1、飛秒脈沖的測(cè)量方案 (Measurement of an ultrashort pulse),Outlines,為什么測(cè)量超短脈沖是一項(xiàng)挑戰(zhàn)? 為什么要對(duì)超短脈沖進(jìn)行測(cè)量? 對(duì)超短脈沖的全面描述需要那些測(cè)量量？ 光譜儀與Michelson 干涉儀 自相關(guān)法 頻率分辨光學(xué)開(kāi)關(guān)法 (FROG) 光譜相位干涉直接電場(chǎng)重構(gòu)法 (SPIDER),超短脈沖的測(cè)量：自相關(guān)法,Outlines,Intensity Autocorrelation Single-shot autocorrelation Third-order Autocorrelation Intensity Cross-Correlation

2、 Interferometric Autocorrelation,強(qiáng)度自相關(guān)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 pulse

3、s and also any SH created by the individual input beams.,Slow detector,Mirror,E(t),E(tt),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,Also called the “Fringe-Re

4、solved Autocorrelation”,Filter,Slow detector,SHG crystal,Lens,Beam- splitter,Input pulse,Delay,Mirror,Mirror,E(t),E(tt),Michelson Interferometer,Diels and Rudolph, Ultrashort Laser Pulse Phenomena, Academic Press, 1996.,干涉自相關(guān)器,Outlines:,The Musical Score and the Spectrogram Frequency-Resolved Optica

5、l Gating (FROG) SHG-FROG and other geometries XFROG, Single-shot FROG and GRENOILLE,超短脈沖測(cè)量：頻率分辨光開(kāi)關(guān)法,FROG： 用復(fù)制的可延遲的脈沖與原脈沖在非線性介質(zhì)中的瞬時(shí)相互作用作為光學(xué)開(kāi)關(guān)；對(duì)開(kāi)關(guān)脈沖隨時(shí)間的變化進(jìn)行光譜分辨。,Use any ultrafast nonlinearity: Second-harmonic generation, etc.,頻率分辨光學(xué)開(kāi)關(guān)法 (FROG),Baltuska, Pshenichnikov, and Weirsma, J. Quant. Electron.,

6、 35, 459 (1999).,SHG FROG Measurements of a 4.5-fs Pulse!,超短脈沖測(cè)量： SPIDER,What is SPIDER? How SPIDER works? SPIDER apparatus X-SPIDER,Outlines:,t,Chirped pulse,t,t,t,This pulse sums with the blue part of the chirped pulse.,This pulse sums with the green part of the chirped pulse.,Two replicas of the

7、pulse are produced, each frequency shifted by a different amount.,Performing SI on these two pulses yields the difference in spectral phase at nearby frequencies (separated by dw). This yields the spectral phase.,Input pulses,Output pulses,Iaconis and Walmsley, JQE 35, 501 (1999).,SFG,How SPIDER works,Spectrometer,SHG crystal,Filter,Focusing Lens,Lens,Delay Line,Delay Line,Gr