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
Baltuska, Pshenichnikov, and Weirsma, J. Quant. Electron., 35, 459 (1999).
超短脉冲测量Ⅲ： SPIDER
Outlines:
What is SPIDER?
How SPIDER works?
SPIDER apparatus X-SPIDER
Mirror
E(t)
Mirrors
E(t–)
Delay
Lens ES H(t, ) E(t)E(t ) IS H(t, ) I (t) I(t )
The Intensity Autocorrelation:
A(2) ( )


I (t )I (t ) dt
Input pulse Beam-splitter Aperture eliminates input pulses and also any SH created by the individual input beams. SHG crystal Slow detector Vd et( ) A (2) ( )

光电子技术精品课程
干涉自相关器
What if we use a collinear beam geometry, and allow the autocorrelato signal light to interfere with the SHG from each individual beam?
SHG-FROG and other geometries
XFROG, Single-shot FROG and GRENOILLE
频率分辨光学开关法 (FROG)
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。
Pulse to be measured
Iaconis and Walmsley, JQE 35, 501 (1999).
光电子技术精品课程
SPIDER apparatus
Delay Line M BS Delay Line
Focusing Lens
Lens
Spectrometer
SHG crystal
Filter Aperture
BS
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:
How SPIDER works
Input pulses
Chirped pulse t
Output pulses Two replicas of the pulse are produced, each frequency shifted by a different amount.
0
Michelson Interferometer
Input pulse
Mirror
E(t) E(t–)
Mirror
SHG Lens crystal Filter
Slow detector
2
Developed by J-C Diels
Diels and Rudolph, Ultrashort Laser Pulse Phenomena, Academic Press, 1996.
Pulse Stretcher
Michelson Interferometer
Grating
Input
BS
BS
Grating
~ ~ ~ ~ S ( , ) | Etest ( 1 ) |2 | Etest ( 2 ) |2 | Etest ( 1 ) || Etest ( 2 ) | cos[ test ( 1 ) test ( 2 ) ]
This pulse sums with the blue part of the chirped pulse.
0

This pulse sums with the green part of the chirped pulse.

t
t
SFG


Performing SI on these two pulses yields the difference in spectral phase at nearby frequencies (separated by ). This yields the spectral phase.
“Polarization Gate” Geometry
Beam splitter E(t-)
I FROG ( , )
45° polarization rotation


2

Esig (t , ) exp( i t ) dt
Camera
Variable delay,
E (t )
2 2
2
Usual Autocorrelation term

Also called the “Fringe-Resolved Autocorrelation”
超短脉冲测量Ⅱ：频率分辨光开关法
Байду номын сангаас
Outlines:
The Musical Score and the Spectrogram
Frequency-Resolved Optical Gating (FROG)
Nonlinear medium (glass)
Esig(t,) = E(t) |E(t-)|2
Use any ultrafast nonlinearity: Second-harmonic generation, etc.
SHG FROG Measurements of a 4.5-fs Pulse!
Beamsplitter
E(t ) E (t )
(2)
[ E(t) E(t )]
Delay
IA ( )
New terms


[E (t ) E (t )]
2 2
dt

IA ( )
(2)


E (t ) E (t ) 2 E(t )E(t ) dt
光电子技术 精品课程
超短脉冲的测量 (Measurement of an ultrashort pulse)
广州市固润光电科技有限公司 电子科学与技术 精密仪器与光电子工程学院
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)