Induced-frequency shift of copropagating ultrafast optical pulses

Abstract
The combined effects of cross‐phase modulation and pulse walk‐off on copropagating optical pulses are investigated. It is shown that ultrafast pulses which overlap in a nonlinear dispersive medium undergo a substantial shift of their carrier frequencies. This new coherent phenomenon of induced‐frequency shift has been demonstrated using strong infrared picosecond pulses which shift the frequency of weak green picosecond pulses propagating in a 1‐m‐long single‐mode optical fiber.