CN105651399A

CN105651399A - Time domain phase recovery all-fiber laser pulse weak phase measuring device and method

Info

Publication number: CN105651399A
Application number: CN201610028749.6A
Authority: CN
Inventors: 乔治; 汪小超; 姚玉东; 井媛媛; 范薇
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2016-01-15
Filing date: 2016-01-15
Publication date: 2016-06-08
Anticipated expiration: 2036-01-15
Also published as: CN105651399B

Abstract

A time-domain phase recovery all-fiber laser pulse weak phase measurement device and measurement method, the device comprises: along the input direction of the laser pulse to be measured is an optical fiber beam splitter, the optical fiber beam splitter divides the laser pulse to be measured into strong and weak Two beams of light, along the direction of the strong beam are the adjustable fiber delay device, high-speed fiber phase modulator, dispersion fiber and oscilloscope, and along the direction of the weak beam are the high-speed PIN photoelectric tube, arbitrary waveform generator, and electrical signal amplifier. The output terminal of the signal amplifier is connected to the modulation input terminal of the high-speed optical fiber phase modulator. The invention utilizes an all-fiber structure for phase modulation and dispersion transmission of laser pulses, which has the characteristics of compact structure, simplicity and flexibility, and is different from other laser pulse phase measurement methods. The invention can measure picosecond or nanosecond laser pulses with weak phases , suitable for both high and low repetition rates.

Description

Time-domain phase recovery all-fiber laser pulse weak phase measurement device and measurement method

技术领域technical field

本发明涉及弱相位激光脉冲，特别是一种时域相位恢复全光纤激光脉冲弱相位测量装置和测量方法。本发明采用光纤波导相位调制器对激光脉冲进行相位调制，再通过时域相位恢复的方法来得到激光脉冲的波形与相位。本发明适用于具有弱相位、弱啁啾的皮秒或者纳秒激光脉冲，可以工作在高重复频率或者低重复频率情况下。本装置采用全光纤的结构可以增加装置稳定性与紧凑性，从而获得稳定可靠的激光脉冲相位分布。The invention relates to a weak phase laser pulse, in particular to a time-domain phase recovery all-fiber laser pulse weak phase measurement device and measurement method. The invention adopts the optical fiber waveguide phase modulator to carry out phase modulation on the laser pulse, and then obtains the waveform and phase of the laser pulse through the method of time domain phase recovery. The invention is suitable for picosecond or nanosecond laser pulses with weak phase and weak chirp, and can work under the condition of high repetition frequency or low repetition frequency. The device adopts an all-fiber structure to increase the stability and compactness of the device, thereby obtaining a stable and reliable laser pulse phase distribution.

背景技术Background technique

自从第一台激光器制造至今，激光和激光器的应用已经逐渐渗透到了社会的各行各业中，尤其是对于精密加工行业，激光的应用大大提升了加工精度。其中高能量纳秒或者皮秒激光脉冲在激光物理研究(激光惯性约束核聚变)、激光精密加工、激光切割、激光雷达、超快光谱学、医学、高能物理等多种领域应用广泛。例如，高能量纳秒激光脉冲可以应用于激光惯性约束核聚变，使得靶丸达到核聚变条件，释放出大量的能量，激光惯性约束核聚变有望在未来实现可控核聚变，从根本上解决能源问题。高能量皮秒脉冲可以应用于激光加工以及激光表面处理，激光短脉冲与物质作用过程中的无热沉积和无接触特性大大提高了加工形貌的可控性、加工精度及表面光滑性等加工特性，在金属、晶体、宝石、玻璃、高分子聚合物甚至炸药等多种材料的加工切割上表现出优良的特性，在汽车工业、医疗器械、工业安全等精密加工领域展现了广阔的应用前景。目前高能量纳秒脉冲激光和皮秒脉冲激光均采用主振荡器+多级放大器的结构。但是在放大过程中，由于非线性效应例如自相位调制的存在，激光脉冲会累积非线性相移，从而对后级放大产生影响。但是不同于超短脉冲的情况，纳秒或者皮秒脉冲在传输过程中累积的非线性相移一般较小，从光谱上看，光谱展宽不明显，但是这些小的非线性相移在后续放大过程中会产生较大的影响。此外，由于存在一些非线性相移的补偿方式，例如直接相位调制的预补偿方法，可以在已知其非线性相移大小的情况下，利用预补偿手段对非线性相移进行补偿。这就需要对这些具有弱相位的激光脉冲的相位进行精确测量。目前脉冲时间相位(光谱相位测量)测量的方式有很多种，包括FROG(频率分辨光学开关)、SPIDER(自参考光谱干涉)以及时间自相关等方式，但是这些方式都是基于自相关/互相关的原理，通过脉冲本身进行相关运算或者与参考脉冲进行相关运算。FROG利用是非线性过程进行相关运算，而SPIDER等算法是通过干涉的方式来进行相关运算。但是这些方式的结构一般都比较复杂，同时相关运算对被测脉冲的强度有一定要求(FROG)，或者分辨率较低(SPIDER等)，而且这些方法对于弱相位纳秒或者皮秒激光脉冲的情况，往往无能为力。Since the first laser was manufactured, the application of lasers and lasers has gradually penetrated into all walks of life in society, especially for the precision processing industry, where the application of lasers has greatly improved the processing accuracy. Among them, high-energy nanosecond or picosecond laser pulses are widely used in laser physics research (laser inertial confinement fusion), laser precision machining, laser cutting, lidar, ultrafast spectroscopy, medicine, high-energy physics and other fields. For example, high-energy nanosecond laser pulses can be applied to laser inertial confinement fusion, so that the target pellet reaches the conditions of nuclear fusion and releases a large amount of energy. Laser inertial confinement fusion is expected to achieve controllable nuclear fusion in the future and fundamentally solve the energy problem. question. High-energy picosecond pulses can be applied to laser processing and laser surface treatment. The heat-free deposition and non-contact characteristics during the interaction between short laser pulses and substances greatly improve the controllability of processing morphology, processing accuracy and surface smoothness. It has excellent characteristics in the processing and cutting of various materials such as metals, crystals, gemstones, glass, polymers and even explosives, and has broad application prospects in precision processing fields such as the automotive industry, medical equipment, and industrial safety. . At present, both high-energy nanosecond pulse laser and picosecond pulse laser adopt the structure of main oscillator + multi-stage amplifier. However, during the amplification process, due to the existence of nonlinear effects such as self-phase modulation, the laser pulse will accumulate nonlinear phase shift, which will affect the subsequent amplification. However, unlike the case of ultrashort pulses, the nonlinear phase shift accumulated during the transmission of nanosecond or picosecond pulses is generally small. From the perspective of the spectrum, the spectral broadening is not obvious, but these small nonlinear phase shifts are amplified in the subsequent process will have a greater impact. In addition, since there are some compensation methods for nonlinear phase shift, such as the pre-compensation method of direct phase modulation, the nonlinear phase shift can be compensated by pre-compensation means when the magnitude of the nonlinear phase shift is known. This requires precise measurements of the phase of these weakly phased laser pulses. At present, there are many ways to measure pulse time phase (spectral phase measurement), including FROG (frequency-resolved optical switch), SPIDER (self-reference spectral interference) and time autocorrelation, but these methods are based on autocorrelation/cross-correlation According to the principle, the correlation operation is performed through the pulse itself or with the reference pulse. FROG uses a nonlinear process to perform correlation operations, while algorithms such as SPIDER perform correlation operations through interference. However, the structure of these methods is generally more complicated, and the correlation operation has certain requirements on the intensity of the measured pulse (FROG), or the resolution is low (SPIDER, etc.), and these methods are not suitable for weak phase nanosecond or picosecond laser pulses. Circumstances, it is often impossible to do anything.

因此本发明提出利用时域相位恢复的方法结合直接相位调制的装置来实现对于弱相位纳秒或者皮秒激光脉冲的高精度相位测量。本方法适合于测量具有弱相位分布的窄光谱激光脉冲，同时迭代过程的数据计算过程可以实现高精度的相位测量。Therefore, the present invention proposes to use the time-domain phase recovery method combined with the direct phase modulation device to realize high-precision phase measurement for weak-phase nanosecond or picosecond laser pulses. The method is suitable for measuring narrow-spectrum laser pulses with weak phase distribution, and the data calculation process of the iterative process can realize high-precision phase measurement.

发明内容Contents of the invention

本发明的目的在于克服上述现有激光脉冲的时间相位测量方法不能测量弱相位纳秒或者皮秒激光脉冲的缺点，提出一种时域相位恢复全光纤激光脉冲弱相位测量装置和测量方法，该方法采用时域相位迭代恢复的方式，利用直接相位调制装置对激光脉冲进行相位调制，通过经过色散介质之后的经过相位调制的激光脉冲的时间波形作为已知条件计算得到初始激光脉冲的波形与相位分布。采用全光纤的结构可以提高装置灵活性与紧凑性，实现对弱相位激光脉冲的时间相位分布的高精度测量。The purpose of the present invention is to overcome the disadvantage that the above-mentioned existing laser pulse time phase measurement method cannot measure weak phase nanosecond or picosecond laser pulses, and propose a time-domain phase recovery all-fiber laser pulse weak phase measurement device and measurement method. The method adopts the time-domain phase iterative recovery method, uses the direct phase modulation device to carry out phase modulation on the laser pulse, and calculates the waveform and phase of the initial laser pulse by using the time waveform of the phase-modulated laser pulse after passing through the dispersive medium as a known condition distributed. The all-fiber structure can improve the flexibility and compactness of the device, and realize the high-precision measurement of the time phase distribution of the weak phase laser pulse.

本发明的技术解决方案如下：Technical solution of the present invention is as follows:

一种时域相位恢复全光纤激光脉冲弱相位测量装置，其特征在于其构成包括：沿待测激光脉冲输入方向是光纤分束器,该光纤分束器将待测激光脉冲分为强、弱两束光，沿强光束方向依次是可调光纤延时器、高速光纤相位调制器、色散光纤和示波器，沿弱光束方向依次是高速PIN光电管、任意波形发生器、电信号放大器，该电信号放大器的输出端接所述的高速光纤相位调制器的调制输入端，所述的可调光纤延时器的延时调节精度为1ps，所述色散光纤的长度满足以下条件：A time-domain phase recovery all-fiber laser pulse weak phase measurement device is characterized in that its composition includes: an optical fiber beam splitter along the input direction of the laser pulse to be measured, and the optical fiber beam splitter divides the laser pulse to be measured into strong and weak Two beams of light, along the direction of the strong beam are the adjustable fiber delay device, high-speed fiber phase modulator, dispersion fiber and oscilloscope, and along the direction of the weak beam are the high-speed PIN photoelectric tube, arbitrary waveform generator, and electrical signal amplifier. The output terminal of the signal amplifier is connected to the modulation input terminal of the high-speed optical fiber phase modulator, the delay adjustment accuracy of the adjustable optical fiber delay device is 1ps, and the length of the dispersion optical fiber satisfies the following conditions:

${β β}_{22} L L > > > > \frac{44 {π π}^{22}}{{((Δ Δ ν ν))}^{22}} - - - - - - ((11))$

其中，β₂为所述的色散光纤的二阶色散，L为色散光纤的长度，Δν为经过高速光纤相位调制器的相位调制之后待测激光脉冲的光谱宽度；Wherein, β ₂ is the second-order dispersion of the described dispersive fiber, L is the length of the dispersive fiber, and Δν is the spectral width of the laser pulse to be measured after the phase modulation of the high-speed optical fiber phase modulator;

所述的任意波形发生器产生的调制电信号为一阶高斯脉冲，且该一阶高斯脉冲的脉冲宽度τ满足τ≤ΔT，ΔT为待测激光脉冲的脉宽。The modulated electrical signal generated by the arbitrary waveform generator is a first-order Gaussian pulse, and the pulse width τ of the first-order Gaussian pulse satisfies τ≤ΔT, and ΔT is the pulse width of the laser pulse to be measured.

利用上述时域相位恢复全光纤激光脉冲弱相位测量装置对待测激光脉冲弱相位的测量方法，其特征在于该方法包括以下步骤：The method for measuring the weak phase of the laser pulse to be measured using the above-mentioned time-domain phase recovery all-fiber laser pulse weak phase measurement device is characterized in that the method includes the following steps:

①设t₀为所述的任意波形发生器产生的经所述的电信号放大器放大输出的调制电信号的中心达到所述的高速光纤相位调制器的时刻相对于待测激光脉冲达到所述的高速光纤相位调制器的时刻的初始相对延时，每次调节所述的可调光纤延时器的延时时间的延时增加为Δt，每调整一次延时，所述的示波器记录一个待测激光脉冲强度I_m，依次得到I₁、I₂、┄、I_m、┄I_2n+1，第m次调节后所述的可调光纤延时器产生的延时为t₀+mΔt，第m次调节后，待测激光脉冲经过所述高速光纤相位调制器和色散光纤之后被所述的示波器采集到该延时时间(t₀+mΔt)下的激光脉冲强度I_m为：1. Let _t be the moment when the center of the modulated electrical signal amplified and output by the electrical signal amplifier that the arbitrary waveform generator produces reaches the described high-speed optical fiber phase modulator relative to the laser pulse to be measured. The initial relative delay of the moment of the high-speed optical fiber phase modulator, the delay of each adjustment of the delay time of the adjustable optical fiber delayer is increased to Δt, and each time the delay is adjusted, the oscilloscope records a test The laser pulse intensity I _m is obtained sequentially from I ₁ , I ₂ , ┄, I _m , ┄I _2n+1 , and the delay produced by the adjustable fiber delay device after the m-th adjustment is t ₀ +mΔt, the second After _m times of adjustment, the laser pulse intensity Im under the delay time (t ₀ +mΔt) collected by the oscilloscope after the laser pulse to be measured passes through the high-speed optical fiber phase modulator and the dispersion fiber is:

I_m＝|A_m|²(2)I _m ＝ |A _m | ² (2)

其中，m＝1,2,3…2n+1，n为任意正整数且满足2n+1≥ΔT/Δt，A_m为待测激光脉冲经过色散光纤(7)之后的光场复振幅；Wherein, m=1,2,3...2n+1, n is any positive integer and satisfies 2n+1≥ΔT/Δt, A _m is the complex amplitude of the light field after the laser pulse to be measured passes through the dispersion fiber (7);

②利用时域相位恢复算法对所述的激光脉冲强度I_m进行数据处理，计算待测激光脉冲的相位分布，具体步骤如下：2. Utilize the time domain phase recovery algorithm to carry out data processing to described laser pulse intensity _Im , calculate the phase distribution of laser pulse to be measured, concrete steps are as follows:

1)数据初始化设置：i为当前迭代次数，m为第m次调节可调光纤延时器的序号，令i＝0,m的最大值为2n+1；N_0,2n+1(t)为计算机随机生成的待测激光脉冲的复振幅分布，β为最小计算误差，K为最大迭代次数；1) Data initialization setting: i is the current number of iterations, m is the serial number of the m-th adjustment of the adjustable fiber delay device, let i=0, the maximum value of m is 2n+1; N _0,2n+1 (t) is the complex amplitude distribution of the laser pulse to be measured randomly generated by the computer, β is the minimum calculation error, and K is the maximum number of iterations;

2)令i＝i+1，m＝0，当前迭代计算的初始待测激光脉冲复振幅N_i,m(t)为i-1次迭代中m＝2n+1对应计算出的光场复振幅，即N_i,m(t)＝N_i-1,2n+1(t)；2) Let i=i+1, m=0, the initial complex amplitude of the laser pulse to be measured N _i,m (t) calculated by the current iteration is the complex amplitude of the light field calculated corresponding to m=2n+1 in the i-1 iteration Amplitude, namely N _i,m (t)=N _i-1,2n+1 (t);

3)令m＝m+1，当前对m的迭代计算中初始待测激光脉冲复振幅E_i,m(t)为m-1次迭代中对应计算出的光场复振幅，即E_i,m(t)＝N_i,m-1(t)；3) Let m=m+1, the initial complex amplitude E _i,m (t) of the laser pulse to be measured in the current iterative calculation of m is the corresponding complex amplitude of the light field calculated in the m-1 iteration, namely E _{i, m} (t)=N _i,m-1 (t);

4)按下式计算经过高速光纤相位调制器之后的光场复振幅 4) Calculate the complex amplitude of the optical field after passing through the high-speed optical fiber phase modulator according to the following formula

${P P}_{i i,, m m}^{i i n no} ((t t)) = = {E E.}_{i i,, m m} ((t t)) exp exp ((j j π π \frac{V V}{{V V}_{π π}} B B ((t t - - m m Δ Δ t t)))) - - - - - - ((33))$

其中，V为调制电信号的电压幅值，V_π为高速光纤相位调制器的半波电压，Among them, V is the voltage amplitude of the modulated electrical signal, V _π is the half-wave voltage of the high-speed optical fiber phase modulator,

B(t-mΔt)为具有mΔt的时间延时的调制电信号；B(t-mΔt) is a modulated electrical signal with a time delay of mΔt;

5)再按下式计算经过色散光纤之后的光场复振幅A_i,m(t)和光场相位分布分别为：5) Then calculate according to the formula Optical field complex amplitude A _i,m (t) and optical field phase distribution after passing through dispersive fiber They are:

其中：F为傅里叶变换，F^-1为傅里叶逆变换，ω为光场角频率；Where: F is the Fourier transform, F ^-1 is the inverse Fourier transform, and ω is the angular frequency of the light field;

6)利用示波器第m次测得的经过高速光纤相位调制器和色散光纤的激光脉冲强度I_m，代替(4)式计算得到的光场复振幅，并保留相位不变，得到更新后的复振幅 6) Use the laser pulse intensity I _m measured by the oscilloscope for the mth time through the high-speed optical fiber phase modulator and the dispersive fiber to replace the complex amplitude of the light field calculated by formula (4), and keep the phase unchanged to obtain the updated complex amplitude

7)将所述的光场复振幅逆向传播到色散光纤的输入端，得到更新后的入射光场复振幅 7) The complex amplitude of the light field Propagate back to the input end of the dispersion fiber to obtain the updated complex amplitude of the incident light field

${P P}_{i i,, m m}^{o o u u t t} ((t t)) = = {F f}^{- - 11} {{F f {{{A A}_{i i,, m m}^{o o}}} exp exp ((- - j j \frac{{β β}_{22} L L}{22} {ω ω}^{22}))}} - - - - - - ((66))$

8)根据下式计算高速光纤相位调制器输入端待测激光脉冲的复振幅N_i,m(t)：8) Calculate the complex amplitude N _i,m (t) of the laser pulse to be measured at the input end of the high-speed optical fiber phase modulator according to the following formula:

$\begin{matrix} {N N}_{i i,, m m} ((t t)) = = {E E.}_{i i,, m m} ((t t)) + + \frac{| | φ φ ((t t - - m m Δ Δ t t)) | |}{{| | φ φ ((t t - - m m Δ Δ t t)) | |}_{max max}} \frac{c c o o n no j j ((φ φ ((t t - - m m Δ Δ t t))))}{{| | φ φ ((t t - - m m Δ Δ t t)) | |}^{22} + + α α} (({P P}_{i i,, m m}^{o o u u t t} ((t t)) - - {P P}_{i i,, m m}^{i i n no} ((t t)))) \\ φ φ ((t t - - m m Δ Δ t t)) = = exp exp ((j j π π \frac{V V}{{V V}_{π π}} B B ((t t - - m m Δ Δ t t)))) \end{matrix} - - - - - - ((77))$

其中，|φ(t-mΔt)|_max为调制电信号加载在高速光纤相位调制器上产生的相位调制，conj(*)为函数复共轭，α为防止除零因子；Among them, |φ(t-mΔt)| _max is the phase modulation generated by the modulated electrical signal loaded on the high-speed optical fiber phase modulator, conj(*) is the complex conjugate of the function, and α is the factor to prevent division by zero;

9)当m<2n+1时，返回步骤3)；当m＝2n+1时，按下式计算当前第i次迭代计算的误差Error为：9) When m<2n+1, return to step 3); when m=2n+1, calculate the error Error calculated by the current iterative iteration according to the following formula:

$E E. r r r r o o r r = = &Integral; &Integral; d d t t \underset{m m}{Σ Σ} \frac{| | | | {A A}_{i i,, m m} ((t t)) {| |}^{22} - - {I I}_{m m} ((t t)) | |}{| | {I I}_{m m} ((t t)) {| |}_{m m a a x x}} / / ((22 n no + + 11)) - - - - - - ((88))$

10)若Error<β,则停止迭代计算，进行下一步骤11)；若Error>＝β,且i<K,则返回步骤2)，若i＝K，则进入步骤12)；10) If Error<β, then stop the iterative calculation, proceed to the next step 11); if Error>=β, and i<K, then return to step 2), if i=K, then enter step 12);

11)N_i,2n+1(t)即为待测激光脉冲的光场复振幅，其相位分布根据光场复振幅N_i,2n+1(t)利用常规的相位解包裹算法得到待测激光脉冲在时间上的相位分布为N_i,2n+1(t)/|N_i,2n+1(t)|；11) N _i,2n+1 (t) is the complex amplitude of the light field of the laser pulse to be measured, and its phase distribution is obtained by using the conventional phase unwrapping algorithm according to the complex amplitude of the light field N _i,2n+1 (t). The phase distribution of the laser pulse in time is N _i,2n+1 (t)/|N _i,2n+1 (t)|;

12)当i＝K时，表明当前m的最大取值2n+1不能满足计算精度的要求，则令n＝n+1，增加激光脉冲强度I_m的测量数，返回步骤1)，继续进行计算。12) When i=K, it shows that the maximum value 2n+1 of current m cannot meet the requirement of calculation accuracy, then make n=n+1, increase the number of measurements of laser pulse intensity I _m , return to step 1), and continue calculate.

本发明优点在于：The present invention has the advantage that:

1.本发明装置采用全光纤化的结构，本发明装置结构紧凑，便于调整。1. The device of the present invention adopts an all-fiber structure, and the device of the present invention has a compact structure and is easy to adjust.

2.采用时间相位恢复的方法，可以对弱相位激光脉冲的相位进行测量。2. The phase of the weak phase laser pulse can be measured by using the time phase recovery method.

3.利用直接相位调制的方法可以灵活控制调制电信号。3. The method of direct phase modulation can flexibly control the modulated electrical signal.

4.可以工作在高重频与低重频情况下。4. It can work in the case of high repetition frequency and low repetition frequency.

附图说明Description of drawings

图1是本发明时域相位恢复全光纤激光脉冲弱相位测量装置的结构框图。Fig. 1 is a structural block diagram of the time-domain phase recovery all-fiber laser pulse weak phase measurement device of the present invention.

图2是本发明弱相位激光脉冲的时间相位恢复方法流程图。Fig. 2 is a flow chart of the time phase recovery method of the weak phase laser pulse in the present invention.

具体实施方式detailed description

下面结合实施例和附图对本发明做进一步说明，但不应以此限制本发明的保护范围。The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the protection scope of the present invention should not be limited thereby.

先请参阅图1，图1是本发明时域相位恢复全光纤激光脉冲弱相位测量装置的结构框图。由图可见，本发明时域相位恢复全光纤激光脉冲弱相位测量装置的构成包括：沿待测激光脉冲In输入方向是光纤分束器1,该光纤分束器1将待测激光脉冲In分为强、弱两束光，沿强光束方向依次是可调光纤延时器5、高速光纤相位调制器6、色散光纤7和示波器8，沿弱光束方向依次是高速PIN光电管2、任意波形发生器3、电信号放大器4，该电信号放大器4的输出端接所述的高速光纤相位调制器6的调制输入端，所述的可调光纤延时器5的延时调节精度为1ps，所述色散光纤7的长度满足以下条件：Please refer to FIG. 1 first. FIG. 1 is a structural block diagram of a time-domain phase recovery all-fiber laser pulse weak phase measurement device of the present invention. As can be seen from the figure, the composition of the time-domain phase recovery all-fiber laser pulse weak phase measurement device of the present invention includes: along the input direction of the laser pulse In to be measured is an optical fiber beam splitter 1, and the optical fiber beam splitter 1 splits the laser pulse In to be measured. There are two beams of light, strong and weak. Along the direction of the strong beam, there are adjustable optical fiber delayer 5, high-speed optical fiber phase modulator 6, dispersion fiber 7 and oscilloscope 8. Along the direction of the weak beam, there are high-speed PIN photoelectric tube 2 and arbitrary waveform Generator 3, electrical signal amplifier 4, the output terminal of this electrical signal amplifier 4 is connected to the modulation input end of described high-speed optical fiber phase modulator 6, and the delay adjustment accuracy of described adjustable optical fiber delayer 5 is 1ps, The length of the dispersion fiber 7 satisfies the following conditions:

其中，β₂为色散光纤7的二阶色散，L为色散光纤7的长度，Δν为经过高速光纤相位调制器6相位调制之后的待测激光脉冲的光谱宽度；Wherein, β ₂ is the second-order dispersion of the dispersion fiber 7, L is the length of the dispersion fiber 7, and Δν is the spectral width of the laser pulse to be measured after the phase modulation of the high-speed optical fiber phase modulator 6;

所述的任意波形发生器3产生的调制电信号为一阶高斯脉冲，该且一阶高斯脉冲的脉冲宽度满足τ≤ΔT，其中τ为调制电信号的脉冲宽度，ΔT为待测激光脉冲的脉宽。The modulated electrical signal generated by the arbitrary waveform generator 3 is a first-order Gaussian pulse, and the pulse width of the first-order Gaussian pulse satisfies τ≤ΔT, where τ is the pulse width of the modulated electrical signal, and ΔT is the pulse width of the laser pulse to be measured pulse width.

入射激光脉冲首先经过光纤分束器1分束为两部分，其中分束比为10％与90％。10％端激光脉冲经过高速光电探测器PIN管2转化为电信号作为任意波形发生器3的触发信号。被触发的任意波形发生器3输出一个脉冲宽度小于或者等于待测激光脉冲宽度的电脉冲信号，该电脉冲信号经过高增益高速电放大器4放大之后作为光纤相位调制器6的调制电信号。90％端待测激光脉冲则经过光纤可调光延时器5的作用，改变其与电调制信号之间的相对时间延时。经过时间延时之后的激光脉冲进入光纤相位调制器6，在时间上得到相位调制，激光脉冲光谱发生展宽。经过相位调制之后的激光脉冲则进入具有较大色散量的色散光纤7，在时间上经过相位调制的激光脉冲被展宽，被示波器8探测到激光脉冲的波形，而其时间波形代表了激光脉冲的光谱特征。The incident laser pulse is firstly split into two parts by the fiber beam splitter 1, wherein the splitting ratio is 10% and 90%. The 10% terminal laser pulse is converted into an electrical signal by the high-speed photodetector PIN tube 2 as the trigger signal of the arbitrary waveform generator 3 . The triggered arbitrary waveform generator 3 outputs an electrical pulse signal whose pulse width is less than or equal to the pulse width of the laser to be measured. The electrical pulse signal is amplified by the high-gain high-speed electrical amplifier 4 and used as the modulated electrical signal of the optical fiber phase modulator 6 . The laser pulse to be measured at the 90% end passes through the action of the optical fiber adjustable optical delay device 5 to change the relative time delay between it and the electrical modulation signal. The time-delayed laser pulse enters the optical fiber phase modulator 6, and the phase is modulated in time, and the laser pulse spectrum is broadened. After the phase modulation, the laser pulse enters the dispersion fiber 7 with a large amount of dispersion, and the time-phase-modulated laser pulse is stretched, and the waveform of the laser pulse is detected by the oscilloscope 8, and its time waveform represents the laser pulse. spectral features.

经过本发明装置示波器8采集到的激光脉冲时间波形数据可以利用时间相位恢复方法来得到激光脉冲的相位分布，时间相位恢复方法的流程图参见图2，其具体过程如下：The laser pulse time waveform data collected by the device oscilloscope 8 of the present invention can utilize the time phase recovery method to obtain the phase distribution of the laser pulse, and the flow chart of the time phase recovery method is referring to Fig. 2, and its specific process is as follows:

假设t₀为所述的任意波形发生器3产生的经所述的电信号放大器4放大输出的调制电信号的中心达到高速光纤相位调制器6上的时刻相对于待测激光脉冲达到所述的高速光纤相位调制器6的时刻的初始相对延时，每次调节所述的可调光纤延时器5的延时时间的延时增加为Δt，则第m次调节所述可调光纤延时器5的延时为t₀+mΔt，第m次待测激光脉冲经过所述高速光纤相位调制器6以及色散光纤7之后被所述的示波器8采集到该延时时间(t₀+mΔt)下的激光脉冲强度I_m为：Assuming that t ₀ is the moment when the center of the modulated electrical signal amplified and output by the electrical signal amplifier 4 produced by the arbitrary waveform generator 3 reaches the high-speed optical fiber phase modulator 6 relative to the laser pulse to be measured. The initial relative delay of the moment of the high-speed optical fiber phase modulator 6, each time the delay of adjusting the delay time of the adjustable optical fiber delay device 5 is increased to Δt, then the mth adjustment of the adjustable optical fiber delay The delay of the device 5 is t ₀ +mΔt, and the mth laser pulse to be measured is collected by the oscilloscope 8 after passing through the high-speed optical fiber phase modulator 6 and the dispersion optical fiber 7 (t ₀ +mΔt) The laser pulse intensity I _m under is:

I_m＝|A_m|²(9)I _m ＝ |A _m | ² (9)

其中，m＝1,2,3…2n+1，n为任意正整数，A_m为待测激光脉冲经过色散光纤7之后的光场复振幅。Wherein, m=1, 2, 3...2n+1, n is any positive integer, A _m is the complex amplitude of the light field after the laser pulse to be measured passes through the dispersion fiber 7 .

1)首先进行数据初始化，令i为当前迭代次数，m为第m次调节可调光纤延时器5，i＝0,m＝2n+1；令N_0,2n+1(t)为当前迭代计算中的待测激光脉冲的复振幅，N_0,2n+1(t)为随机生成的待测激光脉冲的复振幅分布；1) Initialize the data first, let i be the current number of iterations, m be the mth adjustment of the adjustable fiber delay device 5, i=0, m=2n+1; let N _0,2n+1 (t) be the current The complex amplitude of the laser pulse to be measured in the iterative calculation, N _0,2n+1 (t) is the complex amplitude distribution of the laser pulse to be measured randomly generated;

2)令i＝i+1，m＝0，同时当前迭代计算中初始待测激光脉冲复振幅N_i,m(t)为i-1次迭代中m＝2n+1对应计算出的光场复振幅，即N_i,m(t)＝N_i-1,2n+1(t)；2) Let i=i+1, m=0, and the initial complex amplitude N _i,m (t) of the laser pulse to be measured in the current iterative calculation is the light field corresponding to m=2n+1 calculated in the i-1 iteration Complex amplitude, that is, N _i,m (t)=N _i-1,2n+1 (t);

3)令m＝m+1，同时当前对m的迭代计算中初始待测激光脉冲复振幅E_i,m(t)为m-1次迭代中对应计算出的光场复振幅，即E_i,m(t)＝N_i,m-1(t)；3) Let m=m+1, and at the same time, in the current iterative calculation of m, the initial complex amplitude E _i,m (t) of the laser pulse to be measured is the corresponding complex amplitude of the light field calculated in m-1 iterations, namely E _{i ,m} (t)=N _i,m-1 (t);

4)计算经过高速光纤相位调制器6之后的光场复振幅为：4) Calculating the complex amplitude of the optical field after passing through the high-speed optical fiber phase modulator 6 for:

${P P}_{i i,, m m}^{i i n no} ((t t)) = = {E E.}_{i i,, m m} ((t t)) exp exp ((j j π π \frac{V V}{{V V}_{π π}} B B ((t t - - m m Δ Δ t t)))) - - - - - - ((1010))$

其中V为调制电信号的电压幅值，V_π为高速光纤相位调制器(6)的半波电压，Wherein V is the voltage amplitude of the modulated electrical signal, and V _π is the half-wave voltage of the high-speed optical fiber phase modulator (6),

5)再计算经过色散光纤7之后的光场复振幅A_i,m(t)和光场相位分布分别为：5) Recalculate Light field complex amplitude A _i,m (t) and light field phase distribution after passing through dispersion fiber 7 They are:

6)根据示波器8测量得到的经过高速光纤相位调制器6和色散光纤7的激光脉冲强度I_m，代替(11)式计算得到的光场复振幅，并保留相位不变，得到更新后的复振幅其过程如下：6) According to the laser pulse intensity I _m measured by the oscilloscope 8 through the high-speed optical fiber phase modulator 6 and the dispersive optical fiber 7, replace the complex amplitude of the light field calculated by the formula (11), and keep the phase unchanged to obtain the updated complex amplitude The process is as follows:

7)将更新后的光场复振幅逆向传播到色散光纤7的输入端，得到更新后的入射光场复振幅 7) The updated light field complex amplitude Propagate back to the input end of the dispersion fiber 7 to obtain the updated complex amplitude of the incident light field

${P P}_{i i,, m m}^{o o u u t t} ((t t)) = = {F f}^{- - 11} {{F f {{{A A}_{i i,, m m}^{o o}}} exp exp ((- - j j \frac{{β β}_{22} L L}{22} {ω ω}^{22}))}} - - - - - - ((1313))$

8)根据下式计算高速光纤相位调制器6输入端待测激光脉冲的复振幅N_i,m(t)：8) Calculate the complex amplitude N _i,m (t) of the laser pulse to be measured at the input end of the high-speed optical fiber phase modulator 6 according to the following formula:

$\begin{matrix} {N N}_{i i,, m m} ((t t)) = = {E E.}_{i i,, m m} ((t t)) + + \frac{| | φ φ ((t t - - m m Δ Δ t t)) | |}{{| | φ φ ((t t - - m m Δ Δ t t)) | |}_{max max}} \frac{c c o o n no j j ((φ φ ((t t - - m m Δ Δ t t))))}{{| | φ φ ((t t - - m m Δ Δ t t)) | |}^{22} + + α α} (({P P}_{i i,, m m}^{o o u u t t} ((t t)) - - {P P}_{i i,, m m}^{i i n no} ((t t)))) \\ φ φ ((t t - - m m Δ Δ t t)) = = exp exp ((j j π π \frac{V V}{{V V}_{π π}} B B ((t t - - m m Δ Δ t t)))) \end{matrix} - - - - - - ((1414))$

其中：|φ(t-mΔt)|_max为调制电信号加载在高速光纤相位调制器6上产生的相位调制，conj(*)为函数复共轭，α为防止除零因子；Wherein: |φ(t-mΔt)| _max is the phase modulation generated by the modulation electrical signal loaded on the high-speed optical fiber phase modulator 6, conj(*) is the complex conjugate of the function, and α is the factor to prevent division by zero;

9)当m<2n+1时，返回步骤3)；否则当m＝2n+1时，计算当前第i次迭代计算的误差Error为：9) When m<2n+1, return to step 3); otherwise, when m=2n+1, calculate the error Error calculated by the current i-th iteration as:

$E E. r r r r o o r r = = &Integral; &Integral; d d t t \underset{m m}{Σ Σ} \frac{| | | | {A A}_{i i,, m m} ((t t)) {| |}^{22} - - {I I}_{m m} ((t t)) | |}{| | {I I}_{m m} ((t t)) {| |}_{m m a a x x}} / / ((22 n no + + 11)) - - - - - - ((1515))$

10)若Error<β,则停止迭代计算，进行下一步骤11)；否则若Error>＝β,且i<K,则返回步骤2)，其中β为最小计算误差，K为最大迭代次数；若i＝K，则进行步骤(12)；10) If Error<β, then stop the iterative calculation, and proceed to the next step 11); otherwise, if Error>=β, and i<K, then return to step 2), where β is the minimum calculation error, and K is the maximum number of iterations; If i=K, then proceed to step (12);

11)当迭代计算终止，待测激光脉冲的光场复振幅即为最后迭代计算终止时的N_i,2n+1(t)，其相位分布根据光场复振幅N_i,2n+1(t)利用常规的相位解包裹算法得到待测激光脉冲在时间上的相位分布为N_i,2n+1(t)/|N_i,2n+1(t)|；11) When the iterative calculation is terminated, the optical field complex amplitude of the laser pulse to be measured is N _i,2n+1 (t) when the last iterative calculation is terminated, and its phase distribution is according to the optical field complex amplitude N _i,2n+1 (t ) using the conventional phase unwrapping algorithm to obtain the phase distribution of the laser pulse to be measured in time as N _i,2n+1 (t)/|N _i,2n+1 (t)|;

12)当i＝K时，表明当前m的最大取值2n+1不能满足计算精度的要求，则令n＝n+1增加激光脉冲强度I_m的测量数，返回步骤1)，继续进行计算。12) When i=K, it shows that the maximum value 2n+1 of current m cannot meet the requirement of calculation accuracy, then make n=n+1 increase the number of measurements of laser pulse intensity I _m , return to step 1), and continue to calculate .

实践表明,本发明采用全光纤化的结构，本发明装置结构紧凑，便于调整。采用时间相位恢复的方法，可以对弱相位激光脉冲的相位进行测量。利用直接相位调制的方法可以灵活控制调制电信号。可以工作在高重频与低重频情况下。Practice shows that the present invention adopts an all-fiber structure, and the device of the present invention has a compact structure and is easy to adjust. The phase of the weak phase laser pulse can be measured by using the time phase recovery method. The method of direct phase modulation can flexibly control the modulated electrical signal. It can work in the case of high repetition frequency and low repetition frequency.

Claims

1. the time domain phase recovery weak phase measurement device of full optical fiber laser pulse, it is characterized in that its composition includes: be fiber optic splitter (1) along testing laser pulse input direction, testing laser pulse is divided into by force by this fiber optic splitter (1), weak two-beam, it is adjustable optic fibre chronotron (5) successively along strong beam direction, high speed fibre phase-modulator (6), dispersive optical fiber (7) and oscillograph (8), it is high speed PIN photocell (2) successively along weak beam direction, AWG (Arbitrary Waveform Generator) (3), electric signal amplifier (4), the modulation input of the high speed fibre phase-modulator (6) described in output termination of this electric signal amplifier (4), the delay adjustment precision of described adjustable optic fibre chronotron (5) is 1ps, the length of described dispersive optical fiber (7) meets the following conditions:

β_{2} L > > \frac{4 π^{2}}{{(Δ ν)}^{2}} - - - (1)

Wherein, ��₂For the 2nd order chromatic dispersion of described dispersive optical fiber (7), L is the length of dispersive optical fiber (7), and �� is the spectral width of testing laser pulse after the phase-modulation of high speed fibre phase-modulator (6);

The modulation signal that described AWG (Arbitrary Waveform Generator) (3) produces is single order Gaussian pulse, and the pulse width �� of this single order Gaussian pulse to meet �ӡܦ� T, �� T be the pulsewidth of testing laser pulse.

2. utilize the measuring method to the weak phase place of laser pulse to be measured of the time domain phase recovery weak phase measurement device of full optical fiber laser pulse described in claim 1, it is characterised in that the method comprises the following steps:

1. t is set₀Amplify, through described electric signal amplifier (4), the initial relative time delay that the center of modulation signal of output reaches the moment of described high speed fibre phase-modulator (6) and reaches the moment of described high speed fibre phase-modulator (6) relative to testing laser pulse for what described AWG (Arbitrary Waveform Generator) (3) produced, the time delay of the delay time every time regulating described adjustable optic fibre chronotron (5) increases to �� t, often adjust a time delay, described oscillograph (8) one testing laser pulse strength I of record_m, obtain I successively₁��I₂��I_m��I_2n+1, the time delay that after regulating for the m time, described adjustable optic fibre chronotron (5) produces is t₀+ m �� t, after regulating for the m time, testing laser pulse is collected this delay time (t by described oscillograph (8) after described high speed fibre phase-modulator (6) and dispersive optical fiber (7)₀Laser pulse intensity I under+m �� t)_mFor:

I_m=| A_m|²(2)

Wherein, m=1,2,3 ... 2n+1, n are any positive integer and meet 2n+1 >=�� T/ �� t, A_mFor testing laser pulse light field complex amplitude after dispersive optical fiber (7);

2. 3. utilize time domain Phase Retrieve Algorithm to described laser pulse intensity I_mCarry out data process, calculate the PHASE DISTRIBUTION of testing laser pulse, specifically comprise the following steps that

1) data initialization is arranged: i is current iteration number of times, and m is the sequence number of the m time adjustment adjustable optic fibre chronotron (5), and the maximum making i=0, m is 2n+1; N_0,2n+1The COMPLEX AMPLITUDE of t testing laser pulse that () generates for computer random, �� is minimum of computation error, and K is maximum iteration time;

2) i=i+1 is made, m=0, the initial testing laser pulsed reset amplitude N that current iteration calculates_i,mT light field complex amplitude that () calculates for m=2n+1 correspondence in i-1 iteration, i.e. N_i,m(t)=N_i-1,2n+1(t);

3) m=m+1 is made, currently to testing laser pulsed reset amplitude E initial in the iterative computation of m_i,mT () is the light field complex amplitude calculated corresponding in m-1 iteration, i.e. E_i,m(t)=N_i,m-1(t);

4) the light field complex amplitude after high speed fibre phase-modulator (6) it is calculated as follows

P_{i, m}^{i n} (t) = E_{i, m} (t) \exp (j π \frac{V}{V_{π}} B (t - m Δ t)) - - - (3)

Wherein, V is the voltage magnitude of modulation signal, V_��For the half-wave voltage of high speed fibre phase-modulator (6), B (t-m �� t) is the modulation signal of the time delays with m �� t;

5) it is calculated as follows againLight field complex amplitude A after dispersive optical fiber (7)_i,m(t) and light field PHASE DISTRIBUTIONIt is respectively as follows:

A_{i, m} (t) = F^{- 1} {F {P_{i, m}^{i n} (t)} \exp (j \frac{β_{2} L}{2} ω^{2})} - - - (4)

Wherein: F is Fourier transformation, F^-1For inverse Fourier transform, �� is light field angular frequency;

6) the laser pulse intensity I through high speed fibre phase-modulator (6) and dispersive optical fiber (7) that oscillograph (8) records for the m time is utilized_m, replace the calculated light field complex amplitude of (4) formula, and retain phase invariant, the complex amplitude after being updated

7) by described light field complex amplitudeReverse propagation is to the input of dispersive optical fiber (7), the incident field complex amplitude after being updated

P_{i, m}^{o u t} (t) = F^{- 1} {F {A_{i, m}^{o}} \exp (- j \frac{β_{2} L}{2} ω^{2})} - - - (6)

8) the complex amplitude N of high speed fibre phase-modulator (6) input testing laser pulse is calculated according to following formula_i,m(t):

\begin{matrix} N_{i, m} (t) = E_{i, m} (t) + \frac{| φ (t - m Δ t) |}{{| φ (t - m Δ t) |}_{\max}} \frac{c o n j (φ (t - m Δ t))}{{| φ (t - m Δ t) |}^{2} + α} (P_{i, m}^{o u t} (t) - P_{i, m}^{i n} (t)) \\ φ (t - m Δ t) = \exp (j π \frac{V}{V_{π}} B (t - m Δ t)) \end{matrix} - - - (7)

Wherein, | �� (t-m �� t) |_maxBeing carried in the upper phase-modulation produced of high speed fibre phase-modulator (6) for modulation signal, conj (*) is function complex conjugate, and �� is for preventing from removing null divisor;

9) when m < during 2n+1, return step 3); As m=2n+1, the error E rror being calculated as follows the calculating of current ith iteration is:

E r r o r = &Integral; d t \underset{m}{Σ} \frac{| {| A_{i, m} (t) |}^{2} - I_{m} (t) |}{{| I_{m} (t) |}_{m a x}} / (2 n + 1) - - - (8)

10) if Error<��, then stop iterative computation, carry out next step 11); If Error>=��, and i<K, then return step 2), if i=K, then enter step 12);

11)N_i,2n+1T () is the light field complex amplitude of testing laser pulse, its PHASE DISTRIBUTION is according to light field complex amplitude N_i,2n+1T () utilizes conventional phase unwrapping algorithm to obtain testing laser pulse PHASE DISTRIBUTION in time is N_i,2n+1(t)/|N_i,2n+1(t) |;

12) as i=K, it was shown that the maximum occurrences 2n+1 of current m can not meet the requirement of computational accuracy, then make n=n+1, increase laser pulse intensity I_mMeasurement number, return step 1), proceed calculate.