CN111740297B - Double-beam laser system with laser energy monitoring and feedback and control method thereof - Google Patents
Double-beam laser system with laser energy monitoring and feedback and control method thereof Download PDFInfo
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- CN111740297B CN111740297B CN202010652159.7A CN202010652159A CN111740297B CN 111740297 B CN111740297 B CN 111740297B CN 202010652159 A CN202010652159 A CN 202010652159A CN 111740297 B CN111740297 B CN 111740297B
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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
- H01S3/0007—Applications not otherwise provided for
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/10—Ion sources; Ion guns
- H01J49/16—Ion sources; Ion guns using surface ionisation, e.g. field-, thermionic- or photo-emission
- H01J49/161—Ion sources; Ion guns using surface ionisation, e.g. field-, thermionic- or photo-emission using photoionisation, e.g. by laser
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/0014—Monitoring arrangements not otherwise provided for
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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
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/08086—Multiple-wavelength emission
- H01S3/0809—Two-wavelenghth emission
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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
- H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
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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
- H01S3/109—Frequency multiplication, e.g. harmonic generation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
- G01N2021/0106—General arrangement of respective parts
- G01N2021/0112—Apparatus in one mechanical, optical or electronic block
Abstract
The invention discloses a double-beam laser system with laser energy monitoring and feedback, and relates to the technical field of laser energy monitoring. The laser device emits laser to form a first light path, a frequency doubling crystal, a frequency tripling crystal, a wavelength separating mirror and a resonant cavity are sequentially arranged on the first light path, one path of laser is separated by the wavelength separating mirror to form a second light path, and the resonant cavity returns one path of laser to form a third light path; the beam combining sheet is arranged at the intersection of the second light path and the third light path to form a fourth light path, and the quintuple frequency crystal is arranged on the fourth light path; laser energy monitoring and feedback systems are arranged at the double-frequency crystal and the triple-frequency crystal, and the corresponding crystal phase angle is fed back and controlled through detecting the laser energy value behind the crystal in real time. The invention obtains real-time laser energy value while not blocking laser to participate in ionization detection, and can perform feedback control on the crystal according to the real-time energy value, thereby ensuring the intensity and stability of laser energy output.
Description
Technical Field
The invention relates to the technical field of laser energy monitoring, in particular to a double-beam laser system with laser energy monitoring and feedback and a control method thereof.
Background
At present, the detection of trace organic pollution such as dioxin in gas is mainly based on an off-line detection method (HJ77.2), and the purpose of on-line detection cannot be realized. The laser ionization and time-of-flight mass spectrometry technology has great advantages in the aspect of online detection of trace organic pollutants, and is a main development direction of the online detection technology of the trace organic pollutants. The main technical principle is that selective soft ionization and quantitative detection of a sample to be detected are finally realized by combining the absorption ionization characteristic of molecules to be detected on multiphoton and flight time mass spectrum detection. Compared with other traditional ionization source detection technologies such as EI, CI, ultraviolet lamps and the like, the ionization source detection method has the advantages of being strong in selectivity, small in interference, few in ion fragments, strong in anti-pollution capacity and the like. Because trace substances such as dioxin and the like have the characteristics of complex components, large molecular weight, extremely low content and the like, the double-beam deep ultraviolet nanosecond laser is selected as the ionization source for detection.
The laser energy is an important index of a dioxin on-line monitoring system, and the accuracy and reliability of a detection result are directly determined by the quality of the energy intensity and the stability of the laser energy. Therefore, in order to visually control the output laser energy and improve the stability of the energy output of the whole laser system, the energy of each wave band for generating laser needs to be monitored in real time.
Currently, laser energy is monitored by directly contacting the laser with an energy probe, and then reading the laser energy through a connected gauge head. In the laser energy reading process, although the change fluctuation of the laser energy can be obtained in real time, the detection of the dioxin online monitoring system cannot be carried out, namely the laser energy detection and the laser participation ionization detection cannot be carried out simultaneously, and the change of the energy value when the laser participates in the ionization detection is a key technical index of the dioxin online monitoring system, so that the real-time change of the laser energy value is required to be obtained while the laser participation ionization detection is not hindered.
Disclosure of Invention
The invention aims to provide a double-beam laser system with laser energy monitoring and feedback and a method thereof, which can obtain a real-time laser energy value while not blocking laser to participate in ionization detection, and can perform feedback control on a crystal according to the real-time energy value to ensure the intensity and stability of laser energy output.
In order to achieve the purpose, the invention provides the following technical scheme:
a double-beam laser system with laser energy monitoring and feedback is characterized by comprising a laser, a double frequency crystal, a triple frequency crystal, a wavelength separating mirror, a resonant cavity, a beam combining sheet and a quintupling frequency crystal; the laser emits 1064nm laser to form a first light path, a frequency doubling crystal, a frequency tripling crystal, a wavelength separating mirror and a resonant cavity are sequentially arranged on the first light path, the wavelength separating mirror separates a path of 532nm laser to form a second light path, and the resonant cavity returns a path of 355nm laser to form a third light path; the beam combining sheet is arranged at the intersection of the second light path and the third light path, a path of composite light containing 355nm laser and 532nm laser is combined to form a fourth light path, and the quintuple frequency crystal is arranged on the fourth light path; laser energy monitoring and feedback systems are arranged at the double-frequency crystal and the triple-frequency crystal, and the corresponding crystal phase angle is fed back and controlled through detecting the laser energy value after the crystal in real time; and a wavelength tuning system is arranged at the resonant cavity, and the output wavelength is adjusted by rotating the BBO crystal in the resonant cavity.
Further, the laser energy monitoring and feedback system comprises a laser energy monitoring device, a feedback control device and an upper computer;
the laser energy monitoring device comprises a beam splitting sheet and a laser energy probe; the beam splitting sheet is arranged in the original light path and splits the beam in the original light path into a main light path and an auxiliary light path in a fixed proportion; the laser energy probe is arranged below the beam splitting sheet and is used for detecting the laser energy of the split secondary light path;
the feedback control device comprises a constant temperature cover, a hinged rod, a cam, an adjusting rod and a reset mechanism; the constant temperature cover is covered outside the crystal on the main light path to provide a constant temperature environment for the crystal; the hinge rod is arranged on the constant temperature cover; the first end of the adjusting rod is fixedly connected to the constant-temperature cover, the second end of the adjusting rod is abutted against the cam, and the rotation of the cam drives the constant-temperature cover to rotate around the hinge rod; the resetting mechanism is arranged below the constant-temperature cover and provides pressure for the constant-temperature cover to press the cam;
and the upper computer receives the detected laser energy value and sends a driving signal to control the cam to rotate.
Further, the feedback control device further comprises a fixing frame, the hinge rod is fixed on the fixing frame, and the reset mechanism is arranged between the fixing frame and the constant temperature cover.
Further, the reset mechanism is a spring.
Further, the constant temperature hood comprises a bottom plate, a heating layer, a temperature sensor, a hood body and a plane mirror; the heating layer surrounds the periphery of the bottom plate to form an accommodating cavity for placing crystals; the temperature sensor is arranged on the crystal and used for detecting the real-time temperature of the crystal; the cover body covers the outer side of the heating layer; the heating layer is characterized in that first through holes are formed in the opposite positions of two sides of the heating layer, second through holes are formed in the opposite positions of two sides of the cover body, the first through holes and the second through holes are located on the same straight line, and the plane mirror is installed in the second through holes in a sealing mode.
Furthermore, a laser energy monitoring device is arranged behind the quintupling frequency crystal.
Further, an optical filter is further arranged on the first light path, and the optical filter is arranged between the frequency tripling crystal and the wavelength separation mirror.
A control method of a double-beam laser system with laser energy monitoring and feedback is characterized by comprising the following steps:
s1, before the double-beam laser system works formally, the fixed proportion and the optimal phase angle of a main light path and a secondary light path in the laser energy monitoring devices at the two positions of the frequency doubling crystal and the frequency tripling crystal are respectively determined, and corresponding laser energy thresholds are set;
s2, starting a double-beam laser system, and monitoring laser energy values of all places in real time;
s3, if the laser energy value of a single position does not reach the corresponding laser energy threshold value, adjusting the corresponding crystal phase angle through a feedback control device until the laser energy threshold value is reached; if the laser energy values at multiple positions do not reach the corresponding laser energy threshold values, the corresponding crystal phase angles are sequentially adjusted in the direction from the upstream to the downstream of the light path until all the laser energy values reach the corresponding laser energy threshold values.
Further, in S1, the method for determining the fixed ratio between the main optical path and the sub optical path is as follows: and pre-starting the double-beam laser system, respectively detecting the laser energy values of the main light path and the auxiliary light path, wherein the ratio of the laser energy value of the main light path to the laser energy value of the auxiliary light path is the fixed proportion.
Further, in S3, a specific method for adjusting the corresponding crystal phase angle is as follows:
determining whether the current crystal is at the optimal phase angle; if the phase angle is not at the optimal phase angle, adjusting the crystal phase angle to the optimal phase angle; and if the crystal is in the optimal phase angle, controlling the crystal to rotate from the minimum phase angle to the maximum phase angle in real time according to the amplitude of the unit phase angle, recording the corresponding laser energy value at the same time, forming a new curve graph of the laser energy value changing along with the phase angle, selecting the phase angle corresponding to the position with the maximum laser energy value as the optimal phase angle, and adjusting the crystal to the new optimal phase angle.
Compared with the prior art, the invention has the beneficial effects that: the invention carries out feedback control on the phase angle of the crystal in the light path through the laser energy detected in real time, thereby ensuring the intensity and stability of the laser energy output. Meanwhile, in the detection process of the laser energy, the beam splitting of the light path in a fixed proportion achieves the aim of obtaining the real-time change of the laser energy value without influencing the laser ionization detection.
Drawings
Fig. 1 is a schematic overall structure diagram of an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a laser energy monitoring and feedback system according to an embodiment of the invention.
Fig. 3 is a perspective view of an on-line monitoring device according to an embodiment of the invention.
Fig. 4 is a perspective view of a feedback control device according to an embodiment of the invention.
Fig. 5 is a cross-sectional view of a feedback control device according to an embodiment of the present invention.
Fig. 6 is another angle sectional view of the feedback control device according to an embodiment of the present invention.
Fig. 7 is a schematic structural view of a constant temperature cover according to an embodiment of the present invention.
In the figure: 1. a laser; 2. a frequency doubling crystal; 3. a frequency tripling crystal; 4. a wavelength separating mirror; 5. a resonant cavity; 6. combining the binding sheets; 7. a quintupling frequency crystal; 71. a laser energy monitoring device; 72. a first 213nm mirror; 73. a second 213nm mirror; 31. an optical filter; 8. a first laser energy monitoring and feedback system; 9. a second laser energy monitoring and feedback system; 10. a wavelength tuning system; 101. a first 1064nm mirror; 102. a second 1064nm mirror; 103. a first 355nm mirror; 104. a second 355nm mirror; 105. a 532nm mirror; 81. a laser energy monitoring device; 82. a feedback control device; 83. an upper computer; 11. splitting a beam; 12. a laser energy probe; 13. a base; 14. a connecting rod; 21. a constant temperature cover; 211. a hinge hole; 22. a hinged lever; 23. a cam; 24. adjusting a rod; 25. a reset mechanism; 26. a fixed mount; 27. a mechanical motor; 3. an upper computer; 41. a base plate; 411. folding edges; 42. a heating layer; 421. a first through hole; 43. a temperature sensor; 44. a cover body; 441. a second through hole; 45. a plane mirror; 46. and a fin.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows:
referring to fig. 1, the present invention provides a dual-beam laser system with laser energy monitoring and feedback, which includes a laser 1, a frequency-doubling crystal 2, a frequency-tripling crystal 3, a wavelength splitter 4, a resonant cavity 5, a beam combiner 6 and a frequency-quintupling crystal 7 disposed on an optical platform.
The laser is a YAG laser, 1064nm laser is emitted to form a first light path, and a frequency doubling crystal 2, a frequency tripling crystal 3, a wavelength separation mirror 4 and a resonant cavity 5 are sequentially arranged on the first light path. The frequency doubling crystal 2 is an LBO crystal, and generates composite light consisting of 532nm laser and part of 1064nm laser by the nonlinear effect; similarly, the frequency tripling crystal 3 is also an LBO crystal, and generates composite light consisting of 355nm laser, 532nm laser and a small amount of 1064nm laser by the nonlinear effect; the wavelength separation mirror 4 separates a path of composite light consisting of 532nm laser and a small amount of 1064nm laser to form a second light path, and only 355nm laser is reserved on the first light path; 355nm laser enters the resonant cavity 5 to participate in oscillation and outputs required UV light.
In this embodiment, the resonant cavity 5 is an OPO resonant cavity, and is composed of a Porro prism, a wavelength separation lens, a BBO crystal, an OPO output mirror, and other mechanisms. Realize the oscillation and conversion of 355nm light, and then output the UV light of required wavelength. According to the nonlinear optical characteristic of the BBO crystal, the wavelength of the UV light output by the resonant cavity can be made to meet the actual requirement by adjusting the phase angle of the BBO crystal in the resonant cavity.
Meanwhile, the resonant cavity 5 returns a part of 355nm laser to form a third optical path; the beam combining sheet 6 is arranged at the intersection of the second light path and the third light path, a path of composite light containing 355nm laser and 532nm laser is combined to form a fourth light path, and the quintuple frequency crystal 7 is arranged on the fourth light path; the quintuple frequency crystal 7 is a BBO crystal, and a beam of 213nm laser is generated by the sum frequency effect of the crystal, so that the output of the other beam of 213nm laser meeting the requirement of dioxin detection is completed.
In the second optical path of this embodiment, a small amount of 1064nm laser is not needed by the system, and this scheme selects to filter it. Therefore, an optical filter 31 is further arranged on the first light path, and the optical filter 31 is arranged between the frequency tripling crystal 3 and the wavelength separation mirror 4 and used for filtering 1064nm laser.
Meanwhile, in order to control the whole optical path of the double-beam laser system, reflectors are arranged at each position, namely a first 1064nm reflector 101 and a second 1064nm reflector 102 between the laser 1 and the frequency doubling crystal 2; a first 355nm mirror 103 between the wavelength-separating mirror 4 and the resonant cavity 5; a second 355nm mirror 104 between the first 355nm mirror 103 and the beam combining sheet 6; a 532nm mirror 105 between the wavelength separation mirror 4 and the beam combining plate 6; and a first 213nm mirror 72 and a second 213nm mirror 73 after the frequency quintupling crystal 7.
The laser energy is an important index of a dioxin on-line monitoring system, and the accuracy and reliability of a detection result are directly determined by the quality of the energy intensity and the stability of the laser energy. Therefore, in order to visually control the output laser energy and improve the stability of the energy output of the whole laser system, in this embodiment, laser energy monitoring and feedback systems, namely a first laser energy monitoring and feedback system 8 and a second laser energy monitoring and feedback system 9, are arranged at the frequency doubling crystal 2 and the frequency tripling crystal 3. By detecting the laser energy value output by the crystal in real time, the phase angle of the corresponding crystal (LBO crystal) is fed back and controlled under the condition that the detected laser energy value does not meet the requirement, and the stability of the finally output laser energy is further ensured. In addition, a wavelength tuning system 10 is arranged at the resonant cavity 5, and the output wavelength is adjusted by rotating the phase angle of the BBO crystal in the resonant cavity 5. The two phase angle adjustment principles are as follows: the LBO crystal has high energy conversion efficiency, wide phase angle tuning range, large energy change caused by unit phase angle, and optimal phase angle to ensure that the energy output reaches the optimum. According to the nonlinear optical characteristics of the BBO crystal, the output wavelength of the BBO crystal changes correspondingly with the rotation of the phase angle of the BBO crystal.
The first laser energy monitoring and feedback system 8 and the second laser energy monitoring and feedback system 9 are identical in structure. Taking the first laser energy monitoring and feedback system 8 as an example, referring to fig. 2, the first laser energy monitoring and feedback system 8 includes a laser energy monitoring device 81, a feedback control device 82, and an upper computer 83.
The laser energy monitoring device 81 comprises a beam splitting sheet 11 and a laser energy probe 12. The beam splitting sheet 11 is installed in the original light path and splits the original light path into a main light path and an auxiliary light path in a fixed proportion; the laser energy probe 12 is installed below the beam splitting sheet 11, and detects the laser energy of the split sub-optical path. Specifically, the beam splitting sheet can transmit 98% -99% of laser, namely the laser energy of the main light path accounts for 98% -99% of the original light path, and the laser energy of the secondary light path accounts for 1% -2% of the original light path. In one embodiment, the laser energy of the main optical path accounts for 98% of the original optical path, and the laser energy of the sub optical path accounts for 2% of the original optical path. The fixed ratio is 49, and the laser energy of the sub-optical path detected by the laser energy probe 12 multiplied by the fixed ratio 49 is the laser energy of the main optical path. After the on-line monitoring device 1 is set, the relative proportion is not changed, so that the specific value of the fixed proportion can be obtained by respectively detecting the laser energy values of the main light path and the auxiliary light path before formal laser ionization.
Referring to fig. 3, in order to implement the installation of the beam splitting sheet 11 and the laser energy probe 12, the laser energy probe 12 and the connecting rod 14 are fixedly installed on the base 13, the beam splitting sheet 11 is fixedly installed on the top of the connecting rod 14, and the relative positions of the beam splitting sheet 11 and the laser energy probe 12 enable the secondary optical path to be detected by the laser energy probe 12.
Referring to fig. 2 and 4, the feedback control device 82 includes a thermostatic cover 21, a hinge lever 22, a cam 23, an adjustment lever 24, and a return mechanism 25. The constant temperature cover 21 is covered outside the frequency doubling crystal 2 on the main light path to provide a constant temperature environment for the frequency doubling crystal 2. The hinge rod 22 is arranged on the thermostatic cover 21, and the thermostatic cover 21 can rotate around the straight line where the hinge rod 22 is located. The first end of the adjusting rod 24 is fixedly connected to the constant temperature hood 21, the second end of the adjusting rod is abutted to the cam 23, and the rotation of the cam 23 drives the constant temperature hood 21 to rotate around the hinged rod 22, so that the phase angle adjustment of the frequency doubling crystal 2 is realized, and the adjustment of the laser energy value output by the crystal 47 is realized. The reset mechanism 25 is arranged below the constant temperature cover 21 and provides pressure for the constant temperature cover 21 to press the cam 23, so that the angle of the constant temperature cover 21 can be reset and adjusted. It is worth mentioning that the cam 23 is driven in rotation by a mechanical motor 27.
The upper computer 83 is electrically connected with the laser energy probe 12 and the mechanical motor 27. The upper computer 3 receives the laser energy value detected by the laser energy probe 12, calculates the laser energy value of the main optical path according to the fixed proportion, starts a driving signal according to the actual requirement of a user to control the cam 23 to rotate, and adjusts the finally output laser energy value of the main optical path.
Referring to fig. 4 and 5, in order to implement the installation of each component on the feedback control device 82, the feedback control device further includes a fixing frame 26, the hinge rod 22 is fixed on the vertical portion of the fixing frame 26, and a hinge hole 211 for the hinge rod 22 to penetrate is formed in the position of the thermostatic cover 21 corresponding to the hinge rod 22, so that the function of rotating the thermostatic cover 21 around the hinge rod 22 is implemented. The reset mechanism 25 is a spring, is arranged between the bottom of the fixed frame 26 and the bottom of the constant temperature cover 21, and provides upward pressure for the constant temperature cover 21, so that the adjusting rod 24 is in close contact with the cam 23 at any time.
Referring to fig. 6 and 7, the thermostat cover includes a base plate 41, a heating layer 42, a temperature sensor 43, a cover 44, and a plane mirror 45.
The heating layer 42 surrounds the periphery of the bottom plate 41 to form a containing cavity for placing the frequency doubling crystal 2. The heating layer 42 is a temperature-controllable electric heating plate, and can be used for heating the frequency doubling crystal 2 in the accommodating cavity.
The temperature sensor 43 is arranged on the frequency doubling crystal 2 and is used for detecting the real-time temperature of the frequency doubling crystal 2; when the temperature sensor 43 detects that the temperature of the frequency doubling crystal 2 is reduced, the power of the heating layer 42 is increased, otherwise, the power of the heating layer 42 is reduced or the heating layer 42 stops working, so that the effect of keeping the temperature of the frequency doubling crystal 2 constant is achieved, and the performance parameters of the laser are ensured.
The cover body 44 covers the outer side of the heating layer 42 to isolate the heating layer 42 and the frequency doubling crystal 2 from the outside, so that the crystal is in a relatively stable constant-temperature and constant-humidity internal environment. In this embodiment, in order to enhance the sealing performance, the bottom plate 41 extends horizontally outward to form a folded edge 411, and the lower edge of the cover 44 is attached to the folded edge 411. It is worth mentioning that the bottom plate 41 and the cover 44 are made of heat insulating material to avoid heat exchange with the external connection as much as possible.
In order to facilitate the passing of laser, a first through hole 421 is disposed at a position opposite to two sides of the heating layer 42, a second through hole 441 is disposed at a position opposite to two sides of the cover 44, the first through hole 421 and the second through hole 441 are on the same straight line to form a passage for the passing of laser, and it is worth mentioning that the frequency doubling crystal 2 is on the straight line. Meanwhile, the plane mirror 45 is installed in the second through hole 441, so that a sealing effect is achieved.
The heating plate further comprises fins 46, and the fins 46 are uniformly arranged on the inner side of the heating layer 42 except for the first through holes 421. In this embodiment, the heating layer 42 has a smaller thickness and a larger heat conductivity coefficient, so as to ensure no heat loss between the heating layer and the fins, and the fins 46 have uniform distribution and the same temperature, so as to uniformly heat the double-frequency crystal 2.
A laser energy monitoring device 71 is arranged behind the quintuple frequency crystal 7 and used for detecting the energy value of 213nm laser, and the mechanism and the implementation principle of the laser energy monitoring device 71 are the same as those of the laser energy monitoring device 81, and are not described again here. Laser energy monitoring devices are respectively arranged at the 355nm laser input and the 355nm laser output of the resonant cavity 5 and used for detecting 355nm laser energy input into the resonant cavity 5 and 355nm laser energy returned by the resonant cavity 5, and the mechanism and the realization principle are also the same as those of the laser energy monitoring device 81.
The wavelength tuning system 10 is used for adjusting the phase angle of the BBO crystal, and has the same structure as the feedback control device 82, and will not be described in detail herein.
Example two:
the invention also provides a control method of the double-beam laser system with laser energy monitoring and feedback, which comprises the following steps:
and S1, before the double-beam laser system works formally, respectively determining the fixed proportion and the optimal phase angle of a main light path and a secondary light path in the laser energy monitoring devices at the two positions of the frequency doubling crystal and the frequency tripling crystal, and setting corresponding laser energy thresholds.
The method for determining the fixed ratio is as follows: and pre-starting the double-beam laser system, respectively detecting the laser energy values of the main light path and the auxiliary light path, wherein the ratio of the laser energy value of the main light path to the laser energy value of the auxiliary light path is the fixed proportion. Under the condition that the state of the laser energy monitoring device is not changed, the fixed proportion is a fixed value.
The optimal phase angle is the phase angle of the corresponding crystal when the maximum laser energy value is detected, and the determination method of the optimal phase angle is as follows: and adjusting the phase angle of the crystal in the original light path, and simultaneously recording the laser energy value of the main light path to form a curve graph of the laser energy value changing along with the phase angle, wherein the maximum laser energy value is recorded as the optimal laser energy value, and the corresponding phase angle is recorded as the optimal phase angle.
S2, starting a double-beam laser system, and monitoring laser energy values of all places in real time;
s3, if the laser energy value of a single position does not reach the corresponding laser energy threshold value, adjusting the corresponding crystal phase angle through a feedback control device until the laser energy threshold value is reached; if the laser energy values at multiple positions do not reach the corresponding laser energy threshold values, the corresponding crystal phase angles are sequentially adjusted in the direction from the upstream to the downstream of the light path until all the laser energy values reach the corresponding laser energy threshold values. The reason for the reason according to the direction from the upstream to the downstream of the optical path is that the laser energy value at the upstream of the optical path directly affects the laser energy value at the downstream, for example, at a certain time, the laser energy values detected at the frequency doubling crystal 2 and the frequency tripling crystal 3 do not reach the corresponding threshold, the phase angle of the frequency doubling crystal 2 is adjusted first, then the laser energy values at two positions are detected, and both the laser energy values reach the threshold, so that the crystal phase angle adjustment of the frequency tripling crystal 3 can be reduced.
It should be noted that the specific method for adjusting the corresponding crystal phase angle in S3 is as follows:
determining whether the current crystal is at the optimal phase angle; if the phase angle is not at the optimal phase angle, adjusting the crystal phase angle to the optimal phase angle; and if the crystal is in the optimal phase angle, controlling the crystal to rotate from the minimum phase angle to the maximum phase angle in real time according to the amplitude of the unit phase angle, recording the corresponding laser energy value at the same time, forming a new curve graph of the laser energy value changing along with the phase angle, selecting the phase angle corresponding to the position with the maximum laser energy value as the optimal phase angle, and adjusting the crystal to the new optimal phase angle.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (8)
1. A double-beam laser system with laser energy monitoring and feedback is characterized by comprising a laser, a double frequency crystal, a triple frequency crystal, a wavelength separating mirror, a resonant cavity, a beam combining sheet and a quintupling frequency crystal; the laser emits 1064nm laser to form a first light path, a frequency doubling crystal, a frequency tripling crystal, a wavelength separating mirror and a resonant cavity are sequentially arranged on the first light path, the wavelength separating mirror separates a path of 532nm laser to form a second light path, and the resonant cavity returns a path of 355nm laser to form a third light path; the beam combining sheet is arranged at the intersection of the second light path and the third light path, a path of composite light containing 355nm laser and 532nm laser is combined to form a fourth light path, and the quintuple frequency crystal is arranged on the fourth light path; laser energy monitoring and feedback systems are arranged at the double-frequency crystal and the triple-frequency crystal, and the corresponding crystal phase angle is fed back and controlled through detecting the laser energy value after the crystal in real time; a wavelength tuning system is arranged at the resonant cavity, and the output wavelength is adjusted by rotating the BBO crystal in the resonant cavity;
the laser energy monitoring and feedback system comprises a laser energy monitoring device, a feedback control device and an upper computer;
the laser energy monitoring device comprises a beam splitting sheet and a laser energy probe; the beam splitting sheet is arranged in the original light path and splits the beam in the original light path into a main light path and an auxiliary light path in a fixed proportion; the laser energy probe is arranged below the beam splitting sheet and is used for detecting the laser energy of the split secondary light path;
the feedback control device comprises a constant temperature cover, a hinged rod, a cam, an adjusting rod and a reset mechanism; the constant temperature cover is covered outside the crystal on the main light path to provide a constant temperature environment for the crystal; the hinge rod is arranged on the constant temperature cover; the first end of the adjusting rod is fixedly connected to the constant-temperature cover, the second end of the adjusting rod is abutted against the cam, and the rotation of the cam drives the constant-temperature cover to rotate around the hinge rod; the resetting mechanism is arranged below the constant-temperature cover and provides pressure for the constant-temperature cover to press the cam;
the upper computer receives the detected laser energy value and sends a driving signal to control the cam to rotate;
the feedback control device further comprises a fixing frame, the hinge rod is fixed on the fixing frame, and the reset mechanism is arranged between the fixing frame and the constant-temperature cover.
2. A dual beam laser system with laser energy monitoring and feedback as described in claim 1 wherein said return mechanism is a spring.
3. A dual beam laser system with laser energy monitoring and feedback as claimed in claim 1 wherein the thermostatic enclosure comprises a base plate, a heating layer, a temperature sensor, an enclosure and a flat mirror; the heating layer surrounds the periphery of the bottom plate to form an accommodating cavity for placing crystals; the temperature sensor is arranged on the crystal and used for detecting the real-time temperature of the crystal; the cover body covers the outer side of the heating layer; the heating layer is characterized in that first through holes are formed in the opposite positions of two sides of the heating layer, second through holes are formed in the opposite positions of two sides of the cover body, the first through holes and the second through holes are located on the same straight line, and the plane mirror is installed in the second through holes in a sealing mode.
4. A dual-beam laser system with laser energy monitoring and feedback as claimed in claim 1 wherein a laser energy monitoring device is disposed behind the quintuple frequency doubling crystal.
5. The dual-beam laser system with laser energy monitoring and feedback of claim 1, wherein a filter is further disposed on the first optical path, and the filter is disposed between the frequency tripling crystal and the wavelength separation mirror.
6. A control method of the dual-beam laser system with laser energy monitoring and feedback according to any one of claims 1 to 4, comprising the steps of:
s1, before the double-beam laser system works formally, the fixed proportion and the optimal phase angle of a main light path and a secondary light path in the laser energy monitoring devices at the two positions of the frequency doubling crystal and the frequency tripling crystal are respectively determined, and corresponding laser energy thresholds are set;
s2, starting a double-beam laser system, and monitoring laser energy values of all places in real time;
s3, if the laser energy value of a single position does not reach the corresponding laser energy threshold value, adjusting the corresponding crystal phase angle through a feedback control device until the laser energy threshold value is reached; if the laser energy values at multiple positions do not reach the corresponding laser energy threshold values, the corresponding crystal phase angles are sequentially adjusted in the direction from the upstream to the downstream of the light path until all the laser energy values reach the corresponding laser energy threshold values.
7. A method for controlling a dual-beam laser system with laser energy monitoring and feedback as claimed in claim 6, wherein the fixed ratio of the main beam path and the sub beam path in S1 is determined as follows: and pre-starting the double-beam laser system, respectively detecting the laser energy values of the main light path and the auxiliary light path, wherein the ratio of the laser energy value of the main light path to the laser energy value of the auxiliary light path is the fixed proportion.
8. The method for controlling a dual-beam laser system with laser energy monitoring and feedback as claimed in claim 6, wherein the specific method for adjusting the corresponding crystal phase angle in S3 is as follows:
determining whether the current crystal is at the optimal phase angle; if the phase angle is not at the optimal phase angle, adjusting the crystal phase angle to the optimal phase angle; and if the crystal is in the optimal phase angle, controlling the crystal to rotate from the minimum phase angle to the maximum phase angle in real time according to the amplitude of the unit phase angle, recording the corresponding laser energy value at the same time, forming a new curve graph of the laser energy value changing along with the phase angle, selecting the phase angle corresponding to the position with the maximum laser energy value as the optimal phase angle, and adjusting the crystal to the new optimal phase angle.
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| US7916764B2 (en) * | 2006-10-25 | 2011-03-29 | Coherent, Inc. | Output power control for harmonic-generating laser |
| CN102088160B (en) * | 2010-04-20 | 2012-06-27 | 中国科学院理化技术研究所 | Frequency-doubled laser with frequency doubling device |
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Denomination of invention: Dual beam laser system with laser energy monitoring and feedback and its control method Effective date of registration: 20230307 Granted publication date: 20210810 Pledgee: Hangzhou Fuyang sub branch of China Everbright Bank Co.,Ltd. Pledgor: ZHEJIANG FUCHUNJIANG ENVIRONMENTAL TECHNOLOGY RESEARCH Co.,Ltd. Registration number: Y2023980033953 |
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