Development of the stimulated Raman spectrum in single-mode silica fibers

The spectral development of stimulated Raman scattering in single-mode silica fibers was studied both experimentally and by computer modeling. The most striking feature that emerges is the rapid growth of a weak feature at 490 cm−1 at the expense of a broad band at 440 cm−1 as pump power increases. These experimental results are in good agreement with our numerical simulations, although neither experiments nor calculations show the spectral broadening of higher Stokes orders commonly observed with high pump powers and at infrared wavelengths. It is shown that, in general, spectral broadening from four-wave mixing should be important in the development of the stimulated Raman spectrum. However, the present experiments fall into a regime of relatively low pump powers at visible wavelengths in which four-wave mixing is negligible and the stimulated spectrum depends only on the shape of the Raman gain curve.