Regularizing Aperiodic Cycles of Resonant Radiation in Filament Light Bullets

Abstract

We demonstrate an up to now unrecognized and very effective mechanism which prevents filament collapse and allows persistent self-guiding propagation retaining a large portion of the optical energy on axis over unexpected long distances. The key ingredient is the possibility of continuously leaking energy into the normal dispersion regime via the emission of resonant radiation. The frequency of the radiation is determined by the dispersion dynamically modified by photogenerated plasma, thus allowing us to excite new frequencies in spectral ranges which are otherwise difficult to access.

Wavelength-scaled laser filamentation in solids and plasma-assisted subcycle light-bullet generation in the long-wavelength infrared

“…This is also consistent with the calculation in Ref. [29] in which a longer wavelength shows less effects of resonant radiation (2 µm vs. 1.9 µm). Self-compression occurs with all central wavelengths, as shown by the calculated on-axis temporal profiles versus propagation distance in Fig.…”

“…As we will show later, although resonant radiation is observed in our calculations, it is not the dominant mechanism for light bullet formation, in contrast to the 1.9-µm light bullet generated by resonant radiation in Ref. [29].…”

“…These peaks resemble those of resonant radiation (also known as dispersive waves, Cherenkov radiation and nonsolitonic radiation) shown in Fig. 1 of Brée et al [29]. To investigate the possible role of resonant radiation in our calculations, we consider the phase-matching condition for resonant radiation, where the phase of the soliton…”

“…Most notably, we identify highly stable, sub-cycle LWIR light bullets, which are selfcompressed via a combination of anomalous dispersion, self-steepening and plasma. Our LWIR light bullets critically depend on enhanced plasma defocusing and absorption, which is in sharp contrast to 4-µm air light bullets [18] and 1.9-µm light bullets in fused silica [29] stabilized via radiation loss. Because of this stable, self-steepened sub-cycle propagation, mid-IR/LWIR laser filamentation in solids can be an excellent tool for HHG [14,15] and potentially isolating attosecond pulses.…”

“…Light bullets [25,26] are non-diffractive and nondispersive optical pulses. Solids in the anomalous groupvelocity dispersion (GVD) regime have been shown to support light bullets at 1.8 µm [27] and 1.9 µm [28], and light bullets have been predicted to propagate with the aid of resonant radiation [29]. Extending the concept to long wavelengths, Voronin et al [30] predicted optical solitary wave propagation at 3.9 µm in YAG.…”