Abstract

Hollow-core photonic crystal fibers (HC-PCFs) with Kagome-style cladding structure have granted strong guided interactions between light and gaseous media over relatively-long propagation distances with low transmission losses and pressure-tunable dispersion in the visible region [1]. Stimulated Raman scattering processes in gases are characterized by having a very long molecular coherence relaxation time, of the order of hundreds of picoseconds or more. In this work, we analyze the propagation of two non-overlapped pulses, temporally separated by a delay smaller than the relaxation times, in HC-PCFs filled with Raman-active gases. The leading pulse is an ultrashort strong fundamental soliton ‘pump’ with a temporal width shorter than the Raman oscillation period of the gas, while the trailing pulse is a weak ‘probe’ pulse with negligible nonlinearity. The pump induces a lagging sinusoidal temporal modulation of the medium refractive index, which has been observed experimentally [2], due to Raman polarization. This soliton is uniformly accelerated as a result of its Raman-induced spectral redshift. In the reference frame of soliton, we have found that the probe governing equation is the exact analogue of the time-dependent Schrödinger equation of an electron in a periodic crystal in the presence of an external electric field [3]. In our case, we deal with a spatially-dependent Schrödinger equation of a single particle ‘probe’ in an induced temporal crystal by the pump that is uniformly accelerated.

© 2015 IEEE