Simple Measurement for Ultrafast Field Reconstruction

Ultrashort pulses are important for resolving electron motion in semiconductors to measure electronic transport properties. Electron wave packet motion is on the order of attoseconds, requiring temporal resolution on this time scale. However, a major constraint on femtosecond (1 fs = 10−15 s) and attosecond (1 as = 10−18 s) science is how well we can control and compress the excitation and measurement pulses in pump-probe experiments. Such ultrashort pulses require a broad spectrum with careful phase control across its bandwidth to minimize the duration. We discuss a new optical measurement technique that can directly measure the electric field that constitutes the laser pulse. We find that compared to other techniques for electric field measurements, our method is relatively inexpensive and robust in characterizing pulses around 100 fs regime and below. This method requires only a commercially available CCD camera as opposed to spectrometers or other expensive instruments and provides the ability to reconstruct the electromagnetic field without ambiguities. The measurements from our technique only require a small fraction of the incoming beam to give accurate results. In this way, we can directly measure the temporal evolution of the field amplitude and phase. We developed the technique in single shot, providing a real-time access to measurements, hence can be used to optimize pulse compression experiments in real-time. We characterized pulses from 115 fs down to 30 fs using this technique, bench-marked against other well-established pulse characterization methods