CN114526893B - Method and device for measuring stimulated emission section of laser crystal - Google Patents
Method and device for measuring stimulated emission section of laser crystal Download PDFInfo
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- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- 229910017502 Nd:YVO4 Inorganic materials 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
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Abstract
The invention discloses a method and a device for measuring the stimulated emission section of a laser crystal, wherein the method comprises the following steps: measuring the intensity noise of the laser, and acquiring a relaxation oscillation frequency measurement value of the laser from an intensity noise spectral line of the laser; according to the actual parameters of the laser when measuring the intensity noise of the laser, using the theoretical function of the relaxation oscillation frequency of the laser as a function graph; the function graph takes the theoretical value of the stimulated emission section of the laser crystal of the laser as an independent variable, and takes the theoretical value of the relaxation oscillation frequency of the laser as a dependent variable; when the measured value of the relaxation oscillation frequency is equal to the theoretical value of the relaxation oscillation frequency, the value of the abscissa corresponding to the measured value of the relaxation oscillation frequency in the function graph is the actual stimulated emission section of the measured laser crystal of the laser under the operation state of injecting pumping power. The invention has accurate measurement and is suitable for measuring the actual stimulated emission section of the laser crystal of the all-solid-state laser under stable operation.
Description
Technical Field
The invention relates to the technical field of laser, in particular to a method and a device for measuring a stimulated emission section of a laser crystal.
Background
The all-solid-state laser has the characteristics of low noise, narrow linewidth, perfect beam quality and the like when realizing high-power output, and is widely applied to the fields of basic scientific research, industrial manufacturing and processing, national defense safety and the like, such as quantum information, cold atom physics, precise spectrum, precise measurement, laser processing, laser radar, laser remote sensing, photoelectric countermeasure and the like. The laser crystal is a carrier for generating oscillation laser, is one of three elements constituting the laser, the stimulated emission section of the laser crystal is an important parameter, and the stimulated emission section of the optical crystal directly determines the small signal gain coefficient of the laser crystal and the saturated laser intensity of the laser, and finally influences the output power and the light-light conversion efficiency of the laser. In the development of all-solid-state lasers and all-solid-state laser amplifiers, the accurate obtaining of the stimulated emission section of a laser crystal under actual operating conditions is important for the design of the parameter structures of the lasers and the laser amplifiers. Meanwhile, the stimulated emission section of the laser crystal in the actual running state of the laser is accurately measured, a reference basis is provided for judging whether the crystal performance is good or not and whether the crystal temperature control element works normally or not in the maintenance of the laser, and the method plays a key role in the design optimization of the later-stage laser.
Currently, the measurement of the effective emission section of a laser crystal is mainly based on a fluorescence spectrum method, and a monochromator or a fluorescence spectrometer is mainly adopted to measure the fluorescence spectrum emitted by the laser crystal, so that the effective half width of a fluorescence emission band is obtained, and the fluorescence life is obtained according to the attenuation characteristic of the fluorescence intensity along with time. In order to avoid the influence of laser generation in the process, the crystal emission fluorescence spectrum is usually measured under the conditions that the laser crystal is injected with low pumping laser and the laser crystal is in an incubator.
Although there are many reports on the measurement of the stimulated emission section of the laser crystal at present, the stimulated emission section listed by the laser crystal of the same kind has large difference due to different growth conditions of the crystal used for measuring the state. Meanwhile, the fluorescence spectroscopy cannot measure the stimulated emission section of the laser crystal of the laser which is being debugged or already packaged. In the actual operating state of the laser, the pumping laser power is much higher than the laser threshold. And the stimulated emission section of the laser crystal is influenced by the distribution characteristic of the crystal temperature under the actual running state of the laser, and the stimulated emission section of the laser crystal is rapidly reduced along with the increase of the crystal temperature. The temperature distribution characteristic of the laser crystal is influenced by the heat load generated in the laser non-radiation transition process, the actual temperature control effect of the laser crystal temperature control device and other factors. The real stimulated emission section of the laser crystal is influenced by the doping concentration of the crystal and the pumping laser power of the injected crystal, and the higher doping concentration and pumping laser power can exacerbate the thermal load of the laser crystal, reduce the real stimulated emission section of the crystal and reduce the light-light conversion efficiency of the laser.
Therefore, the existing measuring method for the effective emission cross section of the laser crystal has the problem of inaccurate measurement, and the stimulated emission cross section of the laser crystal is not easy to accurately measure in the actual running state of the all-solid-state laser.
Disclosure of Invention
The invention aims to solve the technical problems that the measurement of the effective emission cross section of the existing laser crystal is inaccurate, and the stimulated emission cross section of the laser crystal is not easy to accurately measure in the actual running state of the all-solid-state laser.
The invention aims to provide a method and a device for measuring the stimulated emission section of a laser crystal, which are simple in operation and accurate in result, and are easy to accurately measure the stimulated emission section of the laser crystal in the actual running state of an all-solid-state laser. The invention can accurately measure the stimulated emission section of the laser crystal in the actual running state of the laser, and is beneficial to accurately predicting the output characteristic of the laser and optimizing the design of the structural parameters of the laser.
The invention is realized by the following technical scheme:
In a first aspect, the present invention provides a method of measuring the stimulated emission section of a laser crystal, the method comprising the steps of;
Measuring the intensity noise of the laser, and reading a relaxation oscillation frequency measurement omega m of the laser from the intensity noise spectral line of the laser;
according to the actual parameters of the laser when measuring the intensity noise of the laser, using the theoretical function of the relaxation oscillation frequency of the laser as a function graph; the function graph takes a theoretical value sigma s of a stimulated emission section of a laser crystal of the laser as an independent variable, and a theoretical value omega off of a relaxation oscillation frequency of the laser as a dependent variable;
When the measured value ω m of the relaxation oscillation frequency is equal to the theoretical value ω off of the relaxation oscillation frequency, the value of the abscissa corresponding to the measured value of the relaxation oscillation frequency in the function graph is the actual stimulated emission section of the measured laser crystal of the laser under the operating state of injecting pumping power p in.
The working principle is as follows: the existing measuring methods of the effective emission cross section of the laser crystal are direct measuring methods, have the problem of inaccurate measurement, and are not easy to accurately measure the stimulated emission cross section of the laser crystal in the actual running state of the all-solid-state laser. In the invention, the stimulated emission section of the laser crystal of the laser directly influences the stimulated radiation rate of laser crystal atomic transition and laser cavity mode coupling in the full quantum noise theoretical function of the full solid-state laser; the number of oscillation photons in the laser cavity is a function of the stimulated radiation rate at which the atomic transitions are mode-coupled with the laser cavity; the relaxation oscillation frequency of a laser is a function of the stimulated radiation rate associated with the laser crystal atomic transition and laser cavity mode coupling of the laser and the number of oscillation photons within the laser cavity. Thus, there is a functionally related characteristic between the relaxation oscillation frequency of the laser and the stimulated emission cross section of the laser crystal. According to the invention, under the stable running state of the laser, the intensity noise of the laser can be measured by using the self-homodyne noise detection device, and the laser relaxation oscillation frequency measured value can be obtained from the laser intensity noise spectral line. According to the actual parameters of the laser when measuring the intensity noise of the laser, a function graph taking the stimulated emission section sigma s of the laser crystal of the laser as an independent variable and the relaxation oscillation frequency omega off of the laser as an independent variable is theoretically made. And (3) making the measured laser relaxation oscillation frequency value be the same as the theoretical value of the theoretical function graph laser relaxation oscillation frequency, and reading the corresponding abscissa value to obtain the actual stimulated emission section of the laser crystal in the running state. The invention is especially suitable for measuring the stimulated emission section of the laser crystal of the steady operation all-solid-state laser in the actual operation state.
Compared with the prior art direct measurement method, the method has the following advantages:
1. The invention is an indirect measurement method, which is easy to accurately measure the stimulated emission section of the laser crystal in the actual running state of the all-solid-state laser; when the stimulated emission cross section of the laser crystal of the all-solid-state laser is measured, the device is simple, the operation is convenient, and the cost is low.
2. The invention has universal applicability, and is applicable to the measurement of stimulated emission cross sections of laser diode pumped visible light and near infrared lasers, all-solid-state laser pumped mid-infrared lasers and fiber laser pumped mid-infrared laser crystals in practical states.
3. The invention is applicable to the measurement of the stimulated emission cross section of the laser crystal in the high-power, medium-power and low-power stable operation lasers.
4. The stimulated emission section of the all-solid-state laser crystal obtained by measurement is the value of the stimulated emission section of the laser crystal in the actual running state of the laser, and the influence of the temperature distribution characteristic of the laser crystal on the stimulated emission section of the laser crystal is included.
5. The invention is applicable to the stimulated emission section measurement of the laser crystal of the all-solid-state laser which is being debugged and packaged in the actual running state.
Further, the intensity noise of the measuring laser is the intensity noise of the measuring laser by using a self-homodyne noise detection device.
Further, the laser is an all-solid-state laser.
Further, the laser crystal to be tested is arranged in the all-solid-state laser, so that the laser is in a stable running state in the laser noise measurement process.
Further, the calculation formula of the theoretical value ω off of the relaxation oscillation frequency is:
Where κ is the total cavity decay rate of the laser, g is the stimulated radiation rate of the coupling between the laser crystal atomic transitions and the laser cavity modes, and α is the number of photons in the cavity.
Further, the calculation formula of the total cavity attenuation rate of the laser is as follows:
κ＝κm+κl(2)
In the method, in the process of the invention, Cavity decay rate,/>, caused by coupling mirror for laser outputCavity decay rate,/>, for laser cavity lossesFor the life of the oscillating laser in the resonant cavity of the laser, L 2 is the cavity length of a single round trip of light in the resonant cavity; c is the speed of light;
Further, the calculation formula of the stimulated radiation rate of the coupling between the laser crystal atomic transition and the laser cavity mode is as follows:
Wherein σ s is a laser stimulated emission section, ρ lm＝ρc*cw is the doping atomic density in the gain medium, ρ c is the atomic density corresponding to the doping atomic concentration of 1.0%, c w is the doping concentration of the gain medium, c is the light velocity, L 1 is the doping length of the laser crystal atoms, L 2 is the cavity length of the single round trip of light in the resonant cavity, and n is the refractive index of the laser crystal.
Further, the calculation formula of the number of photons in the cavity is:
In the method, in the process of the invention, For the lower energy level spontaneous emission rate, τ is the lower energy level particle lifetime,/>For the upper level spontaneous emission rate, τ f is the fluorescence lifetime of the upper level inversion particles, j 2 is the ground state population distribution probability, j 2 is expressed as: /(I)Where Γ is the pumping rate, Γ is expressed as: /(I)Wherein p in is pumping power of the laser diode in the corresponding laser when measuring laser intensity noise, η t is pumping light transmission efficiency (ratio of pumping light power entering the gain medium to pumping light power output by the laser diode), η a＝1-exp(-βL1) is absorption efficiency of the gain medium, β is absorption coefficient of the gain medium to pumping laser, and is/isFor quantum efficiency, v l is the output laser frequency, v p is the pump laser frequency, h is the planck constant, N lm is the number of dopant ions utilized in the laser medium, expressed as: n lm＝ρlm*Vm, where V m is the mode volume of the pump laser at the laser crystal, expressed as: /(I)Where ω p is the beam waist radius of the pump laser at the center of the laser crystal and λ p is the wavelength of the pump laser.
As can be seen from formulas (1), (2), (3) and (4), the relaxation oscillation frequency of the laser is a function of the stimulated emission cross section of the laser crystal under the conditions of the laser pumping power and the cavity type structural parameters. Therefore, when the laser is operating stably (p in is a certain value), a graph of the function of the laser crystal stimulated emission section sigma s as an independent variable and the relaxation oscillation frequency omega off of the laser as a dependent variable can be obtained according to the actual parameters of the laser.
When the laser is in stable operation (p in is a determined value), the intensity noise of the laser is measured by using the self-homodyne noise detection device, and the actual relaxation oscillation frequency measurement omega m of the laser can be read from the laser intensity noise spectrum line.
When ω m in the actually measured intensity noise spectrum line is the same as the theoretical oscillation frequency value ω off in the function graph, the value of the abscissa corresponding to ω m in the function graph is the actual stimulated emission section of the laser crystal in the operation state of injecting pumping power p in.
In a second aspect, the present invention further provides an apparatus for measuring a stimulated emission section of a laser crystal, wherein the apparatus supports the method for measuring a stimulated emission section of a laser crystal, the apparatus comprising:
the measuring unit is used for measuring the intensity noise of the laser and reading a relaxation oscillation frequency measured value omega m of the laser from an intensity noise spectral line of the laser;
The theoretical drawing unit is used for drawing a function graph by utilizing a theoretical function of the relaxation oscillation frequency of the laser according to the actual parameters of the laser when the intensity noise of the laser is measured; the function graph takes a theoretical value sigma s of a stimulated emission section of a laser crystal of the laser as an independent variable, and a theoretical value omega off of a relaxation oscillation frequency of the laser as a dependent variable;
And the judging and calculating unit is used for determining the value of the abscissa corresponding to the relaxation oscillation frequency measured value in the function graph when the relaxation oscillation frequency measured value omega m is equal to the relaxation oscillation frequency theoretical value omega off, namely the actual stimulated emission section of the tested laser crystal of the laser under the operation state of injecting pumping power p in.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. The invention is an indirect measurement method, which is easy to accurately measure the stimulated emission section of the laser crystal in the actual running state of the all-solid-state laser; when the stimulated emission cross section of the laser crystal of the all-solid-state laser is measured, the device is simple, the operation is convenient, and the cost is low.
2. The invention has universal applicability, and is applicable to the measurement of stimulated emission cross sections of laser diode pumped visible light and near infrared lasers, all-solid-state laser pumped mid-infrared lasers and fiber laser pumped mid-infrared laser crystals in practical states.
3. The invention is applicable to the measurement of the stimulated emission cross section of the laser crystal in the high-power, medium-power and low-power stable operation lasers.
4. The stimulated emission section of the all-solid-state laser crystal obtained by measurement is the value of the stimulated emission section of the laser crystal in the actual running state of the laser, and the influence of the temperature distribution characteristic of the laser crystal on the stimulated emission section of the laser crystal is included.
5. The invention is applicable to the stimulated emission section measurement of the laser crystal of the all-solid-state laser which is being debugged and packaged in the actual running state.
Drawings
The accompanying drawings, which are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:
FIG. 1 is a flow chart of a method for measuring the stimulated emission section of a laser crystal according to the present invention.
Fig. 2 is a diagram showing an embodiment of a method for measuring a stimulated emission section of a laser crystal according to the present invention.
Fig. 3 is a schematic structural diagram of a device for measuring stimulated emission section of a laser crystal of an all-solid-state laser in an embodiment.
Fig. 4 is a plot of the intensity noise spectrum obtained with a laser measured with a homodyne noise detection apparatus.
Fig. 5 is a demonstration diagram of the stimulated emission section of the laser crystal in the actual running state according to the measured intensity noise spectrum line and the function graphs of the theoretical value sigma s of the stimulated emission section of the laser crystal and the theoretical value omega off of the laser relaxation oscillation frequency.
Fig. 6 is a schematic structural diagram of an apparatus for measuring stimulated emission section of a laser crystal according to the present invention.
Reference numerals and corresponding part names:
1-pumping source, 2-self-homodyne noise detection device, 3-coupling system, 4-input coupling mirror, 5-meniscus lens, 6-plano-concave lens, 7-output coupling mirror, 8-laser crystal and 9-optical isolator.
Detailed Description
For the purpose of making apparent the objects, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, wherein the exemplary embodiments of the present invention and the descriptions thereof are for illustrating the present invention only and are not to be construed as limiting the present invention.
Example 1
As shown in fig. 1, a method of measuring a stimulated emission section of a laser crystal according to the present invention includes the steps of;
Measuring the intensity noise of the laser, and reading a relaxation oscillation frequency measurement omega m of the laser from the intensity noise spectral line of the laser;
According to the actual parameters of the laser when measuring the intensity noise of the laser (the actual parameters of the laser comprise the laser single round trip cavity length L 2, the laser crystal doping length L 1, the laser crystal refractive index n, the reverse particle number fluorescence life tau f, the lower energy level particle life tau, the laser crystal doping ion concentration c w, pumping power P in, pumping laser wavelength lambda p, pumping laser frequency v p, laser frequency v l, beam waist radius omega p of pumping laser in the center of the laser crystal, output coupling mirror transmittance t, laser cavity loss delta, laser wavelength lambda l, pumping laser transmission efficiency eta a, quantum efficiency eta q, the absorption coefficient beta of a gain medium to pumping laser and atomic density rho c corresponding to doping atomic concentration of 1.0 percent), a theoretical function of the relaxation oscillation frequency of the laser is utilized as a function graph; the function graph takes a theoretical value sigma s of a stimulated emission section of a laser crystal of the laser as an independent variable, and a theoretical value omega off of a relaxation oscillation frequency of the laser as a dependent variable;
When the measured value ω m of the relaxation oscillation frequency is equal to the theoretical value ω off of the relaxation oscillation frequency, the value of the abscissa corresponding to the measured value of the relaxation oscillation frequency in the function graph is the actual stimulated emission section of the measured laser crystal of the laser under the operation state of injecting pumping power p in.
The working principle is as follows: in the invention, the stimulated emission section of the laser crystal of the laser directly influences the stimulated radiation rate of laser crystal atomic transition and laser cavity mode coupling in the full quantum noise theoretical function of the full solid-state laser; the number of oscillation photons in the laser cavity is a function of the stimulated radiation rate at which the atomic transitions are mode-coupled with the laser cavity; the relaxation oscillation frequency of a laser is a function of the stimulated radiation rate associated with the laser crystal atomic transition and laser cavity mode coupling of the laser and the number of oscillation photons within the laser cavity. Thus, there is a functionally related characteristic between the relaxation oscillation frequency of the laser and the stimulated emission cross section of the laser crystal. According to the invention, under the stable running state of the laser, the intensity noise of the laser can be measured by using the self-homodyne noise detection device, and the laser relaxation oscillation frequency measured value can be obtained from the laser intensity noise spectral line. According to the actual parameters of the laser when measuring the intensity noise of the laser, a function graph taking the stimulated emission section sigma s of the laser crystal of the laser as an independent variable and the relaxation oscillation frequency omega off of the laser as an independent variable is theoretically made. And (3) making the measured laser relaxation oscillation frequency value be the same as the theoretical value of the theoretical function graph laser relaxation oscillation frequency, and reading the corresponding abscissa value to obtain the actual stimulated emission section of the laser crystal in the running state. The invention is especially suitable for measuring the stimulated emission section of the laser crystal of the steady operation all-solid-state laser in the actual operation state.
Example 2
As shown in fig. 2 to 5, the difference between the present embodiment and embodiment 1 is that the present invention is further described below with reference to fig. 2 to 5 in the specific implementation, but the application scope of the present invention is not limited to the present embodiment. Fig. 2 is a diagram of a general embodiment of the present invention, in which a self-homodyne noise detection arrangement is used to measure the intensity noise of a laser in a steady state operation of an all-solid state laser. Fig. 3 is a schematic structural diagram of a device for measuring the stimulated emission section of a laser crystal of a specific all-solid-state laser to be tested in an embodiment. Specific embodiments of laser crystal stimulated emission cross-section measurements were performed in an all-solid state continuous 1064nm continuous laser of four-mirror annular cavity structure.
As can be seen from fig. 3, the specific device for measuring the stimulated emission section of the laser crystal of the all-solid-state laser to be measured comprises a pump source 1, a coupling system 3, an input coupling mirror 4, a plano-convex lens 5, a plano-concave lens 6, an output coupling mirror 7, a laser crystal 8, an optical isolator 9 and a self-homodyne noise detection device 2; the laser resonant cavity is a butterfly-shaped annular cavity formed by four mirrors of an input coupling mirror 4, a plano-convex lens 5, a plano-concave lens 6 and an output coupling mirror 7, wherein the input coupling mirror 4 is a concave-convex lens with a curvature radius of R=1500 mm, the curvature radius of the plano-convex lens 5 is R=1500 mm, and the plano-concave lens 6 and the output coupling mirror 7 are two plano-concave lenses with a curvature radius of R= -100 mm. The input coupling mirror 4 is coated with 808nm high-transmittance film (T 808nm > 99.5%) and 1064nm high-reflectance film (R 1064nm > 99.7%). The plano-convex lens 5 and the plano-concave lens 6 are plated with 1064nm high-reflection films (R 1064nm is more than 99.7%). The outcoupling mirror 7 is coated with a film having a transmittance of T 1064nm = 20% at 1064 nm. The pump source 1 is an 808nm fiber coupled laser diode, and the core diameter and numerical aperture of the coupled fiber are 400 μm and 0.22, respectively. The pump laser 1 is focused via the coupling system 3 to a waist spot of 0.510mm at the center of the laser crystal 8. The laser crystal 8 is composed of a block of 3mm undoped ends, and a 15mm composite YVO 4/Nd：YVO4(S1,S2：AR808nm;1064nm doped with Nd at 0.2 at.%). The rear end of the laser crystal 8 is cut at a small angle of 1.5 deg. to ensure stable polarization of the laser. To eliminate the spatial hole burning effect and to achieve unidirectional propagation of the laser, an optical isolator 9 consisting of a Terbium Gallium Garnet (TGG) crystal of 6mm length and a half-wave plate is used in the resonator. The cavity length of the butterfly-shaped annular cavity is 450mm. The injection 808nm pump laser power was 52W in the steady operation state. The intensity noise spectrum obtained by the laser measured by the homodyne noise detection apparatus is shown in fig. 4, and the relaxation oscillation frequency measured value ω m = 594.752kHz of the laser. In the state that the pumping laser power at 808nm is 52W, according to the actual parameters of the laser: a laser crystal length L 1＝1.5×10-2 m, a laser single round trip cavity length L 2 =0.45 m, a laser crystal refractive index n=1.976, a fluorescence lifetime τ f＝1×10-4 s, a lower energy level particle lifetime τ=3×10 -8 s, a laser crystal doped Nd +3 ion concentration C w =0.2at%, an Avgaldel constant n a＝6.02×1023, a light velocity c=2.997×10m/s, the planck constant h=6.63×10 -34, the beam waist radius omega p =0.51 mm of pumping laser at the center of laser crystal, the absorption coefficient beta=320/m of gain medium to pumping laser, the transmittance t=0.2 of output coupling mirror, the laser cavity loss delta=0.035, eta t =0.98 (pumping laser transmission efficiency eta a =0.98, quantum efficiency eta q =0.76, pumping power P in =52W of laser diode, pumping laser wavelength lambda p＝808×10-9 m, pumping laser frequencyLaser frequency/>Lambda l＝1064×10-9 m, and the doping atomic density rho lm＝ρc*cw＝1.26*1026*cw in the gain medium. According to the actual parameters of the laser, the graph of the function taking the stimulated emission section sigma s of the laser crystal of the laser as an independent variable and the relaxation oscillation frequency omega off of the laser as a dependent variable is shown in fig. 5. In fig. 5, let ω m＝ωoff be the intersection point generated by the actually measured laser relaxation oscillation frequency line and the function graph, and the abscissa corresponding to the intersection point is the actual stimulated emission section of the laser crystal in the butterfly-shaped ring cavity laser when the pumping laser power of 808nm is 52W: σ s＝2.42275593*10-22m2.
Therefore, the invention is an indirect measurement method, and the measurement is accurate; the stimulated emission section of the laser crystal is easy to accurately measure in the actual running state of the all-solid-state laser; when the stimulated emission cross section of the laser crystal of the all-solid-state laser is measured, the device is simple, the operation is convenient, and the cost is low. The invention has universal applicability, and is applicable to the measurement of stimulated emission cross sections of laser diode pumped visible light and near infrared lasers, all-solid-state laser pumped mid-infrared lasers and fiber laser pumped mid-infrared laser crystals in practical states. The stimulated emission section of the all-solid-state laser crystal obtained by measurement is the value of the stimulated emission section of the laser crystal in the actual running state of the laser, and the influence of the temperature distribution characteristic of the laser crystal on the stimulated emission section of the laser crystal is included.
Meanwhile, the invention is applicable to stimulated emission section measurement of the laser crystal of the all-solid-state laser which is being debugged and packaged in an actual running state.
Example 3
As shown in fig. 6, this embodiment differs from embodiment 1 in that this embodiment provides an apparatus for measuring a stimulated emission section of a laser crystal, which supports a method for measuring a stimulated emission section of a laser crystal described in embodiment 1, the apparatus comprising:
the measuring unit is used for measuring the intensity noise of the laser and reading a relaxation oscillation frequency measured value omega m of the laser from an intensity noise spectral line of the laser;
The theoretical drawing unit is used for drawing a function graph by utilizing a theoretical function of the relaxation oscillation frequency of the laser according to the actual parameters of the laser when the intensity noise of the laser is measured; the function graph takes a theoretical value sigma s of a stimulated emission section of a laser crystal of the laser as an independent variable, and a theoretical value omega off of a relaxation oscillation frequency of the laser as a dependent variable;
And the judging and calculating unit is used for determining the value of the abscissa corresponding to the relaxation oscillation frequency measured value in the function graph when the relaxation oscillation frequency measured value omega m is equal to the relaxation oscillation frequency theoretical value omega off, namely the actual stimulated emission section of the tested laser crystal of the laser under the operation state of injecting pumping power p in.
The invention is suitable for measuring the actual stimulated emission section of the laser crystal of the all-solid-state laser under stable operation.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (6)
1. A method of measuring the stimulated emission cross-section of a laser crystal, the method comprising the steps of:
Measuring the intensity noise of the laser, and acquiring a relaxation oscillation frequency measurement value of the laser from an intensity noise spectral line of the laser;
According to the actual parameters of the laser when measuring the intensity noise of the laser, using the theoretical function of the relaxation oscillation frequency of the laser as a function graph; the function graph takes the theoretical value of the stimulated emission section of the laser crystal of the laser as an independent variable, and takes the theoretical value of the relaxation oscillation frequency of the laser as a dependent variable;
when the measured value of the relaxation oscillation frequency is equal to the theoretical value of the relaxation oscillation frequency, the value of the abscissa corresponding to the measured value of the relaxation oscillation frequency in the function graph is the actual stimulated emission section of the measured laser crystal of the laser under the operation state of injecting pumping power;
The calculation formula of the relaxation oscillation frequency theoretical value is as follows:
wherein omega off is a relaxation oscillation frequency theoretical value, kappa is a total cavity attenuation rate of the laser, g is an stimulated radiation rate of laser crystal atomic transition of the laser and coupling between cavity modes of the laser, and alpha is the number of photons in the cavity;
the calculation formula of the total cavity attenuation rate of the laser is as follows:
κ＝κm+κl
In the method, in the process of the invention, Cavity decay rate,/>, caused by coupling mirror for laser outputThe attenuation rate of the cavity caused by the cavity loss of the laser is t is the transmissivity of the output coupling mirror, delta is the cavity loss of the laser,/>For the life of the oscillating laser in the resonant cavity of the laser, L 2 is the cavity length of a single round trip of light in the resonant cavity; c is the speed of light;
The calculation formula of the stimulated radiation rate of the coupling between the laser crystal atomic transition and the laser cavity mode is as follows:
Wherein σ s is a laser stimulated emission section, ρ lm＝ρc*cw is the doping atomic density in the gain medium, ρ c is the atomic density corresponding to the doping atomic concentration of 1.0%, c w is the doping concentration of the gain medium, L 1 is the doping length of the laser crystal atoms, and n is the refractive index of the laser crystal;
The calculation formula of the number of photons in the cavity is as follows:
In the method, in the process of the invention, For the lower energy level spontaneous emission rate, τ is the lower energy level particle lifetime,/>For the upper level spontaneous emission rate, τ f is the fluorescence lifetime of the upper level inversion particles, j 2 is the ground state population distribution probability, j 2 is expressed as: /(I)Where Γ is the pumping rate, Γ is expressed as: /(I)Wherein p in is pumping power of the laser diode in the corresponding laser when measuring laser intensity noise, eta t is pumping light transmission efficiency, eta a＝1-exp(-βL1) is absorption efficiency of the gain medium, beta is absorption coefficient of the gain medium to pumping laser,/>For quantum efficiency, v l is the output laser frequency, v p is the pump laser frequency, h is the planck constant, N lm is the number of doping ions utilized in the laser medium, expressed as: n lm＝ρlm*Vm, where V m is the mode volume of the pump laser at the laser crystal, expressed as: /(I)Where ω p is the beam waist radius of the pump laser at the center of the laser crystal and λ p is the wavelength of the pump laser.
2. The method of claim 1, wherein the measuring the intensity noise of the laser is measuring the intensity noise of the laser with a self-homodyne noise detection apparatus.
3. A method of measuring the stimulated emission section of a laser crystal as claimed in claim 1, wherein the laser is an all-solid-state laser.
4. A method of measuring the stimulated emission cross section of a laser crystal as claimed in claim 3, wherein the laser crystal under test is mounted in an all-solid-state laser so as to provide for a steady state operation of the laser during the laser noise measurement.
5. A method of measuring the stimulated emission section of a laser crystal according to claim 1, characterized in that the method is adapted to the stimulated emission section measurement of an all-solid-state laser crystal being commissioned or already packaged in an actual operating state.
6. An apparatus for measuring a stimulated emission section of a laser crystal, the apparatus supporting a method for measuring a stimulated emission section of a laser crystal as recited in any one of claims 1 to 5, the apparatus comprising:
The measuring unit is used for measuring the intensity noise of the laser and acquiring a relaxation oscillation frequency measured value of the laser from an intensity noise spectral line of the laser;
The theoretical drawing unit is used for drawing a function graph by utilizing a theoretical function of the relaxation oscillation frequency of the laser according to the actual parameters of the laser when the intensity noise of the laser is measured; the function graph takes the theoretical value of the stimulated emission section of the laser crystal of the laser as an independent variable, and takes the theoretical value of the relaxation oscillation frequency of the laser as a dependent variable;
And the judgment and calculation unit is used for determining the value of the abscissa corresponding to the relaxation oscillation frequency measured value in the function graph when the relaxation oscillation frequency measured value is equal to the relaxation oscillation frequency theoretical value, namely the actual stimulated emission section of the tested laser crystal of the laser under the operation state of injecting pumping power.
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