|
Low-intensity light pulses with energies of ~10fJ and pulse lengths of ~10ps will likely play key roles in next-generation optical telecommunications. While techniques exist that can measure weak pulses, some require a time-synchronized reference pulse, and another requires a high-temperature, aperiodically poled LiNiO3 waveguide, which can be difficult to work with and is not readily available. Others involve difficult alignment procedures, complex apparatuses, and expensive electronics (>$100,000), and still others measure only the coherent artifact. Thus, it has not been possible to reliably and practically measure the complete intensity and phase of ultraweak ps pulses. To solve this problem, we are developing a self-referenced technique based on the simple method, GRENOUILLE. As in standard GRENOUILLE devices, we also use the natural phase-matching angular dispersion of a thick second-harmonic generation (SHG) crystal to spectrally resolve the SH light. To improve the sensitivity, however, we exchange the crossed-beam line-focus geometry and single-shot functionality, for a point-focus collinear-beam geometry and scan the delay, while using and even thicker SHG crystal. This generates an “interferometric FROG” trace from which a conventional SHG FROG trace can be extracted. It is considerably more sensitive than current GRENOUILEs due to the point focus (which yields much higher SHG efficiency than the usual line focus) and FROGs due to its thick crystal.
|
