Observation of optical precursors at pulse propagation in GaAs

The Sommerfeld precursor in photonic crystals

“…Behind this precursor, the ultraviolet Brillouin precursor [11,12] emerges. Both precursors have been observed for microwaves [13] transmitted through guiding structures that have dispersion characteristics similar to those for dielectrics and for optical pulses [14,15] in water and in GaAs. Behind the Brillouin precursor, the period of the transmitted signal tunes to the applied pulse period which marks the transmission of the main part of the pulse.…”

Optical Precursors with Electromagnetically Induced Transparency in Cold Atoms

“…Experimentally, precursors have been reported in gamma rays [9], microwave [10], optical [5,11,12], and sound [13,14] waves. While the features are in qualitative agreement with theory, these data were rather limited in both scope and precision, far below what is required to compare with the theoretical predictions.…”

“…As discussed in Refs. [12,19], the necessary condition for observing optical precursors is s < g . Moreover, to observe precursors with damped …”

“…The first is the oscillation peak duration determined by the Bessel function in Eq. 12,19]. The second is the precursor (intensity) decay time constant ¼ 1=ð2 13 Þ determined by the atomic natural linewidth.…”

Narrowband Biphotons: Generation, Manipulation, and Applications

“…They showed theoretically that the front of a step-modulated optical pulse (as a carrier of 1 bit information) propagating in a dispersive medium always travels at c. This front, in the form of a transient wave now known as the Sommerfeld-Brillouin precursor, is then followed by the main pulse traveling at its group velocity. Study of optical precursors is of great interests not only for fundamental reasons since it is related to Einstein's causality, but also for applications because of its connection to the maximum speed of optical information transmission [65,66,67,68,69,70,71,72]. Now it is clear that the precursor is the fastest part in the propagation of an optical pulse even in a superluminal medium [68,69,71].…”