Stimulated Raman scattering is investigated in a slightly multimode gas-filled hollow-core photonic crystal fiber. Although, second-order Stokes light appears in the fundamental mode below a certain threshold energy, it is observed to switch to a two-lobed higher order mode above this threshold. Conversion to the higher order mode is made possible by the creation of a two-lobed moving coherence wave in the gas that provides both phase-matching and a strong intermodal pump-Stokes overlap. A theoretical model is developed, based on this physical interpretation that agrees quantitatively with the experimental results. The results suggest new opportunities for all-fiber gas-based nonlinear processes requiring phase-matching, such as coherent anti-Stokes Raman scattering, as well as providing a means (for example) of efficiently converting light from a higher order pump mode to a fundamental Stokes mode.
© 2012 Optical Society of America
Nonlinear Optics for Functional Devices and Applications
Original Manuscript: January 12, 2012
Manuscript Accepted: April 16, 2012
Published: June 11, 2012
M. Ziemienczuk, A. M. Walser, A. Abdolvand, and P. St. J. Russell, "Intermodal stimulated Raman scattering in hydrogen-filled hollow-core photonic crystal fiber," J. Opt. Soc. Am. B 29, 1563-1568 (2012)