Direct temporal reconstruction of a picosecond pulse by cross-correlation in a semiconductor device

Introduction: Ultrashort optical pulses are nowadays a basic requirement for numerous applications such as optical communications, nonlinear spectroscopy or terahertz field [1]. As measurement and control of these pulses cannot be achieved by electronic means, alloptical methods have been developed. For example, temporal intensity profiles can be reconstructed from cross correlation records based on an interferometric device which measures the correlation between an unknown pulse and a reference ultrashort pulse through their product in a nonlinear crystal. Although these methods are accurate, a delicate trade-off has to be found between efficiency and spectral bandwidth [2]. This drawback can be partly circumvented by using the two-photon absorption (TPA) process in a semiconductor which permits wideband and ultrashort pulses measurements [2-4], the process being only limited by the peak power of the pulses [4]. Optical cross-correlation between pulses widely different in terms of central wavelength and pulse duration (∆λ > 100 nm and ∆T ratio > 10) has been demonstrated in nonlinear crystals [5] but to the best of our knowledge, it has never been reported in a semiconductor device. Here we present what we believe to be the first cross-correlation between two completely different pulses in a semiconductor device.