| 整形飞秒激光脉冲的成丝超连续辐射控制 |
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| 引用本文： | 常峻巍,朱瑞晗,张兰芝,奚婷婷,郝作强.整形飞秒激光脉冲的成丝超连续辐射控制[J].物理学报,2020(3):147-153. |
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| 作者姓名： | 常峻巍 朱瑞晗 张兰芝 奚婷婷 郝作强 |
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| 作者单位： | 长春理工大学理学院;山东师范大学物理与电子科学学院;中国科学院大学物理科学学院 |
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| 基金项目： | 国家自然科学基金(批准号:11774038,11874056,11474039,11274053);山东省泰山学者建设工程资助的课题~~ |
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| 摘 要： | 飞秒激光成丝超连续辐射具有高强度和高时空相干性等优点,作为一种超宽带光源在很多领域都具有广泛的应用前景.本文提出一种结合微透镜阵列的空间调制和基于液晶空间光调制器的时域整形的飞秒激光脉冲整形方式,利用基于遗传算法的反馈优化控制,实现了飞秒激光在熔融石英中成丝产生的超连续辐射强度的调制,得到了在一定范围内光谱强度可控的超连续辐射光谱;光谱的能量密度可以从0.03μJ/nm调制到0.09μJ/nm,其能量密度变化达到了初始值的3倍.计算了典型迭代代数对应的整形脉冲时域包络,分析了超连续光谱随迭代代数的演化趋势,结果表明,脉冲包络的峰值强度和波形分布是影响超连续光谱展宽和强度的主要物理原因.
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| 关 键 词： | 飞秒激光成丝 超连续辐射 激光脉冲整形 反馈控制 |
Control of supercontinuum generation from filamentation of shaped femtosecond laser pulses |
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| Chang Jun-Wei,Zhu Rui-Han,Zhang Lan-Zhi,Xi Ting-Ting,Hao Zuo-Qiang.Control of supercontinuum generation from filamentation of shaped femtosecond laser pulses[J].Acta Physica Sinica,2020(3):147-153. |
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| Authors: | Chang Jun-Wei Zhu Rui-Han Zhang Lan-Zhi Xi Ting-Ting Hao Zuo-Qiang |
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| Affiliation: | (School of Science,Changchun University of Science and Technology,Changchun 130022,China;Shandong Provincial Engineering and Technical Center of Light Manipulations,Shandong Provincial Key Laboratory of Optics and Photonic Device,School of Physics and Electronics,Shandong Normal University,Jinan 250358,China;School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 101407,China) |
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| Abstract: | Supercontinuum(SC),as one of the most spectacular phenomena occurring in the nonlinear process of intense femtosecond laser-material interaction,has attracted considerable interest.The broadband SC sources have a variety of applications including the spectroscopy,fluorescence microscopy,remote sensing,and generation of few-cycle pulses.Over the last few decades,the SC has been extensively investigated in various optical media,including liquid,gas,and solid.Especially,ultrabroadband SC sources have achieved remarkable development in the photonic crystal and micro-structured fibers.Even so,the generation of the SC with high brightness,high spatiotemporal coherence and good maneuverability,is still a challenging topic.The SC generation from femtosecond filamentation is a unique white light source with high pulse energy,high brightness and high spatiotemporal coherence,whose spectral range spans from ultraviolet to mid-infrared.In recent years,numerous studies have been conducted to optimize the filamentation and SC.The control of filamentation such as the filament length,number and position,as well as the generation of the ultra-broadband spectrum with high spectral energy density has been realized.To date,the optimal control of SC has been realized by the spatial modulation or time-domain shaping of the femtosecond laser pulse.However,there is no report on the control of SC generation and filamentation by spatiotemporally modulating the femtosecond laser pulses as far as we know.In this work,a spatiotemporal modulation for the femtosecond laser pulse is proposed,which combines the spatial modulation by using microlens array(MLA)and the laser pulse shaping based on liquid crystal spatial light modulator.We investigate the control of the SC generation from the filamentation of the spatiotemporally modulated femtosecond laser pulses in fused silica by using the feedback optimal control based on genetic algorithm.In our experiments,with the increase of the iterative generation,the cut-off wavelength in the blue-side extension of the SC becomes shorter gradually,and the spectral intensity of the SC increases significantly.After the eighth iteration,the increase of the spectral intensity slows.With the number of iterations increasing further,the intensity and broadening of SC spectrum will no longer apparently change.Hence,the feedback optimization control of spectral intensity of SC is realized,and the SC with controllable spectral intensity in a certain range is obtained.The maximum intensity variation of SC is more than three times.By integrating the spectral intensities of SC for different iterative generations,we characterize the increase trend of SC conversion efficiency.During the first few iterations,the conversion efficiency increases rapidly.Then it increases slowly after eighth generations and reaches its maximum after several generations(10th generation).The conversion efficiency has a similar evolution to the spectral intensity of the SC.To explain the physical mechanism,the initial envelope of the shaping pulse with typical iteration generation is calculated.It can be concluded that the spatial modulation of MLA allows for higher incident laser energy and for more filaments’generation,which increases the energy of SC radiation directly.The peak intensity and envelope distribution of time domain pulse are the main factors affecting the spectral intensity and broadening the SC. |
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| Keywords: | femtosecond filamentation supercontinuum laser pulse shaping feedback control |
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