CN104184029B - Frequency locking method used for tunable laser in pulse type laser system - Google Patents
Frequency locking method used for tunable laser in pulse type laser system Download PDFInfo
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- CN104184029B CN104184029B CN201410403052.3A CN201410403052A CN104184029B CN 104184029 B CN104184029 B CN 104184029B CN 201410403052 A CN201410403052 A CN 201410403052A CN 104184029 B CN104184029 B CN 104184029B
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Abstract
The invention discloses a frequency locking method used for a tunable laser in a pulse type laser system. In the pulse interval time of the pulse type laser system, modulation is conducted on the frequency of laser output by the tunable seed laser through a servo control system and the light intensity can change along with the frequency after the laser passes through a frequency reference device; a photoelectric detector and a digital acquisition card are used for feeding back light intensity information to the servo control system, the servo control system output signals according to feedback data so as to enable the seed laser to be kept at the set locking frequency until a next pulse ends and the scanning process and the locking process are repeated. Thus, it can be guaranteed that the frequency of the laser output by the seed laser is kept on a locking point before every pulse light comes. The frequency locking method is simple and easy to implement and enables the locking frequency of the tunable seed laser to be locked on any frequency point within the reference range of the frequency reference device, the frequency is kept stable at the cavity die locking stage of a pulse system and no modulation is needed.
Description
Technical field
The present invention relates to laser frequency lock technical field, specifically one kind swash for tunable in pulse type laser system
The frequency locking method of light device.
Background technology
With the development of laser technology, its application is more and more wider.In some application scenarios, such as pulsed difference
Absorption lidar and molecular reaction dynamics research, very high to the live width and stability requirement of pulse laser frequency, at present greatly
Adopt the optical parametric oscillator with reference to injection seeded for yag crystal (nd:yag) pulse laser of injection seeded more
(optical parametric oscillator) is realizing.Transit chamber mode locking technology, can make the pulse light frequency of output
Continuous light is consistent with injection seeded, and therefore the degree of stability of pulse light frequency is directly determined by the degree of stability of seed light frequency.
The tunable laser frequency locking method commonly used at present has lateral edges lock-in techniques and pdh lock-in techniques.The former
Ultimate principle be light intensity after detection laser light frequency reference device (etalon, gas absorption cell etc.), keyed end is set
Put at the halfwidth degree of transmitted spectrum side, once the frequency transmitting of flashlight offsets, the light intensity receiving also can be sent out therewith
Changing, makes it return to keyed end by the frequency that closed loop feedback system adjusts laser.The ultimate principle of the latter is to pass through
Outside chamber or intracavity frequency modulation technology modulate laser frequency, laser is received by a photoelectric detector behind f-p chamber, then will detect
To the mixing of signal and modulated signal to obtain error signal, thus by laser lock-on to specific frequency.
However, these methods all have the shortcomings that certain, the former easily be subject to external environment interference and lasting accuracy is not high.Afterwards
Person, according to outer cavity modulation, can make device complicated；Adjust according to intracavity, then so that output laser frequency is constantly in modulation
State.And, both also there is a problem of one common, if laser instrument is made frequency there occurs significantly by certain interference
Change frequency reference scope (bandwidth of such as etalon and the absorption peak width of molecule so that beyond frequency reference device
Degree) after, may result in loss of lock.
These methods are applicable to the occasion of continuous frequency locking, are not appropriate for pulse type laser system.There is no one kind at present
It can be avoided that disadvantages mentioned above, simple and seed laser be applied to pulse type laser system frequency locking method.
Content of the invention
The present invention is to solve the above problems it is proposed that a kind of frequency of the tunable laser being applied to pulse type laser system
Rate locking means, technical scheme is as follows:
This method can be realized with the device shown in Fig. 1, comprising: tunable seed laser, frequency reference device (standard
Tool, gas absorption cell etc.), photodetector, Data Acquisition Card, servo-control system.The company of tunable seed laser output
A continuous laser part is injected in pulse type laser system, and another part is used for frequency lock.Pulse type laser system transit chamber
Mode locking technology, can export the pulse laser of single longitudinal mode and laser frequency is consistent with injection seeded light.Tunable seed swashs
Light device can export the frequency of laser according to the signal change that servo-control system is given, and frequency reference device swashs to different frequency
The transmitance of light is different, and the optical signal that photodetector will transmit through is converted to the signal of telecommunication, and Data Acquisition Card is defeated by photodetector
Go out electric signal digitising after feed back to servo-control system, servo-control system according to this feedback signal control tunable seed
Laser instrument makes its frequency stable on keyed end.
The concrete control flow of the method is as follows:
Fig. 2 is this device work wave sequential chart.t0Moment pulse laser emission terminates；t1Moment servo-control system is opened
Begin output scanning signal, and now tunable laser output laser frequency can change with scanning signal change, for convenience
For the sake of, the linear Long-term change trend of the laser frequency shown in figure, in fact the method be equally applicable to the occasion of nonlinear change.
Because frequency reference device is different to the transmitance of different frequency laser, the signal of therefore photodetector output also can become
Change, shown in figure is the situation after gas absorption cell；t2Moment corresponding laser frequency ν1It is the frequency needing locking
Point, the transmitance at this frequency and frequency reference device center frequency ν0The ratio of the transmitance at place is a constant c, records t3
Moment mid frequency ν0The amplitude of place's photodetector output signal is v0, this mid frequency is the value of an absolute stability, and
Transmitance at this frequency is not maximum (etalon) is exactly minimum (gas cell), so this point can be easily found.
Then find signal amplitude v1=c*v0The scanning signal value of corresponding servosystem output it is clear that two values can be found, but
Both have sequencing in time, select that value needing to be designated as d1.t4The moment positive direction end of scan, starts along negative side
To scanning, in t5Moment reaches corresponding output valve d of keyed end1, scanning starts until next time to be maintained at this value ever since.t5
To t6This period shorter it is believed that seed laser export laser frequency within this time kept stable, arteries and veins
The formula laser system of punching during this period of time completes chamber mode locking so that the single longitudinal mode pulse light frequency of output is also ν1.At each
Repeat scanner uni lock program it is ensured that the output frequency of pulse laser is locked in ν for a long time during pulse spacing1.
The method that the present invention scans frequency locking by the pulse spacing, can be by the frequency lock of tunable seed laser in frequency
Arbitrary frequency point in rate parametric device term of reference；Keep stable in chamber mode locking stage frequency and no modulate；Even if seed
The frequency of laser instrument is subject to the interference of certain factor within the specific limits saltus step to occur, as long as enabling rate of scanning covering frequence
The term of reference of parametric device, all without the phenomenon that losing lock occurs；Whole frequency locking device is simple, can obtain very high frequency
Rate degree of stability.
Brief description
Fig. 1: apparatus structure schematic diagram of the present invention.
The work wave sequential chart of Fig. 2: device of the present invention.
Specific embodiment
As shown in figure 1, wherein pulse type laser system is the optical parametric oscillator of injection seeded, can be by 532nm's
Pulsed light is converted to the pulsed light of 935nm, completes chamber mode locking using interferometric method, and pulse repetition is 10hz；Tunable seed swashs
Light device is semiconductor laser, can change the frequency of output laser by current-modulation, and its outside control circuit can be by
Voltage modulation signal is converted into current modulated, and voltage is about 10pm/v, by output wave with the corresponding relation of optical maser wavelength
Length is adjusted on the absworption peak 935.6849nm of steam, and by the fiber optic splitter of 95:5, output laser is divided into 2 bundles, and 95%
Energy injection to optical parametric oscillator as seed light, the energy being left 5% is used for frequency lock；Frequency reference device is
Optical fiber low pressure steam gas cell, the inside is filled with pure water vapour, and air pressure is 2500pa, and absorption length is 1.6m；Photodetector is adopted
It is photodiode, and current signal is enlarged into by voltage signal by trans-impedance amplifier；The sample rate of Data Acquisition Card
It is 100m and 14bit respectively with resolution, voltage acquisition scope is 0～2.4v；Servo-control system is by field programmable gate array
(fpga) form with digital to analog converter (dac), the resolution of dac is 12bit, and output voltage range is 0～2.4v, output voltage
It is directly used in the frequency of semiconductor laser modulation.
As shown in Fig. 2 t0Moment impulse ejection terminates, in t after delay 2ms1Moment fpga controls dac to start with 0.01v's
Stepping exports scanning voltage, changes output valve every time, and the frequency of semiconductor laser also can change, therewith now by gas
Light intensity behind body pond also can change, and Data Acquisition Card is recorded photodetector output signal amplitude and fed back to fpga；
Whole scanning process is 15ms, in t4Moment terminates, and then fpga, according to the synopsis of each dac output valve and sampled value, looks for
To v1=1.2v0Locating corresponding dac output valve is d1；Subsequently fpga starts to control dac output valve to be gradually reduced, after 10ms
t5Moment reaches d1；In t5To t6In this 73ms, dac output remains d1, seed laser frequency stable within this time exists
ν1, optical parametric oscillator completes chamber mode locking during this period, and final output frequency is ν1Pulsed light.In the next pulse spacing
Interior repetition is above to be operated, and so ensures that the frequency of seed laser is locked in ν for a long time in the chamber mode locking stage1.
Particular embodiments described above, has carried out detailed further to the purpose of invention, technical scheme and beneficial effect
Illustrate, it is emphasized that the foregoing is only the specific embodiment of the present invention, be not limited to the present invention, every
Within the spirit and principles in the present invention, any modification, equivalent substitution and improvement done etc., should be included in the guarantor of the present invention
Within the scope of shield.
Claims (1)
1. in a kind of system for pulse type laser the frequency locking method of tunable laser it is characterised in that method is as follows:
Within the interpulse period of pulse type laser system, by servo-control system, the output of tunable seed laser is swashed
The frequency of light is modulated, and laser light intensity after frequency reference device can change with frequency change；Using photodetector
With Data Acquisition Card, intensity signal is fed back to servo-control system, according to intensity signal feedback data, servo-control system is defeated
Go out signal so that seed laser is maintained at the locking frequency of setting until next end-of-pulsing, then repeat above scanner uni lock
Determine process, the frequency this ensures that thering tunable seed laser output laser is held at locking before the arrival of each pulsed light
In fixed point；This method optional frequency in frequency reference device term of reference by the frequency lock of tunable seed laser
Point, stablizes in the chamber mode locking stage keep frequency of pulse type laser system and no modulates.
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| CN104568386B (en) * | 2014-12-30 | 2018-02-09 | 北京航天易联科技发展有限公司 | A kind of optical maser wavelength screening technique and its device |
| CN110501728B (en) * | 2018-05-16 | 2022-03-29 | 清华大学 | Frequency discrimination method and device for time hopping signal of positioning base station |
| CN112038881A (en) * | 2020-09-02 | 2020-12-04 | 山西大学 | Pump optical cavity enhanced double-resonance optical parametric oscillator and efficient conversion method |
| CN114295224B (en) * | 2021-11-30 | 2024-03-22 | 天津津航技术物理研究所 | System and method for adjusting line frequency of infrared TDI detector |
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| US5400351A (en) * | 1994-05-09 | 1995-03-21 | Lumonics Inc. | Control of a pumping diode laser |
| US5450207A (en) * | 1993-07-16 | 1995-09-12 | Cymer Laser Technologies | Method and apparatus for calibrating a laser wavelength control mechanism |
| US6542523B1 (en) * | 1998-01-30 | 2003-04-01 | Ando Electric Co., Ltd. | Wavelength-variable light source apparatus |
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| CN101039010A (en) * | 2007-04-27 | 2007-09-19 | 中国科学院上海光学精密机械研究所 | Method for controlling cavity length of seed injection laser driven cavity and its laser |
| CN101604815A (en) * | 2009-06-26 | 2009-12-16 | 哈尔滨工业大学（威海） | The laser frequency stabiliz ation method of a kind of control impuls laser settling time |
| CN101861684A (en) * | 2007-10-15 | 2010-10-13 | 奥兰若技术公共有限公司 | Laser light source and method of operating the same |
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| US5450207A (en) * | 1993-07-16 | 1995-09-12 | Cymer Laser Technologies | Method and apparatus for calibrating a laser wavelength control mechanism |
| US5400351A (en) * | 1994-05-09 | 1995-03-21 | Lumonics Inc. | Control of a pumping diode laser |
| US6542523B1 (en) * | 1998-01-30 | 2003-04-01 | Ando Electric Co., Ltd. | Wavelength-variable light source apparatus |
| CN1819377A (en) * | 2005-02-04 | 2006-08-16 | Jds尤尼弗思公司 | Passively q-switched laser with adjustable pulse repetition rate |
| CN101039010A (en) * | 2007-04-27 | 2007-09-19 | 中国科学院上海光学精密机械研究所 | Method for controlling cavity length of seed injection laser driven cavity and its laser |
| CN101861684A (en) * | 2007-10-15 | 2010-10-13 | 奥兰若技术公共有限公司 | Laser light source and method of operating the same |
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