Chirped pulse amplifiers (CPAs),[1] a kind of complex laser amplification systems,are constructed to create laser pulses of ultra-high power,which promise physical experiments in an environment of extreme electromagnetic fields,pressure,temperature,and acceleration.[2] The seed pulses of CPAs come from mode-locked oscillators and are characterized by tens of nanometer of spectrum width and tens of femtosecond of pulse width.Before being amplified,they are expanded into nanoseconds of frequency chirped pulses for amplification efficiency by a grating expander[3] with normal dispersion.After being amplified,laser pulses are compressed by a grating compressor[4] with negative dispersion in order to pursue at high peak power.[5,6] The wider the dispersionfree bandwidth is,the narrower the output pulse width is.