Trapped pulse generation by femtosecond soliton pulse in birefringent optical fibers

A novel phenomenon of trapped pulse generation by orthogonally polarized femtosecond soliton pulse is discovered in low birefringent optical fiber. As pulse propagation, wavelengths of soliton pulse and trapped pulse are shifted toward longer wavelength side due to effects of soliton self-frequency shift and pulse trapping. The energy of trapped pulse is increased exponentially through Raman gain of soliton pulse and orthogonally polarized and temporally overlapped two colored femtosecond twin pulses are generated. The spectrogram of output pulses is observed using cross-correlation frequency resolved optical gating technique. The characteristics of this phenomenon are also analyzed numerically and numerical results are almost in agreement with experimental ones. (C) 2002 Optical Society of America.