High-contrast laser pulse time domain precise beam combining device and implementation method thereof

Abstract

The invention relates to the technical field of energy photoelectron application, in particular to a high-contrast laser pulse time domain precise beam combining device and an implementation method thereof, and the device comprises a single longitudinal mode fiber laser, a 1 * 2 beam splitter, an arbitrary waveform generator, an amplitude modulator, an adjustable optical attenuator, an adjustable fiber delay line and a 2 * 1 beam combiner, according to the precise beam combining device, by comprehensively adjusting the arbitrary waveform generator, the adjustable optical attenuator and the adjustable optical fiber delay line, multi-step laser pulses with high contrast ratio and high stability can be finally obtained, and the problem that when the pulse energy of laser pulses generated by an existing arbitrary waveform generator is low, the pulse energy of the laser pulses is low is solved. The technical problems of poor pulse stability and difficulty in precise regulation and control of optical fiber optical delay and pulse energy of laser pulses in a laser pulse time domain beam combining device or influence of other beam combining methods on the quality of combined laser beams in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the field of energy optoelectronic application technology, and in particular to a high-contrast laser pulse time-domain precision beam combining device and an implementation method thereof. Background Art

[0002] With the continuous development and maturity of laser technology, high-power lasers have more and more extensive applications, which have profoundly affected the development of many industries. For high-peak power lasers, laser pulses are required to have a certain repetition frequency, pulse width, pulse energy and pulse shape in various application fields. In particular, in the research of laser-driven "inertial confinement fusion" (ICF), it is required to accurately control the waveform and energy of the laser pulse so as to better focus the laser beam into the cavity target, so as to create a high-temperature, uniform and clean irradiation field in the cavity target, thereby compressing the target pellet and realizing the fusion reaction. The specific process is that the beam generated by the strong laser in the process of interacting with the cavity target irradiates and compresses the target pellet. When the temperature and density of the compressed target pellet reach the appropriate conditions, fusion occurs. Shock waves play an important role in the compression stage of the target pellet in ICF, but using a single shock wave, no matter how large the laser intensity applied to the target is, the maximum compression limit factor is within 4. In order to obtain a higher compression factor with a shock wave of smaller energy, it is necessary to perform isentropic compression through a continuous multiple shock waves. Continuous multiple shock waves can be generated using precisely shaped multi-step laser pulses, which gradually increase the pressure on the target surface. The intensity of each shock wave will increase, thereby achieving effective compression and increasing the chance of successful fusion.

[0003] Researchers (Gowda, Di Nicola, J, and Heebner, J. High Fidelity Pulse Shaping for the National Ignition Facility. United States: Np, 2023) used an arbitrary waveform generator, an amplitude modulator, and a two-stage modulator at the NIF device to shape a multi-step laser pulse with a contrast ratio of 275:1 from a 45ns square wave light pulse, but the cost of the device is high and the contrast ratio of the generated multi-step pulse is low.

[0004] Researchers (Zong Zhaoyu, Xu Dangpeng, Tian Xiaocheng, etc. Research on high-precision shaped laser pulse generation technology. Chinese Laser, 2017, 44(01): 237-243) used the cascade amplitude modulator method to generate ultra-high contrast shaped laser pulses. However, precision physics experiments also require that multi-step laser pulses have specific optical delay amounts and pulse energy sizes, not just high contrast.

[0005] Through the above analysis, the problems and defects of the prior art are as follows:

[0006] (1) The NIF device uses an arbitrary waveform generator, an amplitude modulator, and a two-stage modulator to shape a multi-step pulse with a contrast ratio of 275:1 from a 45ns square wave optical pulse. However, its cost is high, and the contrast ratio of the multi-step pulse is low.

[0007] (2) The cascaded amplitude modulator method can generate multi-step pulses with ultra-high contrast. However, precision physics experiments also require that the multi-step laser pulses have a specific optical delay and pulse energy, not just high contrast. Summary of the invention

[0008] The purpose of the present invention is to provide a high-contrast laser pulse time-domain precision beam combining device and its implementation method, which solves the technical problems that the laser pulses generated by the existing arbitrary waveform generator have poor pulse stability when the pulse energy is low, the fiber light delay and pulse energy of the laser pulses in the laser pulse time-domain beam combining device are difficult to precisely control, or other beam combining methods will affect the quality of the laser beam after combining.

[0009] To achieve the above-mentioned purpose, the present invention provides a high-contrast laser pulse time-domain precision beam combining device, wherein a single longitudinal mode fiber laser, a 1×2 beam splitter, an arbitrary waveform generator, an amplitude modulator, an adjustable optical attenuator, an adjustable optical fiber delay line and a 2×1 beam combiner are arranged along the laser signal transmission direction, the single longitudinal mode fiber laser is connected to the 1×2 beam splitter, the 1×2 beam splitter is connected to the amplitude modulator, the arbitrary waveform generator is connected to the amplitude modulator through a radio frequency line, the amplitude modulator is connected to the adjustable optical attenuator, the adjustable optical attenuator is connected to the adjustable optical fiber delay line, and the adjustable optical fiber delay line is connected to the 2×1 beam combiner, and finally the laser pulse precision beam combining output is realized.

[0010] Among them, the number of the amplitude modulators, the adjustable optical attenuators, and the adjustable fiber delay lines are all two, which are respectively the first amplitude modulator, the second amplitude modulator, the first adjustable optical attenuator, the second adjustable optical attenuator, the first adjustable fiber delay line, and the second adjustable fiber delay line; the 1×2 beam splitter, the first amplitude modulator, the first adjustable optical attenuator, the first adjustable fiber delay line, and the 2×1 combiner are connected in sequence; the 1×2 beam splitter, the second amplitude modulator, the second adjustable optical attenuator, the second adjustable fiber delay line, and the 2×1 combiner are connected in sequence; and the arbitrary waveform generator is connected to the first amplitude modulator and the second amplitude modulator, respectively.

[0011] Wherein, the single longitudinal mode fiber laser is used to generate a small broadband continuous wave laser signal, the output power of the single longitudinal mode fiber laser is ≥20mW, and the 1×2 beam splitter is used to equally split the continuous light pulse input by the single longitudinal mode fiber laser.

[0012] Among them, the arbitrary waveform generator is used to first emit an initial shaped electrical pulse according to the working sequence, and load it to the RF receiving end of the first amplitude modulator and the second amplitude modulator, and modulate the laser signal into initial laser shaped pulses A and B respectively, and their amplitudes are both A0.

[0013] Among them, the first amplitude modulator and the second amplitude modulator are both Mach-Zehnder interferometer type light intensity modulators. In the first amplitude modulator and the second amplitude modulator, there is a strict correspondence between the electric pulse injection and the output light intensity. When an electric pulse that changes along the time domain is applied to the first amplitude modulator or the second amplitude modulator, the output light intensity will also change accordingly in the time domain. By precisely controlling the generation time, amplitude size and pulse width of the initial shaping electric pulse, the time domain precise shaping output of the laser signal is achieved.

[0014] Among them, the first adjustable optical attenuator and the second adjustable optical attenuator are respectively used to further accurately and tunably attenuate the pulse amplitudes of the laser pulses initially generated by the first amplitude modulator and the second amplitude modulator as required. The attenuation introduced by the first amplitude modulator and the second amplitude modulator are α1 and α2 respectively. When pulses A and B pass through the optical adjustable attenuators, their amplitudes become α1A0 and α2A0 respectively.

[0015] The first adjustable optical fiber delay line and the second adjustable optical fiber delay line are used to further accurately tune the optical path of the laser pulses initially generated by the first amplitude modulator and the second amplitude modulator as required, respectively, and the introduced delay is Δt. Assuming that the delay of pulse A does not change, the expression of the time function of pulse A is f(t), and the delay introduced by the delay line to pulse B is Δt. After adjustment by the adjustable delay line, the time function of pulse B becomes f(t-Δt).

[0016] The 2×1 combiner is used to combine the two pulse lasers output by the first adjustable optical fiber delay line and the second adjustable optical fiber delay line, and linearly superimpose the two pulses in the time domain. Taking the above factors into consideration, the shape of the combined pulse can be described by the following formula:

[0017] P(t)=α1A0·f(t)+α2A0·f(t-Δt)

[0018] This formula indicates that at time t, the amplitude of the combined pulse is the linear superposition of the amplitudes of the two pulses. Among them, α1A0 and α2A0 represent the amplitudes of the two pulses after attenuation, respectively. Assuming that the delay of pulse A does not change, the expression of the time function of pulse A is f(t), and the delay introduced by the delay line to pulse B is Δt. After the adjustable delay line is adjusted, the time function of pulse B becomes f(t-Δt), and P(t) represents the pulse shape function after the beam is combined.

[0019] Among them, the output ends of the single longitudinal mode fiber laser, the 1×2 beam splitter connection, the amplitude modulator, the adjustable optical attenuator, the adjustable fiber delay line connection, and the 2×1 combiner are all cut at an 8° bevel angle to prevent the reflected light from being reflected back into the laser resonant cavity during the connection process and causing damage to the laser.

[0020] The present invention also provides a method for realizing a high-contrast laser pulse time-domain precision beam combining device, comprising the following steps:

[0021] The small broadband continuous wave laser signal generated by the single longitudinal mode fiber laser is initially and accurately regulated by the first amplitude modulator and the second amplitude modulator under the drive of the initial shaped electrical pulses generated by the channels (1) and (2) of the arbitrary waveform generator to obtain the initial shaped laser pulse;

[0022] Then, the pulse energy of the laser pulse initially generated by the first amplitude modulator and the second amplitude modulator is further precisely and tunably attenuated according to requirements through the first adjustable optical attenuator and the second adjustable optical attenuator;

[0023] Afterwards, the optical path lengths of the laser pulses initially generated by the first amplitude modulator and the second amplitude modulator are further precisely tuned as required through the first adjustable optical fiber delay line and the second adjustable optical fiber delay line;

[0024] Finally, the two links of laser light are combined by a 2×1 beam combiner, and the reverse isolation function of the 2×1 beam combiner is utilized to allow the laser pulses to be transmitted in one direction, and finally input into a measuring instrument for monitoring.

[0025] The invention discloses a high-contrast laser pulse time-domain precision beam combining device and its implementation method. By adopting electro-optical modulation technology in a laser link, the electro-optical modulation characteristics of a lithium niobate crystal are used to initially realize precise shaping of laser pulses for a small broadband continuous wave laser signal. Then, the adjustable optical attenuator and the adjustable optical fiber delay line are used to further accurately realize the pulse energy and optical delay of the laser pulse. Finally, the pulse splicing technology is used in combination with the 2×1 beam combiner to realize laser pulse beam combining and splicing to generate multi-step laser pulses with high contrast and high stability. At the same time, the single longitudinal mode fiber laser, the amplitude modulator, and the adjustable optical attenuator are used to realize precise shaping of laser pulses. The device and the adjustable optical fiber delay line are both module plug-in structures, which are conducive to device maintenance and integrated installation and debugging, and each module plug-in board is connected by a high-precision flange to effectively reduce polarization mode dispersion. In addition, by adopting a full polarization-maintaining fiber optical path structure, the laser signal is transmitted along the optical link with polarization maintenance, making the performance of the laser pulse more reliable and stable, and solving the technical problems that the laser pulse generated by the existing arbitrary waveform generator has poor pulse stability when the pulse energy is low, the fiber optical delay amount and pulse energy of the laser pulse in the laser pulse time-domain beam combining device are difficult to precisely control, or other beam combining methods may affect the quality of the laser beam after beam combining. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0027] Figure 1 It is a schematic diagram of the overall structure of a high-contrast laser pulse time-domain precision beam combining device according to the first embodiment of the present invention.

[0028] Figure 2 It is a conceptual diagram of pulse beam combining and splicing according to the first embodiment of the present invention.

[0029] Figure 3 FIG. 1 is a graph showing pulse beam combining experimental data of the first embodiment of the present invention.

[0030] Figure 4 This is the second figure of pulse beam combining experimental data of the first embodiment of the present invention.

[0031] Figure 5 It is a flowchart of a method for realizing a high-contrast laser pulse time-domain precision beam combining device according to the second embodiment of the present invention.

[0032] In the figure: 1-single longitudinal mode fiber laser, 2-1×2 beam splitter, 3-arbitrary waveform generator, 4-first amplitude modulator, 5-second amplitude modulator, 6-first adjustable optical attenuator, 7-second adjustable optical attenuator, 8-first adjustable fiber delay line, 9-second adjustable fiber delay line, 10-2×1 combiner. DETAILED DESCRIPTION

[0033] Embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0034] First embodiment:

[0035] See also Figures 1 to 4 The present invention provides a high-contrast laser pulse time-domain precision beam combining device, which is provided with a single longitudinal mode fiber laser 1, a 1×2 beam splitter 2, an arbitrary waveform generator 3, an amplitude modulator, an adjustable optical attenuator, an adjustable optical fiber delay line and a 2×1 beam combiner 10 along the laser signal transmission direction. The number of the amplitude modulator, the adjustable optical attenuator and the adjustable optical fiber delay line is two, which are respectively a first amplitude modulator 4, a second amplitude modulator 5, a first adjustable optical attenuator 6, a second adjustable optical attenuator 7, a first adjustable optical fiber delay line 8 and a second adjustable optical fiber delay line 9.

[0036] In this embodiment, by using electro-optical modulation technology in the laser link, the electro-optical modulation characteristics of the lithium niobate crystal are used to initially realize precise shaping of the laser pulse for a small broadband continuous wave laser signal, and then the adjustable optical attenuator and the adjustable optical fiber delay line are used to further accurately realize the pulse energy and optical delay of the laser pulse. Finally, the pulse splicing technology is used, and the 2×1 beam combiner 10 is combined to realize laser pulse beam combining and splicing to generate multi-step laser pulses with high contrast and high stability. At the same time, the single longitudinal mode fiber laser 1, the amplitude modulator, the adjustable optical attenuator and the adjustable optical fiber delay line are used to realize precise shaping of the laser pulse. The lines are all module plug-in structures, which is conducive to device maintenance and integrated installation and debugging, and each module plug-in board is connected with a high-precision flange to effectively reduce polarization mode dispersion. In addition, by adopting a full polarization-maintaining fiber optical path structure, the laser signal is transmitted along the optical link with polarization maintenance, making the performance of the laser pulse more reliable and stable, and solving the technical problems that the laser pulse generated by the existing arbitrary waveform generator 3 has poor pulse stability when the pulse energy is low, the fiber light delay and pulse energy of the laser pulse in the laser pulse time-domain combining device are difficult to precisely control, or other combining methods will affect the quality of the laser beam after combining.

[0037] Among them, the single longitudinal mode fiber laser 1 is connected to the 1×2 beam splitter 2, the 1×2 beam splitter 2 is connected to the amplitude modulator, the arbitrary waveform generator 3 is connected to the amplitude modulator through a radio frequency line, the amplitude modulator is connected to the adjustable optical attenuator, the adjustable optical attenuator is connected to the adjustable optical fiber delay line, and the adjustable optical fiber delay line is connected to the 2×1 combiner 10, and finally the precise beam combining output of laser pulses is realized. The entire optical link adopts polarization-maintaining optical fiber for transmission to ensure that the polarization state of the laser pulse does not change during the transmission process. Each component uses a plug-in board structure to facilitate device maintenance and integrated installation and debugging. At the same time, the plug-ins of each component are connected by high-precision flanges to reduce polarization mode dispersion.

[0038] Secondly, the 1×2 beam splitter 2, the first amplitude modulator 4, the first adjustable optical attenuator 6, the first adjustable optical fiber delay line 8 and the 2×1 combiner 10 are connected in sequence, the 1×2 beam splitter 2, the second amplitude modulator 5, the second adjustable optical attenuator 7, the second adjustable optical fiber delay line 9 and the 2×1 combiner 10 are connected in sequence, and the arbitrary waveform generator 3 is respectively connected to the first amplitude modulator 4 and the second amplitude modulator 5.

[0039] Again, the single longitudinal mode fiber laser 1 is used to generate a small broadband continuous wave laser signal, the output power of the single longitudinal mode fiber laser 1 is ≥20mW, and the 1×2 beam splitter 2 is used to equally split the continuous light pulse input by the single longitudinal mode fiber laser 1.

[0040] At the same time, the arbitrary waveform generator 3 is used to first send out an initial shaped electric pulse according to the working sequence, and load it to the radio frequency receiving end of the first amplitude modulator 4 and the second amplitude modulator 5, respectively modulate the laser signal into initial laser shaped pulses A and B, whose amplitudes are both A0. The first amplitude modulator 4 and the second amplitude modulator 5 are both Mach-Zehnder interferometer type light intensity modulators. In the first amplitude modulator 4 and the second amplitude modulator 5, there is a strict correspondence between the electric pulse injection and the output light intensity. When an electric pulse that changes along the time domain is applied to the first amplitude modulator 4 or the second amplitude modulator 5, the output light intensity will also change accordingly in the time domain. By precisely controlling the generation time, amplitude size and pulse width of the initial shaped electric pulse, the time domain precise shaping output of the laser signal is realized. The first adjustable optical attenuator 6 and the second adjustable optical attenuator 7, The first amplitude modulator 4 and the second amplitude modulator 5 are respectively used to perform further precise tunable attenuation of the pulse amplitude of the laser pulse initially generated by the first amplitude modulator 4 and the second amplitude modulator 5 as required. The attenuation introduced by the first amplitude modulator 4 and the second amplitude modulator 5 are α1 and α2 respectively. After the pulses A and B pass through the optical adjustable attenuator, their amplitudes become α1A0 and α2A0 respectively. The first adjustable optical fiber delay line 8 and the second adjustable optical fiber delay line 9 are respectively used to perform further precise tuning of the optical path of the laser pulse initially generated by the first amplitude modulator 4 and the second amplitude modulator 5 as required. The introduced delay is Δt. The 2×1 combiner 10 is used to combine the two pulse lasers output by the first adjustable optical fiber delay line 8 and the second adjustable optical fiber delay line 9, and linearly superimpose the two pulses in the time domain. Taking the above factors into consideration, the shape of the combined pulse can be described by the following formula:

[0041] P(t)=α1A0·f(t)+α2A0·f(t-Δt)

[0042] In addition, the first adjustable optical attenuator 6 and the second adjustable optical attenuator 7 both use electric tuning, and change the coupling efficiency of the input optical fiber and the output optical fiber by precisely adjusting the reflector to achieve different attenuation amounts. Compared with the mechanical adjustment of the traditional adjustable optical fiber delay line, the adjustable optical fiber delay line of the present invention uses electric adjustment throughout the entire process, which greatly improves the convenience of operation and ensures the adjustment accuracy. The 2×1 combiner 10 has a reverse isolation effect, so that the laser pulse is transmitted in one direction and is finally injected into the subsequent system to provide a pulsed laser after beam combining or splicing or enters related monitoring instruments.

[0043] Finally, the output ends of the single longitudinal mode fiber laser 1, the 1×2 beam splitter 2 connection, the amplitude modulator, the adjustable optical attenuator, the adjustable optical fiber delay line connection, and the 2×1 combiner 10 are all cut at an 8° bevel to prevent the reflected light from being reflected back into the laser resonant cavity during the connection process and causing damage to the laser.

[0044] When using a high-contrast laser pulse time-domain precision combining device of this embodiment, A and B are two identical square wave pulses, which are spliced ​​into a multi-step pulse after passing through the adjustable optical attenuator, the adjustable optical fiber delay line and the 2×1 combiner 10. In order to describe this phenomenon, we can first define a single square wave pulse, then consider the effects of attenuation and delay, and finally give the pulse form after combining.

[0045] Assume that the amplitude of single square wave pulse A and B is A0 and the width is τ, such as Figure 2 Pulse A and Figure 2 As shown in pulse B, a single rectangular pulse can be expressed as:

[0046]

[0047] Assume that the attenuation coefficients of the attenuator for pulses A and B are α1 and α2 respectively. After passing through the optical variable attenuator, the amplitudes of pulses A and B become α1A0 and α2A0 respectively.

[0048] Assuming that the delay of pulse A does not change, the delay introduced by the delay line to pulse B is Δt. After adjustment by the adjustable delay line, the time function of pulse B becomes f(t-Δt).

[0049] Since pulses A and B are the same pulses, but after different attenuation and delay processing, the two pulses are linearly superimposed in the time domain using a 2×1 beam combiner 10. Taking the above factors into consideration, the shape of the combined pulse can be described by the following formula:

[0050] P(t)=α1A0·f(t)+α2A0·f(t-Δt) (2)

[0051] This formula indicates that at time t, the amplitude of the combined pulse is the linear superposition of the amplitudes of the two pulses. Among them, α1A0 and α2A0 represent the amplitudes of the two pulses after attenuation, P(t) represents the pulse shape function after the beam is combined, and Δt represents the time delay of pulse B relative to pulse A.

[0052] like Figure 2Pulse C shows the superposition effect of two identical laser pulses, but with different attenuation and delay. It should be noted that this figure is based on the assumption of rectangular pulses and does not take into account the complex interactions of the overlapping parts between pulses (such as nonlinear effects). In practical applications, it may be necessary to adjust according to specific circumstances.

[0053] like Figure 3 and Figure 4 As shown in the pulse shape diagram, the contrast ratio of the flat-top output laser shaping pulse is 1177:1. The minimum pulse width of the output laser shaping pulse is determined by the shortest duration of the electric pulse emitted by the arbitrary waveform generator 3, and the maximum pulse width is determined by the time window of the first amplitude modulator 4 and the second amplitude modulator 5. In this embodiment, the duration of the electric pulse emitted by the arbitrary waveform generator 3 is continuously adjustable from 0.1ns to 5000ns, with an adjustment accuracy of 0.1ns, and the time window of the first amplitude modulator 4 and the second amplitude modulator 5 is adjustable from 0 to 45ns, and finally a laser shaping pulse with high contrast, high signal-to-noise ratio and high shaping accuracy is output which is continuously adjustable in the range of 0.1ns to 45ns.

[0054] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. A person of ordinary skill in the art will appreciate that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor implementation code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0055] Second embodiment:

[0056] Based on the first embodiment, please refer to Figure 5 The present invention also provides a method for realizing a high-contrast laser pulse time-domain precision beam combining device, comprising the following steps:

[0057] S101, the small broadband continuous wave laser signal generated by the single longitudinal mode fiber laser 1 is initially and precisely regulated by the first amplitude modulator 4 and the second amplitude modulator 5 under the drive of the initial shaped electrical pulses generated by the channels (1) and (2) of the arbitrary waveform generator 3 to obtain an initial shaped laser pulse.

[0058] Specifically, the arbitrary waveform generator 3 first sends out an initial shaping electric pulse according to the working sequence, and loads it to the radio frequency receiving end of the first amplitude modulator 4 and the second amplitude modulator 5, respectively modulating the laser signal into initial laser shaping pulses A and B, whose amplitudes are both A0. The first amplitude modulator 4 and the second amplitude modulator 5 are both Mach-Zehnder interferometer type light intensity modulators. In the first amplitude modulator 4 and the second amplitude modulator 5, there is a strict correspondence between the electric pulse injection and the output light intensity. When an electric pulse that changes along the time domain (the electric pulse is generated by the channel (1) and the channel (2) of the arbitrary waveform generator 3) is applied to the first amplitude modulator 4 or the second amplitude modulator 5, the output light intensity will also change accordingly in the time domain. By precisely controlling the generation time, amplitude and pulse width of the initial shaping electric pulse, the time domain precise shaping output of the laser signal is realized, and the initial shaped laser pulse is obtained.

[0059] S102 , further accurately and tunably attenuate the pulse energy of the laser pulse initially generated by the first amplitude modulator 4 and the second amplitude modulator 5 through the first adjustable optical attenuator 6 and the second adjustable optical attenuator 7 as required.

[0060] Specifically, the pulse amplitudes of the laser pulses initially generated by the first amplitude modulator 4 and the second amplitude modulator 5 are further precisely tuned and attenuated as required through the first adjustable optical attenuator 6 and the second adjustable optical attenuator 7, respectively. The attenuation introduced by the first amplitude modulator 4 and the second amplitude modulator 5 are α1 and α2, respectively. After pulses A and B pass through the optical adjustable attenuators, their amplitudes become α1A0 and α2A0, respectively. The first adjustable optical attenuator 6 and the second adjustable optical attenuator 7 both use electric tuning, and change the coupling efficiency of the input optical fiber and the output optical fiber by precisely adjusting the reflector to achieve different attenuation amounts.

[0061] S103 . Afterwards, the optical paths of the laser pulses initially generated by the first amplitude modulator 4 and the second amplitude modulator 5 are further precisely tuned as required through the first adjustable optical fiber delay line 8 and the second adjustable optical fiber delay line 9 .

[0062] Specifically, the first adjustable optical fiber delay line 8 and the second adjustable optical fiber delay line 9 further accurately tune the optical path of the laser pulses initially generated by the first amplitude modulator 4 and the second amplitude modulator 5 as required, respectively, and the introduced delay is Δt. Compared with the mechanical adjustment of the traditional adjustable optical fiber delay line, the adjustable optical fiber delay line of the present invention uses electric adjustment throughout the entire process, which greatly improves the convenience of operation and ensures the adjustment accuracy.

[0063] S104. Finally, the two links of laser light are combined by a 2×1 beam combiner 10. The reverse isolation function of the 2×1 beam combiner 10 is utilized to allow the laser pulses to be transmitted in one direction, and finally input into a measuring instrument for monitoring.

[0064] Specifically, the two pulse lasers output by the first adjustable optical fiber delay line 8 and the second adjustable optical fiber delay line 9 are combined by the 2×1 combiner 10, and the two pulses are linearly superimposed in the time domain. Taking the above factors into consideration, the shape of the combined pulse can be described by the following formula:

[0065] P(t)=α1A0·f(t)+α2A0·f(t-Δt)

[0066] The 2×1 beam combiner 10 has a reverse isolation function, so that the laser pulse is transmitted in one direction, and is finally injected into the subsequent system to provide a beam-combined pulse laser or enter a related monitoring instrument.

[0067] What is disclosed above is only one or more preferred embodiments of the present application, and cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A high-contrast laser pulse time-domain precision beam combining device, characterized in that: A single longitudinal mode fiber laser, a 1×2 beam splitter, an arbitrary waveform generator, an amplitude modulator, an adjustable optical attenuator, an adjustable optical fiber delay line and a 2×1 beam combiner are arranged along the transmission direction of the laser signal. The single longitudinal mode fiber laser is connected to the 1×2 beam splitter, the 1×2 beam splitter is connected to the amplitude modulator, the arbitrary waveform generator is connected to the amplitude modulator through a radio frequency line, the amplitude modulator is connected to the adjustable optical attenuator, the adjustable optical attenuator is connected to the adjustable optical fiber delay line, and the adjustable optical fiber delay line is connected to the 2×1 beam combiner, and finally the precise beam combining output of laser pulses is realized.

2. The high-contrast laser pulse time-domain precision beam combining device according to claim 1, characterized in that: The number of the amplitude modulators, the adjustable optical attenuators, and the adjustable fiber delay lines are all two, which are respectively the first amplitude modulator, the second amplitude modulator, the first adjustable optical attenuator, the second adjustable optical attenuator, the first adjustable fiber delay line, and the second adjustable fiber delay line; the 1×2 beam splitter, the first amplitude modulator, the first adjustable optical attenuator, the first adjustable fiber delay line, and the 2×1 beam combiner are connected in sequence; the 1×2 beam splitter, the second amplitude modulator, the second adjustable optical attenuator, the second adjustable fiber delay line, and the 2×1 beam combiner are connected in sequence; and the arbitrary waveform generator is connected to the first amplitude modulator and the second amplitude modulator, respectively.

3. The high-contrast laser pulse time-domain precision beam combining device according to claim 2, characterized in that: The single longitudinal mode fiber laser is used to generate a small broadband continuous wave laser signal, the output power of the single longitudinal mode fiber laser is ≥20mW, and the 1×2 beam splitter is used to equally split the continuous light pulse input by the single longitudinal mode fiber laser.

4. The high-contrast laser pulse time-domain precision beam combining device according to claim 2, characterized in that: The arbitrary waveform generator is used to first send out an initial shaped electrical pulse according to a working sequence, and load it to the RF receiving end of the first amplitude modulator and the second amplitude modulator, respectively modulating the laser signal into initial laser shaped pulses A and B, both of which have an amplitude of A0.

5. The high-contrast laser pulse time-domain precision beam combining device according to claim 2, characterized in that: The first amplitude modulator and the second amplitude modulator are both Mach-Zehnder interferometer type light intensity modulators. In the first amplitude modulator and the second amplitude modulator, there is a strict correspondence between the electric pulse injection and the output light intensity. When an electric pulse that changes along the time domain is applied to the first amplitude modulator or the second amplitude modulator, the output light intensity will also change accordingly in the time domain. By precisely controlling the generation time, amplitude size and pulse width of the initial shaping electric pulse, the time domain precise shaping output of the laser signal is achieved.

6. The high-contrast laser pulse time-domain precision beam combining device according to claim 2, characterized in that: The first adjustable optical attenuator and the second adjustable optical attenuator are respectively used to further accurately and tunably attenuate the pulse amplitudes of the laser pulses initially generated by the first amplitude modulator and the second amplitude modulator as required. The attenuation introduced by the first amplitude modulator and the second amplitude modulator are α1 and α2 respectively. When pulses A and B pass through the optical adjustable attenuators, their amplitudes become α1A0 and α2A0 respectively.

7. The high-contrast laser pulse time-domain precision beam combining device according to claim 2, characterized in that: The first adjustable optical fiber delay line and the second adjustable optical fiber delay line are used to further accurately tune the optical path of the laser pulse initially generated by the first amplitude modulator and the second amplitude modulator as required, respectively, and the introduced delay is Δt. Assuming that the delay of pulse A does not change, the expression of the time function of pulse A is f(t), and the delay introduced by the delay line to pulse B is Δt. After adjustment by the adjustable delay line, the time function of pulse B becomes f(t-Δt).

8. The high-contrast laser pulse time-domain precision beam combining device according to claim 2, characterized in that: The 2×1 combiner is used to combine the two pulse lasers output by the first adjustable optical fiber delay line and the second adjustable optical fiber delay line, and linearly superimpose the two pulses in the time domain. Taking the above factors into consideration, the shape of the combined pulse can be described by the following formula: P(t)=α1A0·f(t)+α2A0·f(t-Δt) This formula indicates that at time t, the amplitude of the combined pulse is the linear superposition of the amplitudes of the two pulses. Among them, α1A0 and α2A0 represent the amplitudes of the two pulses after attenuation, respectively. Assuming that the delay of pulse A does not change, the expression of the time function of pulse A is f(t), and the delay introduced by the delay line to pulse B is Δt. After the adjustable delay line is adjusted, the time function of pulse B becomes f(t-Δt), and P(t) represents the pulse shape function after the beam is combined.

9. The high-contrast laser pulse time-domain precision beam combining device according to claim 1, characterized in that: The output ends of the single longitudinal mode fiber laser, the 1×2 beam splitter connection, the amplitude modulator, the adjustable optical attenuator, the adjustable fiber delay line connection, and the 2×1 beam combiner are all cut at an 8° bevel angle to prevent the reflected light from being reflected back into the laser resonant cavity during the connection process and causing damage to the laser.

10. A method for realizing a high-contrast laser pulse time-domain precision beam combining device, applied to the high-contrast laser pulse time-domain precision beam combining device according to any one of claims 1 to 9, characterized in that: The following steps are involved: The small broadband continuous wave laser signal generated by the single longitudinal mode fiber laser is initially and accurately regulated by the first amplitude modulator and the second amplitude modulator under the drive of the initial shaped electrical pulses generated by the channels (1) and (2) of the arbitrary waveform generator to obtain the initial shaped laser pulse; Then, the pulse energy of the laser pulse initially generated by the first amplitude modulator and the second amplitude modulator is further precisely and tunably attenuated according to requirements through the first adjustable optical attenuator and the second adjustable optical attenuator; Afterwards, the optical path lengths of the laser pulses initially generated by the first amplitude modulator and the second amplitude modulator are further precisely tuned as required through the first adjustable optical fiber delay line and the second adjustable optical fiber delay line; Finally, the two links of laser light are combined by a 2×1 beam combiner, and the reverse isolation function of the 2×1 beam combiner is utilized to allow the laser pulses to be transmitted in one direction, and finally input into a measuring instrument for monitoring.

Images