%e report the f~rst experimental verification of Berry's topological phase. The key element in the experiment was a single-mode, helica11y wound optica1 fiber, inside which a photon of a given helicity could be adiabatically transported around a closed path in momentum space. The experiment confirmed at the classical level that the angle of rotation of linearly polarized light in this fiber gives a direct measure of Berry's phase. The topological nature of this effect was also verified, i.e. , the rotation was found to be independent of deformations of fiber path if the solid angle of the path in momentum space stayed constant.

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We report the generation of 0.5 ps full width at half-maximum optical pulses at >0.3 THz (tunable) repetition rate via an induced modulational instability in a single-mode fiber. A 1.319-μm neodymium:yttrium aluminum garnet laser is chosen as the carrier wave and the initial modulation on this carrier is introduced by mixing it with an external-grating-cavity InGaAsP laser. The use of this all-optical modulating scheme and the nonlinear optical propagation effect in fiber (i.e., modulational instability) allows one to reach into the terahertz regime, which is about two orders of magnitude beyond the fastest data limited by the finite response of electronics.

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