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单次SHG-FROG测量的基本原理是:将待测激光分为两束,两束光在单次自相关仪内的KDP倍频晶体上交叉相互作用产生SHG自相关信号,自相关信号经光谱仪在与时间延迟轴正交的方向上进行光谱展开后,用CCD得到时域频域正交的二维谱图,对二维谱图利用FROG程序进行还原,得到脉冲时域内的波形、相位、脉宽与频域内的光谱、相位、带宽等信息。现对已搭建的单次SHG-FROG测量设备进行如下改造:1)利用透镜将自相关仪内的KDP晶体成像在光谱仪狭缝上,避免了信号光的发散带来的误差;2)选取合适的光谱仪准直透镜和成像透镜的焦距比例,使得CCD上光谱轴与时间轴的像素数之比为1:
The basic principle of single-shot SHG-FROG measurement is that the laser to be measured is divided into two beams and the two beams of light cross-interact with each other on a KDP frequency multiplying crystal in a single autocorrelator to generate an SHG autocorrelation signal. The autocorrelation signal is analyzed by a spectrometer After the spectral expansion in the direction orthogonal to the time delay axis, the 2D orthogonal spectrum in the time domain and frequency domain is obtained by CCD, and the FROG program is used to restore the two-dimensional spectrum to obtain the waveform, phase, Pulse width and frequency domain spectrum, phase, bandwidth and other information. Now the single SHG-FROG measuring equipment that has been built has been modified as follows: 1) KDP crystals in the autocorrelator are imaged on the slit of the spectrometer by using a lens, thus avoiding the error caused by the divergence of the signal light; and 2) The ratio of the focal length of the collimator lens and the imaging lens of the spectrometer is such that the ratio of the number of pixels on the CCD to the number of pixels on the time axis is 1: