Abstract

Recently, in an analytical approach based on incommensurate spectral decomposition, Banerjee et al.¹ showed that an AM pulse, upon transmission across a linear, nondispersive/ nonlinear, dispersive interface, appeared to indicate the formation of collinear AM and narrowband FM "channels," each with distinctive phase velocities. This indicated that these modulations would spatially separate after some characteristic distance. The above work was based on a nonlinear Klein-Gordon (NKG) system in which the interface was linear/ nondispersive on one side and nonlinear/ dispersive on the other. In this paper, we assume a nonlinear Schrödinger (NLS) system in which the core is assumed to have a Sellmeier-type material dispersion and an n₂-type quadratic refractive index nonlinearity. The cladding is made similarly nonlinear but nondispersive for simplicity. By numerical simulations that accommodate exact soliton pulses, the nature of the reflected soliton pulses is examined for variable angles of incidence and for dispersion and nonlinearity parameters. We report here the formation of self-phase modulations on the low-amplitude regions of the propagating pulse, as well as possible phase modulation (resembling the narrowband FM channel analytically derived in Ref. ¹) in portions of the reflected pulse. The propagation velocities and amplitudes of the modulations and the carrier are also numerically estimated and are compared with available theory. The case of discrete, incommensurate sidebands is also tested.

© 1992 Optical Society of America