Control method of seed injection type single-frequency pulse laser

Abstract

The invention provides a control method of a seed injection type single-frequency pulse laser, and the method comprises the steps: recognizing the peak time and peak height of a resonance signal at the rising edge of piezoelectric ceramic scanning voltage, pre-judging a peak at the falling edge, recognizing the voltage of the resonance signal within the time range of the pre-judging peak, and starting the control of the seed injection type single-frequency pulse laser when the voltage of the resonance signal is higher than a threshold judgment voltage. When the piezoelectric ceramic is used, a trigger signal is sent out, stable single-frequency pulse laser output is achieved, and the injection locking mode has lower scanning voltage, so that the piezoelectric ceramic has longer service life and higher reliability; that is to say, the problems of high hardware cost, high scanning voltage and low frequency stability of the single-frequency pulse laser are solved, and the large-energy single-frequency pulse laser with high anti-interference capability and high frequency stability can be output.

Description

Technical Field

[0001] The invention belongs to the technical field of single-frequency lasers, and in particular relates to a control method for a seed-injection type single-frequency pulse laser. Background Art

[0002] A single-frequency pulse laser is a laser that outputs a single frequency and pulses laser light. This type of laser is widely used in the fields of differential absorption laser radar, wind laser radar, and coherent imaging laser radar.

[0003] By seed injection, injection locking technology can be used to achieve high-energy single-frequency pulse laser output. The basic principle is: the single-frequency continuous laser output by the single-frequency seed laser is injected into the slave Q-switched laser, and the single-frequency laser output of the pulse laser is achieved by controlling the cavity length to resonate with the single-frequency seed laser and trigger Q-switching. At present, there are still problems such as high scanning voltage, high hardware cost, and frequency stability that needs to be improved in the injection locking control method. Patent CN112636145A discloses an injection locking method, which changes the cavity length through piezoelectric ceramics. When two resonance signal peaks are scanned on the rising edge, the time of occurrence of the third peak is judged, and a trigger signal is given 150-200μs in advance to achieve single-frequency pulse laser output. This method requires scanning at least three resonance peaks, and the resonance cavity corresponding to the scanning voltage needs to cover at least three free spectrum regions, which increases the complexity of the amplifier circuit and reduces the service life of the piezoelectric ceramics. Patent CN104393477A discloses an injection locking method, which controls the cavity length through two piezoelectric ceramics. The first piezoelectric ceramic is used to scan the cavity length through a high-frequency sine wave, and the phase of the resonant signal in the sine wave is detected in each cycle. A bias voltage is applied to the second piezoelectric ceramic to correct the phase of the resonant signal in the next cycle, and finally the peak value is reached at the ideal point, a trigger signal is given, and single-frequency pulse laser output is realized. Although this method only needs to scan at least one resonant peak, the overall structure is complex and the hardware cost is increased. Summary of the invention

[0004] In order to solve the problems of high hardware cost, high scanning voltage and low frequency stability of single-frequency pulse laser in the prior art, the present invention provides a control method for a seed-injected single-frequency pulse laser, which can achieve stable single-frequency pulse laser output and make piezoelectric ceramics have higher life and reliability.

[0005] A control method for a seed injection type single-frequency pulse laser comprises the following steps:

[0006] S1: The continuous single-frequency seed laser 1 outputs the seed laser to the slave Q-switched laser 2, so that interference occurs in the resonant cavity of the slave Q-switched laser 2 to obtain a resonant signal; wherein the length of the resonant cavity is related to the piezoelectric ceramic 2-3 in the slave Q-switched laser 2, and the voltage loaded on the piezoelectric ceramic 2-3 is different, and the expansion and contraction amount generated by the piezoelectric ceramic 2-3 is different, and the corresponding length of the resonant cavity is different;

[0007] S2: the injection locking controller 4 outputs a triangular wave to the piezoelectric ceramic 2-3, and at the same time, the photodetector 2-2 in the slave Q-switched laser 2 receives the resonance signal formed in the resonant cavity of the slave Q-switched laser 2 under the current triangular wave;

[0008] S3: Determine the reference time t according to the peak maximum voltage of the resonance signal at the three consecutive triangular wave rising edges and the time when the peak maximum voltage is located x , and according to the reference time t x Determine the trigger period;

[0009] S4: Determine whether the output voltage of the photodetector 2-2 is greater than the set threshold voltage V in the trigger period. t If yes, the injection locking controller 4 sends a trigger signal to the Q driver 3 to control the Q switch 2-1 to turn on or off, so that the slave Q-switched laser 2 outputs a single-frequency pulse laser.

[0010] Furthermore, the reference time t x The method to determine is:

[0011] The voltage of the highest value of the peak value of the resonant signal at the rising edge of the current triangle wave is recorded as V1, and the time when V1 is recorded as t1;

[0012] Read the voltage V2 of the highest value of the resonance signal peak value at the last rising edge of the triangular wave and the time t2 at which the voltage V2 is located;

[0013] Read the voltage V3 of the highest value of the resonance signal peak value at the last rising edge of the triangular wave and the time t3 at which the voltage V3 is located;

[0014] Differences between time t1, time t2, and time t3. If |t2-t3|<Δt, |t1-t2|>Δt, and |t1-t3|>Δt are satisfied at the same time, then t x =t2, if any one of them is not satisfied, then t x =t1, where Δt is the set difference threshold.

[0015] Furthermore, at the rising edge of the triangular wave, the expansion and contraction amount of the piezoelectric ceramic within the time Δt is less than one quarter of the output wavelength of the laser from the driven Q-switched laser.

[0016] Furthermore, according to the reference time t x The method for determining the trigger period is:

[0017] Get the center point of the trigger period 2×t0-t x , where t0 is the peak voltage moment of the current triangle wave;

[0018] At the same time, the width of the trigger period is greater than twice the full width at half maximum of the resonance signal.

[0019] Furthermore, the cavity length of the piezoelectric ceramic scanned within a triangle wave is greater than the wavelength of the driven Q-switched laser.

[0020] Furthermore, the starting point of the rising edge of each triangle wave cycle is the zero moment of the time record.

[0021] Beneficial effects:

[0022] The present invention provides a control method for a seed injection type single-frequency pulse laser. The method comprises the following steps: identifying the peak time and peak height of a resonance signal at the rising edge of a piezoelectric ceramic scanning voltage, predicting the peak value at the falling edge, and identifying the resonance signal voltage within the time range of the predicted peak value. When the resonance signal voltage is higher than a threshold judgment voltage, a trigger signal is sent to achieve stable single-frequency pulse laser output. The injection locking method has a lower scanning voltage, so that the piezoelectric ceramic has a higher life span and reliability. That is to say, the present invention solves the problems of high hardware cost, high scanning voltage, and frequency stability of a single-frequency pulse laser, and can output a high-energy single-frequency pulse laser with strong anti-interference ability and good frequency stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a laser structure based on a control method for a seed-injection single-frequency pulse laser proposed by the present invention;

[0024] Figure 2 It is the timing relationship between the triangle wave voltage applied to the piezoelectric ceramic, the resonance signal, the trigger signal and the output laser pulse. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0026] Please read first Figure 1 , Figure 1This is a schematic diagram of a laser structure of an injection locking method based on a control method of a seed injection type single-frequency pulse laser proposed by the present invention. It can be seen that based on the method provided by the present invention, its laser structure includes a continuous single-frequency seed laser 1, a slave Q-switched laser 2, a Q driver 3, and an injection locking controller 4;

[0027] The continuous single-frequency seed laser 1 is used to output a single-frequency continuous laser and serves as a frequency reference source for the slave Q-switched laser 2. The slave Q-switched laser 2 includes a Q switch 2-1, a photodetector 2-2, and a piezoelectric ceramic 2-3. The slave Q-switched laser 2 is used to output a single-frequency Q-switched laser and is the core controlled device in injection locking. The Q driver 3 is the driver of the Q switch 2-1. The injection locking controller 4 is the core control device in injection locking.

[0028] Among them, the specific implementation parameters of the device used in the present invention are as follows:

[0029] The continuous single-frequency seed laser is a single non-planar ring cavity Er:YAG laser, with an average output power of >50mW and a line width of less than 10kHz. The slave Q-switched laser is an Er:YAG laser. The pump source is a fiber laser with a continuous power of 30W and a central wavelength of 1532nm. The gain medium is an Er:YAG laser crystal, with a doping concentration of 0.25at.%, and a crystal size of φ4×60mm. The Q switch is an acousto-optic modulator. The piezoelectric ceramics selected are piezoelectric ceramics with a parameter of 0.127μm / V. Under a scanning voltage amplitude of 30V and a corresponding cavity length scanning length of 3.8μm, single-frequency pulses with pulse energy ≥6mJ, repetition frequency ≥500Hz, and line width ≤5MHz are obtained.

[0030] See also Figure 2 , the injection locking control process comprises the following steps:

[0031] S1, injection: the continuous single-frequency seed laser 1 outputs the seed laser to the slave Q-switched laser 2, so that interference occurs in the resonant cavity of the slave Q-switched laser 2 to obtain a resonant signal; wherein the length of the resonant cavity is related to the piezoelectric ceramic 2-3 in the slave Q-switched laser 2, and the voltage loaded on the piezoelectric ceramic 2-3 is different, and the expansion and contraction amount generated by the piezoelectric ceramic 2-3 is different, and the corresponding length of the resonant cavity is different;

[0032] S2, scanning: the injection locking controller 4 outputs a triangular wave to the piezoelectric ceramic 2-3, and at the same time, the photodetector 2-2 in the slave Q-switched laser 2 receives the resonance signal formed in the resonant cavity of the slave Q-switched laser 2 under the current triangular wave;

[0033] S3, Pre-judgment: Determine the reference time t according to the peak value voltage of the resonance signal at the three consecutive triangular wave rising edges and the time when the peak value voltage is located.x , and according to the reference time t x Determine the trigger period;

[0034] Specifically, at the rising edge of the triangle wave, the peak value of the resonant signal is identified, and the starting point of each rising edge is set as the zero time, then the reference time t x The method to determine is:

[0035] The voltage of the highest value of the peak value of the resonant signal at the rising edge of the current triangle wave is recorded as V1, and the time when V1 is recorded as t1;

[0036] Read the voltage V2 of the highest value of the resonance signal peak value at the last rising edge of the triangular wave and the time t2 at which the voltage V2 is located;

[0037] Read the voltage V3 of the highest value of the resonance signal peak value at the last rising edge of the triangular wave and the time t3 at which the voltage V3 is located;

[0038] Differences between time t1, time t2, and time t3. If |t2-t3|<Δt, |t1-t2|>Δt, and |t1-t3|>Δt are satisfied at the same time, then t x =t2, if any one of them is not satisfied, then t x =t1, where Δt is the set difference threshold.

[0039] It should be noted that the main purpose of the above logic judgment is to avoid the lock frequency change caused by the accidental increase in the amplitude of the resonance signal peak in different triangle wave periods, resulting in a large jump in the predicted peak time.

[0040] According to the reference time t x The method for determining the trigger period is:

[0041] Get the center point of the trigger period 2×t0-t x , where t0 is the peak voltage moment of the current triangle wave; at the same time, the width of the trigger period is greater than twice the half-height full width of the resonant signal.

[0042] S4, triggering: determining whether the output voltage of the photodetector 2-2 is greater than the set threshold voltage V in the triggering period. t If yes, the injection locking controller 4 sends a trigger signal to the Q driver 3 to control the Q switch 2-1 to turn on or off, so that the slave Q-switched laser 2 outputs a single-frequency pulse laser.

[0043] That is to say, within the predicted time period of the falling edge of the triangular wave, when the output voltage of the photodetector 2-2 is greater than the set threshold voltage V tWhen , the injection locking controller 4 sends a trigger signal to the Q switch 2-1, so that the Q value of the slave Q-switched laser 2 changes, and the slave Q-switched laser outputs a single-frequency pulse laser.

[0044] In summary, the present invention discloses a control method for a seed-injected single-frequency pulse laser, which identifies the peak time and peak height of the resonance signal at the rising edge of the piezoelectric ceramic scanning voltage, predicts the peak at the falling edge, and identifies the resonance signal voltage within the time range of the predicted peak. When the resonance signal voltage is higher than the threshold judgment voltage, a trigger signal is issued to achieve stable single-frequency pulse laser output. The present invention solves the problems of high hardware cost, high scanning voltage, and frequency stability of single-frequency pulse lasers, and can output high-energy single-frequency pulse lasers with strong anti-interference ability and good frequency stability.

[0045] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may certainly make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A control method for a seed injection single-frequency pulse laser, characterized in that: The following steps are involved: S1: The continuous single-frequency seed laser (1) outputs the seed laser to the slave Q-switched laser (2), so that interference occurs in the resonant cavity of the slave Q-switched laser (2) to obtain a resonant signal; wherein the length of the resonant cavity is related to the piezoelectric ceramic (2-3) in the slave Q-switched laser (2), and the voltage loaded on the piezoelectric ceramic (2-3) is different, and the expansion and contraction amount generated by the piezoelectric ceramic (2-3) is different, and the corresponding length of the resonant cavity is different; S2: the injection locking controller (4) outputs a triangular wave to the piezoelectric ceramic (2-3), and at the same time, the photodetector (2-2) in the slave Q-switched laser (2) receives a resonant signal formed in the resonant cavity of the slave Q-switched laser (2) under the current triangular wave; S3: Determine the reference time t according to the peak maximum voltage of the resonance signal at the three consecutive triangular wave rising edges and the time when the peak maximum voltage is located x , and according to the reference time t x Determine the trigger period; S4: Determine whether the output voltage of the photodetector (2-2) is greater than a set threshold voltage V within the trigger period. t If yes, the injection locking controller (4) sends a trigger signal to the Q driver (3) to control the Q switch (2-1) to turn on or off, so that the slave Q-switched laser (2) outputs a single-frequency pulse laser.

2. A control method for a seed injection type single frequency pulse laser as claimed in claim 1, characterized in that: Reference time t x The method to determine is: The voltage of the highest value of the peak value of the resonant signal at the rising edge of the current triangle wave is recorded as V1, and the time when V1 is recorded as t1; Read the voltage V2 of the highest value of the resonance signal peak value at the last rising edge of the triangular wave and the time t2 at which the voltage V2 is located; Read the voltage V3 of the highest value of the resonance signal peak value at the last rising edge of the triangular wave and the time t3 at which the voltage V3 is located; Differences between time t1, time t2, and time t3. If |t2-t3|<Δt, |t1-t2|>Δt, and |t1-t3|>Δt are satisfied at the same time, then t x =t2, if any one of them is not satisfied, then t x =t1, where Δt is the set difference threshold.

3. A control method for a seed injection type single-frequency pulse laser as claimed in claim 2, characterized in that: At the rising edge of the triangle wave, the expansion and contraction of the piezoelectric ceramic within the Δt time is less than a quarter of the output wavelength of the slave Q-switched laser.

4. The control method of a seed injection type single frequency pulse laser according to claim 1, characterized in that: According to the reference time t x The method for determining the trigger period is: Get the center point of the trigger period 2×t0-t x , where t0 is the peak voltage moment of the current triangle wave; At the same time, the width of the trigger period is greater than twice the full width at half maximum of the resonance signal.

5. The control method of a seed injection type single frequency pulse laser according to claim 1, characterized in that: The cavity length of the piezoelectric ceramic scanned within a triangle wave is larger than the wavelength of the driven Q-switched laser.

6. A control method for a seed injection type single frequency pulse laser as claimed in claim 2, characterized in that: The starting point of the rising edge of each triangle wave cycle is the zero moment of the time record.

Images