阅读说明：本技术 一种激光功率稳定方法及激光功率放大系统 (Laser power stabilizing method and laser power amplifying system ) 是由 潘其坤 郭劲 陈飞 谢冀江 李殿军 于德洋 张阔 孙俊杰 张鲁薇 于 2020-06-22 设计创作，主要内容包括：本发明公开了一种激光功率稳定方法及激光功率放大系统,激光产生装置产生种子激光脉冲,第一光调制装置用于改变通过光的偏振态,偏振元件用于阻止被第一光调制装置改变偏振态的光通过,光放大装置用于将通过偏振元件的光放大功率而输出。触发激光产生装置产生种子激光脉冲,并控制第一光调制装置改变在第一预设时间段内通过光的偏振态,通过第一光调制装置和偏振元件阻止种子激光脉冲的前沿噪声通过而进入光放大装置,从而消除种子激光脉冲的前沿噪声,能够消除种子激光脉冲的前沿噪声对激光放大功率、光增益扰动的影响,从而能够有效地提升对激光放大功率后输出的窄脉宽激光功率的稳定性以及各个脉冲能量的稳定性。(The invention discloses a laser power stabilizing method and a laser power amplifying system.A laser generating device generates seed laser pulses, a first light modulation device is used for changing the polarization state of passing light, a polarization element is used for preventing the light of which the polarization state is changed by the first light modulation device from passing, and a light amplifying device is used for amplifying the power of the light passing through the polarization element and outputting the amplified power. The laser generating device is triggered to generate seed laser pulses, the first light modulation device is controlled to change the polarization state of light passing through the first preset time period, and the leading edge noise of the seed laser pulses is prevented from passing through the first light modulation device and the polarization element to enter the light amplification device, so that the leading edge noise of the seed laser pulses is eliminated, the influence of the leading edge noise of the seed laser pulses on laser amplification power and light gain disturbance can be eliminated, and the stability of the narrow pulse width laser power output after the laser amplification power and the stability of each pulse energy can be effectively improved.)

1. A laser power stabilization method, characterized in that a laser power amplification system is applied which comprises a laser generating device for generating and inputting seed laser pulses to a first light modulation device for changing the polarization state of passing light, a first light modulation device for preventing light whose polarization state is changed by the first light modulation device from passing, a polarization element for outputting light amplification power which has passed through the polarization element, and a light amplification device for outputting light amplification power;

the method comprises the following steps: controlling the first light modulation device to change the polarization state of the passing light within a first preset time period, wherein the first preset time period corresponds to the existence time period of the leading edge noise of the seed laser pulse.

2. The method for stabilizing laser power according to claim 1, wherein the applied laser power amplifying system further comprises an optical stop disposed on the optical path between the polarization element and the optical amplifying device, a second optical modulating device for deflecting the transmission direction of the passing light, and the optical stop for preventing the light propagated by the optical amplifying device and deflected by the second optical modulating device from passing;

the method further comprises the following steps: and controlling the second light modulation device to deflect light transmitted by the light amplification device within a second preset time period, wherein the second preset time period corresponds to a time period between the main peak of the seed laser pulse and the main peak of the next seed laser pulse.

3. The method of claim 2, wherein the aperture size of the stop is consistent with a beam diameter of the seed laser pulse.

4. The method according to claim 2, wherein the second predetermined period of time corresponds to a period of time between an end time of a main peak of the seed laser pulse and a time when a start time of a main peak of a next seed laser pulse leads by a predetermined time.

5. The method of claim 2, wherein the second optical modulation device comprises an acousto-optic modulator that is equivalent to a volume bragg grating when an electrical signal is applied.

6. The method of any of claims 1 to 5, wherein the first optical modulation device is specifically configured to rotate the polarization state of the passing light by a first preset angle, such that the polarization state of the rotated light is orthogonal to the polarization state of the main peak of the seed laser pulse.

7. The method of any of claims 1-5, wherein the seed laser pulse is incident on the polarizing element at an angle that is coincident with the Brewster's angle of the seed laser pulse.

8. A laser power amplification system comprising a laser light generation device for generating and inputting a seed laser light pulse to a first light modulation device for changing a polarization state of passing light, a first light modulation device for preventing the passage of light whose polarization state is changed by the first light modulation device, a polarization element for amplifying power of light passing through the polarization element and outputting, a light amplification device for outputting, and a control device;

the control device is used for controlling the first light modulation device to change the polarization state of the passing light in a first preset time period, and the first preset time period corresponds to the existence time period of the leading edge noise of the seed laser pulse.

9. The laser power amplification system according to claim 8, further comprising an optical stop provided on an optical path between the polarization element and the light amplification device, a second light modulation device for deflecting a transmission direction of the passing light, the optical stop for preventing the light propagated by the light amplification device and deflected by the second light modulation device from passing;

the control device is further configured to control the second light modulation device to deflect light that is propagated by the light amplification device within a second preset time period, where the second preset time period corresponds to a time period between the seed laser pulse main peak and a next seed laser pulse main peak.

10. The laser power amplifying system as claimed in claim 9, wherein the control device is specifically configured to sequentially output square wave signals to the laser generating device, the first optical modulating device and the second optical modulating device respectively to control the respective devices to operate, a duty ratio of a single square wave signal is adjustable, and a time interval between the square wave signals is adjustable.

Technical Field

The invention relates to the technical field of laser, in particular to a laser power stabilizing method. The invention also relates to a laser power amplification system.

Background

Photolithography is the heart of modern large-scale integrated circuit fabrication techniques, and lithographic light sources are important components of lithographic apparatus. According to the rayleigh criterion, the shorter the wavelength of the Light source, the higher the lithographic resolution provided by the Light source, and at present, Extreme ultraviolet Light (EUVL) with a wavelength of 13.5nm becomes a lithography Light source which is of great interest. Laser-Produced Plasma (LPP) can generate extreme ultraviolet light, a preset target is irradiated by long-wave Laser with high repetition frequency, narrow pulse width and high power, and the light with the induced Plasma radiation wavelength of 13.5nm is a mainstream technical approach for generating the extreme ultraviolet light.

The main oscillation Power-Amplifier (MOPA) technology is mainly adopted to obtain high repetition frequency, narrow pulse width and high Power laser, that is, the high repetition frequency and narrow pulse width seed laser is amplified in Power through a multistage laser Amplifier to obtain high Power laser. In the field of extreme ultraviolet lithography light source application, the requirement on the stability of the power of laser with high repetition frequency and narrow pulse width of tens of kHz is extremely high, and each laser pulse is required to effectively hit a preset target, so that the energy of each pulse of the laser with high repetition frequency and narrow pulse width is required to be very stable, and the pulse waveform cannot be distorted.

Disclosure of Invention

The invention aims to provide a laser power stabilizing method and a laser power amplifying system, which can eliminate leading edge noise of narrow pulse width laser pulses and effectively improve the stability of the output narrow pulse width laser power and the stability of each pulse energy.

In order to achieve the purpose, the invention provides the following technical scheme:

a laser power stabilization method is applied to a laser power amplification system which comprises a laser generating device, a first light modulation device, a polarization element and a light amplification device, wherein the laser generating device is used for generating and inputting seed laser pulses to the first light modulation device, the first light modulation device is used for changing the polarization state of passing light, the polarization element is used for preventing the light with the polarization state changed by the first light modulation device from passing, and the light amplification device is used for outputting the amplified power of the light passing through the polarization element;

the method comprises the following steps: controlling the first light modulation device to change the polarization state of the passing light within a first preset time period, wherein the first preset time period corresponds to the existence time period of the leading edge noise of the seed laser pulse.

Preferably, the applied laser power amplifying system further includes an optical stop disposed on an optical path between the polarizing element and the optical amplifying device, a second optical modulating device for deflecting a transmission direction of the passing light, and the optical stop for preventing the light propagated by the optical amplifying device and deflected by the second optical modulating device from passing;

the method further comprises the following steps: and controlling the second light modulation device to deflect light transmitted by the light amplification device within a second preset time period, wherein the second preset time period corresponds to a time period between the main peak of the seed laser pulse and the main peak of the next seed laser pulse.

Preferably, the aperture size of the diaphragm is consistent with the beam diameter of the seed laser pulse.

Preferably, the second preset time period specifically corresponds to a time period from an end time of the main peak of the seed laser pulse to a time when a start time of a main peak of a next seed laser pulse leads by a preset time.

Preferably, the second optical modulation means comprises an acousto-optic modulator which is equivalent to a volume bragg grating when an electrical signal is applied.

Preferably, the first light modulation device is specifically configured to rotate the polarization state of the passing light by a first preset angle, so that the polarization state of the rotated light is orthogonal to the polarization state of the main peak of the seed laser pulse.

Preferably, an incident angle of the seed laser pulse to the polarizing element is consistent with a brewster angle of the seed laser pulse.

A laser power amplification system comprising a laser light generation device for generating and inputting seed laser light pulses to a first light modulation device for changing a polarization state of passing light, a first light modulation device for preventing light whose polarization state is changed by the first light modulation device from passing, a polarization element for outputting light amplification power that has passed through the polarization element, and a control device;

the control device is used for controlling the first light modulation device to change the polarization state of the passing light in a first preset time period, and the first preset time period corresponds to the existence time period of the leading edge noise of the seed laser pulse.

Preferably, the polarization device further includes an aperture provided on an optical path between the polarization element and the light amplification device, a second light modulation device for deflecting a transmission direction of the passing light, and the aperture for blocking passage of the light propagated by the light amplification device and deflected by the second light modulation device;

the control device is further configured to control the second light modulation device to deflect light that is propagated by the light amplification device within a second preset time period, where the second preset time period corresponds to a time period between the seed laser pulse main peak and a next seed laser pulse main peak.

Preferably, the control device is specifically configured to output square wave signals to the laser generation device, the first light modulation device, and the second light modulation device, respectively, in order to control each device to operate, and a duty ratio of a single square wave signal is adjustable, and a time interval between each square wave signal is adjustable.

In the above-described method for stabilizing laser power according to the present invention, the laser generating device generates the seed laser pulse, the first optical modulation device is configured to change the polarization state of the passing light, the polarizer is configured to prevent the light with the polarization state changed by the first optical modulation device from passing, and the optical amplifying device is configured to amplify the power of the light passing through the polarizer for output. The laser generating device is triggered to generate seed laser pulses, the first optical modulation device is controlled to change the polarization state of light passing through within a first preset time period, the first preset time period corresponds to the existing time period of leading edge noise of the seed laser pulses, namely the leading edge noise of the seed laser pulses is prevented from passing through by the first optical modulation device and the polarization element, so that the leading edge noise of the seed laser pulses is eliminated, the influence of the leading edge noise of the seed laser pulses on laser amplification power and optical gain disturbance can be eliminated, and the stability of narrow pulse width laser power output after the laser amplification power and the stability of each pulse energy can be effectively improved.

The invention also provides a laser power amplification system which can achieve the beneficial effects.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a laser power amplification system according to an embodiment of the present invention;

FIG. 2 is a waveform diagram of a seed laser pulse output by a laser generator according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a laser power amplification system according to yet another embodiment of the present invention;

FIG. 4 is a timing diagram illustrating output control to the laser generating device, the first optical modulation device and the second optical modulation device according to an embodiment of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment 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.

Referring to fig. 1, fig. 1 is a schematic diagram of a laser power amplifying system of this embodiment, the laser power amplifying system includes a laser generating device 10, a first optical modulation device 11, a polarization element 12 and a light amplifying device 13, the laser generating device 10 is configured to generate a seed laser pulse and input the seed laser pulse to the first optical modulation device 11, the first optical modulation device 11 is configured to change a polarization state of passing light, the polarization element 12 is configured to prevent the light with the polarization state changed by the first optical modulation device 11 from passing through, and the light amplifying device 13 is configured to output the amplified power of the light passing through the polarization element 12.

The method comprises the following steps: the first light modulation means 11 is controlled to change the polarization state of the passing light within a first preset time period corresponding to the presence time period of the leading edge noise of the seed laser pulse.

The laser generating device 10 generates a seed laser pulse, and due to the factors of the laser generating device, the seed laser pulse output by the laser generating device has leading edge noise, and if the leading edge noise is amplified along with the main peak of the laser pulse, laser gain disturbance is generated, which affects the power stability and pulse energy stability of the laser pulse finally output.

In the laser power amplifying system of the present embodiment, the seed laser pulse generated by the laser generator 10 passes through the first optical modulator 11, the polarizer 12, and the optical amplifier 13 in this order. The laser generation device 10 is triggered to generate seed laser pulses, the first optical modulation device 11 is controlled to change the polarization state of passing light in a first preset time period, the first preset time period corresponds to the existing time period of leading edge noise of the seed laser pulses, namely, the leading edge noise of the seed laser pulses is prevented from passing through by the first optical modulation device 11 and the polarization element 12, so that the leading edge noise of the seed laser pulses is eliminated, the influence of the leading edge noise on laser amplification power and optical gain disturbance can be eliminated, and the stability of narrow pulse width laser power output after the laser amplification power and the stability of each pulse energy can be effectively improved.

The laser generator 10 may be an electro-optical cavity emptying laser, and is capable of generating seed laser with high repetition frequency and narrow pulse width. But the front noise of the laser pulse output by the laser is obvious under the influence of the depolarization characteristic of the photoelectric device in the cavity. Laser generating device 10 may be, but is not limited to, an electro-optical cavity emptying CO₂A laser.

Alternatively, the first light modulation device 11 may be controlled to change the polarization state of the passing light by applying an electrical signal to the first light modulation device 11. The first light modulation device 11 is capable of changing the polarization state of the passing light when the first light modulation device 11 applies an electric signal, and does not change the polarization state of the passing light when the first light modulation device 11 does not apply an electric signal. Preferably, the first optical modulation device 11 may adopt an electro-optical pockels cell, which has an advantage of ultra-fast response time, and can improve the response rate of the system.

Preferably, the first light modulation device 11 may be specifically configured to rotate the polarization state of the passing light by a first preset angle, so that the polarization state of the rotated light is orthogonal to the polarization state of the main peak of the seed laser pulse. The leading edge noise of the seed laser pulse is the same as the polarization state of the main peak of the seed laser pulse, and the polarization state of the leading edge noise of the seed laser pulse is changed by controlling the first optical modulation device 11, so that the leading edge noise of the seed laser pulse is orthogonal to the polarization state of the main peak of the seed laser pulse, and the leading edge noise is blocked from passing through the polarization element 12. For example, the first preset angle may be 90 degrees, the main peak of the seed laser pulse and the leading edge noise are P-polarized light, the vibration plane of the polarized light of the leading edge noise is rotated by 90 degrees to become S-polarized light, and the polarizing element 12 has a high reflection effect on the S-polarized light.

Alternatively, the polarizing element 12 may use an analyzer. Illustratively, the polarizing element 12 may use an optical element that is highly reflective for S-polarized light and highly transmissive for P-polarized light, so as to allow the main peak of the seed laser pulse to transmit therethrough while reflecting away the leading edge noise that changes the polarization state. Preferably, the incident angle of the seed laser pulse to the polarizing element 12 may be set to be the same as the brewster angle of the seed laser pulse, and thus the setting of the angle facilitates the improvement of the transmittance of the P-polarized light and the reflectance of the S-polarized light.

The optical amplifier 13 amplifies the power of the light passing through the polarizer 12 and outputs the amplified power. Alternatively, the optical amplification device 13 may use a radio frequency waveguide CO₂Laser amplifier, radio frequency slab CO₂Laser amplifier, fast axial flow CO₂Laser amplifier or cross current CO₂The laser amplifier is not limited to this, and other types of optical amplifying devices can be used as the optical amplifying device 13, and the present invention is within the protection scope.

In practical applications, triggering the laser generating device 10 to generate the seed laser pulse and controlling the first optical modulating device 11 to change the polarization state of the passing light may be achieved by outputting a trigger signal to the laser generating device 10 and the first optical modulating device 12. Referring to fig. 1, a trigger signal may be output to the laser generating device 10 and the first light modulation device 12 through the control device 16. Referring to fig. 2, fig. 2 is a waveform diagram of the seed laser pulse output by the laser generating device of the present embodiment, as shown in fig. 1, where 1 is a trigger signal input to the laser generating device 10 to control the laser generating device 10 to output the seed laser pulse, and 3 is leading edge noise of the output seed laser pulse. And 2 is the main peak of the output seed laser pulse, which is the laser part to be amplified. The method controls the first light modulation device 11 to change the polarization state of the passing light within a first preset time period, wherein the first preset time period corresponds to the existence time period of the leading edge noise 3 of the seed laser pulse, and therefore the effect of eliminating the leading edge noise is achieved.

Referring to fig. 3, fig. 3 is a schematic diagram of a laser power amplification system of this embodiment, and based on the above embodiment, the applied laser power amplification system further includes a diaphragm 15 and a second light modulation device 14 disposed on a light path between the polarization element 12 and the light amplification device 13. The second light modulation device 14 is used for deflecting the transmission direction of the passing light, and the diaphragm 15 is used for preventing the light which is transmitted by the light amplification device 13 and deflected by the second light modulation device 14 from passing.

The laser power stabilizing method of the embodiment comprises the following steps:

s201: the first light modulation means 11 is controlled to change the polarization state of the passing light within a first preset time period corresponding to the presence time period of the leading edge noise of the seed laser pulse.

S202: controlling the second light modulation device 14 to deflect the light propagated by the light amplification device 13 within a second predetermined time period corresponding to a time period between the main peak of the seed laser pulse and the main peak of the next seed laser pulse.

The backscattered light generated by the optical amplifier 13 will cause a laser gain disturbance, which will affect the power stability and pulse energy stability of the final output laser pulse.

In the laser power amplifying system of the present embodiment, the seed laser pulse generated by the laser generator 10 passes through the first optical modulator 11, the polarizer 12, the stop 15, the second optical modulator 14, and the optical amplifier 13 in this order. The trigger laser generating device 10 generates a seed laser pulse and controls the first optical modulation device 11 to change the polarization state of the passing light within a first preset time period, which corresponds to the existence time period of the leading edge noise of the seed laser pulse, i.e., the leading edge noise of the seed laser pulse is prevented from passing through by the first optical modulation device 11 and the polarization element 12, thereby eliminating the leading edge noise of the seed laser pulse. And, the second optical modulation device 14 is controlled to deflect the light propagated by the optical amplification device 13 within a second preset time period corresponding to a time period between the main peak of the seed laser pulse and the main peak of the next seed laser pulse, that is, the backward scattered light generated by the optical amplification device 13 in the two main peak gaps of the laser pulses is blocked from passing by the second optical modulation device 14 and the aperture 15, thereby eliminating the backward scattered light of the optical amplification device. Therefore, the method can eliminate the influence of the front edge noise and the backward scattering light on the laser amplification power and the optical gain disturbance, thereby effectively improving the stability of the narrow pulse width laser power output after the laser amplification power and the stability of each pulse energy.

Preferably, the aperture size of the diaphragm 15 corresponds to the beam diameter of the seed laser pulse. The light propagated by the light amplification device 13 and deflected by the second light modulation device 14 is blocked by the diaphragm 15. Preferably, the aperture 15 may be an aperture-adjustable metal aperture.

Alternatively, the deflection of the second light modulation device 14 through the direction of transmission of light may be controlled by applying an electrical signal to the second light modulation device 14. When the second light modulation device 14 applies an electric signal, the transmission direction of the passing light can be deflected by a certain angle so that the deflected light cannot pass through the diaphragm 15. When the second light modulation device 14 does not apply an electrical signal, the laser light can freely pass through. The second light modulation device 14 deflects light in the gap between the main peaks of the two seed laser pulses, so that the light only works in the gap between the main peaks of the two seed laser pulses, and the transmission of the laser pulses into the light amplification device is not influenced. By combining the second light modulation device 14 and the diaphragm 15, the backscattered light of the light amplification device 13 can be effectively blocked. Alternatively, the second optical modulation device 14 may employ an acousto-optic modulator that is equivalent to a volume bragg grating when an electrical signal is applied.

The second preset time period corresponds to a time period between the main peak of the seed laser pulse and the main peak of the next seed laser pulse, and in practical application, the second preset time period can specifically correspond to a time period between the ending time of the main peak of the seed laser pulse and the time when the starting time of the main peak of the next seed laser pulse leads the preset time, so that the main peak of the laser pulse can be completely transmitted to the optical amplification device.

In the above embodiments, triggering the laser generating device 10 to generate the seed laser light pulse, controlling the first optical modulation device 11 to change the polarization state of the passing light, and controlling the second optical modulation device 14 to deflect the transmission direction of the passing light may be achieved by outputting the trigger signal to the laser generating device 10, the first optical modulation device 12, and the second optical modulation device 14. Referring to fig. 3, the control device 16 may output a trigger signal to the laser generating device 10, the first light modulation device 12, and the second light modulation device 14.

For example, three square wave signals may be output to the laser generating device 10, the first optical modulating device 12, and the second optical modulating device 14, respectively, and then the square wave signals may be output to the laser generating device 10, the first optical modulating device 12, and the second optical modulating device 14, respectively, in turn, the duty ratio of the single square wave signal may be adjusted, and the time interval between the square wave signals may be adjusted. Referring to fig. 2 and 4 in combination, fig. 4 is a timing chart of output control to the laser generating device, the first optical modulation device and the second optical modulation device in the present embodiment. As shown in the figure, 1 is a trigger signal output to the laser generating device 10 to control the laser generating device 10 to output the seed laser pulse, and 3 is leading edge noise of the output seed laser pulse. And 2 is the main peak of the output seed laser pulse, which is the laser part to be amplified.

In fig. 4, 4 is a trigger signal output to the first optical modulation device 11 for controlling the application of the electrical signal to the first optical modulation device 11, the high-level width of which completely covers the leading edge noise 3 of the laser pulse, and the falling edge of which coincides with the rising start time of the main peak 2 of the laser pulse. Reference numeral 5 denotes a trigger signal to be output to the second optical modulation device 14, which controls the application of an electric signal to the second optical modulation device 14, the rising edge time of which coincides with the end time of the main peak 2 of the laser pulse, and the falling edge of which leads the main peak of the next laser pulse by about 2 μ s.

Accordingly, an embodiment of the present invention further provides a laser power amplifying system, please refer to fig. 1, and fig. 1 is a schematic diagram of the laser power amplifying system provided in this embodiment, where the laser power amplifying system includes a laser generating device 10, a first optical modulating device 11, a polarizing element 12, a light amplifying device 13, and a control device 16, the laser generating device 10 is configured to generate a seed laser pulse and input the seed laser pulse to the first optical modulating device 11, the first optical modulating device 11 is configured to change a polarization state of passing light, the polarizing element 12 is configured to prevent light whose polarization state is changed by the first optical modulating device 11 from passing through, and the light amplifying device 13 is configured to output light amplified by the polarizing element 12.

The control device 16 is configured to control the first light modulation device 11 to change the polarization state of the passing light within a first preset time period, where the first preset time period corresponds to the existence time period of the leading edge noise of the seed laser pulse.

The laser generating device 10 generates a seed laser pulse, and due to the factors of the laser generating device, the seed laser pulse output by the laser generating device has leading edge noise, and if the leading edge noise is amplified along with the main peak of the laser pulse, laser gain disturbance is generated, which affects the power stability and energy stability of the laser pulse finally output.

In the laser power amplifying system of the present embodiment, the seed laser pulse generated by the laser generator 10 passes through the first optical modulator 11, the polarizer 12, and the optical amplifier 13 in this order. The laser generation device 10 is triggered to generate seed laser pulses, the first optical modulation device 11 is controlled to change the polarization state of passing light in a first preset time period, the first preset time period corresponds to the existing time period of leading edge noise of the seed laser pulses, namely, the leading edge noise of the seed laser pulses is prevented from passing through by the first optical modulation device 11 and the polarization element 12, so that the leading edge noise of the seed laser pulses is eliminated, the influence of the leading edge noise on laser amplification power and optical gain disturbance can be eliminated, and the stability of narrow pulse width laser power output after the laser amplification power and the stability of each pulse energy can be effectively improved.

Further preferably, another embodiment of the present invention further provides a laser power amplifying system, on the basis of the above embodiment, referring to fig. 3, fig. 3 is a schematic diagram of the laser power amplifying system provided in this embodiment, where the laser power amplifying system further includes a diaphragm 15 and a second light modulation device 14, which are disposed on a light path between the polarization element 12 and the light amplification device 13. The second light modulation device 14 is used for deflecting the transmission direction of the passing light, and the diaphragm 15 is used for preventing the light which is transmitted by the light amplification device 13 and deflected by the second light modulation device 14 from passing.

The control device 16 is further configured to control the second optical modulation device 14 to deflect the light transmitted from the optical amplification device 13 within a second preset time period, where the second preset time period corresponds to a time period between the main peak of the seed laser pulse and the main peak of the next seed laser pulse.

The backscattered light generated by the optical amplifier 13 will cause a laser gain disturbance, which will affect the power stability and pulse energy stability of the final output laser pulse.

In the laser power amplifying system of the present embodiment, the seed laser pulse generated by the laser generator 10 passes through the first optical modulator 11, the polarizer 12, the stop 15, the second optical modulator 14, and the optical amplifier 13 in this order. The trigger laser generating device 10 generates a seed laser pulse and controls the first optical modulation device 11 to change the polarization state of the passing light within a first preset time period, which corresponds to the existence time period of the leading edge noise of the seed laser pulse, i.e., the leading edge noise of the seed laser pulse is prevented from passing through by the first optical modulation device 11 and the polarization element 12, thereby eliminating the leading edge noise of the seed laser pulse. And, the second optical modulation device 14 is controlled to deflect the light propagated by the optical amplification device 13 within a second preset time period corresponding to a time period between the main peak of the seed laser pulse and the main peak of the next seed laser pulse, that is, the backward scattered light generated by the optical amplification device 13 in the two main peak gaps of the laser pulses is blocked from passing by the second optical modulation device 14 and the aperture 15, thereby eliminating the backward scattered light of the optical amplification device. Therefore, the system can eliminate the influence of the front-edge noise and the backward scattering light on the laser amplification power and the optical gain disturbance, thereby effectively improving the stability of the narrow pulse width laser power output after the laser amplification power and the stability of each pulse energy.

The detailed descriptions of the laser generating device, the first optical modulating device, the polarizing element, the optical amplifying device, the diaphragm, the second optical modulating device, and the control device of the laser power amplifying system of the present embodiment refer to the detailed descriptions of the laser power stabilizing method above.

In one embodiment, laser generating device 10 uses an electro-optic cavity to empty the CO₂The laser outputs a laser pulse waveform as shown in fig. 2, the full-wave full-width at half maximum of the main peak of the laser pulse is about 20ns, the leading edge noise width is about 50ns, and the repetition frequency is more than 10 khz.

The first light modulation device 11 adopts an electro-optical pockels cell and a cadmium telluride crystal, the effective clear aperture is 9mm, and the polarization extinction ratio is more than 500: [email protected] μm, an ultra-fast response time (about 7ns), a single press on time of no more than 3 μ s, and a half wave voltage of about 8 kV.

The polarizing element 12 is a zinc selenide coated sheet arranged at brewster angle (67.8 °), and has an extinction ratio greater than 200: [email protected] 10.6. mu.m.

The second light modulation device 14 adopts an acousto-optic modulator and a Ge acousto-optic device, the effective clear aperture is 9mm, the 1 st-order diffraction light is more than 90 percent, the transmission speed of ultrasonic waves in the Ge crystal is limited, the response time is about 300ns, but the single pressurization working time is not limited.

The optical amplifier 13 adopts radio frequency axial flow CO₂The laser amplifier has excitation power of 20kW, two ends of the laser amplifier are sealed by a high-transmission zinc selenide window sheet, the aperture of a gain area is 21mm, and the length of the gain area is about 4.5 m.

The control device 16 uses a synchronous trigger and uses a 4-channel signal generator. By precisely regulating and controlling the time and the duty ratio of each trigger signal, the disturbance influence of the output front edge noise of the high-repetition-frequency narrow-pulse-width seed laser and the backward scattering light of a laser amplifier on the laser gain can be effectively reduced, and the laser power stability is improved.

The laser power stabilizing method and the laser power amplifying system can solve the problem of slow response time in the laser power closed-loop control stabilizing method at the present stage, can effectively improve the power/pulse energy stability of the high-repetition-frequency narrow-pulse-width laser, and meet the requirement of laser targeting power stability in an EUV lithography light source.

The laser power stabilizing method and the laser power amplifying system provided by the invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.