用自相关仪frog测量超短激光脉冲的方法

1、超短脉冲的测量超短脉冲的测量 (Measurement of an ultrashort pulse)(Measurement of an ultrashort pulse)广州市固润光电科技有限公司Outlv为什么测量超短脉冲是一项挑战为什么测量超短脉冲是一项挑战? 为什么为什么要对超短脉冲进行测量要对超短脉冲进行测量?v对超短脉冲的全面描述需要那些测量量？对超短脉冲的全面描述需要那些测量量？ v光谱仪与光谱仪与Michelson 干涉仪干涉仪v自相关法自相关法v频率分辨光学开关法频率分辨光学开关法 (FROG)v光谱相位干涉直接电场重构法光谱相位干涉直接电场重构法 (SPIDER)Outl

2、ines Intensity Autocorrelation Single-shot autocorrelation Third-order Autocorrelation Intensity Cross-Correlation Interferometric AutocorrelationCrossing beams in an SHG crystal, varying the delay between them,and measuring the second-harmonic (SH) pulse energy vs. delay yields the Intensity Autoco

3、rrelation: A(2)() I(t)I(t)dtThe Intensity Autocorrelation:ES H(t,) E(t)E(t )ISH(t,) I(t)I(t )DelayBeam-splitterInputpulseAperture eliminates input pulsesand also any SH created by the individual input beams.Slow detectorMirrorE(t)E(t)Vdet() A(2)()MirrorsSHGcrystalLensWhat if we use a collinear beam

4、geometry, and allow the autocorrelatorsignal light to interfere with the SHG from each individual beam?Developed by J-C DielsIA(2)() E(t) E(t )22dtIA(2)() E2(t) E2(t ) 2E(t)E(t )2dtUsualAutocor-relationtermNewtermsAlso called the “Fringe-Resolved Autocorrelation”FilterSlow detectorSHGcrystalE(t) E(t

5、 )E(t) E(t )2LensBeam-splitterInputpulseDelayMirrorMirrorE(t)E(t)Michelson InterferometerDiels and Rudolph, Ultrashort Laser Pulse Phenomena, Academic Press, 1996.干涉自Outlines: The Musical Score and the Spectrogram Frequency-Resolved Optical Gating (FROG) SHG-FROG and other geometries XFROG, Single-s

6、hot FROG and GRENOILLEFROG： 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互作用作为光学开关光学开关；对开关脉冲随时间的变化进行；对开关脉冲随时间的变化进行光谱分辨光谱分辨。Use any ultrafast nonlinearity: Second-harmonic generation, etc.“Polarization Gate” GeometryNonlinearmedium (glass)Pulse to be measuredVariable delay, CameraSpec-trome

7、terBeamsplitterE(t)E(t-)Esig(t,) = E(t) |E(t-)|245 polarization rotation2( , )( , )exp()FROGsigIEti t dt 频率分辨光学开Baltuska, Pshenichnikov, and Weirsma,J. Quant. Electron., 35, 459 (1999).SHG FROG Measureme What is SPIDER? How SPIDER works? SPIDER apparatus X-SPIDER Outlines:tChirped pulsett00This puls

8、e sums with the blue part of the chirped pulse.This pulse sums with the green part of the chirped pulse.Two replicas of the 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 ). This yields the spectral phase.Input pulsesOutput pulsesIaconis and Walmsley, JQE 35, 501 (1999).SFGHow SPIDSpectrometerSHGcrystalFilterFocusingLensLensDelayLineDelayLineGratingGra