Yb
3+Tellurate glass doubly-clad optical fiber that mixes and preparation method thereof
Technical field
The present invention relates to doubly clad optical fiber, particularly a kind of Yb
3+Tellurate glass doubly-clad optical fiber that mixes and preparation method thereof.
Background technology
Fiber laser is that optical fiber and the bulk of optical feedback element by some rare earth element of mixing constitutes laserresonator, under the effect of pump light, doped fiber produces stimulated emission in medium, and launch the device of certain wavelength laser, have advantages such as low threshold value, high-level efficiency, narrow linewidth, tunability.Initial fiber laser is that pump light directly is coupled into the fibre core of diameter less than 10 μ m, causes coupling efficiency low, and the output power of fiber laser is low, has limited its range of application.In order to improve coupling efficiency, in recent years, developed a kind of doubly clad optical fiber in the world, because it has the inner cladding of larger cross-section and numerical aperture, can effectively absorb the big pump light of the angle of divergence, utilize cladding pumping, overcome the shortcoming of above-mentioned single covering, make output power obtain greatly to improve, promoted the development of high-capacity optical fiber laser greatly.U.S. light torch (SDL) company is (referring to V.Dominc, S.MacCormack, R.Waarts.et al.110W fiber Laser.Electronics letters, 1999, Vol35:1158~1160) reported that in 1999 output power is the cladding pumping laser instrument of 110W.
Because Yb
3+Have simple electron configuration, have only a ground state
2F
7/2With an excited state
2F
5/2, its excited ion of using as laser instrument is compared with other rare earth ion has series of advantages: absorption band is in 0.8~1.1 mum wavelength scope, can effectively be coupled with the InGaAs semiconductor pumping sources; There is not excited state absorption (ASE), the light conversion efficiency height; Pumping wavelength and laser output wavelength are very approaching, and quantum efficiency can be up to 90%; Concentration quenching and multi-phonon relaxation phenomena can not appear under the high-dopant concentration; Fluorescence lifetime is long, gain bandwidth (GB) is wide, thermal load is low etc.Therefore, the appearance from late nineteen eighties high power ti sapphire laser and laser diode has solved Yb
3+After the pumping source that excites, mix Yb
3+The research of the laser material of ion has obtained the development of advancing by leaps and bounds.
The Yb that is used for cladding pumping at present
3+The fiber amplifier that mixes or the material of doubly clad optical fiber fibre core on the fiber laser and inner cladding all are quartz substrate basically.There is following weak point in doubly clad optical fiber for quartz substrate:
(1) Yb
3+Ion doping content in quartz substrate lower (<2wt%).Because Yb
3+The cluster phenomenon easily takes place in ion in quartz substrate, cause that fluorescence lifetime sharply reduces, and has had a strong impact on the absorption efficiency of pump light.
(2) Yb
3+Gain in quartz substrate is less.This mainly is because Yb
3+The stimulated emission cross section of ion in quartz substrate is less.
(3) the doubly clad optical fiber composition adjustable extent of quartz substrate is little.
(4) the doubly clad optical fiber complicated process of preparation of quartz substrate, cost is higher.This mainly is because the prefabricated rods of the doubly clad optical fiber of quartz substrate is to adopt inside deposition method (for example: MCVD (modified chemical vapor deposition process (MCVD)) and PCVD (chemical vapour deposition technique of plasma-activated) etc.) preparation, the deposition process complexity, the equipment requirements costliness, wire-drawing temperature is higher.Referring to US 6345141; Date of publication is: Feb.5.2002; Title: Double-clad optical fiber with improvedinner cladding geometry has proposed the doubly clad optical fiber of the quartz substrate of multiple different inner cladding shapes.
Matrix is the Yb of glass
3+The research of doping double-cladding optical fiber still is in the progress stage at present, and its main research work also concentrates in the searching and the research to its spectrum property of new material.Reported as Honninger.C in 1999 etc. and to have adopted the phosphate (QX/Yb) and the silicate glass (Q-246/Yb) of mode-locking technique and LD pumping all to realize ultra-short pulse laser output.Its tunable wave length scope be respectively 1025nm-1065nm (referring to H nninger C, Paschotta R, Graf M, et al.Appl.Phys.B, 1999,69:3).From present present Research, Yb
3+The host material of the laser glass optical fiber that mixes mainly is phosphate and silicate glass, and silicate glass matrix has outstanding chemical stability, but its Yb
3+Doping content is low, causes its lower stimulated emission cross section and narrower gain bandwidth (GB); Though phosphate glass matrix has higher Yb
3+Doping content, but water absorptivity is strong, poor chemical stability, and the emission live width is not high equally.Therefore from emission cross section and fluorescence linewidth, these two kinds of glass matrixs can not satisfy the high energy tuned laser, the particularly requirement of short pulse tuner-type fiber laser.Tellurate glass is owing to the infrared permeation scope with broad, lower phonon energy, higher doping concentration of rare earth ion and good chemical stability become the focus of research in recent years.Yb
3+The fluorescence linewidth that doped tellurate glass has bigger emission cross section and a broad becomes the ideal basis material of laser instrument, but its relatively poor anti-crystallization ability makes the fiber laser of present tellurate glass matrix still be in the development phase.Domestic for Yb
3+The research of doped fiber laser instrument is in the starting stage, for Yb
3+The research of doped tellurate glass optical fiber still less.Tellurate glass among the present invention forms that not only chemical stability is good, and engineering properties is good, and anti-crystallization ability is strong, and has very big absorption and stimulated emission cross section, has the long fluorescence lifetime and the fluorescence linewidth of broad simultaneously.Yb of the present invention
3+The doped tellurate glass doubly-clad optical fiber possesses very big practical application foreground on miniature solid fiber laser and the tunable formula fiber laser of high power pulse.
Summary of the invention
The Yb that the object of the present invention is to provide a kind of fiber laser to use
3+Tellurate glass doubly-clad optical fiber that mixes and preparation method thereof is compared with technology in the past, and this kind optical fiber should have the raising of effect Yb
3+Stimulated emission cross section and effective fluorescence linewidth.The doubly clad optical fiber that this method is made has higher Yb
3+The doping content of ion, work simplification, production cost reduces.
Technical solution of the present invention is as follows:
A kind of Yb
3+The tellurate glass doubly-clad optical fiber that mixes is made of fibre core, inner cladding and surrounding layer three parts, it is characterized in that the fibre core of this doubly clad optical fiber and inner cladding material constitute by tellurate glass, and its compositing formula is as follows respectively:
Component fibre core (mol%) inner cladding (mol%)
TeO
2???????65-85???????????65-83
PbO?????????0-20????????????0-18
ZnO?????????5-15????????????5-15
La
2O
3????0-5?????????????2.5-5
K
2O???????0-5?????????????1.5-3
Na
2O??????0-5?????????????3-5.5
Yb
2O
3????0.5-5???????????0-2.5
And the refractive index of inner cladding is lower than fiber core refractive index, i.e. n (interior)<n (core); Surrounding layer is made of polymeric material, and shape of cross section is circular, and its refractive index is lower than inner cladding, i.e. n (outward)<n (interior).
The diameter of described fibre core is φ 5~60 μ m, and wherein φ 5~12 μ m are single-mode fiber, and φ 12~60 μ m are multimode optical fiber.
The inner cladding of described optical fiber is square or rectangle.
Described Yb
3+The preparation method of the tellurate glass doubly-clad optical fiber that mixes is characterized in that comprising the following steps:
(1) choose the composition of raw materials of fibre core and inner cladding: the prescription of fibre core and inner cladding should mate mutually, when selecting prescription, at first determine the fibre core prescription, determine the prescription of inner cladding then at the matching relationship that exists aspect three of the refractive indexes, expansion coefficient, softening temperature according to fibre core and inner cladding, concrete principle is: 1. the refractive index of fibre core should be slightly larger than the refractive index of inner cladding, i.e. n
Core>n
In, (n
Core-n
In)/n
In=0.15-2.5%; 2. generally differ between the thermal expansivity of glass of fiber core thermal expansivity and inner cladding glass ± 20 * 10
-7/ ℃, both do not produce internal stress and are as the criterion with Cheng Sihou; 3. transition temperature (the T between fibre core and the inner cladding
g) differ and should be lower than 30 ℃, softening temperature (T
f) be lower than 50 ℃;
(2) preparation of glass of fiber core: by selected prescription raw materials weighing, after dusty raw materials mixed, be placed in silica crucible or the platinum crucible and melt, temperature of fusion is 700~900 ℃, raw material melts fully, after the homogenizing clarification, take out, rapidly glass metal is cast on the swage tool of preheating, fast this glass is put into then and be warming up to glass transformation temperature (T
g) near muffle furnace in anneal, annealing process is: at glass transformation temperature (T
g) near insulation 2 hours, be cooled to 100 ℃ with 2~5 ℃/hour speed then, close the muffle furnace power supply then and be cooled to room temperature automatically, glass sample is taken out in the cooling back fully;
(3) preparation of inner cladding glass: except that forming difference, its preparation process is with the preparation process of glass of fiber core;
(4) making of prefabricated rods: the glass of fiber core of above-mentioned preparation through cutting, polish, be polished to round bar shape, is processed into the fibre core prefabricated rods of required size, is called for short plug, it is 2 grades that mandrel surface smooth finish requires; The above-mentioned inner cladding glass that makes is polished into square or rectangle through cutting, passes through steps such as frosted, polishing successively; Hole in the axial centre of rod then, the diameter in hole is identical with the diameter of above-mentioned plug, form a cover rod, and polish overlapping excellent endoporus, with ultrasound wave or hydrofluorite the plug and the excellent surface of inner cladding cover that process are cleaned, the plug after processing is disposed inserts in the center hole of inner cladding cover rod, and guarantees that both closely contact again, the coincidence of both central axis, thus make prefabricated rods;
(5) drawing of optical fiber: the above-mentioned prefabricated rods that makes is fixed on the wire drawing machine, under 480~620 ℃ temperature, prefabricated rods is drawn into optical fiber, optical fiber is passed as the coating liquid of surrounding layer and with the xenon lamp irradiation solidify to form surrounding layer, finally be drawn into tellurate double clad glass optical fiber.
The principal feature of double clad tellurate glass optical fiber of the present invention:
(1) Yb
3+Doping content higher (0.5~6.0mol%);
(2) owing to use tellurate glass matrix, stimulated emission cross section quartz, silicate and phosphate glass more in the past is big, and the prepared optical fiber unit length gain that goes out is also big;
(3) because sandwich layer and inner cladding are tellurate glass, and component is complementary, the optional scope of glass ingredient is bigger;
(4) adopt rod-in-tube technique to prepare prefabricated rods, drawing process is simple, and cost is lower.
The invention provides the tellurate glass doubly-clad optical fiber that the tunable formula fiber laser of miniature solid fiber laser and high power pulse is used, and, the Yb that the present invention makes
3+Doped tellurate optical fiber has bigger stimulated emission cross section, reaches 1.35 * 10
-20Cm
2, wideer effective fluorescence linewidth reaches 80nm, higher rear-earth-doped concentration, Yb
2O
3Reach 6.0mol%, make this kind optical fiber have bigger gain performance and tunable range.
Description of drawings
Fig. 1 is 1 of a doubly clad optical fiber cross sectional shape of the present invention
Fig. 2 is 2 of a doubly clad optical fiber cross sectional shape of the present invention
Fig. 3 is the spectral line that the 6th assembly side of the embodiment of the invention is drawn
Embodiment
Doubly clad optical fiber cross sectional shape of the present invention comprises that fibre core 1, inner cladding 2 and surrounding layer 3 three parts constitute as depicted in figs. 1 and 2, and wherein inner cladding has square and two kinds of forms of rectangle.Fibre core and inner cladding material are made of tellurate glass, and its compositing formula sees Table 1, and the refractive index of inner cladding requires a little less than fibre core, i.e. n
In<n
Core, surrounding layer is made of polymeric material, and shape of cross section is circular, and its refractive index is lower than inner cladding, i.e. n
Outward<n
InCore diameter is φ 5~60 μ m, and wherein φ 5~12 μ m are single-mode fiber, and φ 12~60 μ m are multimode optical fiber.
The tellurate glass prescription that table 1 fibre core and inner cladding are used
Component (mol%) | ??TeO
2 | ??PbO | ??ZnO | ??La
2O
3 | ??K
2O
| ??Na
2O
| ??Yb
2O
3 |
Fibre core | ??65~85 | ??0~20 | ??5~15 | ??0~5 | ??0~5 | ??0~5 | ??0.5~5 |
Inner cladding | ??65~83 | ??0~18 | ??5~15 | ??2.5~5 | ??1.5~3 | ??3~5.5 | ??0~2.5 |
The concrete steps of tellurate glass doubly-clad optical fiber preparation process of the present invention:
(1) fibre core and inner cladding prescription chooses.The prescription of fibre core and inner cladding should mate mutually, when selecting prescription, at first determines the fibre core prescription, determines the prescription of inner cladding then at the matching relationship of existence aspect three of the refractive indexes, expansion coefficient, softening temperature according to fibre core and inner cladding.Concrete principle is: 1. the refractive index of fibre core should be slightly larger than the refractive index of inner cladding, i.e. n
Core>n
In, (n
Core-n
In)/n
In=0.15-2.5%; 2. generally differ between the thermal expansivity of glass of fiber core thermal expansivity and inner cladding glass ± 20 * 10
-7/ ℃, both do not produce internal stress and are as the criterion with Cheng Sihou; 3. transition temperature (the T between fibre core and the inner cladding
g) differ and should be lower than 30 ℃, softening temperature (T
f) be lower than 50 ℃.The prescription of fibre core and inner cladding is chosen in table 1 according to above principle among the present invention.Because fibre core and inner cladding all adopt tellurate glass, coupling is better mutually among the present invention, and the anti-crystallization ability of glass is strong, and chemical stability and machining property are good.
(2) preparation of fibre core and inner cladding glass.In table 1, choose prescription according to mentioned above principle, after dusty raw materials is mixed, be placed in silica crucible or the platinum crucible and melt, temperature of fusion is 700~900 ℃, raw material melts fully, takes out after the homogenizing clarification, rapidly glass metal is cast on the swage tool of preheating.Fast this glass is put into then and be warming up to glass transformation temperature (T
g) near muffle furnace in anneal.Annealing process is: at glass transformation temperature (T
g) near insulation 2 hours, be cooled to 100 ℃ with 2~5 ℃/hour speed then, close the muffle furnace power supply then and be cooled to room temperature automatically.Glass sample is taken out in the cooling back fully.Except the difference of filling a prescription, the mode of founding of fibre core and inner cladding is identical.
(3) making of prefabricated rods.The glass of fiber core of above-mentioned preparation through cutting, polish, be polished to round bar shape, is processed into the fibre core prefabricated rods (abbreviation plug) of required size, and it is 2 grades that mandrel surface smooth finish requires.The above-mentioned inner cladding glass that makes is polished into square or rectangle through cutting, passes through steps such as frosted, polishing then successively; Hole in the axial centre of rod then, the diameter in hole is identical with the diameter of above-mentioned plug, be equivalent to form a cover rod, and polish, with ultrasound wave or hydrofluorite the plug and the excellent surface of inner cladding cover that process are cleaned again overlapping excellent endoporus at the inner cladding center glass rod.Plug after processing disposed inserts in the center hole of inner cladding cover rod, and guarantees both the tight contacts and the coincidence of both central axis, thereby is worth prefabricated rods.
(4) drawing of optical fiber.The above-mentioned prefabricated rods that makes is fixed on the wire drawing machine, under 480~620 ℃ temperature, prefabricated rods is drawn into optical fiber, optical fiber is passed as the coating liquid of surrounding layer and with the xenon lamp irradiation be solidified into surrounding layer, finally be drawn into the tellurate double clad glass optical fiber that meets the demands.
The invention will be further described below in conjunction with specific embodiment.
At first determine the prescription of tellurate glass fibre core and inner cladding.The mole of its prescription is formed referring to table 1.
Specific embodiment:
The first step: choose suitable fibre core and inner cladding prescription (mol%), see Table 2;
Second step: the technological process of founding the fibre core and the inner cladding of tellurate glass: the preparation of (1) glass of fiber core: with highly purified TeO
2, ZnO, PbO, Na
2O, K
2O, La
2O
3And Yb
2O
3Dusty raw materials is placed in the platinum crucible and founds in the Elema electric furnace after mixing by the fibre core prescription, feeds dry oxygen in the glass smelting process and carries out atmosphere protection.Fusing
Six groups of fibre cores of table 2 specific embodiment and inner cladding prescription
| ??TeO
2 | ??PbO | ??ZnO | ??La
2O
3 | ??K
2O
| ??Na
2O
| ??Yb
2O
3 | ????n | ??T
f(℃)
|
First | Fibre core | ??65 | ??20 | ??5 | ??4.5 | ??0 | ??5 | ??0.5 | ????2.092 | ??442 |
Group | Inner cladding | ????65 | ????18 | ????5 | ????5 | ????1.5 | ????5.5 | ????0 | ????2.057 | ????444 |
Second group | Fibre core | ????70 | ????15 | ????5 | ????4 | ????5 | ????0 | ????1 | ????2.076 | ????439 |
Inner cladding | ????70 | ????13.5 | ????5 | ????3.5 | ????1.5 | ????5 | ????1.5 | ????2.039 | ????440 |
The 3rd group | Fibre core | ????70 | ????5 | ????15 | ????4 | ????2.5 | ????2.5 | ????1 | ????1.985 | ????457 |
Inner cladding | ????68.5 | ????4.5 | ????15 | ????5 | ????3 | ????3 | ????1 | ????1.979 | ????455 |
The 4th group | Fibre core | ????75 | ????10 | ????5 | ????3 | ????0 | ????5 | ????2 | ????2.057 | ????449 |
Inner cladding | ????75.5 | ????8.5 | ????5 | ????2.5 | ????1.5 | ????4.5 | ????2.5 | ????2.049 | ????448 |
The 5th group | Fibre core | ????80 | ????5 | ????5 | ????2 | ????2.5 | ????2.5 | ????3 | ????2.049 | ????463 |
Inner cladding | ????78.5 | ????5 | ????6 | ????4.5 | ????3 | ????3 | ????0 | ????2.023 | ????465 |
The 6th group | Fibre core | ????85 | ????0 | ????5 | ????0 | ????2.5 | ????2.5 | ????5 | ????2.032 | ????481 |
Inner cladding | ????83 | ????0 | ????6 | ????4.5 | ????3 | ????3.5 | ????0 | ????2.007 | ????483 |
Temperature is 700-900 ℃.Treat that raw material melts fully, and after homogenizing clarification, come out of the stove in 650~850 ℃, glass metal is cast on the swage that preheating is of a size of 150mm * 70mm * 60mm.Rapidly this glass is put into then and is warming up to material transition temperature (T
g) near muffle furnace in anneal.Annealing process is to be incubated 2 hours earlier near the transition temperature of this glass material, lowers the temperature 100 ℃ with 2-5 ℃/hour speed then, closes the muffle furnace power supply then and is cooled to room temperature automatically.(2) preparation of inner cladding glass: choose the inner cladding prescription, preparation process is identical with the preparation of fibre core.
The 3rd step: the making of prefabricated rods.If single-mode fiber, core diameter<12 μ m then, single-mode fiber must meet the following conditions:
Wherein a is the radius of fibre core, and λ is a transmission light wavelength in the optical fiber, n
CoreBe the refractive index of core fibre, n
InRefractive index for inner cladding.So fibre core can be processed into diameter is 2mm, length is 60mm, and surface finish becomes the plug of 3 grades of smooth finish.The prefabricated rods processing dimension of inner cladding is 25mm * 25mm * 80mm, and positive center, upper and lower end face drill diameter is the endoporus of 2mm, and the degree of depth is 60mm, and bore area will polish.After with ultrasound wave plug and surrounding layer being overlapped excellent surface and carry out the decontamination cleaning treatment, plug is inserted inner cladding overlap in the excellent center pit, constitute and have the prefabricated rods of core package zoarium.
The 4th step: the drawing of optical fiber.The prefabricated rods of handling well is put into the heating furnace of wire drawing machine, with furnace temperature slowly rise to 480 ℃ (heating rate be 2~5 ℃/min), after falling down etc. the stub bar of prefabricated rods, be drawn into optical fiber with wire drawing machine with the speed of 10m/min, and make oven-fresh optical fiber pass plastics liquid to make its surface be coated with last layer plastic coat layer, through uv oven coating liquid is solidified into surrounding layer then.Can obtain the fibre core numerical aperture by the drawing speed of regulating wire drawing machine is NA=0.100, and core diameter is 8 μ m, and the inner cladding cross-sectional shape is that the square length of side is 125 μ m, and the surrounding layer diameter is the Yb of φ 185 μ m
3+The doped tellurate glass doubly-clad optical fiber.Adopt the qualified optical fiber of method for preparing can reach more than the 2Km at every turn.
The Yb of preparation gained
3+The test and the description of drawings of doped tellurate glass of fiber core spectral quality:
Absorption spectrum of the present invention is by Perkin-Elmer 900 spectrophotometric determinations, and fluorescence spectrum and fluorescence lifetime are by the LD940 pump excitation, and measured result draws absorption and emission cross section, effective line width and fluorescence lifetime through data processing.The spectral line that accompanying drawing 3 is drawn for the 6th assembly side of embodiment.Wherein absorption peak is at the 977nm place, and absorption cross section is 2.79pm
2Emission time peak-to-peak value is at the 1006nm place, and emission cross section is 1.38pm
2, be much higher than phosphate glass (1.1pm
2) and silicate glass (0.7pm
2); Effectively fluorescence linewidth is 75nm, is far longer than phosphate and silicate glass (about 40nm); Actual measurement fluorescence lifetime is 1.12ms.Therefore, Yb of the present invention
3+The doped tellurate glass of fiber core has big stimulated emission cross section and wide effective line width, has very big practical prospect and exploitation value on miniature solid fiber laser and the tunable formula fiber laser of high power pulse.
Yb of the present invention
3+The tellurate glass doubly-clad optical fiber that mixes has Yb
3+Concentration is higher, stimulated emission cross section is big, tunable range is than broad, Heat stability is good, characteristics such as the preparation method is fairly simple, production cost is lower.This glass optical fiber can be used for fields such as miniature solid fiber laser and the tunable formula fiber laser of high power pulse.