A laser amplifier control system and method

Abstract

The application provides a kind of laser amplifier control system and method, the system includes the seed source, amplifier, phase modulator, nonlinear frequency conversion module and dichroic mirror arranged in sequence on optical path;The light output by nonlinear frequency conversion module is divided into two ways through dichroic mirror, one of which is used as system output light, and the direction of the other light path is provided with optical garbage bin;Adjust the phase modulator, so that the polarization direction of laser matches the nonlinear frequency conversion module, the system output light is the light after nonlinear frequency conversion, and the other way of fundamental light is recycled by optical garbage bin;Otherwise, the nonlinear frequency conversion module only outputs the fundamental light.By using the application, whether there is system output light, laser always passes through the crystal in nonlinear frequency conversion module, and the crystal will not exist the temperature drift caused by selective laser passing, to ensure the stability of system output light.

Description

Technical Field

[0001] This invention belongs to the field of laser amplifier control, and specifically relates to a laser amplifier control system and method. Background Technology

[0002] Current laser amplifier control uses an acousto-optic driver to diffract the laser output from the amplifier, causing the laser to deviate from its original optical path. This method allows control of the laser output time and pulse count by switching the acousto-optic driver on and off. However, this approach results in temperature fluctuations in the frequency doubling module when output is needed and vice versa. This temperature fluctuation affects the laser output power and stability, ultimately impacting the processing results in high-precision laser machining. Summary of the Invention

[0003] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention proposes a laser amplifier control system and method, which can improve the stability of laser output.

[0004] To achieve the above objectives, according to a first aspect of the present invention, a laser amplifier control system is provided, comprising a seed source, an amplifier, a phase modulator, a nonlinear frequency conversion module, and a dichroic mirror arranged sequentially in an optical path; the light output from the nonlinear frequency conversion module is split into two paths by the dichroic mirror, one of which serves as the system output light, and the other optical path is provided with an optical trash can.

[0005] When the phase modulator is adjusted so that the polarization direction of the laser matches that of the nonlinear frequency conversion module, the nonlinear frequency conversion module outputs the fundamental frequency light and the light after nonlinear frequency conversion. After being separated by the dichroic mirror, the system output light is the light after nonlinear frequency conversion, and the other fundamental frequency light is collected by the optical waste bin. When the polarization direction of the laser does not match that of the nonlinear frequency conversion module, the nonlinear frequency conversion module only outputs the fundamental frequency light. After passing through the dichroic mirror, there is no system output light, and the other fundamental frequency light is collected by the optical waste bin.

[0006] According to the above system, the nonlinear frequency conversion module is a frequency doubling module, a sum frequency module, or a difference frequency module. When the polarization direction of the laser matches the nonlinear frequency conversion module, the system output light corresponds to frequency doubling light, sum frequency light, or difference frequency light, respectively.

[0007] According to the above system, the phase modulator has a preset modulation depth obtained by calibration. By turning on the phase modulator, the polarization direction of the laser is matched with the nonlinear frequency conversion module. By turning off the phase modulator, the polarization direction of the laser is mismatched with the nonlinear frequency conversion module.

[0008] The system described above also includes a control unit for controlling the on / off state of the phase modulator or the modulation depth.

[0009] According to the above system, the phase modulator is an electro-optic phase modulator, a photoelastic modulator, or a liquid crystal phase modulator.

[0010] According to a second aspect of the present invention, a laser amplifier control system is provided, comprising an optical fiber seed source, an optical fiber phase modulator, an amplifier, a nonlinear frequency conversion module, and a dichroic mirror arranged sequentially on an optical path; the light output by the nonlinear frequency conversion module is split into two paths by the dichroic mirror, one of which is used as the system output light, and the other optical path is provided with an optical trash can.

[0011] When the fiber phase modulator is adjusted so that the polarization direction of the laser matches that of the nonlinear frequency conversion module, the nonlinear frequency conversion module outputs both the fundamental frequency light and the light after nonlinear frequency conversion. After being separated by a dichroic mirror, the system output light is the light after nonlinear frequency conversion, while the other path, the fundamental frequency light, is collected by the optical waste bin. When the polarization direction of the laser does not match that of the nonlinear frequency conversion module, the nonlinear frequency conversion module only outputs the fundamental frequency light. After passing through the dichroic mirror, there is no system output light, and the other path, the fundamental frequency light, is collected by the optical waste bin.

[0012] According to a third aspect of the present invention, a laser amplifier control method is provided, wherein the laser emitted from the seed source passes sequentially through an amplifier, a phase modulator, a nonlinear frequency conversion module, and a dichroic mirror; the light output from the nonlinear frequency conversion module is split into two paths by the dichroic mirror, one path being used as the system output light, and the other path being input into the light trash can.

[0013] When the system output light needs to be light after nonlinear frequency conversion, the modulation depth of the phase modulator is adjusted so that the polarization direction of the laser output by the phase modulator matches that of the nonlinear frequency conversion module.

[0014] When no system output light is required, the modulation depth of the phase modulator is adjusted so that the polarization direction of the laser output by the phase modulator does not match that of the nonlinear frequency conversion module.

[0015] Using the above method, the preset modulation depth of the phase modulator is calibrated, and the modulation depth makes the polarization direction of the laser output by the phase modulator match the nonlinear frequency conversion module.

[0016] When the system output light needs to be light that has undergone nonlinear frequency transformation, turn on the phase modulator;

[0017] When the system output light is not required, turn off the phase modulator.

[0018] According to the above method, the nonlinear frequency conversion module is a frequency doubling module. When the system output light needs to be frequency-doubled light, the modulation depth of the phase modulator is adjusted, thereby adjusting the polarization direction of the laser output by the phase modulator. Thus, in the frequency doubling module, based on the birefringence characteristics of the frequency doubling crystal, the refractive index of the fundamental frequency light and the frequency doubling light are equal.

[0019] According to a fourth aspect of the present invention, a laser amplifier control method is provided, wherein the laser emitted by the optical fiber seed source passes sequentially through an optical fiber phase modulator, an amplifier, a nonlinear frequency conversion module, and a dichroic mirror; the light output by the nonlinear frequency conversion module is split into two paths by the dichroic mirror, one of which is used as the system output light, and the other is input to the optical trash can.

[0020] When the system output light needs to be light after nonlinear frequency conversion, the modulation depth of the fiber phase modulator is adjusted so that the polarization direction of the laser output by the fiber phase modulator matches that of the nonlinear frequency conversion module.

[0021] When no system output light is required, the modulation depth of the fiber phase modulator is adjusted so that the polarization direction of the laser output by the fiber phase modulator does not match that of the nonlinear frequency conversion module.

[0022] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0023] 1. By controlling the polarization of the laser, the phase matching condition during nonlinear frequency conversion is changed. When the laser polarization direction matches the nonlinear frequency conversion module, the output light undergoes nonlinear frequency conversion; otherwise, the laser does not undergo nonlinear frequency conversion. With this configuration, regardless of whether there is system output light, the laser always passes through the crystal in the nonlinear frequency conversion module. Thus, the crystal does not experience temperature drift caused by selective laser passage, ensuring the stability of the system output light. Simultaneously, this control method eliminates the diffraction loss of the phase modulator, improving output power.

[0024] 2. When the seed source is an optical fiber seed source, the phase modulator can be an optical fiber phase modulator, which is placed between the seed source and the amplifier to avoid the risk of the phase modulator being damaged by high-power laser. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a system structure provided in an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of another system structure provided in an embodiment of the present invention.

[0027] In the diagram: 1-Seed source, 1.1-Fiber optic seed source, 2-Amplifier, 3-Phase modulator, 3.1-Fiber optic phase modulator, 4-Nonlinear frequency change module, 5-Diograph, 6-Optical trash can. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] This embodiment provides a laser amplifier control system, such as Figure 1 As shown, the system includes a seed source 1, an amplifier 2, a phase modulator 3, a nonlinear frequency conversion module 4, and a dichroic mirror 5 arranged sequentially on the optical path. The light output from the nonlinear frequency conversion module 4 is split into two paths by the dichroic mirror 5. One path serves as the system output light, while the other path has a light trash can 6.

[0030] Adjusting the phase modulator 3 ensures that: when the polarization direction of the laser matches that of the nonlinear frequency conversion module 4, the nonlinear frequency conversion module 4 outputs both the fundamental frequency light and the light after nonlinear frequency conversion. After being separated by the dichroic mirror 5, the system output light is the light after nonlinear frequency conversion, while the other path, the fundamental frequency light, is collected by the optical waste bin 6; when the polarization direction of the laser does not match that of the nonlinear frequency conversion module 4, the nonlinear frequency conversion module 4 only outputs the fundamental frequency light. After passing through the dichroic mirror 5, there is no system output light, and the other path, the fundamental frequency light, is collected by the optical waste bin 6.

[0031] The nonlinear frequency conversion module 4 can be a frequency doubling module, a sum-frequency module, a difference-frequency module, or any other nonlinear frequency conversion module. When the polarization direction of the laser matches that of the nonlinear frequency conversion module, the fundamental frequency light entering the nonlinear frequency conversion module 4 outputs the fundamental frequency light + frequency doubling light, the fundamental frequency light + sum-frequency light, or the fundamental frequency light + difference-frequency light, respectively. After being separated by the dichroic mirror 5, the fundamental frequency light enters the optical waste bin, while the frequency doubling light, sum-frequency light, or difference-frequency light is output as the system output light. When the polarization direction of the laser does not match that of the nonlinear frequency conversion module 4, the nonlinear frequency conversion module 4 only outputs the fundamental frequency light into the optical waste bin 6, with no system output light. It should be noted that although there is no system output light, the seed source 1 is still in the on state at this time.

[0032] In some embodiments, the nonlinear frequency conversion module 4 is a frequency doubling module, and the system output light, i.e. the light that undergoes a nonlinear frequency change, is the frequency doubling light, while the other light, i.e. the light that does not undergo a nonlinear frequency change, is the fundamental frequency light.

[0033] When performing frequency conversion, the axis of a nonlinear crystal should match the specific polarization direction of the fundamental frequency light. Taking a frequency doubling crystal as an example, the highest frequency doubling efficiency can only be obtained when the refractive indices of the fundamental and frequency-doubled light are equal. In isotropic media, different frequencies of light correspond to different refractive indices, making it impossible to make the refractive indices of the fundamental and frequency-doubled light equal, thus hindering high-efficiency frequency conversion. The birefringence property of a frequency doubling crystal can be utilized to make the refractive indices of the fundamental and frequency-doubled light equal. Different polarization directions of the fundamental frequency light correspond to different refractive indices. By cutting the frequency doubling crystal at a specific angle, the refractive indices of linearly polarized fundamental and frequency-doubled light in a specific direction can be made equal, thus generating efficient frequency conversion. A sum-frequency crystal yields both the fundamental and sum-frequency light, while a difference-frequency crystal yields both the fundamental and difference-frequency light.

[0034] Taking a frequency-doubled crystal as an example, a certain frequency-doubled crystal is configured to achieve frequency doubling output by requiring vertically polarized laser light to achieve phase matching. When no light output is needed, the phase modulator is not working, or the laser's deflection direction is deflected to a non-vertical polarization. In this case, although the laser light passes through the frequency-doubled crystal, frequency doubling cannot be completed within the crystal, and there is no frequency-doubled light output. The fundamental frequency light after passing through the frequency-doubled crystal is recycled through the optical waste bin. When frequency-doubled light output is needed, the phase modulator deflects the laser's polarization direction to vertical polarization. The laser light passes through the frequency-doubled crystal, where efficient frequency doubling is achieved, outputting fundamental frequency light + frequency-doubled light. After passing through the dichroic mirror, the fundamental frequency light is again recycled through the optical waste bin, while the frequency-doubled light is output as the system's output light.

[0035] With this setup, the laser always passes through the frequency-doubling crystal, regardless of whether frequency-doubled light is being output. This eliminates the temperature drift caused by selective laser passage, ensuring the stability of the frequency-doubled light output. Furthermore, this control method eliminates the diffraction loss of a phase modulator, thus improving output power.

[0036] The above control can be implemented as follows: The preset modulation depth of the phase modulator is calibrated; the phase modulator is turned on to match the polarization direction of the laser with that of the nonlinear frequency conversion module; and the phase modulator is turned off to prevent the polarization direction of the laser from matching that of the nonlinear frequency conversion module. The turning on and off is performed by the control unit.

[0037] The above control can also be implemented by controlling the modulation depth of the phase modulator in real time according to the requirements of the system output light. For example, the power is highest when vertically polarized, and the power is zero when the phase modulator is turned on to become horizontally linearly polarized. The phase modulator can be slowly adjusted, thereby controlling the power.

[0038] Phase modulators can be electro-optic phase modulators, photoelastic modulators, or liquid crystal phase modulators. Electro-optic phase modulators are based on the electro-optic effect; an applied electric field changes the refractive index of the electro-optic material, thereby altering the phase of the optical signal. Photoelastic modulators utilize the photoelastic effect; by applying a periodic high-voltage signal, the medium vibrates, periodically changing the refractive index to achieve phase modulation. Liquid crystal phase modulators utilize the electro-controlled birefringence effect of liquid crystals; an applied voltage changes the alignment of the liquid crystal molecules, thus altering the refractive index and achieving phase modulation.

[0039] Based on the above system, this embodiment provides a laser amplifier control method. The laser emitted from the seed source sequentially passes through an amplifier, a phase modulator, a nonlinear frequency conversion module, and a dichroic mirror. The light output from the nonlinear frequency conversion module is split into two paths by the dichroic mirror, one path being the output light and the other being input to a light bin. Specifically, this method includes: when the system output light needs to be nonlinearly frequency converted, adjusting the modulation depth of the phase modulator so that the polarization direction of the laser output by the phase modulator matches that of the nonlinear frequency conversion module; when the system output light is not needed, adjusting the modulation depth of the phase modulator so that the polarization direction of the laser output by the phase modulator does not match that of the nonlinear frequency conversion module.

[0040] Furthermore, the switching between having system output light and not having it is achieved through the following method: The preset modulation depth of the phase modulator is calibrated to match the polarization direction of the laser output by the phase modulator with that of the nonlinear frequency conversion module; when the system output light is required to be light after nonlinear frequency conversion, the phase modulator is turned on; when the system output light is not required, the phase modulator is turned off. The on / off operation can be implemented through the control unit.

[0041] Switching between having system output light and not having it can also be achieved in the following way: The modulation depth of the phase modulator can be controlled in real time according to the requirements of the system output light. For example, the power is highest when vertically polarized; when the phase modulator is turned off, the power is zero when horizontally polarized. The phase modulator can be slowly adjusted to control the power.

[0042] Taking the nonlinear frequency conversion module as a frequency doubling module as an example, when the system output light needs to be frequency-doubled light, the modulation depth of the phase modulator is adjusted, thereby adjusting the polarization direction of the laser output by the phase modulator. Thus, in the frequency doubling module, based on the birefringence characteristics of the frequency doubling crystal, the refractive index of the fundamental frequency light and the frequency doubling light are equal.

[0043] In some embodiments, the seed source is an optical fiber seed source. In this case, the phase modulator can be an optical fiber phase modulator, which can be connected to the back end of the optical fiber seed source before being connected to the amplifier. This avoids the risk of the modulator being damaged by the high-power laser when placed after the amplifier. The laser amplifier control system in this case is as follows: Figure 2As shown, the system includes an optical fiber seed source 1.1, an optical fiber phase modulator 3.1, an amplifier 2, a nonlinear frequency conversion module 4, and a dichroic mirror 5, arranged sequentially along the optical path. The light output from the nonlinear frequency conversion module 4 is split into two paths by the dichroic mirror. One path is the system output light, and the other path has an optical "trash can" 6. When the optical fiber phase modulator 3.1 is adjusted so that the polarization direction of the laser matches that of the nonlinear frequency conversion module 4, the system output light is the light after nonlinear frequency conversion. When the polarization direction of the laser does not match that of the nonlinear frequency conversion module 4, there is no system output light.

[0044] Based on the aforementioned laser amplifier control system, this embodiment provides a laser amplifier control method. Laser light emitted from an optical fiber seed source sequentially passes through an optical fiber phase modulator, an amplifier, a nonlinear frequency conversion module, and a dichroic mirror. The light output from the nonlinear frequency conversion module is split into two paths by the dichroic mirror, one path being the system output light, and the other path being input to an optical waste bin. Specifically, this method includes: when the system output light needs to be nonlinearly frequency converted, adjusting the modulation depth of the optical fiber phase modulator so that the polarization direction of the laser output from the optical fiber phase modulator matches that of the nonlinear frequency conversion module; when the system output light is not needed, adjusting the modulation depth of the optical fiber phase modulator so that the polarization direction of the laser output from the optical fiber phase modulator does not match that of the nonlinear frequency conversion module.

[0045] This invention provides a highly efficient and simple laser amplifier control system and method. By controlling the modulation depth of the phase modulator, the output light after passing through the nonlinear frequency conversion module is controlled to be either nonlinearly frequency-converted light or conventional laser light (i.e., fundamental frequency light). The final system output light is either nonlinearly frequency-converted light or no system output light. In either case, the seed source is always emitting laser light, and the laser light always passes through the crystal in the nonlinear frequency conversion module. Thus, the crystal does not experience temperature drift caused by selective laser passage, ensuring the stability of the output light. Simultaneously, this control method eliminates the diffraction loss of the phase modulator, improving the output power.

[0046] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser amplifier control system, characterized in that: It includes a seed source, an amplifier, a phase modulator, a nonlinear frequency conversion module, and a dichroic mirror arranged sequentially along the optical path; The light output from the nonlinear frequency conversion module is split into two paths by a dichroic mirror. One path serves as the system output light, while the other path has a light trash can. When the phase modulator is adjusted so that the polarization direction of the laser matches that of the nonlinear frequency conversion module, the nonlinear frequency conversion module outputs the fundamental frequency light and the light after nonlinear frequency conversion. After being separated by the dichroic mirror, the system output light is the light after nonlinear frequency conversion, and the other fundamental frequency light is collected by the optical waste bin. When the polarization direction of the laser does not match that of the nonlinear frequency conversion module, the nonlinear frequency conversion module only outputs the fundamental frequency light. After passing through the dichroic mirror, there is no system output light, and the other fundamental frequency light is collected by the optical waste bin.

2. The laser amplifier control system according to claim 1, characterized in that: The nonlinear frequency conversion module can be a frequency doubling module, a sum-frequency module, or a difference-frequency module. When the polarization direction of the laser matches the nonlinear frequency conversion module, the system output light corresponds to frequency doubling light, sum-frequency light, or difference-frequency light, respectively.

3. The laser amplifier control system according to claim 1, characterized in that: The phase modulator has a preset modulation depth obtained by calibration. By turning on the phase modulator, the polarization direction of the laser is matched with that of the nonlinear frequency conversion module. By turning off the phase modulator, the polarization direction of the laser is mismatched with that of the nonlinear frequency conversion module.

4. The laser amplifier control system according to claim 1 or 3, characterized in that: It also includes a control unit for controlling the phase modulator to turn on, off, or modulate the depth.

5. The laser amplifier control system according to claim 1, characterized in that: The phase modulator can be an electro-optic phase modulator, a photoelastic modulator, or a liquid crystal phase modulator.

6. A laser amplifier control system, characterized in that: It includes an optical fiber seed source, an optical fiber phase modulator, an amplifier, a nonlinear frequency conversion module, and a dichroic mirror arranged sequentially along the optical path; The light output from the nonlinear frequency conversion module is split into two paths by a dichroic mirror. One path serves as the system output light, while the other path has a light trash can. When the fiber phase modulator is adjusted so that the polarization direction of the laser matches that of the nonlinear frequency conversion module, the nonlinear frequency conversion module outputs the fundamental frequency light and the light after nonlinear frequency conversion. After being separated by a dichroic mirror, the system output light is the light after nonlinear frequency conversion, and the other fundamental frequency light is collected by the optical waste bin. When the polarization direction of the laser does not match that of the nonlinear frequency conversion module, the nonlinear frequency conversion module only outputs the fundamental frequency light. After passing through the dichroic mirror, there is no system output light, and the other fundamental frequency light is collected by the optical waste bin.

7. A laser amplifier control method, characterized in that: The laser emitted from the seed source passes sequentially through an amplifier, a phase modulator, a nonlinear frequency conversion module, and a dichroic mirror; The light output from the nonlinear frequency conversion module is split into two paths by a dichroic mirror. One path is used as the system output light, and the other path is input into the light trash can. When the system output light needs to be light after nonlinear frequency conversion, the modulation depth of the phase modulator is adjusted so that the polarization direction of the laser output by the phase modulator matches that of the nonlinear frequency conversion module. When no system output light is required, the modulation depth of the phase modulator is adjusted so that the polarization direction of the laser output by the phase modulator does not match that of the nonlinear frequency conversion module.

8. The laser amplifier control method according to claim 7, characterized in that: The preset modulation depth of the phase modulator is obtained through calibration. The modulation depth makes the polarization direction of the laser output by the phase modulator match that of the nonlinear frequency conversion module. When the system output light needs to be light that has undergone nonlinear frequency transformation, turn on the phase modulator; When the system output light is not required, turn off the phase modulator.

9. The laser amplifier control method according to claim 7 or 8, characterized in that: The nonlinear frequency conversion module is a frequency doubling module. When the system output light needs to be frequency-doubled, the modulation depth of the phase modulator is adjusted, thereby adjusting the polarization direction of the laser output by the phase modulator. Thus, in the frequency doubling module, based on the birefringence characteristics of the frequency doubling crystal, the refractive index of the fundamental frequency light and the frequency doubling light are equal.

10. A laser amplifier control method, characterized in that: The laser emitted from the fiber optic seed source passes sequentially through a fiber optic phase modulator, amplifier, nonlinear frequency conversion module, and dichroic mirror. The light output from the nonlinear frequency conversion module is split into two paths by the dichroic mirror, one of which serves as the system output light, and the other is input into the optical waste bin. When the system output light needs to be light after nonlinear frequency conversion, the modulation depth of the fiber phase modulator is adjusted so that the polarization direction of the laser output by the fiber phase modulator matches that of the nonlinear frequency conversion module. When no system output light is required, the modulation depth of the fiber phase modulator is adjusted so that the polarization direction of the laser output by the fiber phase modulator does not match that of the nonlinear frequency conversion module.

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