Abstract

The generation of temporal dark solitons has proved to require considerable experimental effort,^1,2 where a longer pulse was modulated either in the time¹ or frequency domain.² Recently it was predicted³ that, by nonlinearly copropagating a delayed pulse pair in an optical fiber, one naturally forms a train of dark pulses that adiabatically follow the dark soliton solution. Previous attempts to observe these soliton trains using averaged cross-correlation techniques were hampered by the great sensitivity of the time position of the dark pulses to the shape, intensity, and relative phase of the input pulse pair. These parameters vary somewhat over many input pulses and thus the sharp dark pulses wash out in the background. However, by using a high-resolution single shot streak camera, this difficulty is eliminated, thus enabling the direct observation of the generated dark soliton trains. Experimentally, the dark soliton trains were generated by passing a pair of 2-psec pulses within 5-10 psec delay between them through a 100-m polarization preserving fiber. It is observed that periodic dark pulse trains are formed, and the pulse isolation and sharpness demonstrates that the intensity modulation has nonlinearly evolved from the sinusoidal interference one expects from linear propagation into dark solitons. A comparison performed between measurement and theory yields good qualitative agreement.

© 1991 Optical Society of America