Abstract

In Raman generation photons from an intense pump pulse are spontaneously scattered into a red-shifted Stokes pulse. The spontaneously generated Stokes pulse is then amplified by stimulated scattering as it propagates with the pump pulse, and it grows at an exponential rate until it begins to significantly deplete the pump. This coupling of a random start-up with exponential growth produces a macroscopic Stokes pulse with a highly unpredictable energy. [1-4] There has been extensive work on the pulse energy statistics associated with Raman generation in high pressure gas cells [1,2], but there has been very little work on Raman generation in a waveguide geometry. [3,4] In a waveguide the transverse spatial mode of the pump and Stokes light can be tightly controlled, permitting maximum spatial overlap between the two signals; furthermore, the use of optical fiber permits long interaction lengths for long temporal pulses where dispersive walk-off between the Stokes and pump pulses is minimal. [5] Multiple order Stokes generation occurs at modest pump powers in a waveguide, allowing one to investigate the coupling between pulse energy fluctuations of different Stokes orders. We will present a systematic experimental study of the pulse energy statistics of the first Stokes order under conditions of multi-order Raman generation in single-mode optical fiber. This study will look at the evolution of the pulse energy statistics and histograms as the scattering strength changes. The role played by the broad Raman gain spectrum of glass in shaping the statistics of the generated light will also be discussed.

© 1998 Optical Society of America