Interferometric cross correlation with a numerical lock-in: Nonlinear polariton pulse propagation through GaAs

Summary form only given. We present a ultrasensitive method for measuring the ultrafast optical response of a sample with respect to its amplitude and phase. Combining interferometric cross correlation, a wavemeter and a numerical lock-in technique, the method is distinguished by its dynamic range (7 orders of magnitude in the intensity) and phase resolution (/spl Delta//spl Phi//2/spl pi/=1/50). Time resolution depends on residual dispersion of the set-up but is limited to /spl ap/40 fs by the width of the input pulses. We demonstrate, as an example, high precision measurements of nonlinear 1s-exciton-polariton propagation through GaAs.