The Research On The Ultra-short Pulse Precise Dispersion Compensation Based On Temperature Characteristics Of Chirped Fiber Bragg Grating

With the continuous development of laser applications,the performance of the laser is required to improve.Femto-second lasers are widely used in various fields with their unique advantages.However,when the pulse width reaches the order of the femtosecond,there may be uncertainties in the various devices in the system,such as the introduction of third-order dispersion or non-linear effects,resulting in deterioration of the shape of the pulse.This will be a great limitation on the application of the laser.Based on the temperature characteristics of chirped fiber Bragg grating(CFBG),the CFBG in the chirp pulse amplifier(CPA)system is controlled by temperature to achieve fine dispersion adjustment,which compensates the dispersion in the system and optimizes the output pulse shape.When the CFBG temperature is changed,the reflection spectrum will drift and the amount of dispersion will change.In theory,the temperature field of CFBG needed to compensate the third order dispersion in the compensation system is calculated,but the accuracy of compensation is not high and the optical path adjustment more difficult.The use of temperature tuning method,not only reduces the difficulty of the optical path adjustment,but also improving the adjustment accuracy,adjust accuracy can reach3fs/?in experiment.It is easy to get the system's minimum output pulse width.Due to lack of direct measurement of the dispersion,it is proposed using autocorrelation instrument to measure the pulse width after compression.It indirectly reflects the change of dispersion by the pulse width.For the second-order dispersion,the CFBG is used as the compressor of the fiber CPA system for accurate dispersion compensation.The grating pairs can control the grating distance and angle to achieve the system dispersion compensation.Third-order dispersion compensation is more complex.According to the third-order dispersion theory,grating pair and CFBG,a relatively simple calculation model is established.According to the theoretical calculation of the required temperature field,this paper uses five Thermo Electric coolers(TEC)to fit the required temperature field,and get a certain effect,the pulse base is significantly reduced.However,since the temperature field introduced is not continuous,a higher order dispersion is introduced,and the base of the pulse is reduced but widened.Inorder to study the effect of temperature field on the pulse base,the paper divides it into three groups,and studies the influence of each group on the pulse base.The experimental results show that the higher the temperature in the middle,the lower the pulse base and spread to both sides,and near the middle of the TEC higher temperature,the pulse base will move closer to the pulse center.Of course,the compensation for the third-order dispersion remains to be further studied,and the non-linear effect of the system is not taken into account,and the non-linearity will have a certain effect on the final pulse output,so the temperature-tuned CFBG accurately compensates for the dispersion But also need to continue to study hard.