展宽器元件失调及带通分析

Analysis of Misalignment and Spectrum Bandpass of Pulse Stretcher

通过光线追迹法给设计的反射式单光栅展宽器建立了一个数学计算模型。利用这个数学模型计算和分析了元件失调对反射式单光栅展宽器二阶色散量和输出光束发散角的影响,并考虑了反射式单光栅展宽器中衍射光栅和球形凹面镜的尺寸与展宽器带通的关系。发现当平面反射镜 M1 的纵向偏离角为 0. 2°时,展宽器的二阶色散量最大,偏离角大于或小于0 .2°时,展宽器的二阶色散量随之减小;得到了元件失调会增加输出光束发散角的结论;并发现展宽器中衍射光栅和球形凹面镜尺寸的有限大小对带通有限制作用。提出了利用反射镜 M1 纵向的适当偏离增大展宽器二阶色散量的方法,以及增大衍射光栅和反射镜尺寸来提高展宽器带通的方法,从而进一步减少展宽过程中的光谱剪切。

An analytical pulse stretcher model for the single-grating stretcher based on ray-tracing is presented. By this model, the effect of misalignment of optical element of stretcher on the second dispersion and on the deviation angle of the output pulse is analyzed. When the misalignment angle for the plane reflective mirror M1 is 0.2 degree, the second order dispersion of the stretcher reaches the maximum. Increasing or decreasing misalignment angle, the second order dispersion of the stretcher decreases. That indicates that the misalignment of optical element of stretcher increases deviation angle of output pulse. The finite size of the diffraction grating and the concave mirror in the stretcher has constraint effect on spectrum bandwidth. A new way of increasing second order dispersion by misaligning reflective mirror, and improving bandwidth by increasing size of the diffraction grating and the concave mirror in the stretcher is proposed. It is important to the design of the stretcher.