CN113437626B - Device and method for enhancing self-excited Raman laser - Google Patents
Device and method for enhancing self-excited Raman laser Download PDFInfo
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- CN113437626B CN113437626B CN202110598181.2A CN202110598181A CN113437626B CN 113437626 B CN113437626 B CN 113437626B CN 202110598181 A CN202110598181 A CN 202110598181A CN 113437626 B CN113437626 B CN 113437626B
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/094042—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a fibre laser
- H01S3/094046—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a fibre laser of a Raman fibre laser
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
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- H—ELECTRICITY
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
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Abstract
The invention relates to a device and a method for enhancing self-excited Raman laser, wherein the device comprises: a laser for providing excitation light; a first transmission optical fiber for transmitting excitation light; a luminescent film coated on the microsphere cavity, wherein the luminescent film is SiO codoped with rare earth ions and heavy metal oxides2The film is used for generating fundamental frequency laser and self-excited Raman laser; the biconical optical fiber is mutually coupled with the coated microsphere cavity to couple the pump laser into the microsphere and couple the generated fundamental frequency laser and Raman laser out of the microsphere; the second transmission optical fiber is used for transmitting fundamental frequency laser and multi-stage self-excited Raman laser; one end of the first transmission optical fiber is connected with the laser, the other end of the first transmission optical fiber is connected with one end of the biconical optical fiber, the conical waist of the biconical optical fiber is tangentially coupled with the equator of the coated microsphere cavity, one end of the second transmission optical fiber is connected with the other end of the biconical optical fiber, and the other end of the second transmission optical fiber is a fundamental frequency laser and multistage self-excited Raman laser output port. The device and the method are beneficial to obtaining the enhanced self-excited Raman laser.
Description
Technical Field
The invention belongs to the field of laser wavelength expansion, and particularly relates to a device and a method for enhancing self-excited Raman laser.
Background
In the laser application fields of physics, chemistry, biology and the like, in consideration of the energy level difference of atoms and molecules, if and only if the excitation light has a specific frequency, the energy carried by the light wave can be efficiently utilized, which requires that the excitation light source has monochromatic laser output with high energy and high power density. However, the limited laser gain media and their independent excitation modes determine that each laser needs a set of matching excitation-oscillation-radiation device, and usually only one wavelength laser can be output, which is disadvantageous to scientific research, production and the like in terms of efficiency and cost.
With the progress of technology, lasers have evolved toward integration and miniaturization, and micro lasers are attracting attention of researchers. The self-excited Raman laser is a pumping light excited gain medium, the excited radiation generates fundamental frequency laser, and the fundamental frequency laser transmits Raman laser which generates frequency shift due to excited scattering in the medium. The self-excited raman laser uses the same gain medium and the same resonant cavity to simultaneously generate laser based on two mechanisms. The self-excited Raman laser generation mode reduces optical devices, reduces the volume of a laser, and enables the structure of a laser system to be more compact. The advantages of such a laser are: on the one hand, the reduction of optical elements in the laser means less useless loss such as heat generation and the like, and the conversion efficiency of the pump light is higher; on the other hand, optical elements in the laser are reduced, so that the abnormity caused by relative vibration between a laser medium and a Raman frequency shift medium in a laser system is avoided, and the stability is improved.
In order to enhance the self-excited raman laser, the third-order nonlinear coefficient of the matrix glass material is determined according to the raman gain factor, and the third-order nonlinear coefficient of the glass is largely determined by the polarizability of the anion and cation bonds doped in the glass to form a lattice. The factors for limiting the ion polarization mainly include electronegativity representing the electron binding ability of an atomic nucleus and repulsion potential representing that polarized electrons have shielding polarization effect on unpolarized electrons, and the electronegativity and the repulsion potential decrease with the increase of the radius, so that the heavy metal ions have more electron layers, larger radius, higher polarization rate and larger nonlinear coefficient, and self-excited Raman laser can be enhanced by doping oxides containing the heavy metal ions and having low loss in excitation light and Raman light bands.
Disclosure of Invention
The invention aims to provide a device and a method for enhancing self-excited Raman laser, which are beneficial to obtaining the enhanced self-excited Raman laser.
In order to achieve the purpose, the invention adopts the technical scheme that: an apparatus and method for enhancing self-excited Raman laser, comprising:
a laser for providing excitation light;
a first transmission optical fiber for transmitting excitation light;
a film-coated microsphere cavity which is a SiO film plated with a rare earth ion and heavy metal oxide co-doped film2The microsphere cavity is used for generating fundamental frequency laser and self-excited Raman laser;
the biconical optical fiber is connected with the first transmission optical fiber in a low-loss manner and is used for being mutually coupled with the coated microsphere cavity to couple the pump laser into the microsphere and couple the generated fundamental frequency laser and Raman laser out of the microsphere; and
the second transmission optical fiber is used for transmitting fundamental frequency laser and multi-stage self-excitation Raman laser;
one end of the first transmission optical fiber is connected with the laser, the other end of the first transmission optical fiber is connected with one end of the biconical optical fiber, the conical waist of the biconical optical fiber is tangentially coupled with the equator of the coated microsphere cavity, one end of the second transmission optical fiber is connected with the other end of the biconical optical fiber, and the other end of the second transmission optical fiber is a fundamental frequency laser and multistage self-excited Raman laser output port.
Furthermore, the coating microsphere cavity is formed by coating a functional film on the microsphere cavity by a sol-gel method, the thickness of the functional film is 0.5-2 μm, the microsphere cavity is formed by fusing a single-cone optical fiber, and the diameter of the microsphere cavity is 20-5000 μm.
Further, the single-taper fiber is made by heating a length of standard single-mode fiber with a hydrogen flame and drawing.
Further, the sol-gel method is to realize heavy metal oxide and SiO2And a method for co-doping rare earth ions, wherein the rare earth ions are ytterbium ions Yb3+Er ion3+Or Tm of thulium ions3+The heavy metal oxide is zirconium dioxide ZrO2Titanium oxide TiO2Or a combination thereof, the ytterbium ions being added via ytterbium nitrate or ytterbium chloride.
Further, the sol-gel method adopts Yb3+With Zr4+Or Ti4+A co-doped sol comprising the steps of:
step S1: TEOS, absolute ethyl alcohol EtOH and deionized water H2O, HCL, dimethyl-formamide DMF and the required element doping raw materials are put into a beaker together, and the volume ratio is TEOS: EtOH: h2O: DMF: HCL = 5.6: 5.6: 2.7: 0.15: 0.3, wherein the function of DMF is to protect the gel film layer, so that the finally obtained functional film is compact and has no crack; since the Si element in the mixture is provided only by TEOS, the volume of TEOS participating in the reaction and SiO in the finally obtained sol2The mass ratio is TEOS: SiO 22=5.6 mL: 1.502 g; according to the proportion formula, the sol doped with rare earth elements and SiO with other yields can be further obtained2The mass ratio or the molar ratio therebetween; the purity of the used reagent is 99.9%; the above mixed reagent volume V is placed in a beaker;
step S2: adding calculated amount of rare earth nitrate or chloride and zirconium n-propoxide or tetrabutyl titanate into a beaker to enable the rare earth ions of the film to be 2-10% mol and the oxide proportion of the film to be 5-20% mol; putting a magnetic vibrator into the container, sealing the beaker and putting the beaker on a magnetic stirrer;
step S3: starting a magnetic stirrer, and stirring for 3-6 hours at normal temperature;
step S4: and turning off the magnetic stirrer, standing the beaker for 5-15 hours to form sol, and storing the sol in an environment of 20-25 ℃ for later use.
Further, the method for plating the luminescent functional film outside the microsphere cavity by adopting the sol-gel method comprises the following steps:
step P1: and (3) firing the microspheres by electrode arc discharge light or high-temperature hydrogen flame: placing the tip of the single-cone optical fiber in the middle of the tip connecting line of the discharge electrode, setting specific discharge intensity and discharge time, naturally cooling the surface of the liquid to form a microsphere cavity after the tip of the single-cone optical fiber is melted by discharge, and placing the microsphere cavity under a microscope for observation and measuring and recording the diameter;
step P2: repeating the step P1 until the diameter of the microsphere cavity is between 20 μm and 5000 μm;
step P3: immersing the microsphere cavity into gel for 3-10 min, taking out and airing for 3-10 min, placing the microsphere cavity attached with the aired gel at the connecting line of the tips of the discharge electrodes, setting specific discharge intensity and discharge time, heating and melting the gel, naturally cooling the gel to form a compact luminous functional film, observing the coated microsphere cavity under a microscope, measuring and recording the diameter of the coated microsphere cavity;
step P4: and repeating the step P3 until the thickness of the luminescent functional film is between 0.5 and 2 μm.
Furthermore, the laser is a semiconductor laser with the output wavelength of 980nm or 1500-1600 nm and is used for exciting rare earth ions in the microspheres to generate stimulated radiation laser, namely fundamental frequency laser.
Further, the first transmission optical fiber and the second transmission optical fiber are both standard communication quartz optical fibers, plastic optical fibers or nylon optical fibers.
Further, the generated fundamental laser and the self-excited raman laser intensity are detected by a spectrum analyzer, an optical power meter or an optical wavelength meter.
The invention also provides a method for enhancing self-excited Raman laser based on the device, which comprises the steps of coupling the coated microsphere cavity with the biconical optical fiber, starting the laser, transmitting light emitted by the laser to the biconical optical fiber through the first transmission optical fiber as excitation light, coupling the excitation light into the coated microsphere cavity through evanescent waves, and generating fundamental-frequency laser through stimulated radiation; the fundamental frequency laser is enhanced along with the increase of the pumping power and is in SiO2Stimulated scattered light, namely self-excited Raman laser, is generated in the microsphere; the Raman laser generated by the fundamental frequency light is first-order self-excited Raman laser; when the first-order self-excited Raman laser is strong enough, second-order self-excited Raman laser is generated; in the same way, a third-order self-excited Raman laser is generated, … …, so that the expansion of the laser wavelength is realized; because the doping of heavy metal oxide can increase the Raman system number of the medium, the method can enhance the multi-order self-excitation RamanMangan laser.
Compared with the prior art, the invention has the following beneficial effects:
(1) self-excited Raman laser is easy to realize. The invention uses the coated microsphere cavity to obtain the quality factor and the power density of a far-exceeding Fabry-Perot microcavity or a photonic crystal microcavity, which is beneficial to realizing a nonlinear optical process and obtaining self-excited Raman laser.
(2) Enhancing the self-excited Raman laser. The invention enhances the self-excited Raman laser by enhancing the stimulated Raman scattering, and further obtains the self-excited Raman laser with higher intensity by enhancing the Raman gain factor when the rare earth ions serving as the luminescent center reach the optimal concentration and limit the highest intensity of the self-excited Raman laser.
(3) The loss is small. The excitation light adopted by the invention is infrared light or near infrared light (such as 980nm and 1550nm wavelength), the loss of the light in the wave band is smaller when the light is transmitted in the optical fiber, and the loss of the generated self-excited Raman laser in the optical fiber is similar, so that the self-excited Raman laser output with higher power can be realized.
(4) The cost is low. The laser, the first transmission optical fiber, the second transmission optical fiber and the like adopted by the invention are common products with reliable technology, and the cost of the self-excited Raman laser can be greatly reduced.
Drawings
Fig. 1 is a schematic structural diagram of an apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of the coupling of a biconical fiber and a coated microsphere cavity according to an embodiment of the present invention.
Fig. 3 is a graph showing output power test of the fundamental laser, the first-order, the second-order, and the third-order self-excited raman lasers generated in the embodiment of the present invention varying with the power of the pump light.
Fig. 4 is a self-excited raman laser enhancement test chart in the embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and specific embodiments.
As shown in fig. 1-2, the present embodiment provides a device based on heavy metal oxide doped enhanced self-excited raman laser, including:
a laser for providing excitation light;
a first transmission optical fiber for transmitting excitation light;
the coating film microsphere cavity is a melting cone optical fiber prepared microsphere, a sol-gel method is adopted to mix tetraethoxysilane, absolute ethyl alcohol, deionized water, hydrochloric acid, dimethyl-formamide, rare earth nitrate or chloride and a chemical reagent of zirconium n-propoxide or tetrabutyl titanate in a certain proportion to prepare gel to be coated on the outer layer of the microsphere, and SiO doped film of rare earth ions and heavy metal oxides is formed after high-temperature melting2The microsphere cavity is used for generating fundamental frequency laser and self-excited Raman laser;
the biconical optical fiber is connected with the first transmission optical fiber in a low-loss manner and is used for being mutually coupled with the coated microsphere cavity to couple the pump laser into the microsphere and couple the generated fundamental frequency laser and Raman laser out of the microsphere; and
the second transmission optical fiber is used for transmitting fundamental frequency laser and multi-stage self-excited Raman laser;
one end of the first transmission optical fiber is connected with the laser, the other end of the first transmission optical fiber is connected with one end of the biconical optical fiber, the conical waist of the biconical optical fiber is tangentially coupled with the equator of the coated microsphere cavity, one end of the second transmission optical fiber is connected with the other end of the biconical optical fiber, and the other end of the second transmission optical fiber is a fundamental frequency laser and multistage self-excited Raman laser output port.
The coated microsphere cavity is prepared by coating a functional film on the microsphere cavity by a sol-gel method, the thickness of the functional film is between 0.5 and 2 mu m, the microsphere cavity is prepared by fusing a single-cone optical fiber, and the diameter of the microsphere cavity is between 20 and 5000 mu m. In this embodiment, the functional film has a thickness of 0.5 μm and the microsphere cavity has a diameter of 68 μm.
In this embodiment, the single-taper fiber is made by heating a small piece of standard single-mode fiber with a hydrogen flame and drawing.
In the present embodiment, the sol-gel method is to realize heavy metal oxide, SiO2Rare earth ion co-doped methodThe rare earth ions are ytterbium ions Yb3+Er ion3+Or Tm of thulium ions3+The heavy metal oxide is zirconium dioxide ZrO2Titanium oxide TiO2Or a combination thereof, the ytterbium ions being added via ytterbium nitrate or ytterbium chloride. The existing self-excited Raman laser generally adopts doped rare earth ions as a sensitizing agent to enhance the conversion efficiency of the rare earth ions generating the fundamental frequency light to a pump light source, and obtains the high-power self-excited Raman laser by enhancing the fundamental frequency light; the sensitizer adopted by the invention is heavy metal ions, and the high-power self-excited Raman laser is obtained by enhancing the stimulated Raman scattering.
In this example, the sol-gel method employed Yb3+With Zr4+Or Ti4+A co-doped sol comprising the steps of:
step S1: TEOS, absolute ethyl alcohol EtOH and deionized water H2O, HCL, dimethyl-formamide DMF and the required element doping raw materials are put into a beaker together, and the volume ratio is TEOS: EtOH: h2O: DMF: HCL = 5.6: 5.6: 2.7: 0.15: 0.3, wherein the function of DMF is to protect the gel film layer, so that the finally obtained functional film is compact and has no crack; the dosage of the raw materials can be designed according to the actual requirements by doping the rare earth elements, and because Si element in the mixture is only provided by TEOS, the volume of the TEOS participating in the reaction and SiO in the finally obtained sol2The mass ratio is TEOS: SiO 22=5.6 mL: 1.502 g; according to the proportion formula, the sol doped with rare earth elements and SiO with other yields can be further obtained2A mass ratio or a molar ratio therebetween; the purity of the used reagent is 99.9%; the above mixed reagent volume V is put in a beaker;
step S2: adding calculated amount of rare earth nitrate or chloride (such as ytterbium nitrate pentahydrate, erbium nitrate pentahydrate), and zirconium n-propoxide or tetrabutyl titanate into beaker to make rare earth ion (such as Yb) of film3+) 2 to 10 mol%, and the proportion of the oxide of the film is 5 to 20 mol%; putting a magnetic vibrator into the container, sealing the beaker and putting the beaker on a magnetic stirrer;
step S3: starting a magnetic stirrer, and stirring for 3-6 hours at normal temperature;
step S4: turning off the magnetic stirrer, standing the beaker for 5-15 hours to form sol, and storing the sol in an environment of 20-25 ℃ for later use.
In this embodiment, the method for plating the luminescent functional film on the exterior of the microsphere cavity by using the sol-gel method includes the following steps:
step P1: and (3) firing the microspheres by electrode arc discharge light or high-temperature hydrogen flame: placing the tip of the single-cone optical fiber in the connecting line of the tip of the discharge electrode, setting specific discharge intensity and discharge time, naturally cooling the surface of the liquid to form a microsphere cavity after the tip of the single-cone optical fiber is subjected to discharge melting, and placing the microsphere cavity under a microscope to observe and measure and record the diameter;
step P2: repeating the step P1 until the diameter of the microsphere cavity is between 20 μm and 5000 μm;
step P3: immersing the microsphere cavity into gel for 3-10 min, taking out and airing for 3-10 min, placing the microsphere cavity attached with the aired gel at the connecting line of the tips of the discharge electrodes, setting specific discharge intensity and discharge time, heating and melting the gel, naturally cooling the gel into a compact luminous functional film, and observing and measuring and recording the diameter of the coated microsphere cavity under a microscope;
step P4: and repeating the step P3 until the thickness of the luminescent functional film is between 0.5 and 2 μm.
Studies have shown that 976nm laser is coupled into Yb3+When the film-coated microsphere cavity is doped, strong fundamental frequency light can be generated, and the wavelength of the fundamental frequency light is 1070nm to 1130 nm. When the fundamental frequency light is strong enough, a first-order self-excited Raman laser is generated, and the wavelength ranges from 1130nm to 1175 nm. When the first-order self-excited Raman laser is strong enough, second-order self-excited Raman laser is generated, and the wavelength range is 1175nm to 1225 nm. When the second-order self-excited Raman laser is strong enough, the third-order self-excited Raman laser is generated, and the wavelength range is 1260nm to 1310 nm. Ordinary communication single-mode quartz optical fibers with the diameter of 125 mu m are selected as the first transmission optical fiber and the second transmission optical fiber, and ordinary communication single-mode quartz optical fibers with the diameter of 125 mu m are also selected as raw materials of the biconical optical fiber.
Experimental research shows that the self-excited Raman laser gain factor of the sample changes with the heavy metal doping concentration. For Yb with a doping concentration ranging from 0% to 20%3+-Ti4+The optimal doping concentration of the co-doped film-coated microsphere cavity is 15%, and the first-order self-excited Raman gain coefficient is 67 times, the second-order self-excited Raman gain coefficient is 13 times and the third-order self-excited Raman laser gain coefficient is 29 times respectively enhanced.
In this embodiment, the laser is a semiconductor laser with an output wavelength of 980nm or 1500-1600 nm, and is used for exciting rare earth ions (such as ytterbium, erbium, and thulium ions) in the microsphere to generate stimulated radiation laser, which is called fundamental laser.
In this embodiment, the first transmission fiber and the second transmission fiber are both standard communication silica fiber, plastic fiber or nylon fiber.
In the present embodiment, the intensity of the generated self-excited raman laser is detected by a spectrum analyzer, an optical power meter, or an optical wavelength meter.
The embodiment also provides a method for enhancing the self-excited raman laser based on the device, the coated microsphere cavity is coupled with the biconical optical fiber, the laser is started, light emitted by the laser is transmitted to the biconical optical fiber through the first transmission optical fiber as excitation light, the excitation light is coupled into the coated microsphere cavity through evanescent waves, and fundamental frequency laser is generated through stimulated radiation. The fundamental frequency laser is enhanced along with the increase of the pumping power and is in SiO2Stimulated scattered light, i.e., self-excited raman laser, is generated in the microsphere. The raman laser generated by the fundamental frequency light is a first-order self-excited raman laser. When the first-order self-excited Raman laser is strong enough, the second-order self-excited Raman laser is generated. Similarly, a third-order self-excited raman laser, … …, is generated, thereby achieving the expansion of the laser wavelength. The substrate SiO of the invention2The heavy metal oxide with a certain proportion is doped in the material, which is beneficial to enhancing the Raman gain coefficient of the material, so that the self-excitation laser of first order, second order, third order and the like is enhanced. The doping of the heavy metal oxide can increase the Raman system number of the medium, so the method can enhance the multi-order self-excited Raman laser.
Laser in the present embodimentThe laser is 976nm laser, the output laser as pump light passes through a 125 μm diameter quartz fiber (i.e. first transmission fiber) and then enters into a biconical fiber, and the laser is coupled into a functional film with a diameter of 68 μm and a thickness of 0.5 μm by the biconical fiber and doped with Yb3+、Ti4+In the combined film-coated microsphere cavity, the generated self-excited Raman laser is coupled out of the microsphere cavity, enters the biconical optical fiber and is output through another quartz optical fiber (namely, a second transmission optical fiber) with the diameter of 125 mu m. In this embodiment, the output end is connected with the spectrum analyzer, and the self-excited raman laser with higher power is output under the condition that the coupling power into the microsphere cavity is the same through actual measurement.
Fig. 3 is a self-excited raman laser enhancement test chart generated in this example. Wherein each concentration of Ti4+The intensity of each-order self-excited Raman laser output by the doped microsphere cavity changes along with the trend of the coupling power. Fig. 3(a) shows the trend of the output fundamental laser of the microsphere cavity with different doping concentrations varying with the coupling power, fig. 3 (b) shows the trend of the output first-order self-excited raman laser of the microsphere cavity with different doping concentrations varying with the coupling power, fig. 3 (c) shows the trend of the output second-order self-excited raman laser of the microsphere cavity with different doping concentrations varying with the coupling power, and fig. 3 (d) shows the trend of the output third-order self-excited raman laser of the microsphere cavity with different doping concentrations varying with the coupling power.
Fig. 4 is a graph of the self-excited raman laser enhancement test in this embodiment. The main graph is Yb under 976nm laser pumping3+Single doping with Yb3+-Ti4+The spectrum of the co-doped microsphere self-excited Raman laser is shown, and an inset is a local detail view of the highest-order self-excited Raman laser. FIG. 4(a) shows Yb at a pump power of 18.5dBm3+SiO single doping2A first-order self-excited Raman laser spectrum of the microsphere cavity; FIG. 4 (b) shows Yb at a pump power of 24.3dBm3+SiO single doping2A microsphere cavity three-order self-excited Raman laser spectrum; FIG. 4(c) shows Yb at a pump power of 18.5dBm3+-Ti4+Co-doped SiO2And (3) three-order self-excited Raman laser spectrum of the microsphere cavity.
In summary, the device and the method for enhancing the self-excited raman laser based on the heavy metal oxide doping have the advantages of simple structure, low cost and high reliability, and can obtain the self-excited raman laser with higher power under the condition that the power of the coupled spherical cavity is not changed.
The above-mentioned preferred embodiments, further illustrating the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned are only preferred embodiments of the present invention and should not be construed as limiting the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. An apparatus for enhancing self-excited raman laser, comprising:
a laser for providing excitation light;
a first transmission optical fiber for transmitting excitation light;
a film-coated microsphere cavity which is SiO coated with a rare earth ion and heavy metal oxide co-doped film2The microsphere cavity is used for generating fundamental frequency laser and self-excited Raman laser;
the biconical optical fiber is connected with the first transmission optical fiber in a low-loss manner and is used for being mutually coupled with the coated microsphere cavity to couple the pump laser into the microsphere and couple the generated fundamental frequency laser and Raman laser out of the microsphere; and
the second transmission optical fiber is used for transmitting fundamental frequency laser and multi-stage self-excitation Raman laser;
one end of the first transmission optical fiber is connected with the laser, the other end of the first transmission optical fiber is connected with one end of the biconical optical fiber, the conical waist of the biconical optical fiber is tangentially coupled with the equator of the coated microsphere cavity, one end of the second transmission optical fiber is connected with the other end of the biconical optical fiber, and the other end of the second transmission optical fiber is a fundamental frequency laser and multistage self-excited Raman laser output port;
the coated microsphere cavity is prepared by coating a functional film on the microsphere cavity by a sol-gel method, wherein the sol-gel method is used for realizing heavy metal oxide and SiO2And a method for co-doping rare earth ions, wherein the rare earth ions are ytterbium ions Yb3+Er ion3+Or thuliumIon Tm3+The heavy metal oxide is zirconium dioxide ZrO2Titanium oxide TiO2Or a combination thereof, the ytterbium ions being added via ytterbium nitrate or ytterbium chloride.
2. The device of claim 1, wherein the functional film has a thickness of 0.5 μm to 2 μm, and the microsphere cavity is made of single-taper fiber fused with a diameter of 20 μm to 5000 μm.
3. The device of claim 2, wherein the single-tapered fiber is made by heating a length of standard single-mode fiber with a hydrogen flame and stretching.
4. The device of claim 2, wherein the sol-gel method employs Yb3+With Zr4+Or Ti4+A co-doped sol comprising the steps of:
step S1: TEOS, absolute ethyl alcohol EtOH and deionized water H2O, HCL, dimethyl-formamide DMF and the required element doping raw materials are put into a beaker together, and the volume ratio is TEOS: EtOH: h2O: DMF: HCL = 5.6: 5.6: 2.7: 0.15: 0.3, wherein the function of DMF is to protect the gel film layer, so that the finally obtained functional film is compact and has no crack; since the Si element in the mixture is provided only by TEOS, the volume of TEOS participating in the reaction and SiO in the finally obtained sol2The mass ratio is TEOS: SiO 22=5.6 mL: 1.502 g; according to the proportion formula, the sol doped with rare earth elements and SiO with other yields can be further obtained2The mass ratio or the molar ratio therebetween; the purity of the used reagent is 99.9%; the mixed reagent volumes are placed in a beaker together;
step S2: adding calculated amount of rare earth nitrate or chloride and zirconium n-propoxide or tetrabutyl titanate into a beaker to enable the rare earth ions of the film to be 2-10% mol and the oxide proportion of the film to be 5-20% mol; putting a magnetic vibrator into the container, sealing the beaker and putting the beaker on a magnetic stirrer;
step S3: starting a magnetic stirrer, and stirring for 3-6 hours at normal temperature;
step S4: turning off the magnetic stirrer, standing the beaker for 5-15 hours to form sol, and storing the sol in an environment of 20-25 ℃ for later use.
5. The device for enhancing self-excited raman laser according to claim 2, wherein the sol-gel method is adopted to plate a luminescent functional film outside the microsphere cavity, and comprises the following steps:
step P1: and (3) firing the microspheres by electrode arc discharge light or high-temperature hydrogen flame: placing the tip of the single-cone optical fiber in the middle of the tip connecting line of the discharge electrode, setting specific discharge intensity and discharge time, naturally cooling the surface of the liquid to form a microsphere cavity after the tip of the single-cone optical fiber is melted by discharge, and placing the microsphere cavity under a microscope for observation and measuring and recording the diameter;
step P2: repeating the step P1 until the diameter of the microsphere cavity is between 20 μm and 5000 μm;
step P3: immersing the microsphere cavity into gel for 3-10 min, taking out and airing for 3-10 min, placing the microsphere cavity attached with the aired gel at the connecting line of the tips of the discharge electrodes, setting specific discharge intensity and discharge time, heating and melting the gel, naturally cooling the gel into a compact luminous functional film, and observing and measuring and recording the diameter of the coated microsphere cavity under a microscope;
step P4: and repeating the step P3 until the thickness of the luminescent functional film is between 0.5 and 2 μm.
6. The device of claim 1, wherein the laser is a semiconductor laser with an output wavelength of 980nm or 1500-1600 nm, and is used for exciting rare earth ions in the microsphere to generate stimulated emission laser, i.e. fundamental laser.
7. The apparatus of claim 1, wherein the first and second transmission fibers are standard communication silica, plastic or nylon fibers.
8. The apparatus of claim 1, wherein the generated fundamental laser light and the intensity of the self-excited raman laser light are detected by a spectrum analyzer, an optical power meter or an optical wavelength meter.
9. A method for enhancing self-excited raman laser based on the device of any of claims 1-8, wherein the coated microsphere cavity is coupled with a biconical fiber, the laser is turned on, light emitted from the laser is transmitted to the biconical fiber via a first transmission fiber as excitation light, the excitation light is coupled into the coated microsphere cavity by evanescent wave, and fundamental laser light is generated by excitation radiation; the fundamental frequency laser is enhanced along with the increase of the pumping power and is in SiO2Stimulated scattered light, namely self-excited Raman laser, is generated in the microsphere; the Raman laser generated by the fundamental frequency light is first-order self-excited Raman laser; when the first-order self-excited Raman laser is strong enough, second-order self-excited Raman laser is generated; in the same way, third-order self-excitation Raman laser is generated, so that the wavelength of the laser is expanded; the doping of the heavy metal oxide can increase the Raman system number of the medium, so the method can enhance the multi-order self-excited Raman laser.
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