the optical fiber is drawn to obtain the final optical fiber.

When preparing the optical fiber of the above structure, the specific method steps used are as follows.

(1) Ingredients: take rare earth ion oxide, Bi ₂ O ₃ and GeO ₂ as raw materials, weigh the raw materials according to the molar percentage and molar ratio of the above components, put them in an agate mortar and grind for 40-60 minutes, and mix the raw materials evenly.

(2) Pressing: the raw materials prepared in step (1) are pressed under the water pressure of 48-75MPa to form a rod.

(3) Sintering material: put the bar material in step (2) into the muffle furnace, according to the heating rate of 80-150 °C/h, the temperature is increased to 650-800 °C, the constant temperature is 20-30 h, and the cooling rate is 60-120℃/h.

(4) Growth of the fiber core: Prepare a silicate fiber core doped with rare earth ions with a diameter of 1-2mm by using the micro-pull-down method or the laser heating pedestal method.

(5) Core annealing treatment: put the fiber into a muffle furnace for annealing.

(6) Processing of cladding tube: Using Bi ₄ Ge ₃ O ₁₂ structure as raw material, a hollow tube structure with a certain length and an inner diameter of 1.1-2.1 mm is prepared.

(7) Preform: insert the fiber core in step (5) into the hollow tube structure in step (6) to obtain a preform.

(8) Optical fiber drawing: fix the preform in step (7) on the drawing tower, and draw the preform into an optical fiber at a temperature of 900-1050 degrees Celsius.

In step (4), the pulling speed of the micro-pull-down method is 0.2-0.5 mm/min; the pulling rate of the laser heating pedestal method is 3-20 mm/h. In step (7), the fiber core and the hollow tube structure have the same initial length, which is used in the drawing process of step (8), which saves production time and costs.

The accompanying drawings of the present invention are further described below with reference to the embodiments.

Example 1 .

A preparation method of rare earth ion doped silicate optical fiber and its cladding method, the rare earth ion is selected as Yb ³⁺ , and is specifically prepared by the following method.

(1) Ingredients: Yb ₂ O ₃ , Bi ₂ O ₃ , and GeO ₂ are used as raw materials, and the raw materials are introduced in a molar ratio of 0.5:2:3, and put into an agate mortar and ground for 50 minutes, so that the raw materials are mixed evenly.

(2) Pressing: Press the prepared raw materials into rods under the water pressure of 60MPa.

(3) Sintering material: put the material rod into the muffle furnace, the heating rate is 80°C/h, the constant temperature is 700°C, the constant temperature time is 20h, and the cooling rate is 60-120°C/h.

(4) Growth of fiber cores: Rare earth ion-doped silicate fibers with a diameter of 1 mm were prepared by micro-pull-down method or laser heating pedestal method. Among them, the pulling speed of the micro-pull-down method is: 0.2-0.35mm/min. The pulling degree of the laser heating pedestal method is 3-12mm/h.

(5) Annealing treatment: put the optical fiber into a muffle furnace for annealing.

(6) Processing of cladding tube: use Bi ₄ Ge ₃ O ₁₂ structure as raw material to make BGO glass tube, and then make the length of BGO glass tube the same as that of bismuth germanate single crystal fiber, and the inner diameter is 1.1-2.1mm.

(7) Preform: insert the bismuth germanate single crystal fiber core into the BGO glass tube to obtain a preform.

(8) Optical fiber drawing: fix the optical fiber preform on the drawing tower, and draw the glass optical fiber preform into an optical fiber at a temperature of 900 degrees Celsius.

Example 2 .

A preparation method of rare earth ion doped silicate optical fiber and its cladding method, the rare earth ion is selected as Yb ³⁺ , and is specifically prepared by the following method.

(1) Ingredients: Yb ₂ O ₃ , Bi ₂ O ₃ , and GeO ₂ are used as raw materials, and the raw materials are introduced in a molar ratio of 0.65:2:3, and then put into an agate mortar and ground for 60 minutes, so that the raw materials are mixed evenly.

(2) Pressing: Press the prepared raw materials into rods under the water pressure of 75MPa.

(3) Sintering material: put the material rod into the muffle furnace, the heating rate is 120°C/h, the constant temperature is 800°C, the constant temperature time is 25h, and the cooling rate is 60-120°C/h.

(4) Growth of fiber core: A silicate fiber doped with rare earth ions with a diameter of 2 mm was prepared by the micro-pull-down method or the laser heating pedestal method. Among them, the pulling speed of the micro-pull-down method is: 0.3-0.5mm/min. The pull rate of the laser heating pedestal method is 10-20mm/h.

(5) Annealing treatment: put the optical fiber into a muffle furnace for annealing.

(6) Processing of cladding tube: use Bi ₄ Ge ₃ O ₁₂ structure as raw material to make BGO glass tube, and then make the length of BGO glass tube the same as that of bismuth germanate single crystal fiber, and the inner diameter is 1.1-2.1mm.

(7) Preform: insert the bismuth germanate single crystal fiber core into the BGO glass tube to obtain a preform.

(8) Optical fiber drawing: The optical fiber preform is fixed on the drawing tower, and the glass optical fiber preform is drawn into an optical fiber at a temperature of 1050 degrees Celsius.

Example 3 .

A preparation method of rare earth ion doped silicate optical fiber and its cladding method, the rare earth ion is selected as Tm ³⁺ , and is specifically prepared by the following method.

(1) Ingredients: take Tm ₂ O ₃ , Bi ₂ O ₃ , and GeO ₂ as raw materials, introduce the raw materials according to the molar component ratio of 0.003:2:3, and put them into an agate mortar and grind for 40 minutes, so as to mix the raw materials evenly.

(2) Pressing: Press the prepared raw materials into rods under the water pressure of 48MPa.

(3) Burning material: Put the material rod into the muffle furnace. The heating rate is 150°C/h, the constant temperature is 650°C (constant temperature time is 30h), and the cooling rate is 60-120°C/h.

(4) Growth of fiber cores: Rare earth ion-doped silicate fibers with a diameter of 1.5 mm were prepared by micro-pull-down method or laser-heated susceptor method. Among them, the pulling speed of the micro-pull-down method is: 0.3-0.5mm/min. The pull rate of the laser heating pedestal method is 10-20mm/h.

(5) Annealing treatment: put the optical fiber into a muffle furnace for annealing.

(6) Processing of cladding tube: use Bi ₄ Ge ₃ O ₁₂ structure as raw material to make BGO glass tube, and then make the length of BGO glass tube the same as that of bismuth germanate single crystal fiber, and the inner diameter is 1.1-2.1mm.

(7) Preform: insert the bismuth germanate single crystal fiber core into the BGO glass tube to obtain a preform.

(8) Optical fiber drawing: Fix the optical fiber preform on the drawing tower, and draw the glass optical fiber preform into an optical fiber at a temperature of 1000 degrees Celsius.

Example 4 .

A preparation method of rare earth ion doped silicate optical fiber and its cladding method, the rare earth ion is selected as Nd ³⁺ , and the preparation is specifically carried out by the following method.

(1) Ingredients: take Nd ₂ O ₃ , Bi ₂ O ₃ , GeO ₂ as raw materials, introduce the raw materials according to the molar component ratio of 0.003:2:3, and put them into an agate mortar and grind for 55 minutes, so as to mix the raw materials evenly.

(2) Pressing: Press the prepared raw materials into rods under the water pressure of 68MPa.

(3) Sintering material: put the material rod into the muffle furnace. The heating rate is 150°C/h, the constant temperature is 650°C (constant temperature time is 30h), and the cooling rate is 60-120°C/h.

(4) Growth of fiber core: Rare earth ion-doped silicate fiber with diameter of 1.6 mm was prepared by micro-pull-down method or laser heating pedestal method. Among them, the pulling speed of the micro-pull-down method is: 0.3-0.5mm/min. The draw rate of the laser heating pedestal method is 10-20mm/h.

(5) Annealing treatment: put the optical fiber into a muffle furnace for annealing.

(6) Processing of cladding tube: use Bi ₄ Ge ₃ O ₁₂ structure as raw material to make BGO glass tube, and then make the length of BGO glass tube the same as that of bismuth germanate single crystal fiber, and the inner diameter is 1.1-2.1mm.

(7) Preform: insert the bismuth germanate single crystal fiber core into the BGO glass tube to obtain a preform.

(8) Optical fiber drawing: Fix the optical fiber preform on the drawing tower, and draw the glass optical fiber preform into an optical fiber at a temperature of 980 degrees Celsius.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are more specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims (5)

1. A rare earth doped bismuth germanate single crystal fiber is characterized in that it comprises two parts: an outer cladding and an inner core, the core is a Bi4Ge3O12 single crystal structure doped with rare earth ions of a certain concentration, and the cladding It is a Bi4Ge3O12 structure, and the raw materials used in the preparation of the fiber core are rare earth ion oxide, Bi2O3, GeO2, wherein the molar ratio of Bi2O3 and GeO2 is 1~2:3~4.
2. The rare earth doped bismuth germanate single crystal fiber according to claim 1, wherein the rare earth ion is any one of Yb3+, Nd3+, Tm3+, wherein when the raw material is Yb3+ ion oxide, the Yb3+ ion concentration accounts for 0.5~0.75 mol.% of the fiber core; when the raw material is Nd3+ ion oxide, the Nd3+ ion concentration accounts for 0.2~0.35 mol.% of the fiber core; when the raw material is Tm3+ ion oxide, the Tm3+ ion concentration accounts for 3% of the fiber core -5.5 mol.%.
3. A preparation method of rare earth doped bismuth germanate single crystal optical fiber, characterized in that the specific preparation steps are as follows:

   (1) Ingredients: take rare earth ion oxide, Bi2O3, GeO2 as raw materials, weigh the raw materials according to the molar percentage and molar ratio of each component in claim 2, put them in an agate mortar and grind for 40-60min, and mix the raw materials uniform;

   (2) Pressing: the raw materials prepared in step (1) are pressed under the water pressure of 48-75MPa to form a rod;

   (3) Sintering material: put the bar material in step (2) into the muffle furnace, according to the heating rate of 80-150 °C/h, the temperature is increased to 650-800 °C, the constant temperature is 20-30 h, and the cooling rate is 60-120℃/h;

   (4) Growth fiber core: prepare a silicate fiber core doped with rare earth ions with a diameter of 1-2mm by micro-pull-down method or laser heating pedestal method;

   (5) Fiber core annealing treatment: put the fiber into the muffle furnace for annealing;

   (6) Processing of cladding tube: Using Bi4Ge3O12 structure as raw material, a hollow tube structure with a certain length and an inner diameter of 1.1-2.1mm is prepared;

   (7) Preform: insert the fiber core in step (5) into the hollow tube structure in step (6) to obtain a preform;

   (8) Optical fiber drawing: fix the preform in step (7) on the drawing tower, and draw the preform into an optical fiber at a temperature of 900-1050 degrees Celsius.
4. The method for preparing rare earth doped bismuth germanate single crystal fiber according to claim 3, characterized in that: in step (4), the pulling speed of the micro-pull-down method is: 0.2-0.5mm/min; the base is heated by laser The pull degree of the method is 3-20mm/h.
5. The method for preparing a rare-earth doped bismuth germanate single crystal fiber according to claim 3, characterized in that: in step (7), the fiber core and the hollow tube structure have the same initial length.