Simply Measuring the Electric Field of Very Long, Complex Pulses

We introduce a method for measuring both the intensity and the phase of arbitrary ultrafast waveforms in time ($\sim $1 ns long, with $<$100-fs substructure). It is an extension of a simple version of spectral interferometry called SEA TADPOLE, and we call it MUltiple Delay for Temporal Analysis by Dispersing a Pair of Light E-fields (MUD TADPOLE). In contrast to standard versions of spectral interferometry, MUD TADPOLE utilizes, not one, but a train of identical parallel-propagating reference pulses. These multiple reference pulses are used because each pulse broadens in time inside the spectrometer by the reciprocal of the spectrometer spectral resolution, $t_{sp}$. In the case of standard spectral interferometry, one reference pulse can, at best, measure light only $t_{sp}$ long. In contrast, by utilizing a train of $N$ reference pulses, MUD TADOPLE has the capability to measure light which is $N*t_{sp}$ long. MUD TADPOLE has been demonstrated to measure complex pulses up to 71ps in length. We believe this simple, compact, and inexpensive device can measure pulses with time-bandwidth products in excess of 100,000 using off-the-shelf components.