Acousto-optic filter for femtosecond laser pulse shaping, gain narrowing and phase distortion compensation

Summary form only given. The acousto-optic programmable dispersive filter (AOPDF) recently proposed creates an optical output E/sub out/(t) that is the convolution between an optical input E/sub in/(t) and a time scaled electrical signal S(/spl alpha/t). E/sub out/(t)=E/sub in/(t)/spl otimes/S(/spl alpha/). The scaling factor or /spl alpha/=/spl Delta/n.v/c is the ratio of the speed of sound to the speed of light times the index difference between the ordinary and extraordinary wave in the birefringent material used. We thus synthesize a filter of impulse response S(/spl alpha/t), and because /spl alpha/ is of order 10/sup -7/ we can manipulate an optical signal in the hundred-THz range with an electrical signal in the ten-MHz range. In our setup, the S(t) signal is applied to a piezoelectric transducer to generate an acoustic wave in a 2.5-cm-long TeO/sub 2/ crystal. The center frequency of S(t) is 50 MHz. The bandwidth is larger than 20 MKz. This translates into an optical bandwidth of 150 THz around 375 THz. The associated time resolution is 6.7 fs yielding 450 resolution points in the 3-ps group delay allowed by the crystal length.