CN106932318B - Diagnostic device and method for semiconductor pumping alkali metal vapor laser - Google Patents
Diagnostic device and method for semiconductor pumping alkali metal vapor laser Download PDFInfo
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- 150000001340 alkali metals Chemical class 0.000 title claims abstract description 57
- 229910052783 alkali metal Inorganic materials 0.000 title claims abstract description 54
- 239000004065 semiconductor Substances 0.000 title claims abstract description 40
- 238000000034 method Methods 0.000 title claims abstract description 21
- 238000005086 pumping Methods 0.000 title claims description 16
- 238000001514 detection method Methods 0.000 claims abstract description 67
- 150000001335 aliphatic alkanes Chemical class 0.000 claims abstract description 65
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 41
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000002245 particle Substances 0.000 claims abstract description 39
- 230000008021 deposition Effects 0.000 claims abstract description 32
- 238000012545 processing Methods 0.000 claims abstract description 30
- 230000008859 change Effects 0.000 claims abstract description 18
- 238000010521 absorption reaction Methods 0.000 claims abstract description 17
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 53
- 230000003287 optical effect Effects 0.000 claims description 18
- 238000003745 diagnosis Methods 0.000 claims description 11
- 229910052792 caesium Inorganic materials 0.000 claims description 8
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 claims description 8
- 230000008878 coupling Effects 0.000 claims description 8
- 238000010168 coupling process Methods 0.000 claims description 8
- 238000005859 coupling reaction Methods 0.000 claims description 8
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 7
- 229910052700 potassium Inorganic materials 0.000 claims description 7
- 239000011591 potassium Substances 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 229910052701 rubidium Inorganic materials 0.000 claims description 6
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 claims description 6
- 239000000523 sample Substances 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims 1
- 239000007789 gas Substances 0.000 description 52
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 18
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 9
- 239000001294 propane Substances 0.000 description 9
- 238000011109 contamination Methods 0.000 description 8
- 238000002310 reflectometry Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 235000013405 beer Nutrition 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910000661 Mercury cadmium telluride Inorganic materials 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000003667 anti-reflective effect Effects 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- MCMSPRNYOJJPIZ-UHFFFAOYSA-N cadmium;mercury;tellurium Chemical compound [Cd]=[Te]=[Hg] MCMSPRNYOJJPIZ-UHFFFAOYSA-N 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002405 diagnostic procedure Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/04—Investigating sedimentation of particle suspensions
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Abstract
The invention provides a diagnostic device and a method for a semiconductor pump alkali metal vapor laser, wherein a light source subsystem of the diagnostic device generates two paths of wavelengths lambda1And λ2Similar but alkane gasThe detection light and the reference light with larger difference of absorption coefficients pass through the detection light path subsystem and the reference light path subsystem, the detection light is partially absorbed by the alkane gas through the detection light path subsystem, the signal acquisition processing subsystem receives the detection light and the reference light of the light path subsystem to obtain the concentration change of the alkane gas, and the carbon particle deposition speed of the semiconductor alkali metal vapor laser is obtained based on the concentration change of the alkane gas.
Description
Technical Field
The invention relates to the technical field of laser, in particular to a diagnostic device and a diagnostic method for a semiconductor pumping alkali metal vapor laser.
Background
A semiconductor Pumped Alkali metal vapor Laser (DPAL) is a new type of optically Pumped gas Laser, which has extremely high quantum efficiency and is one of Laser systems with single-aperture MW-level average power output potential. The gain medium of DPAL is an alkali metal (mainly potassium, K), rubidium (Rb), or cesium (cesium, Cs)) in a vapor state. Since the concept of DPAL was proposed by Krupke et al, lawrence lipvermore national laboratory in 2003, DPAL has passed through a period of rapid development, and the highest average power reported at present has reached 1kW and the highest luminous efficiency has reached 62%. However, the problem of damage to the window plate of the alkali metal vapor cell has plagued such lasers, making them difficult to operate for extended periods of time.
There are two main contamination scenarios for window contamination of DPAL. The first window contamination scenario is the infiltration of alkali metals into the window. In 2012, Quarrie studied the influence of alkali metal atoms on various material window sheets, and analyzed the permeation of alkali metal atoms on various material window sheets by measuring the mass of the window sheets after the alkali metal atoms are placed for a long time. The second is contamination of the window by carbon particles produced by the reaction of alkali metal with alkane buffer gas at high power density laser and high temperature. The addition of a proper amount of alkane gas can accelerate the relaxation rate between two upper energy levels, is beneficial to improving the utilization rate of pump light, and plays an important role in reducing the threshold value of a laser and improving the optical efficiency. However, the alkane gas reacts with alkali metal under the action of high temperature and high power density laser, generating carbon particles, and polluting the window. Currently, there is no quantitative diagnosis and analysis of the second window contamination situation, and it is generally determined whether contamination is present by visually observing the deposition of carbon particles on the window after a longer laser run. Fig. 1 shows a typical DPAL window with a central area that is contaminated or damaged, which does not allow online observation of the window contamination and even quantitative analysis.
Disclosure of Invention
Technical problem to be solved
In view of the above, the main objective of the present invention is to provide a diagnostic device and method for a semiconductor pumped alkali metal vapor laser, which can diagnose the deposition condition of carbon particles of the alkali metal laser on line in real time, quantitatively describe the deposition speed of carbon particles, and characterize the deposition condition of carbon particles.
(II) technical scheme
The invention provides a diagnostic device of a semiconductor pumping alkali metal vapor laser, which comprises a light source subsystem, a light path subsystem and a signal acquisition processing subsystem; wherein the light source subsystem generates detection light and reference light, both of which have two paths of wavelengths lambda1And λ2The light beam combination of the laser light which is similar but has larger difference of absorption coefficients of the alkane gas; the light path subsystem comprises a detection light path subsystem and a reference light path subsystem, wherein the detection light is partially absorbed by the alkane gas through the detection light path subsystem; the signal acquisition and processing subsystem receives the detection light and the reference light of the light path subsystem, obtains the concentration change of the alkane gas through photoelectric conversion, signal acquisition and processing, and obtains the carbon particle deposition speed of the semiconductor alkali metal vapor laser based on the concentration change of the alkane gas.
The invention also provides a method for diagnosing the semiconductor pumping alkali metal vapor laser by using the diagnosis device, which comprises the following steps: step A: obtaining the light intensity of the detection light and the initial light intensity of the detection light by using a diagnosis device; and B: obtaining the concentration of the alkane gas based on the light intensity of the detection light and the initial light intensity of the detection light; and C: obtaining the mole number of the alkane gas loss based on the concentration of the alkane gas, the temperature of the alkane gas, the volume of a steam chamber and the pressure of the steam chamber; step D: the speed of carbon particle deposition is obtained based on the number of moles of alkane gas lost, and the diagnostic result of the semiconductor pumped alkali metal vapor laser is obtained.
(III) advantageous effects
According to the technical scheme, the invention has the following beneficial effects:
(1) the concentration change of methane in the steam chamber is detected by adopting a differential absorption method, so that the detection precision is high;
(2) the method can quantitatively describe the deposition speed of the carbon granules, diagnose the deposition condition of the carbon granules of the alkali metal laser on line in real time, and can find the deposition of the carbon granules in time to represent the deposition condition of the carbon granules.
Drawings
FIG. 1 is a window of typical DPAL contamination;
FIG. 2 is a block diagram of a semiconductor pumped alkali metal vapor laser;
FIG. 3 is a block diagram of a diagnostic device for a semiconductor pumped alkali metal vapor laser according to an embodiment of the present invention;
FIG. 4 is a flow chart of a method for diagnosing a semiconductor pumped alkali metal vapor laser according to an embodiment of the present invention.
[ notation ] to show
11-highly reflective concave mirrors; 12-a vapor chamber; 13-a polarizer; 14-an output coupling mirror; 15-a focusing mirror; 16-semiconductor pump light; 17-alkali metal laser;
21-a first mid-infrared laser; 22-a second mid-infrared laser; 23-a chopper; 24-half reflecting and half transmitting mirror; 25-a first mirror; 26-a light splitting sheet;
31-a first dichroic film lens; 32-a second dichroic film lens; 33-a second mirror;
41-a first focusing mirror; 42-a second focusing mirror; 43-a first photodetector; 44-a second photodetector; 45-signal acquisition and processing device.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
The semiconductor pumping alkali metal vapor laser generally comprises a semiconductor light source, a resonant cavity and other components, the resonant cavity structure is shown in fig. 2, and comprises a high-reflection concave mirror 11, a vapor chamber 12, a polarizer 13, an output coupling mirror 14 and a focusing mirror 15 which are coaxially arranged in sequence, the focusing mirror 15 is used for converging semiconductor pumping light 16 and improving the pumping efficiency of the semiconductor pumping light 16, the semiconductor pumping light 16 is focused by the focusing mirror 15 and then projected to the polarizer 13 and reflected into the vapor chamber 12, the vapor chamber 12 contains alkane buffer gas, helium and alkali metal vapor, the alkali metal vapor is used as a gain medium of the laser, the population inversion of an upper energy level of a D1 line and a lower energy level of the D1 line is realized under the action of the semiconductor pumping light 16, an alkali metal D1 line photon is radiated from a window of the vapor chamber 12, and the alkali metal D1 line photon is continuously reflected between the high-reflection concave mirror 11 and the output coupling mirror 14 to realize resonant amplification, the output of the alkali metal laser 17 is realized via the output coupling mirror 14. In the process, the alkali metal vapor and the alkane buffer gas react under high-temperature and high-power-density laser to generate carbon particles, and the carbon particles can pollute and damage the window of the vapor chamber 12.
Examples of the present invention will be described below by taking methane and rubidium vapor as examples, but the present invention is not limited thereto, and is also applicable to other alkane gases such as ethane and propane, and other alkali metal vapors such as potassium and cesium.
The principle of the invention is as follows: under the condition that the steam chamber is good in airtightness, the alkane gas and alkali metal atoms react or act as the only factor influencing the number density of alkane gas particles, and the deposition speed of carbon particles can be obtained by detecting the concentration change of the alkane gas.
Taking a vapor chamber with methane as one of the buffer gases as an example, the reaction process for generating carbon particles in the vapor chamber is as follows:
due to loss of one methane (CH)4) Molecule, producing one carbon (C) atom, the carbon atom producing speed is equal to the methane molecule consumption speed, and the methane concentration C (t) in the rubidium steam chamber at the t moment is obtained from t according to C (t)1To t2The change in methane concentration at that moment, i.e. C (t)1)-C(t2) (ii) a Since the rate of carbon formation from methane and rubidium vapor is small, the rate of reduction of methane concentration is believed to be related to the total gas pressure P in the vapor chamberbufferWithout influence, the change in partial pressure of methane Δ P ═ P due to the change in methane concentration according to the partial pressure theorembuffer(C(t1)-C(t2) From partial pressure changes, based on the ideal gas equation of state, the equation of state from t) is derived1To t2The loss of methane at any moment is as follows:
wherein R is an ideal gas constant, 8.314472J/(mol x K), PbufferIs the vapor chamber pressure, T is the vapor chamber gas temperature, and V is the vapor chamber volume.
According to the slave t1To t2The loss of the number of moles of methane at any given time gives the rate of carbon particle deposition per unit time.
In the formula, NaIs the Avogastron constant. Therefore, the carbon particle deposition speed can be obtained by detecting the concentration change of methane, and the diagnosis of the semiconductor pumping alkali metal laser is realized.
Fig. 3 shows a diagnostic device for a semiconductor pumped alkali metal vapor laser, which uses a differential absorption method to detect the change of the concentration of methane in the vapor chamber 12, according to an embodiment of the present invention, and the diagnostic device includes a light source subsystem, an optical path subsystem, and a signal acquisition processing subsystem. Wherein the light source subsystem generates detection light and reference light, both of which have two paths of wavelengths lambda1And λ2The combined beam of laser light of (1), wherein the wavelength λ1And λ2The difference of the two wavelengths is less than or equal to 0.5 mu m, and the absorption coefficient of the alkane gas to the laser with one wavelength is more than 5 times of that of the laser with the other wavelength; the optical path subsystem comprises a detection optical path subsystem and a reference optical path subsystem, wherein the detection light is partially absorbed by methane through the detection optical path subsystem; the signal acquisition processing subsystem receives the detection light and the reference light of the light path subsystem, and concentration change of methane is obtained through photoelectric conversion, signal acquisition and processing, and finally window pollution and damage conditions of the semiconductor alkali metal vapor laser are obtained.
The light source subsystem comprises a first intermediate infrared laser 21, a second intermediate infrared laser 22, a chopper 23, a semi-reflecting and semi-transmitting mirror 24, a first reflector 25 and a beam splitter 26, wherein the first intermediate infrared laser 21 and the second intermediate infrared laser 22 are arranged side by side, the chopper 23 is opposite to laser outlets of the first intermediate infrared laser 21 and the second intermediate infrared laser 22, the semi-reflecting and semi-transmitting mirror 24 and the beam splitter 26 are 135 degrees and are longitudinally and coaxially arranged in front of the chopper 23 and opposite to the laser outlet of the first intermediate infrared laser 21, and the first reflector 25 is 135 degrees and is transversely and coaxially arranged with the semi-reflecting and semi-transmitting mirror 24 in front of the chopper 23 and opposite to the laser outlet of the second intermediate infrared laser 22.
The optical path subsystem comprises a detection optical path subsystem and a reference optical path subsystem, wherein the detection optical path subsystem comprises a first dichroic film lens 31 and a second dichroic film lens 32, the first dichroic film lens 31 and the second dichroic film lens 32 are coaxial with a semiconductor pumped alkali metal vapor laser resonant cavity, the first dichroic film lens 31 is placed between the polarizing plate 13 and the output coupling mirror 14 or between the vapor chamber 12 and the polarizing plate 13, the second dichroic film lens 32 is placed between the high-reflection concave mirror 11 and the vapor chamber 12, and the first dichroic film lens 31 is transversely coaxial with the light splitting plate 26 of the light source subsystem. The reference optical path subsystem includes a second mirror 33, the second mirror 33 being longitudinally coaxial with the beam splitter 26 of the light source subsystem.
The signal acquisition processing subsystem includes a first focusing mirror 41, a second focusing mirror 42, a first photodetector 43 and a second photodetector 44, and a signal acquisition processing device 45. The first focusing lens 41 and the first photodetector 43 are sequentially and coaxially arranged with the second dichroic film lens 32 in the transverse direction, the second focusing lens 42 and the second photodetector 44 are sequentially and coaxially arranged with the second reflecting mirror 33 in the transverse direction, and the signal acquisition and processing device 45 is connected with the first photodetector 43 and the second photodetector 44.
Wherein, the first intermediate infrared laser 21 and the second intermediate infrared laser 22 are used as laser sources of a differential absorption method and respectively generate a wavelength lambda1And a wavelength of λ2Of a first laser and a second laser, wherein the wavelength λ1Is equal to the characteristic peak of alkane gas in the middle infrared region and has the wavelength lambda2And wavelength lambda1A difference of less than or equal to 0.5 [ mu ] m, wavelength lambda of the alkane gas1The absorption coefficient of the laser light is the wavelength lambda2More than 5 times of laser; the chopper 23 modulates the first laser and the second laser by adopting different modulation frequencies, the modulated second laser is reflected to the half mirror through the first reflector 25, is coaxial with the modulated first laser in the half mirror, and after being combined with the first laser with different modulation frequencies, the reflected light of the beam splitter 26 is probe light, and the transmitted light is reference light; the first dichroic film lens 31 and the second dichroic film lens 32 are anti-reflective at the ray wavelength of a rubidium laser D1, and when the detection light wavelength is high reflective, the detection light is reflected by the first dichroic film lens 31 and then coaxial with the laser (for convenience of displaying the detection light, the detection light in fig. 3 is parallel to the laser, and the detection light of the actual device is coaxial with the laser), enters the steam chamber 12 through the polarizing plate 13, the methane in the steam chamber 12 absorbs part of the detection light, the detection light is reflected to the first focusing lens 41 through the second dichroic film lens 32 after passing through the steam chamber 12, and is received and converted into an electrical signal through the first photoelectric detector 43 after being focused by the first focusing lens 41; the reference light is reflected by the second lensThe reflector 33 is focused by a second focusing lens 42, and the focused signal is received by a second photoelectric detector 44 and converted into an electric signal; the signal acquisition and processing device 45 receives the electrical signal of the detection light and the reference photoelectric signal, and processes the electrical signal based on Fourier transform to obtain the light intensity I (lambda) of the detection light1T) and I (lambda)2T) and the intensity of the reference light Ir(λ1T) and Ir(λ2T), further obtaining the concentration change of methane, and finally obtaining the window pollution and damage condition of the semiconductor alkali metal vapor laser.
Wherein, the high reflection concave mirror 11 has high reflection at 700-900nm, the reflectivity is more than 99%, and the curvature is 20 cm; the output coupling ratio of the output coupling mirror 14 is 30%; the first intermediate infrared laser 21 is a second type interband cascade distributed feedback semiconductor laser with the laser wavelength of 3.357 μm, and the second intermediate infrared laser 22 is a second type interband cascade distributed feedback semiconductor laser with the laser wavelength of 3.550 μm; the chopper 23 can be two disks with sector notches, the driving device drives the disks to rotate and modulate the first laser and the second laser, the modulation frequencies of the chopper 23 on the first laser and the second laser are respectively 500Hz and 750Hz, the reflectivity of the half-reflecting and half-transmitting mirror 24 is 50%, and the transmissivity is 50%; the reflectivity of the spectroscope 26 is 90%, the transmittance is 10%, the first dichroic film lens 31 and the second dichroic film lens 32 are anti-reflection at 795nm, and the reflection is high at 3.39 mu m; the first photodetector 43 and the second photodetector 44 are mercury cadmium telluride devices with high response to mid-infrared band laser; the signal acquisition and processing device 45 includes a lock-in amplifier, a frequency divider, a filter, a detector, an A/D converter and a computer, amplifies, divides, and performs analog-to-digital conversion on the detection photoelectric signal and the reference photoelectric signal, and processes the electric signals based on Fourier transform to obtain the detection light intensity I (lambda)1T) and I (lambda)2T) and the intensity of the reference light Ir(λ1T) and Ir(λ2T), further obtaining the concentration change of methane, and finally obtaining the window pollution and damage condition of the semiconductor alkali metal vapor laser. The signal acquisition and processing device 45 may further be provided with an oscilloscope for observing the received probe photoelectric signal and the reference photoelectric signal.
The above embodiments are equally applicable to other alkane gases such as ethane and propane, and when applied to ethane and propane, the first laser wavelength λ1Characteristic absorption peaks of ethane and propane; the first and second dichroic film lenses 31, 32 are highly reflective at selected characteristic absorption peaks. The above embodiment is also applicable to other alkali metal vapor such as potassium and cesium, and when the embodiment is applied to other alkali metal vapor such as potassium and cesium, the detection light is introduced into the vapor chamber 12 through the first dichroic film lens 31, and the detection light is led out to the signal acquisition processing subsystem through the second dichroic film lens 32. The first mid-infrared laser 21 and the second mid-infrared laser 22 may also adopt other types of mid-infrared laser sources, such as mid-infrared he-ne laser, optical parametric oscillator, etc., the output wavelength of the selected laser source should be tunable, and there are two laser wavelengths, the wavelengths are similar, but one wavelength is strongly absorbed by the alkane gas, and the other wavelength is less absorbed by the alkane gas, and the alkane gas concentration is detected by a differential method.
In another embodiment of the present invention, there is provided a method for diagnosing a semiconductor pumped alkali metal vapor laser using the above diagnostic apparatus, including:
step A: the diagnostic device is used for obtaining the light intensity of the detection light and the initial light intensity of the detection light.
The step A specifically comprises the following steps:
substep a 1: the light source subsystem of the diagnosis device generates detection light and reference light, the detection light and the reference light are respectively received by the signal acquisition processing subsystem after passing through the detection light path subsystem and the reference light path subsystem, and the signal acquisition processing subsystem obtains the light intensity I (lambda)1T) and I (lambda)2T) and the intensity of the reference light Ir(λ1T) and Ir(λ2，t)。
Substep a 2: the light intensity I of the reference light obtained by the signal acquisition processing subsystemr(λ1T) and Ir(λ2T) as the initial intensity I of the probe light0(λ1T) and I0(λ2，t)。
And B: and obtaining the concentration of the alkane gas based on the light intensity of the detection light and the initial light intensity of the detection light.
The derivation of the calculation formula is described below:
firstly, establishing the relation between the light intensity of the detection light and the initial light intensity of the detection light based on the Lambert beer law,
the method specifically comprises the following steps:
according to the lambert beer law, the relationship between the light intensity of the detection light and the initial light intensity of the detection light is as follows:
I(λ1，t)＝I0(λ1，t)k1(λ1，t)exp[-α(λ1)LC(t)] (4)
I(λ2，t)＝I0(λ2，t)k2(λ2，t)exp[-α(λ2)LC(t)] (5)
in the formula, k1(λ1) And k2(λ2) Respectively, the attenuation coefficient caused by carbon particle deposition, window pollution, lens absorption and the like, due to lambda1And λ2Very close to k1(λ1，t)≈k2(λ2，t)；α(λ1) And α (λ)2) Under certain air pressure and gas proportion respectively, alkane gas is opposite to lambda1And λ2The absorption coefficient of (a) is obtained by measuring a sample cell of known gas composition and composition; l is the vapor chamber 12 length.
Then, the concentration of the paraffin gas is calculated based on the formulas (4) and (5):
and C: and obtaining the mole number of the alkane gas loss based on the concentration of the alkane gas, the temperature of the alkane gas, the volume of the steam chamber and the pressure of the steam chamber.
The step C specifically comprises the following steps:
substep C1: calculating t based on the alkane gas concentration expression1And t2Alkane gas concentration C (t) at time1) And C (t)2)。
C(t1) And C (t)2) Are respectively:
substep C2: based on t1And t2Alkane gas concentration C (t) at time1) And C (t)2) The mole number of the alkane gas loss is calculated according to the alkane gas temperature, the steam chamber volume and the steam chamber pressure.
The expression of the mole number n of the alkane gas loss is as follows:
wherein R is an ideal gas constant, 8.314472J/(mol x K), PbufferThe air pressure of the steam chamber 12 can be measured by a barometer; t is the gas temperature of the vapor chamber 12, which can be measured by a temperature sensor; v is the volume of the vapor chamber 12.
Step D: the speed of carbon particle deposition is obtained based on the number of moles of alkane gas lost, and the diagnostic result of the semiconductor pumped alkali metal vapor laser is obtained.
The step D specifically comprises the following steps:
substep D1: the rate of carbon particle deposition is obtained based on the moles of alkane gas lost.
When the alkane gas is methane, the rate of carbon particle deposition, n, is expressed as:
wherein N isaIs an Avogastron constant; n is a radical ofdepositIs the rate of carbon particle deposition.
Substep D2: and obtaining the diagnosis result of the semiconductor pumped alkali metal vapor laser according to the deposition speed of the carbon particles.
The substep D2 specifically comprises:
when N is presentdepositWhen 0, it is considered that no carbon particles were produced and the window was not contaminated and damaged; when N is presentdepositWhen > 0, carbon particles are considered to be being produced, and the window is contaminated and damaged; n is a radical ofdepositThe larger the value of (a), the more the window becomes contaminated and damaged.
Similar to the above-mentioned diagnostic apparatus, the above-mentioned embodiments are also applicable to other alkane gases such as ethane and propane, and also applicable to other alkali metal vapors such as potassium and cesium, and the first mid-infrared laser 21 and the second mid-infrared laser 22 may also adopt other types of mid-infrared laser sources, such as a mid-infrared he-ne laser, an optical parametric oscillator, and the like. When applied to ethane, propane, the carbon particle deposition rate is calculated as ethane calculated from the consumption of one molecule of ethane to produce two carbon atoms and propane calculated from the consumption of one molecule of propane to produce three carbon atoms.
It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. In addition, the above definitions of the various elements and steps are not limited to the specific structures, shapes and steps described in the embodiments, and may be modified or replaced simply by one of ordinary skill in the art, for example:
(1) the invention can also be suitable for other alkane gases such as ethane, propane and the like, and is also suitable for other alkali metal vapor such as potassium, cesium and the like, and the first intermediate infrared laser and the second intermediate infrared laser can also adopt other types of intermediate infrared laser sources;
(2) the optical path element may be other types of elements as long as the same function is achieved;
(3) examples of parameters that include particular values may be provided herein, but the parameters need not be exactly equal to the corresponding values, but may be approximated to the corresponding values within acceptable error tolerances or design constraints;
(4) directional phrases used in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., refer only to the orientation of the attached drawings and are not intended to limit the scope of the present invention;
(5) the embodiments described above may be mixed and matched with each other or with other embodiments based on design and reliability considerations, i.e. technical features in different embodiments may be freely combined to form further embodiments.
In summary, the diagnosis device and method for the semiconductor pumping alkali metal vapor laser provided by the invention can detect the concentration change of methane in the vapor chamber by adopting the differential absorption method, diagnose the carbon particle deposition condition of the alkali metal laser on line in real time, find the carbon particle deposition in time, quantitatively describe the carbon particle deposition speed and represent the carbon particle deposition condition.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit 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 (6)
1. A diagnostic device of a semiconductor pumping alkali metal vapor laser is characterized by comprising a light source subsystem, a light path subsystem and a signal acquisition processing subsystem; wherein the content of the first and second substances,
the light source subsystem generates detection light and reference light, both of which have two paths of wavelengths lambda1And λ2Combined beam of laser light of similar but widely different absorption coefficient by alkane gas, wherein, the wavelength lambda1Is equal to the characteristic peak of alkane gas in the middle infrared region and has the wavelength lambda2And wavelength lambda1A difference of less than or equal to 0.5 [ mu ] m, wavelength lambda of the alkane gas1The absorption coefficient of the laser light is the wavelength lambda2More than 5 times of laser;
the light path subsystem comprises a detection light path subsystem and a reference light path subsystem, wherein the detection light is partially absorbed by the alkane gas through the detection light path subsystem;
the signal acquisition and processing subsystem receives the detection light and the reference light of the light path subsystem, obtains the concentration change of the alkane gas through photoelectric conversion, signal acquisition and processing, and obtains the carbon particle deposition speed of the semiconductor alkali metal vapor laser based on the concentration change of the alkane gas.
2. The diagnostic device of claim 1,
the light source subsystem comprises a first intermediate infrared laser (21), a second intermediate infrared laser (22), a chopper (23), a semi-reflecting and semi-transmitting mirror (24), a first reflector (25) and a beam splitter (26), wherein the first intermediate infrared laser (21) and the second intermediate infrared laser (22) are arranged side by side, the chopper (23) is right opposite to laser outlets of the first intermediate infrared laser (21) and the second intermediate infrared laser (22), the semi-reflecting and semi-transmitting mirror (24) and the beam splitter (26) are 135 degrees, are longitudinally and coaxially arranged in front of the chopper (23) and right opposite to the laser outlet of the first intermediate infrared laser (21), and the first reflector (25) is 135 degrees, is transversely and coaxially arranged in front of the chopper (23) with the semi-reflecting and semi-transmitting mirror (24) and is right opposite to the laser outlet of the second intermediate infrared laser (22);
the first intermediate infrared laser (21) and the second intermediate infrared laser (22) are used as laser sources of a differential absorption method and respectively generate a wavelength lambda1And a wavelength of λ2The first laser light and the second laser light;
the chopper (23) modulates the first laser and the second laser by adopting different modulation frequencies, the modulated second laser is reflected to the half-transmitting and half-reflecting mirror through the first reflecting mirror (25) and is coaxial with the modulated first laser in a beam combination way of the half-transmitting and half-reflecting mirror, the reflected light of the beam splitting sheet (26) after the first laser and the second laser with different modulation frequencies are combined is probe light, and the transmitted light is reference light.
3. The diagnostic device of claim 1,
the optical path subsystem comprises a detection optical path subsystem and a reference optical path subsystem, wherein the detection optical path subsystem comprises a first dichroic film lens (31) and a second dichroic film lens (32), the first dichroic film lens (31) and the second dichroic film lens (32) are coaxial with a resonant cavity of the semiconductor pumped alkali metal vapor laser, the first dichroic film lens (31) is placed between a polarizing plate (13) and an output coupling mirror (14) or between a vapor chamber (12) and the polarizing plate (13), the second dichroic film lens (32) is placed between a high-reflection concave mirror (11) and the vapor chamber (12), and the first dichroic film lens (31) is transversely coaxial with a light splitting plate (26) of the light source subsystem;
the reference light path subsystem comprises a second reflector (33), and the second reflector (33) is longitudinally coaxial with the light splitting piece (26) of the light source subsystem;
the first dichroic film lens (31) and the second dichroic film lens (32) are used for increasing the reflection at the wavelength of an alkali metal laser D1, the detection light wavelength is high in reflection, the detection light is reflected by the first dichroic film lens (31) and then coaxial with the laser, enters the steam chamber (12) through the polarizing plate (13), the alkane gas in the steam chamber (12) absorbs part of the detection light, and the detection light is reflected to the signal acquisition and processing subsystem through the second dichroic film lens (32) after passing through the steam chamber (12); the reference light is reflected to the signal acquisition processing subsystem by a second reflector (33).
4. The diagnostic device of claim 1,
the signal acquisition processing subsystem comprises a first focusing mirror (41), a second focusing mirror (42), a first photoelectric detector (43), a second photoelectric detector (44) and a signal acquisition processing device (45), wherein the first focusing mirror (41) and the first photoelectric detector (43) are sequentially and transversely coaxially arranged with the second dichroic film lens (32), the second focusing mirror (42) and the second photoelectric detector (44) are sequentially and transversely coaxially arranged with the second reflecting mirror (33), and the signal acquisition processing device (45) is connected with the first photoelectric detector (43) and the second photoelectric detector (44);
the detection light is focused by a first focusing lens (41), and then is received and converted into an electric signal by a first photoelectric detector (43); the reference light is focused by a second focusing lens (42), and then is received by a second photoelectric detector (44) and converted into an electric signal; the signal acquisition processing device (45) receives the detection photoelectric signal and the reference photoelectric signal, and processes the electric signals based on Fourier transform to obtain the light intensity I (lambda) of the detection light1T) and I (lambda)2T) and GinsengLight intensity I of test lightr(λ1T) and Ir(λ2T), and the concentration change of the alkane is obtained, and the carbon particle deposition speed of the semiconductor alkali metal vapor laser is obtained.
5. The diagnostic device of any one of claims 1 to 4, wherein the alkane gas is methane or other alkane gas and the alkali metal is rubidium, potassium or cesium.
6. A method of diagnosing a semiconductor pumped alkali metal vapor laser using the diagnostic device of claim 1, comprising:
step A: obtaining the light intensity of the detection light and the initial light intensity of the detection light by using a diagnosis device;
and B: obtaining the concentration of the alkane gas based on the light intensity of the detection light and the initial light intensity of the detection light;
and C: obtaining the mole number of the alkane gas loss based on the concentration of the alkane gas, the temperature of the alkane gas, the volume of a steam chamber and the pressure of the steam chamber;
step D: obtaining the deposition speed of carbon particles based on the mole number of the alkane gas loss, and further obtaining the diagnosis result of the semiconductor pumping alkali metal vapor laser;
the step A specifically comprises the following steps:
substep a 1: the light source subsystem of the diagnosis device generates detection light and reference light, the detection light and the reference light are respectively received by the signal acquisition processing subsystem after passing through the detection light path subsystem and the reference light path subsystem, and the signal acquisition processing subsystem obtains the light intensity I (lambda)1T) and I (lambda)2T) and the intensity of the reference light Ir(λ1T) and Ir(λ2，t)；
Substep a 2: the light intensity I of the reference light obtained by the signal acquisition processing subsystemr(λ1T) and Ir(λ2T) as the initial intensity I of the probe light0(λ1T) and I0(λ2，t)；
In the step B, the concentration of the alkane gas is calculated based on the following formula:
I(λ1，t)＝I0(λ1，t)k1(λ1，t)exp[-α(λ1)LC(t)]
I(λ2，t)＝I0(λ2，t)k2(λ2，t)exp[-α(λ2)LC(t)]
wherein k is1(λ1) And k2(λ2) The attenuation coefficient caused by carbon particle deposition, window pollution and lens absorption is due to lambda1And λ2Very close to k1(λ1，t)≈k2(λ2，t)；α(λ1) And α (λ)2) Under certain air pressure and gas proportion respectively, alkane gas is opposite to lambda1And λ2The absorption coefficient of (a); l is the length of the steam chamber (12);
the step C specifically comprises the following steps:
substep C1: calculating t based on the alkane gas concentration expression1And t2Alkane gas concentration C (t) at time1) And C (t)2)：
And
substep C2: according to the formula, based on t1And t2Alkane gas concentration C (t) at time1) And C (t)2) Calculating the mole number n of alkane gas loss by using the alkane gas temperature, the vapor chamber volume and the vapor chamber pressure:
wherein, R is an ideal gas constant and is 8.314472J/(mol × K); pbufferIs the pressure of the steam chamber (12); t is the gas temperature of the vapor chamber (12); v is the volume of the vapor chamber (12);
the step D specifically comprises the following steps:
substep D1: obtaining the rate of carbon particle deposition based on moles of alkane gas lost;
when the alkane gas is methane, the rate N of carbon particle depositiondepositThe expression of (a) is:
wherein N isaIs an Avogastron constant; n is a radical ofdepositIs the rate of carbon particle deposition;
substep D2: obtaining the diagnosis result of the semiconductor pumping alkali metal vapor laser according to the deposition speed of the carbon particles;
the substep D2 specifically comprises:
when N is presentdepositWhen 0, it is considered that no carbon particles were produced and the window was not contaminated and damaged; when N is presentdepositWhen > 0, carbon particles are considered to be being produced, and the window is contaminated and damaged; n is a radical ofdepositThe larger the value of (a), the more the window becomes contaminated and damaged.
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