【作者】 刘静；

【导师】 郑臻荣；

【作者基本信息】 浙江大学 ， 测试计量技术及仪器， 2017， 硕士

【摘要】 超短脉冲自出现以来,发展十分迅速,飞秒脉冲具有脉冲持续时间短、光谱范围宽、峰值功率高、聚焦范围小等优点,可以实现超高空间分辨率以及时间分辨率,引发了基础科学和技术科学广泛而深刻的变革,已被广泛应用于物理、化学、光谱学、生物医学、微加工、三维存储等领域。飞秒脉冲在光学系统中传输时,光学器件的色散、像差、面型误差、装调误差等,将对脉冲产生严重影响,导致脉冲展宽甚至形变以及光束质量下降等现象,致使整个光学系统的性能不佳。因此,我们需要通过脉冲整形技术改善脉冲质量。到目前为止,有关超短脉冲的研究范围十分广泛,研究方法多种多样,但大多仅局限于理想透镜或简单光学系统,缺乏飞秒脉冲在实际复杂光学系统中传输问题的研究。本文中,基于超短脉冲的传输特性,采用波动光学与几何光线追迹相结合的方法,对飞秒脉冲在光学系统中的传输进行了仿真模拟,尤其是复杂光学系统中,该方法充分考虑了球差、色差等光学像差对飞秒脉冲的影响,并可对脉冲的展宽与形变现象进行分析。通常,光学系统中的材料具有正色散特性,使得超短脉冲在传输过程中,不同频谱成分的传播速度不同,红光比蓝光传输速度快,红光成分与蓝光成分将逐渐分开,造成脉冲宽度增大以及脉冲峰值功率降低。而棱镜、光栅是负色散器件,蓝光传输速度比红光快,可以对脉冲光束进行压缩,用于进行普通光学材料的色散校正,从而使脉冲的所有频率分量同时到达,脉冲宽度和峰值功率保持不变。利用该方法首先对飞秒脉冲在平行平板的传输做了仿真模拟,随后模拟了超短脉冲在三片式镜头中的展宽,并采用棱镜对系统对其色散进行补偿。最后仿真模拟超短脉冲在计算摄像物镜中的传输,由于物镜的复杂性,导致出射脉冲存在严重展宽与形变,为此,采用棱栅结构——光栅与棱镜的组合,进行校正,补偿复杂物镜的色散。当校正系统选择合适参数时,对实际复杂光学镜头的校正效果较好,可保持超短脉冲的特性,满足实际需求。更多还原

【Abstract】 Ultra-short pulse has been developing rapidly since its appearance.The femtosecond pulse has the advantages of short pulse duration,wide spectral range,high peak power and small focusing range,so that it can realize ultra-high spatial resolution as well as temporal resolution,which results in extensive and profound technological revolution.Ultra-short pulse has been widely used in physics,chemistry,spectroscopy,biomedicine,micro-processing,three-dimensional storage and other fields.When the femtosecond pulse is transmitted in the optical system,characteristics of the optical devices,such as the dispersion,aberration,surface-shape error and adjusting error,will have a serious impact on the pulse,resulting in pulse’broadening and even deformation and degradation of beam’ quality,which brings about the poor performance of the whole optical system.Therefore,it is necessary to improve the pulse’ quality by pulse shaping technology.So far,the research scope about ultrashort pulse is very wide,and the research methods are varied,but most of the research is confined to ideal lens or simple optical system,lacking the study about transmission of femtosecond pulse in practical complicated optical system.In this paper,based on the transmission characteristics of ultrashort pulses,the propagation of femtosecond pulses in optical systems is simulated by the combination of wave optics and geometrical ray tracing,especially in complex optical systems.In this way,the effect of spherical aberration and chromatic aberration on the femtosecond pulse is fully considered,and the broadening and deformation of the pulse can be analyzed.Generally,the positive dispersion of the optical material makes the propagation speed of the different spectral components different,i.e.the red light is faster than the blue one,so the red component and the blue component will gradually separate.As a result,the pulse width will increase,and the pulse peak power is reduced.The prism as well as the grating is a device with negative dispersion,through which blue light’ transmission speed is faster than the red light’.The pulse light beam can be compressed and correction for the dispersion of ordinary optical materials,so that all the frequency components of the pulse propagates at the same time,and pulse width and peak power could be maintained.This method is used to simulate the propagation of femtosecond pulse in parallel plate.And then the extension of ultrashort pulse in three-piece lens is simulated,whose dispersion is compensated by prism.Finally,the simulation of ultrashort pulse in a large computational imaging instrument is made.Due to the complexity of the objective lens,the outgoing pulse experiences a serious extension and deformation.The grism(a combination of the grating and the prism)is proposed as a pre-correction scheme to compensate the dispersion of the complex optical system.When the suitable parameters are selected,the correction effect is much better,and the characteristics of the ultrashort pulse can be maintained to meet the actual demand.更多还原