飞秒激光超短激光脉冲测量.ppt

光电子技术精品课程 电子科学与技术 精密仪器与光电子工程学院 飞秒脉冲的测量方案 (Measurement of an ultrashort pulse) Outlines 为什么测量超短脉冲是一项挑战? 为什么要对超短脉冲进行测量? 对超短脉冲的全面描述需要那些测量量？ 光谱仪与Michelson 干涉仪 自相关法 频率分辨光学开关法 (FROG) 光谱相位干涉直接电场重构法 (SPIDER) 超短脉冲的测量Ⅰ：自相关法 Outlines Intensity Autocorrelation Single-shot autocorrelation Third-order Autocorrelation Intensity Cross-Correlation Interferometric Autocorrelation 强度自相关器 Crossing beams in an SHG crystal, varying the delay between them, and measuring the second-harmonic (SH) pulse energy vs. delay yields the Intensity Autocorrelation: The Intensity Autocorrelation: Delay Beam-splitter Input pulse Aperture eliminates input pulses and also any SH created by the individual input beams. Slow detector Mirror E(t) E(t–t) Mirrors SHG crystal Lens What if we use a collinear beam geometry, and allow the autocorrelator signal light to interfere with the SHG from each individual beam? Developed by J-C Diels Usual Autocor- relation term New terms Also called the “Fringe-Resolved Autocorrelation” Filter Slow detector SHG crystal Lens Beam- splitter Input pulse Delay Mirror Mirror E(t) E(t–t) Michelson Interferometer Diels and Rudolph, Ultrashort Laser Pulse Phenomena, Academic Press, 1996. 干涉自相关器 Outlines: The Musical Score and the Spectrogram Frequency-Resolved Optical Gating (FROG) SHG-FROG and other geometries XFROG, Single-shot FROG and GRENOILLE 超短脉冲测量Ⅱ：频率分辨光开关法 FROG： 用复制的可延迟的脉冲与原脉冲在非线性介质中的瞬时相互作用作为光学开关；对开关脉冲随时间的变化进行光谱分辨。 Use any ultrafast nonlinearity: Second-harmonic generation, etc. “Polarization Gate” Geometry Nonlinear medium (glass) Pulse to be measured Variable delay, t Camera Spec- trometer Beam splitter E(t) E(t-t) Esig(t,t) = E(t) |E(t-t)|2 45° polarization rotation 频率分辨光学开关法 (FROG) Baltuska, Pshenichnikov, and Weirsma, J. Quant. Electron., 35, 459 (1999). SHG FROG Measurements of a 4.5-fs Pulse! 超短脉冲测量Ⅲ： SPIDER What is SPIDER? How SPIDER works? SPIDER apparatus X-SPIDER Outlines: t Chirped pulse t t t This pulse sums with the