Detailed Description
The present invention will be described in more detail with reference to the accompanying drawings by way of example, but the embodiments of the present invention are not limited thereto, and process parameters not specifically described may be performed with reference to the conventional art.
The embodiment of the invention provides a high-gain rare earth doped germanate glass core composite glass fiber, wherein a cladding layer is made of quartz glass, a fiber core precursor is multi-component germanate glass highly doped with rare earth ions, the fiber core is prepared by a fiber core melting method, the obtained composite glass fiber has no crystallization, and the maximum unit gain in a 2 mu m wave band is more than 2.5 dB/cm.
Further, the multicomponent germanate glass highly doped with rare earth ions is prepared by a melting-annealing method, then is cold-processed into a thin rod shape by a machine, is used as the fiber core precursor after being physically and chemically polished, is assembled with the quartz glass tube into an optical fiber preform, and is drawn to obtain the composite glass optical fiber.
Further, in the drawing process of the composite glass optical fiber, the drawing furnace is firstly heated to 1500-1700 ℃, then the optical fiber perform is placed in the drawing furnace, the temperature is raised to 1800-2000 ℃ at the speed of 20-30 ℃/min, the optical fiber perform is rapidly drawn at the speed of 200-400 m/min, and the optical fiber perform is vacuumized in the drawing process. Because the softening temperatures of germanate glass and quartz glass are greatly different, the drawing process is reasonably controlled, the optical fiber preform is drawn at low temperature quickly, and the retention time of the optical fiber preform in a high-temperature area is reduced, so that the diffusion of cladding elements into a fiber core in the drawing process is effectively controlled, and the fiber core is prevented from deforming.
Further, in the drawing process of the composite glass optical fiber, the drawing furnace is firstly heated to 1580-1620 ℃, then the optical fiber preform is placed in the drawing furnace, the temperature is increased to 1880-1920 ℃ at the speed of 24-26 ℃/min, the drawing is rapidly carried out at the speed of 280-320 m/min, and the optical fiber preform is vacuumized in the drawing process.
Further, the multicomponent germanate glass includes an oxide component and an oxide component of a rare earth ion; the oxide component comprises BaO and Ga2O3And GeO2And La2O3And/or Nb2O5The physical and chemical properties of the glass are adjusted; the oxide component of the rare earth ion is Tm2O3、Tm2O3/Yb2O3、Tm2O3/Ho2O3、Ho2O3/Yb2O3、Er2O3/Tm2O3、Er2O3/Ho2O3、Nd2O3/Ho2O3、Bi2O3/Tm2O3、Bi2O3/Ho2O3、Nd2O3/Ho2O3/Yb2O3、Tm2O3/Ho2O3/Yb2O3、Cr2O3/Tm2O3/Ho2O3、Er2O3/Tm2O3/Ho2O3Any one of the above.
Further, in the multi-component germanate glass, the proportion of the oxide component of the rare earth ions in the oxide component is more than 5 wt.%, and the highly doped rare earth luminescent ions are a precondition for realizing high gain, which is also a doping concentration requirement of the aforementioned "highly doped". Other active ions are equally suitable, such as Yb for 1 μm band lasers3+And Nd3+Er for 1.5 mu m wave band laser3+Main group metal elements Bi and Te for near-infrared broadband luminescence, and transition metal elements Cr, Ni and Mn.
Further, the oxide component includes at least Nb2O5,Nb2O5The proportion of the oxide component is 2.5-7.5 wt.%. By adding Nb2O5The proportion of non-bridge oxygen and bridge oxygen in the matrix glass is controlled to regulate and control the network structure of the glass, so that the solubility and the dispersibility of rare earth ions in the matrix glass are improved, and high-efficiency luminescence is realized.
Furthermore, the preparation method of the high-gain rare earth doped germanate glass core composite glass optical fiber comprises the following steps:
(1) melting the bulk rare earth doped germanate glass by adopting a traditional melting-annealing method, and weighing oxide component raw material BaCO according to a proportion3、Ga2O3And GeO2And adding La2O3And/or Nb2O5And an oxide component Tm of rare earth ion2O3、Tm2O3/Yb2O3、Tm2O3/Ho2O3、Ho2O3/Yb2O3、Er2O3/Tm2O3、Er2O3/Ho2O3、Nd2O3/Ho2O3、Bi2O3/Tm2O3、Bi2O3/Ho2O3、Nd2O3/Ho2O3/Yb2O3、Tm2O3/Ho2O3/Yb2O3、Cr2O3/Tm2O3/Ho2O3、Er2O3/Tm2O3/Ho2O3Any one of the components is uniformly mixed, added into a crucible, placed in a high-temperature furnace for melting, and precisely annealed after molding to obtain bulk high-doped rare earth germanate glass;
(2) processing the large block of highly doped rare earth germanate glass into a thin glass rod by adopting a mechanical cold processing method, and assembling the thin glass rod and a quartz glass tube into an optical fiber perform after physical and chemical polishing;
(3) the assembled optical fiber preform was hung on a commercial optical fiber drawing tower, and a composite glass optical fiber was drawn according to the drawing process as described above.
Furthermore, a 'reaction atmosphere method' is adopted in the melting process in the step (1) to remove water.
Still further, the crucible in step (1) is a platinum crucible; and/or the melting temperature is 1300-1500 ℃, and the time is 3-7 h.
Further, in the melting process in the step (1), the platinum crucible is replaced by an alumina crucible when the water is removed.
Furthermore, the diameter of the glass thin rod in the step (2) is 3-5 mm.
Still further, one end of the quartz glass tube is closed in the step (2).
Furthermore, in the drawing process in the step (3), the optical fiber preform is vacuumized, so that air in the core package is reduced, and a negative pressure environment can be provided for the fiber core, so as to ensure that the fiber core has good circularity and continuity.
Embodiments of the present invention also provide a device whose components include a high gain rare earth doped germanate glass core composite glass optical fiber as described above. Further, the device is a laser device.
Specifically, an embodiment of the present invention provides an all-fiber single-frequency fiber laser, the components of which include the high-gain rare-earth-doped germanate glass core composite glass fiber, the fiber grating, the Wavelength Division Multiplexer (WDM), the resonant cavity and the isolator;
the two ends of the composite glass fiber are respectively welded with the fiber bragg gratings to form a linear short cavity, pumping light enters the resonant cavity from the low-reflection fiber bragg gratings after passing through the Wavelength Division Multiplexer (WDM), photons generated by stimulated radiation pass through the Wavelength Division Multiplexer (WDM) after being continuously oscillated and amplified by the resonant cavity, and 2 mu m waveband single-frequency laser is output through the isolator.
Understandably, the fiber grating comprises a low-reflection fiber grating and a high-reflection fiber grating; the low reflection means that the reflectivity to the central wavelength is low, generally 40-85%, and the high reflection means that the reflectivity to the central wavelength is high, generally more than 99%.
Furthermore, the power of the single-frequency laser of 2 μm waveband directly output by the all-fiber single-frequency fiber laser is more than 100mW, and the slope efficiency is more than 20%.
Another embodiment of the present invention provides an all-fiber mode-locked fiber laser, the components of which include the high-gain rare-earth doped germanate glass core composite glass fiber as described above, a narrow-band grating, a saturable absorber, a Wavelength Division Multiplexer (WDM), and a resonant cavity;
one end of the composite glass fiber is welded with the narrow-band grating, the other end of the composite glass fiber is tightly attached to the saturable absorber to form a linear short cavity, the pumping light enters the resonant cavity from the narrow-band grating end after passing through the Wavelength Division Multiplexer (WDM), and the photons generated by the stimulated radiation are output after passing through the Wavelength Division Multiplexer (WDM) after being continuously oscillated and amplified by the resonant cavity to generate 2 mu m wave band mode-locked laser.
It is understood that the "narrow band" of the narrow band grating means that the bandwidth of the fiber grating is narrow, and the 3dB bandwidth is less than or equal to 0.1 nm.
Furthermore, the repetition frequency of the mode-locked laser of 2 μm waveband directly output by the all-fiber mode-locked fiber laser is more than 25MHz, and the pulse width is less than 100 ps.
Specific examples are as follows.
Example 1
The embodiment is a high-gain rare earth doped germanate glass core composite glass fiber and a device.
Preparing gain optical fiber
(1) Melting the bulk rare earth doped germanate glass by adopting a traditional melting-annealing method, and weighing a high-purity (more than or equal to 99.99 percent) raw material BaCO according to a proportion3、Ga2O3、GeO2、Nb2O5And rare earth oxide Tm2O3Wherein Tm is2O3The ratio of the raw material of glass oxide is 6 wt.%, and Nb is2O5The glass oxide raw material accounts for 7.5 wt%, the mixture is uniformly mixed, added into a platinum crucible, melted at 1400 ℃ for 5 hours, and precisely annealed after molding to obtain bulk high-doped rare earth germanate glass;
(2) processing the large block of the highly doped rare earth germanate glass into a thin glass rod by adopting a mechanical cold processing method, wherein the diameter of the thin rod is 3mm, and assembling the thin rod and a quartz glass tube into an optical fiber perform after physical and chemical polishing;
(3) and hanging the assembled optical fiber preform on a commercial optical fiber drawing tower, and drawing the composite glass optical fiber according to a preset temperature rising system. The drawing furnace is firstly heated to 1600 ℃, then the prefabricated rod is lowered to be in a high-temperature area, then the temperature is raised to 1900 ℃ at the speed of 25 ℃/min, the fiber is rapidly drawn at the speed of 300m/min, and the optical fiber prefabricated rod is vacuumized in the drawing process. The prepared composite glass fiber has no crystallization, and the unit gain at 1950nm is 3.8 dB/cm.
(II) constructing a fiber laser
Constructing an all-fiber single-frequency fiber laser based on the composite glass fiber prepared in the step one, wherein an optical path diagram is shown in figure 1, 11 is a 1568nm pump source, 12 is 1550/1950 WDM, 13 is a low-reflection fiber grating, 14 is the composite glass fiber prepared in the step one, 15 is a high-reflection fiber grating (the reflectivity at 1950nm is 99.9%), 16 is a 1950nm isolator, and 17 is a laser output end; the two ends of the composite glass fiber are respectively welded with the fiber gratings to form a linear short cavity, 1568nm pump light enters the resonant cavity from the fiber grating with low reflection (the reflectivity at 1950nm is 50%) after passing through 1550/1950 WDM, 1950nm single-frequency laser generated after photons generated by stimulated radiation are continuously oscillated and amplified by the resonant cavity passes through 1550/1950 WDM and then is output by a 1950nm isolator, the power of the 1950nm single-frequency laser directly output is 230mW, and the slope efficiency is 35%;
constructing an all-fiber mode-locked fiber laser based on the composite glass fiber prepared in the step one, wherein an optical path diagram is shown in figure 2, wherein 21 is a 1568nm pump source, 22 is 1550/1950 WDM, 23 is a narrow-band grating, 24 is the composite glass fiber prepared in the step one, 25 is a standard quartz fiber, 26 is a saturable absorber, and 27 is a mode-locked laser output end; one end of the composite glass fiber is welded with a narrow-band grating (the reflectivity at 1950nm is 50%, the 3dB bandwidth is 0.09nm), and the other end is tightly attached to a saturable absorber (the modulation depth is 12%, the recovery time is 10ps, and the saturation integral flux is 65 muJ/cm2The unsaturated reflectance and group delay dispersion at 1950nm were 86% and 890fs, respectively2) The 1568nm pump light enters the resonant cavity from the fiber grating end after passing through 1550/1950 WDM, the photons generated by the excited radiation are continuously oscillated and amplified by the resonant cavity to generate 1950nm mode-locked laser light, which is then transmitted through 1550/1950 WDM to form a linear short cavityThe repetition frequency of the directly output 1950nm mode-locked laser is 125MHz, and the pulse width is 88 ps.
Example 2
The embodiment is a high-gain rare earth doped germanate glass core composite glass fiber and a device.
Preparing gain optical fiber
(1) Melting the bulk rare earth doped germanate glass by adopting a traditional melting-annealing method, and weighing a high-purity (more than or equal to 99.99 percent) raw material BaCO according to a proportion3、Ga2O3、GeO2、La2O3、Nb2O5And rare earth oxide Tm2O3And Ho2O3Wherein Tm is2O3And Ho2O35 and 7.5 wt.% of the glass oxide raw material, and Nb2O5The glass oxide raw material accounts for 2.5 wt%, the mixture is uniformly mixed, added into a platinum crucible, melted at 1400 ℃ for 5 hours, and precisely annealed after molding to obtain bulk high-doped rare earth germanate glass;
(2) processing the large block of the highly doped rare earth germanate glass into a thin glass rod by adopting a mechanical cold processing method, wherein the diameter of the thin rod is 5mm, and assembling the thin rod and a quartz glass tube into an optical fiber perform after physical and chemical polishing;
(3) and hanging the assembled optical fiber preform on a commercial optical fiber drawing tower, and drawing the composite glass optical fiber according to a preset temperature rising system. The drawing furnace is firstly heated to 1600 ℃, then the prefabricated rod is lowered to be in a high-temperature area, then the temperature is raised to 1900 ℃ at the speed of 25 ℃/min, the fiber is rapidly drawn at the speed of 300m/min, and the optical fiber prefabricated rod is vacuumized in the drawing process. The prepared composite glass fiber has no crystallization, and the unit gain at 2050nm is 4 dB/cm.
(II) constructing a fiber laser
Constructing an all-fiber single-frequency fiber laser based on the composite glass fiber prepared in the step one: the two ends of the composite glass fiber are respectively welded with the fiber gratings to form a linear short cavity, 1570nm pump light enters the resonant cavity from the low-reflection (the reflectivity at 2050nm is 70%) fiber gratings after passing through 1550/2050 WDM, 2050nm single-frequency laser light generated after photons generated by stimulated radiation are continuously oscillated and amplified by the resonant cavity is output through 1550/2050 WDM and 2050nm isolator, the power of the directly output 2050nm single-frequency laser light is 300mW, and the slope efficiency is 36%;
constructing an all-fiber mode-locked fiber laser based on the prepared composite glass fiber: one end of the composite glass fiber is welded with a narrow-band grating (the reflectivity at 2050nm is 70%, the 3dB bandwidth is 0.09nm), the other end is tightly attached to a saturable absorber (the modulation depth is 10%, the recovery time is 12ps, and the saturation integral flux is 70 muJ/cm2The unsaturated reflectance and the group delay dispersion at 2050nm were 88% and 870fs, respectively2) The 1570nm pump light enters the resonant cavity from the fiber grating end after passing through 1550/2050 WDM, the photons generated by the excited radiation are output after passing through 1550/2050 WDM which generates 2050nm mode-locked laser after continuously oscillating and amplifying through the resonant cavity, the repetition frequency of the 2050nm mode-locked laser which is directly output is 225MHz, and the pulse width is 76 ps.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.