Amplified spontaneous emission (ASE) and its restraint in a femtosecond Ti
: sapphire chirped-pulse amplifier were investigated. The noises arising fr
om ASE were effectively filtered out in the spatial, temporal and spectral
domain. Pulses as short as 38 fs were amplified to peak power of 1.4 TW. Th
e power ratio between the amplified femtosecond pulse and the ASE was highe
r than 10(6) : 1.